Matthew Todd

Regulatory and Scientific Affairs

1220 L Street, NW Washington, DC 20005

- 4070 USA Telephone: 202

- 682

- 8 319 Fax: 202

- 682

- 8031 Email: ToddM@api.org www.api.org

June 13 , 2014

Mr. Chris Frantz US EPA 109 T.W. Alexander Drive Mail Code: #143

- 05 Research Triangle Park, NC 27709

Re: EPA VOC /Methane White Paper on Oil and Natural Gas Sector Pneumatic Devices

Dear Mr. Frantz :

The American Petroleum Institute (API) appreciates the opportunity to provide feedback on EPA’s White Papers on Methane and Volatile Organic Compound (VOC) Emissions in the Oil and Natural Gas Sector. On April 15, 2014, EPA released, for external peer review, white papers that focus on technical issues covering emissions and mitigation techniques targeting methane and VOCs from five separate emission
sources. As noted in the Obama Administratio n’s Strategy to Reduce Methane Emissions, EPA will use the papers, along with the input from the peer reviewers and the public, to determine how to best pursue additional reductions from these sources. As described below, API does not believe additional

me thane controls should be required at this time.

API represents over 590 oil and natural gas companies, leaders of a technology

- driven industry that supplies most of America’s energy, supports more than 9.8 million jobs and 8 percent of the U.S.

economy, and, since 2000, has invested nearly $2 trillion in U.S. capital projects to advance all forms of energy, including alternatives. Many of our members will be directly impacted by any policy decisions that may arise from this effort regardless of whether it informs either regulatory action by the federal
government or states

.

API provide d technical feedback and expertise throughout the de velopment of the New Source Performance Standard (NSPS) Subpart OOOO rule

. Each source addressed by the white papers w as considered for regulation during th e development of the NSPS and EPA, ultimately, chose not to regulate them

. While our understanding of emissions from oil and gas production continues to evolve,
the fundamental merits of requiring additional regulatory control of these sources is un changed

. A s such

, API continues to believe that no addition al regulation of oil and gas produ ction sources is

necess ary prior to the full implementation of the NSPS OOOO rule and a subsequent evaluation of
emissions

.Page 2

Considering the potential for significant impact on our members that may arise from any policy decision stemming from the white papers

, API has developed significant technical comments (see attached) to
address a number of technical inaccuracies about the sources and the conclusions that have been
drawn. Barring significant revision, API believes that the current white papers are simply insuff icient to inform sound policy decisions and that simply posting comments on the current version will not result in an informed process . As such , API recommends the EPA take the following steps:

 R evise the white papers to correct any fundamental flaws or i naccuracies that were identified in response to peer review and stakeholder comment (e.g., improved source description s , improved understanding of emission quantification , misconceptions about emission mitigation options )

 Develop a response to comments doc ument that clearly identify the changes the EPA makes to the revised white papers and explains the Agency’s rationale for those changes

 Identify emission studies in progress that will better inform EPA’s understanding of these source
emissions and await th e pending study reports

In recent years, there have been significant swings in the national emission estimates from oil and gas production sources, including those covered by the white papers, which indicate a necessity to continue collecting data to impr ove our understanding. Much of this learning will come from improved reporting under Subpart W of EPA’s Greenhouse Gas Reporting Program as well as current studies and others planned in the coming years, which involve taking direct measurements of the sour ces. EPA and industry
would both be well served by allowing these studies to inform policy.

Again, we appreciate the work by EPA to initiate these white papers and the opportunity to provide
feedback on this effort. API and its members are dedicated to working with EPA to improve our collective understanding of these emissions and providing the technical operator experience that’s
needed to do so. Recognizing the potential for these white papers to inform not only EPA but other government agency policy d ecisions, w e request the opportunity to provide additional feedback to the Agency in response to any of our comments in advance. Furthermore, we again offer our experience and expertise as EPA moves into the policy evaluation phase of this effort.

Sincerely, /s/

Matthew Todd

Cc: Peter Tsirigotis, EPA David Cozzie, EPA

Bruce Moore , EPA

### i 

# Comments on

Oil & Natural Gas Sector
Pneumatic Devices
by EPA Office of Air Quality Planning and Standards

June, 2014

Prepared by
The American Petroleum Institute (API)

### API Comments on Submitted to EPA

Oil & Natura l Gas Sector Pneumatic Devices June 1 3 , 2014

ii 

## Table of Contents

A. Executive Summary

................................ ................................ ................................ ............... 1

1. Section 1.1.1 Pneumatic Controllers

- Definition of the Source

................................ ..... 2

2. Actions Controllers Can Take

................................ ................................ ............................. 4

3. Section 1.1.2 Pneumatic Pumps

- Definition of the Source

................................ ............ 6

4. Section 1.2.1 Pneumatic Controllers

- Background

................................ ......................... 7

5. Section 1.2.2 Pneumatic Pumps

................................ ................................ ...................... 10
a) Pneumatic Chemical and Methanol Pumps

................................ ............................... 10
b) Pneumatic Diaphragm Pumps

................................ ................................ .................... 11
c) Gas Assist Glycol Dehydrator Pumps

................................ ................................ ............. 11

B. Charge Questions:

................................ ................................ ................................ ............... 13
Charge Q uestion 1

................................ ................................ ................................ ................... 13
a) Missing Information:

................................ ................................ ................................ . 16
b) Missing Validation:

................................ ................................ ................................ .... 17
c) Missing Limitations Discussion:

................................ ................................ ............... 19
Charge Question 2

................................ ................................ ................................ ................... 20
Charge Question 3

................................ ................................ ................................ ................... 21
Charge Question 4

................................ ................................ ................................ ................... 22
a) Pneumatic Controllers:

................................ ................................ ............................. 22
b) Pneumatic Pumps:

................................ ................................ ................................ .... 24
c) Pneumatic Controllers 

### and Pumps in the ICF/EDF Study

................................ ........ 26
Charge Question 5

................................ ................................ ................................ ................... 28
Charge Question 6

................................ ................................ ................................ ................... 29
Charge Que stion 7

................................ ................................ ................................ ................... 30
Charge Question 8

................................ ................................ ................................ ................... 30
Charge Question 9

................................ ................................ ................................ ................... 30

C. Conclusion

................................ ................................ ................................ ............................. 31

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 13 , 2014

iii 

## List of Figures

Figure 1: Continuous Bleed Controller

................................ ................................ ........................... 3 Figure 2: Intermitten t Vent Pilot

................................ ................................ ................................ .... 4 Figure 3: Integral Controller

................................ ................................ ................................ ........... 6 Figure 4: Pneumatic Pumps

................................ ................................ ................................ ......... 10 Figure 5: Double Diaphragm Pneumatic Pump

................................ ................................ ............ 11 Figure 6: Glycol Recirculation Pneumatic Pump

................................ ................................ .......... 12 Figure 7: Glycol Recirc Pump Schematic

................................ ................................ ...................... 12 Figure 8: Mizer Retrofit

................................ ................................ ................................ ................ 22

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 1 3 , 2014

1 

## A. Executive Summary

The U.S. Environmental Protection Agency (EPA) has developed a draft document titled Oil and Natural
Gas Sector Pneumatic Devices (hereinafter “the White Paper”) to, as stated in the Preface, seek input and solidify its understanding of the methane and volatile organic compounds (VOCs) emissions from leaks in this industry sector. The American Petroleum Institute (API) hereby submits its input and
comments in this document.

The White Paper does not meet the goal of being a high quality technical document intended as a resource to inform EPA’s deliberations regarding emissions due to pneumatic devices. Rather than a robust compilation and analysis of available information, the White Pap er appears to be a summary of the information sources referenced. In some instances, the summaries of the underlying sources are incomplete and information is incorrectly mischaracterized. There are misunderstandings and incorrect/inaccurate statements s cattered throughout the White Paper. No discussion regarding the limitations of the underlying sources is presented in the White Paper and there is no critical analysis of the accuracy or validity of the underlying sources or the information summarized fr om them in the White Paper. The logic and underpinning evidence leading to the conclusions and assertions made in the White Paper is not clearly presented.
The White Paper needs significant improvement in content, organization, and data sources to be usef ul if is intended to inform EPA’s understanding and evaluation of potential options to reduce emissions
from pneumatic devices

. Following the public announcement that a white paper was being drafted on emissions associated with pneumatic devices , API sub mitted early feedback (March 2014) to EPA and those comments and presentation are attached for further consideration.
Highlights of key review comments discussed in more detail later in this document follow:

 Confusing terminology and descriptions of these devices , some of which has been complicated
b y industry’s own misuse of terms, is ubiquitous in the reports , studies, and emission mitigation
claims . Tackling this is a critical first step.

 It is a common misconception that intermittent controllers cannot replace continuous bleed controllers. This is not correct. In most instances, a continuous bleed controller can be replaced by an intermittent vent controller regardless of the application. The choice of controller types for a particular application is di ctated by the process needs/demands while ensuring safe and reliable operation. For most applications, intermittent controllers are the lower emission option than continuous bleed controllers. If the process can tolerate the inherent delay in response

as sociated with a low

- bleed continuous controller, a low

- bleed continuous controller may, in limited situations, be a lower emission option.

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

2 

## 1. Section 1.1.1 Pneumatic Controllers

- Definition of the Source

The definition s of: “natural gas

- driven pneumatic controller” and “non

- natural gas

- driven pneumatic controller” in the White Paper are unclear , indicate a potential misunderstanding, and should be
modified. The White Paper says:
Natural gas

- driven pneumatic controller mean s a pneumatic controller powered by pressurized natural gas.

Non

- natural gas

- driven pneumatic controller means an instrument that is actuated using other sources of power than pressurized natural gas; examples include solar, electric, and
instrument air.

1. It is not clear whether th ese definition s are specific to the controller itself or also include the end

device that the controller acts on to modify a process condition. For example, controllers with an electric input and relays that convert an electric input signal into a pneumatic output signal to an
end device are common. 2. The definition of “ Non

- natural gas

- driven pneumatic controller ” implies that the controller is actuated which is not a correct understanding. A controller converts an input signal, t ypically mechanical (e.g. float level) or electric (e.g. pressure transducer), into an output signal

. The output signal is typically pressurized gas (including natural gas) or electric, to actuate an end device, typically a valve operator that opens or closes a control valve

- either partially or fully

. 3. M ore appropriate definition s with additional clarity would be:

a. Natural gas

- driven pneumatic controller means an instrument that converts an input signal (mechanical, electric, etc.) into a natural gas pneumatic output signal
to an end device.
b. Non

- natural gas

- driven pneumatic controller means an instrument that converts an input signal into an output signal that is other than natural gas pressure to an end
device.

The White Paper definitions of the different types/designs of controllers introduce a third set of definitions that do not conform with the existing regulatory definitions in Subpart OOOO or Subpart W.
These definitions are not technically correct, and do not provide additional clarity to mitigate the
current confusion. These definitions would benefit from some changes to better reflect their emissions
characteristics , add clarity and cor rect errors

.

Continuous Bleed Controllers
Continuous bleed pneumatic controllers are those with a continuous flow of pneumatic supply natural gas to the process control device (e.g., level control, temperature control, pressure control) where the supply gas pressure is modulated by the process condition, and then flows to the valve controller where the signal is compared with the process set

- point to adjust gas pressure in the valve actuator. For the purposes of this paper, continuous bleed
controllers ar

e further subdivided into two types based on their bleed rate:

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

3  Low bleed, having a bleed rate of less than or equal to 6 standard cubic feet per hour (scfh).

 High bleed, having a bleed rate of greater than 6 scfh.

1. Describing a continuous bleed controller a s having “a continuous flow of pneumatic supply natural gas to the process control device” is both incorrect and confusing. The defining characteristic of a continuous bleed controller is that it bleeds gas to the atmosphere at a
continuous rate determine d by the supply gas pressure (fixed), the restriction

- orifice (in the controller) diameter, and the gas specific gravity. The continuous bleed controller is the “process control device” which is not readily apparent in the definition and hence is confusing.
2. In a continuous bleed controller the supply gas pressure is not modulated by the process
condition

- the supply gas pressure is fixed and the pressure of the gas to the end devic e (valve controller) is varied by the controller. The controller accomplishes this by partially or fully blocking the atmospheric bleed port to the extent that the rate of gas released to atmosphere is less than the rate of gas entering the controller thr ough the restriction orifice hence causing pressure to build in the control loop ( i.e., the controller, the tubing from the controller to the end device and the end device) which causes the valve actuator to move the position of the
valve ( Figure 1 ) . The controller reverses this action by moving the block off of the bleed port (which is larger and has a higher flow rate capacity than the restriction orifice) which causes the pressurized gas in the control loop to once again bleed to atmosphere along with t he gas entering the controller through the restriction orifice. Although the bleed rate of a continuous bleed controller temporarily decreases during actuation (bleed port partially or fully blocked) and temporarily increases during de

- actuation (bleed po rt not blocked) the overall bleed rate per unit of time is essentially the rate that gas will enter the controller through the critical
orifice

. From the perspective of understanding emissions and functioning of a continuous bleed controller

a more appro priate definition would be:

1. Continuous bleed pneumatic controller: A pneumatic controller that does not have a mechanical barrier between supply gas and the end device. These units rely on a bleed port that is covered by a block or flapper to increase the amount of pressure sent to the end device (close the bleed port) o r decrease the amount of pressure sent to the end device (open the bleed port). This type of controller continuously bleeds supply gas to the atmosphere when not fully actuating an end device (bleed port fully closed). For purposes of this paper, continu ous bleed controllers are further subdivided into two types based on their bleed rate: Figure 1 : Continuous Bleed Controller

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

4 a. Low bleed, having a bleed rate of less than or equal to 6 standard cubic feet per hour (scfh).
b. High bleed, having a bleed rate of greater than 6 scfh.

Intermittent Vent Controllers
White Paper Definition: Intermittent pneumatic controller means a pneumatic controller that

vents non

- continuously. These natural gas

- driven pneumatic controllers do not have a continuous bleed, but are actuated using pressurized natural gas.

1. An intermittent pneumatic controller is not “actuated using pressurized natural gas” as the definition states. An intermittent pneumatic controller controls the flow of supply gas to the end device (valve actuator) in order to raise the pressure and actua te the end device. The end device (valve actuator) is the component in the control loop that is “actuated”

. 2. The defining characteristic of an intermittent pneumatic
controller is that it has a physical barrier between the supply gas and the end device, usually in the form of a small three way valve often termed a “pilot valve” or “pilot plug” ( Figure 2 ) . In response to an input signal (mechanical, electric, etc.) an intermittent pneumatic con troller either 1) closes the vent to atmosphere and opens supply gas flow to the end device hence actuating the end device; or 2) closes the supply gas flow and opens the vent to atmosphere hence de

- actuating the end
device.
3. When not required to de

- pressu re the end device, an intermittent pneumatic controller is designed to have near zero emissions to the atmosphere.
From the perspective of understanding emissions and functioning of an intermittent pneumatic controller, a more appropriate
definition would be:
Intermittent vent pneumatic controller: An intermittent vent controller has a mechanical barrier between the supply gas and the end device and does not allow supply gas and a vent port to both be open at the same time. This type of pneumatic controller vents gas periodically to de

- actuate (de

pressure) an end device (valve actuator).



## 2. Actions Controllers Can Take

One common misunderstanding regarding pneumatic controllers is that on

- off controllers are intermittent and throttling controllers are continuous bleed. Either a continuous bleed or intermittent pneumatic controller can function in an on

- off or throttling service. The defining characteristic of a pneumatic controller in on/off service is that the controller is not required
to hold an end

- device in an intermediate position (i.e. at the end of a control cycle the Figure 2 : Intermittent Vent Pilot

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

5 control

- gas pressure to the end

- device goes to zero). The defining characteristic of a pneumatic controller in throttling service is that the controller is required to control an end

device in an intermediate position (i.e. the control

- gas pressure to the end device is maintained at a pressure betw een atmospheric and supply pressure).
Combining the type of controller and the service yields a simple matrix that describes both
continuous bleed and intermittent controller emissions in each service.

Another common misunderstanding regarding pneumat ic controllers is equating an intermittent controller with snap

- acting action (as in the Subpart OOOO definition) or equating proportional action with throttling service. Snap

- acting and proportional describes the type of action a controller in on/off

ser vice may take and does not have a great impact on emissions. Either a continuous bleed or intermittent pneumatic controller in on/off service can operate in a snap

- acting or proportional mode dependent on its design.

A snap acting on/off controller will never send a partial pressure signal. It will wait until the input parameter has reached a maximum value and then snap open and stay in that fully

- open position until the input parameter reaches a minimum value and then will snap shut and an exhaust port will snap

open.
A proportional on/off controller will send a partial pressure signal as soon as the input parameter increases above a minimum and as the input parameter continues to increase, the rate that the controller sends gas to increase the pressu re signal to the end device increases. A proportional on/off
controller service will allow supply gas to increase the pressure signal to the end device until the differential pressure across the controller pilot plug is zero (i.e., actuation pressure equa ls supply pressure). If the process variable is satisfied prior to reaching zero differential pressure then the controller will shut off supply gas and open the vent without ever fully opening the end device and will vent slightly less gas than a snap

- act ing on/off controller. Proportional on/off controllers can be thought of as soft open and soft close actions.

Snap acting on/off controllers tend to reposition end

- devices open and shut very quickly which can cause serious process problems in some sit uations. Proportional on/off controllers tend to ease into a

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

6 change of state with fewer problems with slugging and surging. It is important to understand that the type of pneumatic device used and the configuration of the action is dependent upon the pro cess being controlled.

Zero Bleed Controller
White Paper Definition: Zero bleed pneumatic controller means a pneumatic controller that does not bleed natural gas to the atmosphere. These natural gas

- driven pneumatic controllers are self

- contained devices that release gas to a downstream pipeline instead of to the atmosphere.

Unlike a continuous bleed or intermittent pneumatic controller a zero bleed pneumatic controller does not use pneumatic supply gas from a reduced pressure supply source (Figure 3)

. Pneumatic supply g as to a zero bleed controller is taken from the process gas upstream of the controller at the process pressure. I ntroducing this new term in the White Paper ignores the Subpart OOOO Technical Support Document ( TSD ) which said “(3) self

- contained devices release gas to a down stream pipeline instead of to the atmosphere”. “Self

- contained” or “ integral ” is a far better term, especially since the terms “Zero Bleed” and “No Bleed” have been assigned to other concepts within current regulations (e.g., in recent Colorado regulation s “No Bleed” controllers were defined as those controllers that use instrument air for actuation) or have been used historically to describe intermittent controllers which do not bleed gas continuously.

From the perspective of understanding the functionin g of this type of pneumatic controller, a more appropriate definition would be:
Integral pneumatic controller means a pneumatic controller that is physically built into an end device, receives its supply gas untreated from the process being controlled, and exhausts excess supply gas back into the process stream without any gas exhausting to the atmosphere



## 3. Section 1.1. 2 Pneumatic Pumps

- Definition of the Source

The W hite P aper characterization of pneumatic pumps as:
Pneumatic pumps are devices that use gas pressure to drive a fluid by raising or reducing the pressure of the fluid by means of a positive displacement, a piston or set of rotating impellers. Pneumatic pumps are generally used at oil and natural gas produc tion sites where electricity is not readily available (GRI/EPA, 1996d). The supply gas for these pumps can be compressed air, but most often these pumps use natural gas from the production stream (GRI/EPA, 1996e). Figure 3 : Integral Controller

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

7 This definition should be corrected in th e paper . The inclusion of pumps “reducing the pressure of a fluid” is not correct

- pumps increase the pressure of a fluid. Pneumatic pumps that drive “rotating impellers” are not believed to exist and certainly are not in common use in the Oil and Gas P roduction sector if they exist at all. The excerpts from GRI/EPA 1996e, although correct, are not complete with
respect to gas

- assist lean glycol pumps discussed later in the document. The primary energy source for these pumps is the high pressure “rich glycol” from the glycol/gas contactor tower on a glycol dehydration unit with natural gas used to supplement the energy scavenged.



## 4. Section 1.2.1 Pneumatic Controllers

- Background

Due to the incorrect information provided in t he White Paper background discussion regarding pneumatic controllers the entire section has been excerpted (italics) and comments incorporated into the section (non

- italics).
Pneumatic controllers are automated instruments used for maintaining a pro cess condition such as liquid level, pressure, pressure differential, and temperature. In many situations, across all segments of the oil and gas industry, pneumatic controllers make use of the available high

-

pressure natural gas to operate control of a v alve.

Comment: Except for integral pneumatic controllers, p neumatic controllers do not use “high

- pressure natural gas” in their operation. Instead, they use reduced pressure “pneumatic supply gas” which is generally in the 15

- 35 psig pressure range. Most end devices have a supply gas upper pressure limitation of 35 psig

. In these natural gas

- driven pneumatic controllers, natural gas is released with every actuation of the valve, i.e., valve movement.

Comment: Natural gas is actually released on de

- actuation of an end device when pressure is vented
rather than on actuation.

In some designs, natural gas is also released continuously from the valve control pilot.

Comment: Continuous bleed controllers do no t have a “pilot” which is a commonly used term for the
small three

- way valve in an intermittent controller. Please see the discussion of intermittent controllers and pilots provided above in these comments.

The rate at which the continuous release occur s is referred to as the bleed rate. Bleed rates are dependent on the design and operating characteristics of the device.

Comment: Bleed rates from a continuous bleed controller are a function of the size of the restriction orifice controlling supply gas flow into the controller, the supply gas pressure, and the supply gas gravity. Please see the discussion of continuous bleed controllers provided above in these comments.
Similar designs will have similar steady

- state rate s when operated under similar conditions. There are three basic designs of natural gas

- driven pneumatic controllers: (1) continuous bleed controllers are used to modulate flow, liquid level, or pressure, and gas is vented continuously at a rate that may va ry over time;

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

8 Comment: Continuous bleed controllers can be used in throttling service to “modulate” a process parameter or in on/off service to fully actuate or de

- actuate an end device. The rate of gas release only changes when the controller is actuat ing (decreases) or de

- actuating (increases). The rate of gas release per unit time is essentially equivalent to the rate of supply gas entering the controller through
the restriction orifice. Please see the discussion of throttling and on/off service pro vided above in these

comments.
(2) intermittent controllers release gas only when they open or close a valve or as they throttle the gas flow;

Comment: Intermittent controllers only release gas when de

- actuating an end device (releasing
pressure to rev erse a positive control action). This de

- actuation may open or close a valve, partially or fully dependent on whether the controller is in on/off service or throttling service, and dependent on the configuration of the control loop

- i.e. pressure to open or pressure to close.
and (3) zero bleed controllers, which are self

- contained devices that release gas to a downstream pipeline instead of to the atmosphere (EPA, 2011a).
As noted above, intermittent controllers are devices that only emit gas during ac tua tion and
do not have a continuous bleed rate.

Comment: As previously noted, intermittent controllers only emit gas on de

- actuation rather than on
actuation.
Thus, the actual amount of emissions from an intermittent controller is dependent on the amount of natural gas vented per actuation and how often it is actuated. Continuous bleed controllers also vent an additional volume of gas during actuation, in addition to the device’s
continuous bleed stream. Thus, actual emissions from a continuous b leed device also depend, in part, on the frequency of activation and the amount of gas vented during
activation.

Comment: The temporary bleed rate of a continuous bleed controller during actuation will be less than the static bleed rate. During de

- actu ation, the bleed rate will be temporarily higher due to bleeding both the gas entering the controller and the pressurized gas from the actuated end device. However, the temporary reduction during actuation and increase during de

- actuation will balance eac h other with the result that a continuous bleed controller’s emissions per unit of time will be basically equal to the amount of gas that passes through the restriction orifice. At all times, a continuous bleed controller’s maximum emissions are capped by the amount of gas that can pass through the restriction
orifice.
As the name implies, zero bleed controllers are considered to emit no natural gas to the atmosphere (EPA, 2011a).
In general, intermittent controllers serve functionally different purposes than bleed controllers and, therefore, cannot replace bleed controllers in most (but not all) applications.

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

9 Comment: This statement is incorrect. In most instances a continuous bleed controller can be replaced by an intermittent vent controller regardl ess of the application. The choice of controller types for a particular application is dictated by the process needs/demands while ensuring safe and reliable operation. For most applications, intermittent controllers are the lower emission option than

co ntinuous bleed controllers. If the process can tolerate the inherent delay in response associated with
a low

- bleed continuous controller, a low

- bleed continuous controller may, in limited situations, be a lower emission option.

Furthermore, zero bleed c ontrollers are “closed loop” systems that can be used only in applications with very low pressure and therefore may not be suitable to replace continuous bleed pneumatic controllers in many applications.

Comment: Zero bleed controllers (integral controllers) are not limited to applications “with very low pressure” and can operate over a wide range of pressures provided that the pressure downstream of
the controller is sufficiently lower than the pressure upstream of the controller for the controller to
function and allow upstream gas to discharge into the process flow downstream. Integral controllers
source the ir pneumatic supply gas from the process pressure upstream of the controller and are not limited by the n ormal pneumatic supply pressure of 15

- 35 psig. They are common in high pressure applications.

Non

- natural gas

- driven pneumatic controllers can be used in some applications. These controllers can be mechanically operated or use sources of power oth er than pressurized natural gas, such as compressed “instrument air.” Instrument air systems are feasible only at oil and natural gas locations that have electrical service sufficient to power an air compressor. At sites without electrical service sufficie nt to power an instrument air compressor, mechanical or electrically powered pneumatic controllers can be used.

Comment: Instrument air systems are only economically feasible at sites where the pneumatic supply gas demand is sufficient to justify the cap ital and operating expen s e of an instrument air compressor. At single well sites this is rarely the case.

Mechanical controllers are limited in the scope of applications where they can be used and are not

common. Mechanical controllers have typically been limited to level

- control applications because of the inherent difficulty in providing mechanical force to reposition a valve in other services. The amount of force required to reposition an end device is largely a function of differential pressure ac ross the process side of the valve. As this differential pressure increases, the amount of force required to open the valve rapidly exceeds the force that can be provided through the buoyancy of a float. Consequently, mechanical controllers are limited t o low pressure operations.

Electric controllers convert an input signal into an electrical output signal. Historically the output signal
has been limited to solenoid valves in electro

- pneumatic control loops. Only recently have electric end

devices bec o me available in a form that can operate on low

- power solar electricity and can eliminate the requirement for control gas in the control loop

. As industry gains more experience with their reliability and safe functioning they may become more common.

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

10 Figure 4 : Pneumatic Pumps Non

- na tural gas

- driven controllers do not directly release methane or VOCs, but may have secondary impacts related to generation of required electrical power (EPA, 2011a).

Comment: This is correct , except for mechanical controllers

. 

## 5. Section 1.2.2 Pneumatic Pumps

There are two types of pneumatic pumps that are commonly used in the oil and natural gas sector: piston and diaphragm (GRI/EPA, 1996d ).

Comment: There are three common types of pneumatic pumps that are used in the oil and gas sector
rather than the two noted in the White Paper from the GRI/EPA 1996d reference. These three types of pneumatic pumps are: 1) Pneumatic chemical and methanol pumps (both piston and diaphragm gas ends) ; 2 ) Pneumatic diaphragm pumps; and 3) Energy scavenging gas assist pu mps that pump lean glycol on glycol dehydrator systems where electricity is not readily available. These three types of pumps account for the vast majority of pneumatic pumps in field use, and are responsible for the majority of emissions attributable to pneumatic pumps

. These pumps have very different uses and emission profiles, and function very differently.

a) Pneumatic Chemical and Methanol Pumps
Pneumatic chemical and methanol pumps are widely used in the upstream oil and gas industry where electricity is not available. These types of pumps are generally used to pump fairly small volumes of chemicals or methanol (often
measured in pints or quarts per day)
into well

- bores, surface equipment, and pip elines. They are typically plunger pumps with a diaphragm or large piston on the gas end and a smaller p iston on the liquid end to enable a high discharge pressure
with a varied but much lower pneumatic supply gas pressure ( Figure 4 ) . The usage of these pumps, the volumes of fluid pumped and the discharge pressure (hence pressure multiple rs ) needed from the pump will vary between different areas, reservoirs, and from well

- to

- well although they will tend to be used semi

- continuously rather than episodic. There is often a seasonal variation in the usage of these pumps as well (e.g. in colder production areas more methanol is generally pumped in winter to inhibit freezing and hydrates). Emissions occur when the gas used on the pump stroke is exhausted to t he atmosphere to enable the liquid side of the pump to fill with liquid in preparation for another pump stroke. Emissions are a function of the amount of fluid pumped, the pressure of the pneumatic supply gas, the number of pressure ratio’s between the pn eumatic supply gas pressure and the fluid discharge pressure, and the mechanical inefficiency of the pump.

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

11 Pneumatic “gas recovery” chemical/methanol pumps are available that discharge gas at a high enough pressure to use as fuel or to enable recovery. Manufacturer’s information regarding gas usage is available for pneumatic chemical and methanol pumps. The majority of pneumatic pumps in the Onshore Production sector are chemical and methanol pumps.

b) Pneumatic Diaphragm Pumps
Pneumatic diaphragm pumps are also widely used in the upstream oil and gas industry where electricity is not available. They are generally used to move larger volumes of liquids per unit of time a t lower discharge pressures than chemical/methanol injection pumps. Their typical uses include transferring bulk liquids such as motor oil, pumping out sumps, and
circulation of heat trace medium at well sites in cold climates during winter months. They are designed with a diaphragm separating the gas and liquid sides with the liquid pumped by deforming the diaphragm with pneumatic gas ( F igure 5 ) . These types of pumps generally have a 1:1 liquid:gas pump pressure ratio

. Emissions are a function of the a mount of fluid pumped, the supply gas pressure, pressure multiples between the pneumatic gas pressure and the liquid discharge pressure, and the mechanical inefficiency of the pump. Emissions occur when the gas used in the pump stroke is exhausted to
enab le liquid filling of the liquid chamber side of the diaphragm. The usage of these pumps tends to be episodic when needed except for the pumps in heat medium circulation where they are typically used during the winter months in cold climes. The frequency of usage of these pumps and the volumes of fluid pumped will vary from area to area

, operation to operation
, and seasonally

.

c) Gas Assist Glycol Dehydrator Pumps Figure 5 : Double Diaphragm Pneumatic Pump

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

12 Pumps on field dehydrator units where electricity is not available are typically gas

- assist ( often inappropriately termed “ Kimray ” ) type pumps. These pumps are used to pump re

- generated “lean” glycol from atmospheric pressure to the glycol/gas contactor on a glycol dehydrator unit. Since the contactor is typically at fairly high pressure the pum ps must have the capability for multiple pump ratios. Consequently , they are more complicated than the chemical/methanol pumps discussed earlier as they “scavenge” energy from the high pressure (rich) glycol flowing from the contactor to the regenerator t o provide the bulk of the energy needed to pump the lean glycol into the contactor. Energy loss through piping friction and mechanical inefficiency is “made

- up” by assist gas at the contactor pressure (Figure 6

and 7 ) . Glycol dehydrator lean glycol pumps operate continuously when the dehydrator is in operation.
Emissions are a function of the lean glycol circulation rate, the pressure of the contactor, and the model of the pump. The assist gas enters the “rich glycol” stream routed to the reboiler/regenerator and is emitted via the overhead vent from the regenerator distillatio n column unless control systems are in place.
Emissions from gas assist glycol dehydrator pumps can be calculated using GRI

- GLYCalc, a processs engineering program, or manufacture’s specification sheets. Emissions are a function of the lean glycol
circul ation rate, the pressure of the contactor, and the model of the pump.
These pumps have two major components, a driver side and a motive side, which operate in the same manner but with different reciprocating mechanisms.

Comment: It is not clear what “r eciprocating mechanisms” refers to in this sentence. It is true that pumps differ in their designs.
Pressurized gas provides energy to the driver side of the pump, which operates a piston or flexible diaphragm to draw fluid into the pump.

Comment: The pressurized gas does not “draw fluid into the pump” . After a pumping stroke the pump piston is returned to its prior position by a spring and the fluid chamber is filled at that time. Pressurized gas provides the energy to pump the fluid on the pumping stroke. For dehydration unit Figure 6 : Glycol Recirculation Pneumatic Pump Figure 7 : Glycol Recirc Pump Schematic

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

13 lean glycol pumps with gas assist pumps (e.g. Kimray glycol pumps) the primary energy supply to the driver side of the pump is the high

- pressure rich glyco l from the contactor tower with energy loss made up via gas assist with contactor pressure gas.
The motive side of the pump delivers the energy to the fluid being moved in order to discharge the fluid from the pump. The natural gas leaving the exhaust p ort of the pump is either directly discharged into the atmosphere or is recovered and used as a fuel gas or stripping gas (GRI/EPA, 1996d).

Comment: It should be noted that the only use of pneumatic gas from a pump for stripping gas is on glycol units w here a flash tank is installed downstream of the lean glycol pump and the flash tank gas (mostly pump assist gas) is used as stripping gas. Gas assist energy scavenger lean glycol pumps discharge the assist gas into the low pressure rich

- glycol stream dow nstream of the pump
where it is routed to the glycol reboiler /regenerator and the gas, along with absorbed water and hydrocarbons, are emitted from the reboiler distillation vent stack. Emissions from t he reboiler
distillation vent stack are typically, tho ugh not always, controlled using a condenser to recover condensable hydrocarbons . The non

- condensable gas may be combusted in the glycol reboiler or other heaters, returned to the process by compression, or vented.
The majority of pneumatic pumps used in oil and natural gas production are used for chemical injection or glycol circulation (GRI/EPA, 1996d). Pneumatic pumps used for chemical injection are needed in oil and natural gas production to inject small amounts of chemicals to limit processing problems and protect equipment. Typical chemicals that are injected into the process include: biocides, demulsifiers, clarifiers, corrosion inhibitors, scale inhibitors, hydrate inhibitors, paraffin dewaxers, surfactants, o xygen scavengers and hydrogen sulfide scavengers (GRI/EPA, 1996d). These chemicals are normally injected using pneumatic pumps at the wellhead, and into gathering lines or at production separation facilities (GRI/EPA, 1996d). Pneumatic pumps, commonly refe rred to as “Kimray” pumps, used for glycol circulation recover energy from the high

- pressure rich glycol/gas mixture leaving the absorber and use that energy to pump the low

- pressure lean glycol back into the absorber (GRI/EPA, 1996

e)

Comment: It should be noted that the energy recovery lean glycol pumps also use gas assist from the
absorber to make

- up the energy recovery loss.



## B. Charge Questions:

Charge Question 1

Did this paper appropriately characterize the different studies and data sources that quantify emissions from pneumatic controllers and pneumatic pumps in the oil and gas sector?

Although the paper attempts to summarize the studies referenced it is not con sistent, is confusing in spots, and is not complete. The paper lacks a table that summarizes the results of the studies referenced using consistent units. As it currently is configured it is difficult to

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

14 compare data across the different sources referenc ed or parse the data from the exceptions and opinions

. The White Paper does not include validation or analysis of the underlying information
from the sources used. The White Paper would benefit from inclusion of tables similar to the following.



## Pneumatic Controller Emission Factors

Source Production Sector

Methane Emissions from the Natural Gas Industry (GRI/EPA

1996c) Continuous Bleed Intermittent Vent Overall

scfh gas/controller scfh gas/controller scfh

gas/controller

36.33 0.00 18.24

Canadian Petroleum Association (Picard, 2992) Throttling On/Off

scfh gas/controller scfh

gas/controller

3.92 8.88

Estimates of Methane Emissions from the US Oil Industry (ICF,

1999) Continuous High Bleed Continuous

Low Bleed

scfh gas/controller scfh

gas/controller

18.24 1.85

Inventory of US GHG Emissions and Sinks: 1990

- 2012 (EPA, 2014) Natural Gas Systems Overall potential scfh gas/controller

17.99

Inventory of US GHG Emissions and Sinks: 1990

- 2012 (EPA, 2014) Petroleum Systems Continuous High Bleed Continuous

Low Bleed Overall

scfh gas/controller scfh

gas/controller potential scfh gas/controller

16.51 2.60 7.49
Inventory of US GHG Emissions and Sinks: 1990

- 2012 (EPA, 2014) Natural Gas and Petroleum Systems Combined Overall

net scfh gas/controller

6.15

Greenhouse Gas Reporting Program (EPA, 2013) Continuous High Bleed Continuous

Low Bleed Intermittent

Vent
scfh gas/controller scfh

gas/controller scfh

gas/controller

37.3 1.39 13.5

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

15 Measurements of Methane Emissions from Natural Gas Production Sites in the United States (Allen, 2013) Continuous Low Bleed Intermittent

Vent Overall

scfh gas/controller scfh

gas/controller scfh

gas/controller

5.1 17.4 11.2

Determining Bleed Rates for Pneumatic Devices in British Columbia (Prasino, 2013) Continuous High Bleed High Bleed Intermittent
scfh gas/controller scfh gas/controller

9.199 8.744



## Pneumatic Controller Emission Factors

Source Processing Sector Transmission/Storage Sector

Methane Emissions from the Natural Gas Industry (GRI/EPA 1996c) Continuous Bleed Overall Continuous Bleed Overall

scfh gas/controller scfh

gas/controller scfh

gas/controller scfh gas/controller

56.79 22 56.79 20
Inventory of US GHG Emissions and Sinks: 1990

- 2012 (EPA, 2014) Natural Gas Systems Overall Overall
potential scfy CH4/plant potential scfh gas/controller
164,721 19.82 Inventory of US GHG Emissions and Sinks: 1990

- 2012 (EPA, 2014) Natural Gas and Petroleum Systems Combined Overall

net scfh gas/controller

18.82

Greenhouse Gas Reporting Program (EPA, 2013) Continuous High Bleed Continuous

Low Bleed Intermittent

Vent

scfh gas/controller scfh

gas/controller scfh

gas/controller

18.2 1.37 2.35

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

16 

## Pneumatic Pump Emission Factors

Source Production Sector

Methane Emissions from the Natural Gas Industry (GRI/EPA 1996c) Diaphragm Piston Overall scfh gas/pump scfh gas/pump scfh gas/pump

23.58 2.59 35.32

Canadian Petroleum Association (Picard,

1992) Overall scfh gas/pump

13.92
Inventory of US GHG Emissions and Sinks: 1990

- 2012 (EPA, 2014) Natural

Gas Systems Overall scfh gas/pump

12.29
Inventory of US GHG Emissions and Sinks: 1990

- 2012 (EPA, 2014) Petroleum

Systems Overall scfh gas/pump

12.42

Greenhouse Gas Reporting Program

(EPA, 2013) Overall scfh gas/pump

13.3
Determining Bleed Rates for Pneumatic Devices in British Columbia (Prasino,

2013) Diaphragm Piston scfh gas/pump scfh gas/pump

37.2 20.9 Economic Analysis of Methane Emission Reduction Opportunities in the US Onshore Oil and Natural Gas Industries

(ICF, 2014) Overall scfh gas/pump

32.7



### a) Missing I nformation :

The White Paper does not include information from relevant sources readily available to EPA or complete information from the referenced sources

. For instance:

 T he TSD for either of the relevant regulation s (Subpart OOOO and Subpart W) or the industry and e

- NGO comments posted on the Subpart OOOO docket are not included in the White Paper references or discussion. All of these sources are relevant to “the EPA’s understanding” of this issue.

 No manufacturer’s data or information, readily available for almost all pneumatic controller models and configurations and pneumatic pump models and services, is included in the White Paper analysis despite being the most comp lete information
available. This is a major omission which should be addressed (the EPA/GRI 1996 study estimates use manufacturers information in part).

 Table 2

- 1 in the White Paper does not indicate any pneumatic pump measurements
collected as part of the Prasino study when the study reported measurements and data

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

17 for 184 pneumatic pumps. However, this measurement data is briefly discussed in section 2.2.4 of the White Paper.

b) Missing Validation:

The White Paper reviews of cited references appear to be simply an effort to provide a synopsis
of the studies with no discussion of the validity of the study results

. The White Paper missed an opportunity to provide an analysis of the reliability of the data presented. For exa mple:

 The Allen et al, 2013 study did not capture any pneumatic controller metadata (e.g., manufacturer, model, supply pressure, service , actuation frequency ) for their 30 second to just over 2 minute measurement periods and were forced to discard any data for sites that operators did not report as all low bleed or all intermittent types in developing their “average” emission factors

. The average study measured emissions and differences between the EPA emission factors for low bleed pneumatic controllers a nd intermittent
controllers , shown in Table 2

- 8 of the White Paper, were based on 60 measurements and 129 measurements respectively (189 total) rather than the 350 measurements noted in the White Paper. Additionally, the very short duration of the measure ments almost certainly did
not measure across an entire control (actuation=> de

- actuation=> static=> actuation) cycle

. For an intermittent controller measuring for these short time periods would either “miss” a
de

- actuation and return a zero emission resu lt or measure just an actuation and grossly overstate the emissions per unit of time. For example, if a controller that actuates once every 10 minutes was measured for a 2 minute period that happened to include a de

act uation , then the resultant volume attributed to 2 minutes would overstate the emissions
b y a factor of 5. Coupled with the statement in A ppendix G of the study that “At some sites, however, the controllers that were observed to have emissions were selected for sampli ng.” it is likely that the reported emission factors are biased high

- perhaps significantly. Despite the White Papers claim that the Allen et al, 2013 study did not include sampling times;
The sampling time for each controller was not specified in the st udy,
detailed information regarding each measurement made is available on the study website at http://dept.ceer.utexas.edu/methane/study/datasets3.cfm in three separate excel files. The text of the study report and supplemental information indicate that only level controllers (which tend to have higher valve actuator volumes) were measured , although some temperature controllers and pressure controllers are noted in the detailed inform ation referenced above and appear to be attributed incorrectly as leaks rather than pneumatic
controllers . If correct, this does not represent the full population of pneumatic controllers and hence the "emission factors" for the pneumatic controllers pres ented in the paper are not representative of the full population

. Th e re appear to be major shortcoming s in the pneumatics portion of this study but that assessment is absent in the White Paper

. API
understands that additional study was undertaken to add ress these issues and EPA would
be well served to await the results of this additional work.

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

18  For the pneumatic controller measurements, t he P ra sino study called an R 2 value (i.e., a measure of the fidelity of the result to the data) of gr eater than 0.25 as “Positive”. As noted
in the W hite P aper the “supply pressure coefficients have R 2 values of 0.41 and 0.35 for high bleed and high bleed intermittent controllers, respectively. In common usage, R 2 values less
than 0.70 are taken as “no correlation” , and many studies disregard values less than 0.80

. Treating values of 0.25 as “positive” is incorrect

.

 For pneumatic controller measurements, n one of the studies clearly explain how they deal
with zero

- flow measurements/ records or malfunctioning controllers

. Failure to properly and consistently address questionable data leads to questionable conclusions in these studies. For example , assume there are 30 occurrences of a given make and model number
controller for a one

- hour tes t, and the measured data indicates the following :



### Count Unit exhaust Population exhaust
20 0 0
7 0.2 SCF/hr 1.4 SCF/hr
2 99.0 SCF/hr 198.0 SCF/hr
1 205.6 SCF/hr 205.6 SCF/hr Total 405.0 SCF/hr Average 13.5 SCF/hr

A careful analysis of this data would indicate a properly functioning device having an emissions rate of 0.2 SCF/ hr (with the 3 outliers having a mechanical issue that is not a
function of the controller and should not be included in an emi ssions character ization),
but a statistical average of the population would yield an emission rate of 13.5 SCF/hr.
Since intermittent

- device emissions are dominated by process

- driven “events”, a better characterization would be 0.2 SCF/actuation since any other hour chosen would have a different population of zeros and 0.2 SCF measurements.

An example is the Prasino study data for a Fisher 4660 Hi/Lo Pressure Pilot. As background, a Fisher 4660 is a process safety under/over pressure protection device that
holds a fail

- closed valve open in normal operation and emits about 0.05 scf/hr (manufacturers data sheet) when not in an over/under pressure condition. These pilots, and similar ones by other manufacturers, are generally used on well

- site separators to shut

- in a well in the event of an unsafe condition. Thirty of these devices were
measured in the Prasino study w ith 28 having zero or essentially zero emissions and two having measurable emissions and simply listed 0.0151 m 3 /hr (0.5 SCF/hr) as the “average bleed rate”. With knowledge of how these devices function it is obvious that
either the two with emissions wer e damaged or malfunctioning in some manner or the process was in an overpressure/underpressure condition. However, the Prasino paper did not evaluate or include the reason for abnormal emissions and the White Paper
failed to not e this deficiency

.

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

19 c) Missing Limitations Discussion:

The White P aper provides a synopsis of the sources cited with no apparent effort to highlight or
discuss the limitations of the se sources or their underlying origin. For example:

 The White Paper erroneously characterizes the US inventory ; the GHGRP data ; ICF Consulting, 1999; Roy et al., 2014; and ICF, 2014; as “ studies ” . Rather than studies

, these
reports are inventory estimates using emission factors and activity estimates often developed from reinterpretation or speculative analysis of the EPA/GRI, 1996 information
and other data sources. An end result of an emission study (measurement) is develop ing a basis for assigning emissions factors to pneumatic controllers. The sources cited simply identified and applied an “emissions factor” to estimated device counts to reach an
emissions number.

 EPA/GRI, 1996 Study: The White Paper discussion of the EPA/GRI, 1996 study did not note
that : ( 1 ) I t is outdated
, ( 2) T here is in sufficient information regarding actual measured
controller emissions to evaluate whether the data is a good representation of the diverse population of pneumatic controller types, services, and applications ; ( 3) T here is in sufficient information to judge whether the type of controller and service was correctly identified, ( 4)

T here is no information provided to judge whether the appropriate methodologies, sampling populations, and sampling times were used to adequately measure emissions from
controllers. The EPA/GRI , 1996 data for pneumatic pumps has many of the same type of
data

- validation limitations . The EPA/GRI, 1996 data for Gas

- Assisted Glycol Pumps is calculated based on two assumptions of process conditions, wa ter removal, and information from Kimray. These process assumptions are significant limitations for the resultant emission factors derived in the report.

 Greenhouse Gas Reporting Program (GHGRP): The GHGRP has required reporting of emissions from pne umatic controllers and pneumatic pumps since 2011 and data has been reported and publically released for 2011 and 2012. It is important to understand the limitations of this data and potential errors before using it for any purpose. The GHGRP divides pne umatic controllers into high

- bleed continuous (>6scf/hr), low

- bleed continuous (<6scf/hr) and intermittent categories. For each category the GHGRP has an emission factor (EF): These are:

o Continuous low

- b leed

- 1.39 scf/hr;

o Continuous high

- bleed

– 37. 3 scf/hr;

o Intermittent

– 13.5 scf/hr.

Reporters use a “count” of controller types in each category multiplied by the emission
factor to estimate the volume of gas emissions for each category of controller in each “facility” (covered basin). For the 201 1 and 2012 reports, these counts were allowed to be estimated using engineering judgment. For the 2013 emission year, to be reported by March 31, 2014, pneumatic controllers in each category are required to be counted. Obviously the accuracy of the repor ted emissions is contingent on the accuracy of both the

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

20 emission factors and the counts of controllers in each category. With controller populations estimated for 2011 and 2012, the reported number of controllers is likely not accurate and
the 2013 data s hould provide a much more accurate report of the population of controllers in each category. Given how an intermittent controller operates vs. a continuous bleed controller and very straightforward engineering calculations, the intermittent controller
emi ssion factor is likely very high

– perhaps by an order of magnitude or more

– hence, the emission estimates from this category are likewise high. Several studies soon to be published will provide some additional information to inform this question. Users of the GHGRP data for pneumatic controllers should wait for the 2013 reporting for a higher quality population count. Unfortunately, until the emission factors for each category can be validated and corrected, the GHGRP reported emissions for pneumatic c ontrollers will remain highly uncertain. For pneumatic pumps the GHGRP uses a count multiplied by an
emission factor to estimate the volume of gas emissions from each pump. In the GHGRP data, emissions from gas assist lean glycol pumps are included in the glycol dehydrator emissions rather than the pump emissions.

 U.S. Greenhouse Gas Emissions and Sinks (Inventory): The National Inventory, which is updated annually, uses a n estimate of the number of pneumatic controllers and a n emission
f actor to estima te potential methane emissions for pneumatic controllers (called devices) for the “Natural Gas Systems” and “Petroleum Systems” categories by NEMS regions

. Reductions in emissions attributable to Natural Gas Star voluntary taken and reported actions and regulatory required reductions (if required) are subtracted from these potential emission estimates. It is not clear what the genesis is for the pneumatic controller population estimate or emission factor hence it is not clear whether the estimate is valid or what uncertainty bands might apply.

A similar approach is used for pneumatic pumps although the estimates in the NEI have activity factors and emissi ons separated from glycol process emissions for gas assist lean glycol pumps (called Kimray pumps in the NEI)

. 

## Charge Question 2

Please discuss explanations for the wide range of emission rates that have been observed in direct measurement studies of pneumatic controller emissions (e.g., Allen et al., 2013 and Prasino 2013). Are these differences driven purely by the design of the monitored controllers or are there operational characteristics, such as supply pressure, that play a crucial role in determining emissions?

The majority of the differences between the two studies are more likely relate d to sampling times, methodologies, controller type identification, and data analysis assumptions rather than
actual differences du e to operational characteristics or actual differences in emissions

.

 For example, as discussed above, the UT Phase 1 study measured pneumatic controllers for very short periods, did not collect any metadata, likely misidentified the types of

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

21 controllers measured, concentrated measurement on level controllers which tend to have larger valve actuator volumes and , therefore, higher emissions from these
intermittent vent controllers . The study also “screened” a large proportion of the controllers measured with an infrared camera and only measured those which were emitting which would likely bias the measurements towards continuous bleed or actuating intermittent controllers or intermittent controlle rs with some malfunction

. This would create a bias towards much higher emissions.

 The Prasino study purposefully concentrated on measurement of “high emitting”
controllers and measured each for only a 15 minute period

.

 Both studies used the measurement per iod and measured rate to extrapolate an hourly emission rate which for intermittent vent controllers is not a valid approach absent measurement across an entire control cycle and knowing the frequency of actuation. If

a field experiment is connecting meas urement equipment to a controller and running
for 15 minutes , then if a device which actuates once a month happens to actuate during that 15 minutes it appears to be a high emissions rate. Any other 15 minute period during the month would show zero emissi ons. This means that if that particular controller in that particular stream vents 0.2 SCF/event and the vent event lasts 3 seconds, some of the current studies would calculate a vent rate of 0.8 SCF/hr (0.2 SCF/15 min * 60 min/hr) instead of the actual v alue of 0.00027 SCF/hr (0.2 SCF/730 hr/month). The exact same combination of supply

- gas pressure, controller, end

- device, and tubing in another flow stream might operate twice an hour (actual value of 0.4 SCF/hr), but may not have an actuation event durin g the selected 15 minutes . The study
would show zero emissions even though its actual emissions rate in that service on that
location is 1500 times larger than the controller that actuated once a month

.

The available underlying data from the various stud ies indicate that most controllers show zero emissions during the tests and that a small number of controllers showed very high emissions

. It is not clear how the researchers accommodated both the zero emissions controllers and the obviously malfunctioning controllers in their estimation of emission factors. A c areful, unbiased
evaluation of the data would likely reach very different conclusions than were reached in any of
the studies. 

## Charge Question 3

Did this paper capture the f ull range of technologies available to reduce emissions from pneumatic controllers and pneumatic pumps at oil and gas facilities?
Any list of mitigating technologies will by necessity be limited to currently available technologies. Equipment innovations f or oil and gas operations are occurring continuously. For example, there
has never been a viable low

- power (solar power enabled) electric

- actuated end

- device for liquid removal (i.e., dump valve) until early in 2013 when such a device came on the market. The marketplace may very well broadly adopt this technology. Or users might find a fatal flaw that

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

22 Figure 8 : Mizer Retrofit precludes its use in most applications. Any list of mitigation technologies that is included in regulations will likely stifle innovation at that point.
EPA should refrain from prescribing technology or attempting to specify solutions to engineering problems. Regulatory or policy approaches should enable industry to assess technologies to meet desired performance standards and make the appropriate and saf e selections for each process
need.
One of the most prevalent emissions

- reduction strategies in use today for pneumatic controllers is adapting continuous

- bleed controllers to become intermittent

- ven t controllers via installation of a “pilot valve” (often termed a Mizer
retrofit

– Figure 8 ). This strategy has been very successful, widely reported by Natural Gas Star partners, and known to EPA but this strategy is not discussed in the White Paper.



## Charge Question 4

Please comment on the pros and cons of the different emission reduction technologies. Please discuss efficacy, cost and feasibility for both new and existing pneumatics.

The emissions

- reduction technologies , the technical limitations on their applicability, and economic
limitations are not clear ly described in the White Paper

. The costs for implementing a particular action or technology discussed in the White Paper are not on a current (2014) dollar basis, not presented on a
consistent b asis, and do not have the base year clearly noted for many actions or technologies

. These
deficiencies make it difficult to evaluate the White Paper’s cost estimates. A coherent strategy for reducing emissions from pneumatics or evaluating what such a str ategy might cost cannot be developed from the White Paper information.

a) Pneumatic Controllers:

The information regarding technologies for reducing emissions from pneumatic controllers is primarily contained in Table 3.1 of the White Paper. Table 3.1 is replete with inaccuracies, misunderstandings, and naïveté. For example:

 Option: Install Zero Bleed Controller in Place of Continuous Bleed controllers. The devices that the
W hite P aper describes as “zero bleed” use process gas for actuation and exhaust actuation gas downstream of the control valve. These devices require a differential pressure across the control valve and are only an option in a process which forces a gas pressure drop (i.e., pressu re regulators and backpressure valves). Level control, temperature control, or flow control

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

23 processes do not have the ability to use this equipment, but under Applicability, the W hite P aper
states : “Applicable only for relatively low

- pressure control val ves, e.g., in gathering, metering and regulation stations, power plant and industrial feed, and city gate stations/distribution applications (U.S. EPA, 2011a)”.

T hese devices can be used in very high pressure applications, contrary to the only limitation provided
in the W hite P aper.

 Option: Convert to Instrument Air: ” The limitation on applicability of instrument air systems to those instances where reliable grid or integrated generator with backup emergency electrical power is available is not clearly s tated. Also, the discussion of instrument air systems notes:

“In some instances, solar

- powered battery

- operated air compressors can be effective for remote locations, which reduce both methane emissions and energy consumption. Small natural gas powered fu el cells are also being developed.”

This statement is completely speculative with no references or demonstrated instances where this type of technology has been deployed and should be noted as such in the White Paper.
The emissions associated with generation of electricity, often by coal powered power plants, should be taken into consideration when determining the potential emission benefits of instrument air systems.

 Option: Install Low Bleed Controller in Place of High Bleed Controller (U.S. EPA, 2006b ). The historical approach for mitigating emissions from pneumatic controllers has been to replace continuous high

- bleed controllers with intermittent

- vent (often improperly called no

- bleed controllers due
to their near zero emissions between de

- act uation e vents) or continuous low

- bleed controllers.
This practice remains a viable strategy for sharply reducing emissions from pneumatic controllers and should remain as a primary option. N ote that replacement with an intermittent

vent controller will ty pically provide the lowest emission solution with the widest process demand applicability. However, there are process control applications where either a lower emitting controller is not available or where the process demands require a continuous high

ble ed type and the option to continue use should be preserved. The White Paper does not adequately or clearly discuss the limitations on use of continuous low

- bleed controllers inherent in their design that limits the amount of gas available for process cont rol. Low bleed rates (<6 scf/hr) are achieved by decreasing the diameter of the restriction orifice that controls the amount of pneumatic supply gas that can enter the controller and limits the rate that pneumatic supply gas can enter the controller. For a process application that demands more than 6 scf/hr to enable process control or demands process control at a faster rate (overall demand may be
<6 scf/hr) than a continuous low

- bleed controller can supply using a continuous low

- bleed
controller is not possible. Lower emissions and better control are generally available from
intermittent vent controllers.

 Option: Enhanced Maintenance . Under Description, the W hite P aper states

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

24 “Instrumentation in poor condition typically bleeds 5 to 10 scfh more than representative
conditions due to worn seals, gaskets, diaphragms; nozzle corrosion or wear; or loose control tube fittings. ”
To say that a worn seal, worn bleed port, worn restriction orifice, or failed diaphragm “increases emissions” is correct, but assigning “5 to 10 scfh” to that increased emissions is not
substantiated and appears to be an opinion. Diaphragms do not “wear

, ” they hold pressure or they don’t hold pressure. A failed diaphragm can easily result i n an exhaust rate that is an order of magnitude higher than “5 to 10 scfh”. W orn seal s are unlikely to exhaust as much as 5 SCF/hr.

 Option: Mechanical and Solar

- Powered Systems in Place of Bleed Controller (U.S. EPA, 2006a, U.S. EPA, 2006b):

o Low power electrical controllers and actuators capable of running on a solar & battery electrical supply system are beginning to appear on the market. However, the availability of electric

- powered controllers safe for use in flammable gas service and capable of mee ting all process control needs is somewhat limited. Currently, the price on these controllers is several times that of an equivalent pneumatic controller plus the additional cost for an array of solar panels and batteries for reliable electrical power. S ince they are fairly new, the range of available controllers is limited and their reliability and safety performance is not yet proven. Additionally, questions regarding the “fail safe” capabilities of these controllers and
actuators have been raised. Th e manufacture of new batteries, and the subsequent generation of used batteries as a waste, should be taken into consideration when determining the potential emission benefits of solar

- electric controllers and

actuators.

o Mechanical controllers are limited to those level

- control applications where the separator pressure is close to the water

- exhaust pressure. If this differential pressure exceeds certain low value then the buoyancy of the float cannot provide enough force to move the valve.

b) Pneumatic Pumps:

Unlike electric powered controllers and actuators discussed above, use of electric motor driven pumps is a mature technology that is widely and typically used when reliable electric supply is available. Electric motor driven pumps also tend to be more reliable and overall more energy efficient than

pn eumatic driven pumps

. Conversion of pneumatic pumps to electric motor

- driven pumps where reliable electricity is available should be the number 1 option listed in Table 3

- 5 and discussed in the White Paper

. Conversion of gas

- assist lean glycol recirculation pumps (a.k.a. Kimray glycol pumps) to electric motor driven pumps is the only option available and requires reliable electric power availability with greater power capacity than can feasibly be supplied by solar.
Option 1: Replace natural gas

- assisted pump with instrument air pump (U.S. EPA, 2011b ) Section: 3.2.1 Instrument Air Pump

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

25 The discussion of this option in the White Paper makes an incorrect and potentially hazardous recommendation of replacing the natural

- gas assist for a lean glycol recirculation pump (a.k.a. Kimray glycol pump) with instrument air. However, in this type of pump the assist gas is discharged into the rich glycol flowing to the glycol rebo iler/regener ator. Adding air (o xygen) to this stream could create an explosive mixture which is clearly not safe and could be potentially deadly. Additionally, adding air/oxygen would cause oxidation/degradation of the glycol and corrosion in the entire system which would lead to premature failure. This section needs to be rewritten to eliminate this recommendation regarding nat ural

- g as assist lean glycol recirculation pumps.

This erroneous recommendation appears to have developed from a mis understanding of the me thane reduction project presented by the Natural Gas Star partner regarding “glycol circulation pumps” by the contractor that developed “Pro Fact Sheet 202” (referenced as U.S. EPA, 2011b) and a fabrication of the case study economic details in the Pro Fac t Sheet . The project presented by the Natural Gas Star partner was a pilot project replacing natural gas powered pneumatic diaphragm pumps used to circulate hot glycol from the heated glycol

- bath separator on well

- sites around the well

- site as heat

trace medium to prevent freezing in winter. The pilot project had nothing to do with glycol dehydration or glycol dehydrator gas assist lean glycol circulation pumps.

This example illustrates the critical necessity for the White Paper process to subject the u nderlying information sources and documents that the White Papers rely on to a rigorous and complete
technical evaluation and validation

. T he White Papers should not rely on non

- reviewed Natural Gas Star Lessons Learned, Pro Fact Sheets, and partner presentations. The documents underpinning the White Papers must be subjected to a valid technical review to provide credibility to this
characterization of emission source s
.
Using instrument air rather than natural gas to power chemical injection and pneumatic diaphragm pumps is sometimes a viable option. However, the discussion in the White Paper presumes that an instrument air system with excess capacity already exists and that an operator would not have had the foresight to evaluate this possibility and would continue to use natural gas pressure (very inefficient) to drive the pumps

– all of which is highly unlikely. I f the White Paper is recommending installin g an air

compressor, then the underlying assumption is that reliable electric power is available and it would certainly be more effective and efficient to electrify the pumping function tha n to install a new compressed air system.

The White Paper discussion of r eplacing pneumatic chemical pumps with solar

- powered electric

pumps makes assumptions about maximum pressures and flow rates that came from a single case study in Natural Gas STAR. These assumptions were based on the subset of technology re viewed by the STAR partner at the time of the project and do not reflect the range of availability or limitations

. The White Paper also notes that larger volume capacity solar operated pumps with high discharge pressures are available which is not a valid conclusion from the source c ited (U.S. EPA, 2011b).

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

26 c) Pneumatic Controllers and Pumps in the ICF/EDF Study

The ICF/EDF study used the GHGRP data (discussed above) to adjust the 2011 inventory data for pneumatic controllers with the end result of a 41% in crease in the 2011 baseline. Using the GHGRP data, the authors subdivided the population of pneumatic controllers into the three categories of continuous high

- bleed, continuous low

- bleed, and intermittent controllers; established the population
of devices in each category, and used the GHGRP data to assign emission factors to each category. Using a series of assumptions the authors then subdivided the population of intermittent controllers into "dump valve intermittent controllers" and "non

- dump valve int ermittent controllers" with assumed different emission factors for each. Additionally, based on the API/ANGA survey report issued in September 2012, the authors added 23,000 pneumatic controllers to the number derived from the GHGRP data to account for pn eumatic controllers at Gathering and Boosting stations which
are not covered under the GHGRP. These additional controllers were subdivided into the three categories based on the GHGRP population distribution . The paper makes two recommendations for
emissi on mitigation from pneumatic controllers:

 Replace high bleed controllers with low bleed controllers

 Replace high

- emitting intermittent controllers (not dump valves) with low bleed controllers

Given the uncertainty in the US Inventory, the uncertainty in t he GHGRP data for pneumatic controller counts and emissions, and the additional uncertainty added by the authors assumptions

, these recommendations need to be viewed with a significant degree of skepticism.

As previously discussed, replacement of continu ous high

- bleed controllers with lower emission controllers is a well demonstrated approach to mitigating emissions from pneumatic controllers. However, the author's conclusion that the replacement should be done with a continuous low

- bleed
controller rath er than an intermittent

- vent controller is not a valid recommendation overall. Replacement of a continuous high

- bleed controller with either an intermittent

- vent or continuous low

bleed controller, where the process can tolerate the delay in response inhe rent to a low

- bleed controller, is a more appropriate recommendation.

The author's recommendation to replace "high

- emitting intermittent controllers (not dump valves) with low bleed controllers" would likely result in higher emissions overall. As previou sly discussed, the GHGRP data (used by the authors to establish emission factors) for intermittent

- vent controllers is very likely significantly overstated which would make the author's recommendation suspect from an emission reduction perspective. Also, the ability of the process to properly function with the slow response time inherent to a continuous low

- bleed controller must be taken into account. There are cases where the slow response time can be tolerated and a continuous low

- bleed device would be a lower emission selection. T hese instances demand a case

- by

- case evaluation and determination.

The ICF/EDF methane mitigation paper conclusions for pneumatic pumps are even more suspect than the conclusions for pneumatic controllers. The ICF/EDF metha ne mitigation paper determines a count of 30,600 pneumatic chemical/methanol pumps and attributes this count to data reported into Subpart W and notes that this count is higher than the 28,000 pump estimate in the National

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

27 Inventory. However, the ICF/EDF count is not consistent with our estimate of about 84,000 pneumatic chemical/methanol pumps derived from the Subpart W data or the count of 63,715 pneumatic chemical/methanol pumps in the 2013 National I nventory. The White Paper does not clearly explain
h ow ICF arrived at this significantly different count of pneumatic chemical/methanol pumps but it appears the count in the White P aper is incorrect and this should be indicative of the validity of the

paper ’ s conclusions.

Similar differences occur in the paper’s attribution of emissions from pneumatic chemical/methanol

pumps.

 Table 3

- 2 attributes 5.9 BCF of emissions to pneumatic chemical/methanol pumps in 2018

 The discussion of pneumatic chemical pumps in Section 3.5 attributes 180 mcf of reduction per year to each pump replaced and notes that replacement of 80% of the pumps (presumably ICF’s 30,600 pumps) was assumed for the analysis presented. Applying the described approach yields about 4.4 BCF /year in emission reduction from 80% of the pneumatic pumps considered.

 In the description of how the 2011 ICF baseline was computed, the paper notes application of a portion of the National Inventory reductions attributed to Kimray glycol dehydrator pumps to pneumatic chemical pumps but does n ot describe how this portion was determined. In Section 3.1.8 the paper arrives at an “updated” increase in emissions from pneumatic chemical pumps
of about 2% to over 3 BCF of gas

 Section B4.1.4 again notes the allocation of a portion of the “Gas Star” r eductions to the National Inventory emissions from pneumatic chemical pumps (not allocated in the inventory) and notes a 30% decrease to just over 2 BCF of gas.

 Table 4.1 shows 4.8 BCF of methane reduced per year from pneumatic chemical pumps if the

recomm endations of the paper were applied. Applying the 80% replacement rate would imply
total emissions of 6.0 BCF of methane which is close to the National Inventory pre

- reduction
emissions of 5.9 BCF of methane emissions from pneumatic chemical pumps. Howev er this emission quantity occurs from a much smaller population of pumps in the paper. Also, whole gas emissions rather than methane emissions are the relevant measure to use in the analysis the paper purports to conduct. Using an assumed methane content of 85% (mole) the paper ’ s claimed reductions imply whole gas emissions of about 7.1 BCF which is close to the Subpart W data but again from a much smaller (30,600 vs. 71,000) number of pumps.

The 180 mcf of whole gas reduction per pump replacement i mplies an emission rate of about 20.5 scf/hr which is substantially higher than the 13.3 scf/hr in Subpart W or the 12.5 scf/hr (whole gas) rate
derived from the National I nventory. If the stated reduction per pump is methane rather than whole gas, which is not clear in the paper, the emission rate would be about 24.2 scf/hr (whole gas) which is
almost double the Subpart W and National Inventory emission rates. Given the paper’s representation of emissions from pneumatic chemical/methanol pumps that rang e from 2.0 BCF/year to 7.1 BCF/year coupled with the difference in the paper’s emission rates vs. the Subpart W and National Inventory emission rates, which are not explained in the White P aper, the conclusions of this paper need to be viewed with a high d egree of skepticism.

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

28 The economics of pneumatic chemical pump replacement in the ICF/EDF m itigation paper are not clear . The paper reports using an initial cost of $5,000 per pump, $75 in annual operating cost, a recovery of 180 mcf of gas/year, a $4.00 gas price, and a 10% discount percentage. The paper does not report the replacement pump lifetime assumption or any component replacement assumptions (or lack of inclusion) in whatever lifetime was modeled. The paper concludes that replacing a pneumatic chemical pump with a solar driven pump yields a positive return of $0.22/mcf of gas recovered over the life of the solar driven pump. A Net Present Value (NPV ) analysis shows that reaching a “pay

- back” value with the discount rate reported would take ab out 13 years while reaching the positive $0.22 per/mcf of gas reduced would take about 17 years.

Although 17 years of solar pump system lifetime is likely valid for the solar panel portion of the systems; the battery pack, pump, and pump drive motor would likely have much shorter lives and require replacement at interim periods. Consequently, additional costs need to be added for replacement of these components which would lengthen the time necessary to reach the break

- even point or the positive return not ed in the White P aper. However, API is not aware of any information regarding the frequency of needed replacements as no/most solar powered chemical pump systems have been in place less than a decade.

The above analysis is in stark contrast with the Sec tion D.7 presentation of economics where the unnumbered table titled “Cost Benefit Analysis: Convert Natural Gas

‐ Driven Chemical Pumps” states a 1 to 16 month payback. At 180 mcf/year recovered gas, $4.00 per mcf, and $5,000 initial cost

, this payback est imate is not correct
, even based on the low cost estimates. A payback of the initial cost with no annual costs or discounting would take about 7 years.

Also, by arriving at a smaller number of pumps responsible for essentially the same emissions as
ind icated by Subpart W and the National Inventory the White P aper , overstates the emission reduction benefit and the economic returns from replacement of pneumatic chemical/methanol pumps with solar powered pumps. If actual pump emissions are closer to the S ubpart W emission rate then the
economic benefits are overstated about 55%.

In view of the internal inconsistencies of the White P aper regarding emissions, the obvious erroneous pneumatic chemical/methanol pump count, and the unrealistic economic payback periods claimed in the paper

, the conclusions should be viewed as speculati ve . This paper should not be any part of the basis for any regulatory/policy initiative aimed at pneumatic chemical/methanol pumps. 

## Charge Question 5

Please comment on the prevale nce of the different emission control technologies and the different types of pneumatics in the field. What particular activities require high bleed pneumatic controllers and how prevalent are they in the field?

API is not aware of any study or industry su rvey that documents the prevalence of solar electric operated controllers and actuators, solar electric powered chemical injection pumps, solar powered pneumatic diaphragm pumps, instrument air powered pneumatic controllers outside of

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

29 natural gas processin g facilities, or instrument air or electric powered pneumatic pumps. There is some anecdotal information in the Natural Gas Star program information but it does not provide
broad or complete information. However, the implication in this question is that the occurrence of such technologies/practices is an emission control technology rather than an appropriate engineering and economics choice for the particular application to oil and gas operations

An estimate of the numbers of intermittent vent, continuous bleed low

- bleed, and continuous bleed high

- bleed controllers can be derived from the 2012 GHGRP data by dividing the CH4 emissions shown for each category by the emission factors in Subpart W and then correcting for
methane content

– which is similar to t he approach taken in the ICF/EDF 2014 report . However, this requires assuming that each controller operated 8760 hours per year and using the correct methane content to develop a count as the factors are in whole gas. Also, as discussed above,
the 2011 a nd 2012 GHGRP counts of controllers in each category were allowed to be estimated by reporters based on engineering knowledge with an actual count required to be completed by the end of the 2013 emission year. The 2013 emission reports should provide a be tter basis for estimating controllers in each category due to the actual count underlying the emissions reported. In 2015, data reported for the 2014 emission year and prior years (2 011, 2012, and
2013 ) will include “deferred” data elements including cont roller counts in each category. This will eliminate the necessity to estimate a count from the GHGRP data

. Pneumatic pump counts can be estimated from the GHGRP data using the same approach described for pneumatic controllers and subject to the same limit ations. Please note that gas

assist lean glycol pumps are not included in the GHGRP data for pumps and are included in the glycol dehydrator emissions in the GHGRP data.

The number of dehydrators with an annual throughput greater than or equal to 0.4 MMSCFD can be directly derived from the GHGRP data along with emissions for each such dehydrator reported. The emissions reported for each dehydrator can be used to determine whether the unit had a gas

- assist pump or not. For dehydrators less than 0.4 MM SCFD
, the count can be estimated by dividing the reported CH4 emissions by the Subpart W emission factor although this will not provide any way to distinguish the percentage of these units with gas

- assist pumps. 

## Charge Question 6

What are the b arriers to installing instrument air systems for converting natural gas

- driven pneumatic pumps and pneumatic controllers to air

- driven pumps and controllers?

Installing instrument air systems in field locations is limited to those instances where reliable electricity, most often from the grid, is available. Running small generators or small engines directly powering instrument air compressors and dryers is not reliable, demands much more maintenance resources, and has offsetting air emissions that make suc h an approach undesirable and not feasible. Solar arrays and battery systems necessary to power an air compressor are very large, expensive, and not used. From an economic standpoint, installing an instrument air system at a site where electricity is ava ilable depends on the pneumatic controller air demand being high enough to

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

30 make an installation economic

– pumps will most likely already be electrically driven if electricity is
available. In cold weather areas

, instrument air systems require assured dry ing to prevent freezing which translates into oversized drying units and increased maintenance resources.

As previously discussed, instrument air cannot replace the natural gas used in gas

- assist lean glycol recirculation pumps. The only option for this type of pump replacement is an electric motor driven pump. Again, solar arrays and battery systems large e nough to power these types of pumps are not feasible

. 

## Charge Question 7

Are there situations where it may be infeasible to use air driven pumps and controllers in place of natural gas

- driven pumps and controllers even where it is feasible to install an
i nstrument air system?

As previously discussed, instrument air cannot replace the natural gas used in gas

- assist lean glycol recirculation pumps. The only option for this type of pump replacement is an electric motor driven pump. Again, solar arrays and b attery systems large enough to power these types of

pumps are not feasible

. 

## Charge Question 8

Did this paper correctly characterize the limitations of electric

- powered pneumatic controllers and pneumatic pumps? Are these electric devices applicable to a br oader range of the oil and gas sector than this paper suggests?

Electric driven pumps are applicable to a broader range of applications than suggested by the White Paper where reliable grid electricity is available. Unfortunately grid electricity is not available at a majority of the individual well sites and a reliable, low cost, and clean method for generating the small amount of power needed does not yet exist.

Process control loops, controller and valve actuat or, powered completely by solar electricity are newly emerging in the marketplace. The range of available units is limited and the cost is several times that of an equivalent pneumatic controller. Most importantly, sufficient operational history has not been accumulated using such installations to broadly prove their reliability and safe operation. If they are found to work well, function reliably, and operate safely

, the use is likely to increase, which will tend to push the prices down. 

## Charge Questi on 9

Are there ongoing or planned studies that will substantially improve the current understanding of VOC and methane emissions from pneumatic controllers and pneumatic pumps and available techniques for increased product recovery and emissions reductio ns?
API is aware of the UT Phase 2 study, with improved methodologies, that is measuring emissions from a wider population of pneumatic controllers and is due to be published later this year.

### API Comments on Submitted to EPA

Oil & Natural Gas Sector Pneumatic Devices June 16, 2014

31 In addition, API is aware of a study commissioned by Pioneer Nat ural Resources, one of the UT Phase 1 and Phase 2 study sponsoring companies, which is reportedly planning to publish the results of an independent pneumatic controller measurement study in the near future.



## C. Conclusion

The White Paper titled “Oil and Natur al Gas Sector Pneumatic Devices” represents a step backwards from the knowledge demonstrated in earlier EPA efforts (especially the Subpart OOO O Technical Support Document). The EPA would benefit from using the Subpart OOOO TSD as a starting point and commissioning a competent oil and gas engineering company with pneumatic controller and pump experience to assist in updating the TSD . While the TSD has significant errors and weak sections it is markedly closer to a n adequate reference product than the “ White Paper”.API

– March 24, 2014

Pneumatic Controllers

The category of pneumatic devices includes both pneumatic controllers and pneumatic pumps. These two types of pneumatic devices are very different and are discussed separately

.
Pneumatic Controller Background

Process controllers are devices that sense a physical state and direct an end

- device (typically a valve) to take an action to modify that physical state. These controllers can use a range of motive

- force media such as pneumatic, hydraulic, or electric. Electric, hydraulic, and electro

- hydraulic controllers do not release any gases to the atmosphere

. Integral controllers that use gas directly from the process to increase actuation pressure and then exhaust excess gas back into the process to decrease act uation
pressure do not emit

. Pneumatic controllers that emit natural gas to the atmosphere, either continuously or intermittently, are the focus of this document

.
Pneumatic controllers may be the most misunderstood category from both an emission and proper classification perspective. This confusion is predominantly due to inconsistent use of terminology and use of different terms for the same type of controllers by industry, regulators, vendors, and others over many years. This has led to erroneous emission estimates
, erroneous emission factors, and classifications of controllers that are not reflective of how controllers are designed, constructed, and used.

From an emission perspective, pneumatic controllers that emit can be classified by a c ombination of their design type and the type of service they perform

.
The two types are : 1) C ontinuous bleed controllers : These are designed to bleed gas to atmosphere on a continuous basis and send a pressure signal to an end device (valve with actuator) by fully or partially blocking the bleed port. 2) Intermittent vent controllers : These are typically designed with a small 3

- w ay valve (pilot) that sends a pressure signal to an end device on demand and vents actuation gas to reverse the action on demand . Between actuation/de

- actuation cycles intermittent vent controllers are designed for near zero emissions.

The two services a re : 1) On/off: The defining characteristic of an on/off controller is that the controller is not required to hold an end

- device in an intermediate position (i.e. at the end of a control cycle the control

- gas pressure to the end

- device goes to zero); 2) Th rottling: The defining characteristic of a throttling controller is that the controller is required to control an end

- device in an intermediate position (i.e. the control

- gas pressure to the end device is maintained at a pressure between atmospheric and supply pressure).API

– March 24, 2014

Combining the type and service yields the following matrix:

Additionally, on/off controllers can differ in the type of action taken and may either be snap

- acting or proportional. Snap acting is often mistakenly used as an analogue f or an intermittent controller or for an intermittent controller in on/off service. Proportional is often mistakenly used as an analogue for throttling controllers. Snap

- acting and proportional describes the type of action a controller in on/off service m ay take and does not have a great impact on emissions.

 A snap acting on/off controller will never send a partial pressure signal. I t will wait until the input parameter has reached a maximum value and then snap open and stay in that fully

- open position until the input parameter reaches a minimum value and then will snap shut and an exhaust port will
snap open.

 A proportional on/off controller will send a partial pressure signal as soon as the input parameter increases above a minimum and as the input p arameter continues to increase, the rate that the controller sends gas to increase the pressure signal to the end device increases. A proportional on/off controller service will only allow gas to enter the process until the differential pressure across the controller pilot plug is zero (i.e., actuation pressure equals supply pressure). If the process variable is satisfied prior to reaching zero differential pressure then the controller will shut off supply gas and open the vent without ever fully opening the end device and will vent slightly less gas than a snap

- acting on/off controller. Proportional on/off controllers can be thought of as soft open and soft close ac tions.

Snap acting on/off controllers tend to reposition end

- devices open and shut very quickly which can cause serious process problems in some situations. Proportional on/off controllers tend to ease into a change of state with fewer problems with slugging and surging. It is important to understand that the type of pneumatic device used and the configuration of the action is dependent upon the process being controlled.

As sh own in the table, both continuous

- bleed or intermittent

- vent controllers can be either snap

- acting or proportional. Snap

- acting or proportional action is not a defining function of a controller for the purposes of determining emissions.API

– March 24, 2014

Emission Estimate s and Studies:

Engineering Calculations

Time based emissions (e.g. scf/hr) from an intermittent controller in on/off service can be calculated based on the volume of gas needed to actuate an end

- device (actuation volume) and the number of
times the contro ller vents for de

- actuation in the time period (cycles)

. The important parameters are the volume of the valve actuator, the length and diameter (volume) of the tubing from the controller to the valve actuator, the pressure of the gas signal to the actuator, and the frequency of actuation cycles. For example

, an intermittent on/off temperature controller on a field heater that requires firing every 5 minutes (12 times/hr), with an actuator volume of 1.1 cubic inches and 6 feet of 3/8 inch diameter tubing and a supply gas pressure of 25 psig would have emissions of ~0.18 scf/hr. An intermittent on/off level controller on a well separator producing 10 bbls/day of liquids that dumps 1.3 gallons per cycle (13.5 cycles/hr), with an actuator volume of 110 cubic inches and 10 feet of 3/8 in diameter tubing and a suppl y gas pressure of 25 psig would have emissions of ~2.6 scf/hr.

Time

- based emissions from an intermittent controller in throttling service are more difficult to calculate since the controller is holding a set

- point and partially actuating/de

- actuating an end device to partially open or close a valve. The volume vented per partial de

- actuation is determined by the change in pressure in the tubing and actuator and the actuation volume and is much smaller than a full de

actuation. However, the throttling co ntroller would likely make adjustments somewhat more frequently and it is reasonable to use a percentage of the on/off controller emissions based on engineering judgment. Emissions will normally be less than an on/off controller in the same exact applicat ion. However, throttling controllers cannot be used in many process control applications.

Determining the number of cycles in a particular time period and the actuation volume for an average
intermittent controller that is representative of the population of intermittent controllers and types of service is very difficult . Therefore, the development of an average emission per unit of time for the broad class of intermittent controllers will not accurately represent real world emissions unless a very large a nd broad set of data is accumulated

.
In contrast, continuous bleed controllers lend themselves to calculating a time

- based emission rate due to their design. Continuous bleed controllers have a restrictive orifice that controls the rate that supply

g as can enter the control loop and either bleed to atmosphere or be used in actuation and then added
to the bleed on de

- actuation. An emission rate can be calculated using a standard orifice calculation with the most important parameters being the orifice size, supply gas pressure, supply gas properties (gas specific gravity), and the tubing/passage size downstream of the orifice. For a continuous bleed
controller with 2 0 psig supply gas, a specific gravity of 0.63, a 0.030 inch orifice, and 3/8 diameter t ubing
the bleed rate would be ~ 56.8 scf/hr. An orifice size of 0.010 inch would yield a bleed rate of about 6.3 scf/hr with the other parameters held constant . Because continuous bleed controllers emit the actuation gas, in addition to the gas that passe s through the orifice, their average emissions per unit of time is equivalent to the rate that gas will pass through the orifice.API

– March 24, 2014

For both types of controllers malfunctions can occur which will change the emission profile. For an
intermittent

- vent cont roller, debris or deposits on the pilot ball (s) may affect the seat and cause higher emissions during the actuation portion of the cycle or during the idle portion of the cycle between actuation/de

- actuation sequences. Both types of controllers can also have diaphragm, o

- ring, and/or spring failures which may increase or decrease emissions with the effect dependent on the design of the individual device. Sufficient data to evaluate the frequency of these types of malfunction events and their materiality from an emission perspective is not yet available.

Pneumatic Controller Information/D ata Sources and Studies

EPA Question: What are the different studies and data sources that quantify emissions from pneumatic controllers in the oil and gas sector?

All information sources and studies should be carefully evaluated prior to use. Considering the confusion and mistaken information surrounding different types of pneumatic controllers and their emissions
, this is critically important. For pneumatic cont rollers:

 All studies need to be evaluated to judge whether they are a good representation of the diverse population of pneumatic controller types, services, and applications.

 All studies need to be QA/QC’d to judge whether the type of controller and servic e was correctly identified.

 All studies need to be QA/QC’d to judge whether the appropriate methodologies, sampling populations, and sampling times were used to adequately measure emissions from controllers.

 All studies need to be QA/QC’d to judge whethe r the data collected was appropriately analyzed and attributed.

Greenhouse Gas Reporting Program (GHGRP) and National Inventory of GHG Sources and Sinks (Inventory) :

The GHGRP has required reporting of emissions from pneumatic controllers since 2011 and d ata has been reported and publically released for 2011 and 2012. It is important to understand the limitations of this data and potential errors before using it for any purpose. The GHGRP divides pneumatic controllers into high

- bleed continuous (>6scf/hr ), low

- bleed continuous (<6scf/hr) and intermittent categories. For each category the GHGRP has an emission factor (EF) : These are: Continuous low

- Bleed

- 1.39 scf/hr; Continuous high

- bleed

– 37.3 scf/hr; Intermittent

– 13.5 scf/hr. Reporters use a
“c ount” of controller types in each category multiplied by the emission factor to determine the volume of gas emissions for each category of controller in each “facility” (covered basin). For the 2011 and 2012
reports , these counts were allowed to be estima ted using engineering judgment. For the 2013 emission year, to be reported by March 31, 2014, pneumatic controllers in each category are required to be counted. Obviously the accuracy of the reported emissions is contingent on the accuracy of both the

em ission factors and the counts of controllers in each category. With controller populations estimated
for 2011 and 2012

, the reported number of controllers is likely not accurate and the 2013 data should provide a much more accurate report of the populatio n of controllers in each category. Given how an intermittent controller operates vs. a continuous bleed controller and very straightforward engineering calculations, the intermittent controller emission factor is likely very high

– perhaps by an order ofAPI

– March 24, 2014

magnitude or more

– hence , the emission estimates from this category are likewise high. Several studies (discussed below) soon to be published will provide some additional information to inform this question. Users of the GHGRP data for pneumatic control lers should wait for the 2013 reporting for a higher quality population count. Unfortunately, until the emission factors for each category can be validated and corrected, the GHGRP reported emissions for pneumatic controllers will remain highly
uncertain.

U.S. Greenhouse Gas Emissions and Sinks (Inventory) :

The National Inventory , done annually, uses a single estimate of the number of pneumatic devices and a single emi ssion factor to calculate potential methane emission s for pneumatic controllers (called devices) for the “Natural Gas Systems” and “Petroleum Systems” categories. Reductions in emissions attributable to Natural Gas Star voluntary taken and reported actions and regulatory required reductions (if required) ar e subtracted from these potential emission estimates. It is not clear what the genesis is for the pneumatic controller population estimate or emission factor hence it is not clear whether the estimate is valid or what uncertainty bands might apply.

UT Phase 1 Study

This study, led by the University of Texas with support from EDF and 9 Oil and Gas Companies, sampled some 305 controllers with a paper published in the Proceedings of the National Academy of Sciences in mid

- 2013

. Of the controllers measur ed, some 60 were identified as “low

- bleed” and 129 as ”intermittent” for a subset of 189 controllers where the type was noted. Based on the subset of identified controllers, t he study concluded: Intermittent and low bleed pneumatic devices measured in th is work averaged 5.9 ± 2.4 and 1.7 ± 1.0 g of natural gas per device per minute, 29% and 270% higher than EPA emission factors, respectively (SI Appendix, section S2). However, questions have been raised regarding whether the types of controllers (low

- ble ed or intermittent) were identified correctly and whether the sampling periods were long enough to reflect the variation of emissions from a controller throughout a single cycle and the length of a cycle. The UT Phase 2 Study is reported to be using impro ved methodologies for properly identifying pneumatic controllers and measuring emissions from pneumatic controllers.

GRI/EPA 1996 study

This study was mostly based on manufacturer’s emissions information

, site inventories /counts of pneumatic controller s , and engineering calculations . The study did include measurements of 19 controllers made in a 1992 Canadian Association of Petroleum study and information provided by Chevron and Tenneco Gas Transportation. Despite the age of the data and the small

sam ple/measurement set this study is still used as the basis for many emission estimates for the industry.

Canadian Association of Petroleum Producers 2002 & 2003

The CAPP 2002 report concluded that the emission factor for an average pneumatic controller was ~7 scf/hr which was based on information from measurements made in Alberta. This report did not distinguish between types of controllers or types of services.API

– March 24, 2014

2013 Prasino Report

The Prasino grou p published the results of a pneumatic controller measurement study conducted on behalf of the province of British Colombia and a consortium of producing operators in December of 2013. This study intentionally focused on “high emitting” controllers where the manufacturers emission rate was g reater than 0.119 m3/hr (~4.2 scf/hr). However, during the measurement campaign controllers with lower manufacturer’s rates were also measured. During the measurement campaign

, some 581 individual controller s spread amongst 15 model numbers plus one “other” category were measured . Average emission rates for each model measured were determined and reported. These ranged from ~0.5 scf/hr to ~14.8 scf/hr. The author’s determination that R 2 values above 0.65 represente d a “strong” correlation and over 0.25 a positive correlation does raise concerns. The underlying raw data for this study has been requested to enable a more robust analysis.

UT Phase 2 Study

The UT Phase 2 study, with improved methodologies, is me asuring emissions from a wider population of pneumatic controllers and is due to be published later this year.

Pioneer Natural Resources Study

Pioneer Natural Resources, one of the UT Phase 1 and Phase 2 study sponsoring companies, is reportedly planni ng to publish the results of a n independent pneumatic controller measurement study in the near future.

Intermittent, Snap

- acting, Continuous Bl eed, and Throttling Controllers

EPA Question: Are there significant emissions from snap acting (intermittent) pneumatic controllers?

As discussed above, snap

- acting is descriptive of a type of action an on/off controller may be configured to take, can apply to either continuous bleed or intermittent controllers, and is not an analogue for intermittent. Similarly, throttling describes a type of action an on/off controller may be configured to take and is not an analogue for continuous bleed.

Emissions from an intermittent controller occur when the actuation volume is vented to reverse the actuation action. Emissions per unit of time are dependent on the volume per actuation cycle and the number of actu ation cycles in the unit of time. In most applications, an intermittent vent controller, which does not bleed between de

- actuations, is the low emission option. However, i f an intermittent controller is in an application with a large actuation volume and frequent actuations it can have greater emissions per hour than a low

- bleed continuous controller. Replacing such an intermittent controller with a low

- bleed continuous controller to lower emissions is only possible where the process control demands can tolerate the delay inherent in the design of a low

- bleed controller. For instance, a low

bleed controller (6scf/hr) in level control service with a 110 cubic inch valve actuator (typical for a 2” valve in medium/high pressure service) , 10 feet of 3/8” tub ing , and 25 psig pneumatic supply gas will take about 58 seconds to reach 5 psi and begin moving the controlled valve and about 116 seconds to fully actuate the valve actuator to the supply pressure of 25 psi. If the process cannot tolerate this scale of delay

, then replacement of the intermittent controller with a low

- bleed continuous controller is precluded. This type of determination requires a case

- by

- case evaluation and operators need to have the flexibility to use the type of controller needed for s afe and reliable process control.API

– March 24, 2014

Pneumatic Controller Emission Mitigation

EPA Question s : What are the technologies or practices available to mitigate emissions from pneumatic controllers? W

hat are the pros and cons of the different options, inclu ding efficacy, cost, and feasibility?

Instrument Air and Electric

Using instrument air rather than natural gas as the pneumatic supply gas will eliminate gas emissions while providing the same level of process control. However
, most well sites are remot e from electrical grid supply to operate a compressor and drying system and instrument air systems are not feasible. Where grid electricity is available, sufficient demand for pneumatic air must exist to make an instrument air system cost effective. Inst rument air systems, like any mechanical system, do experience failures and reliability needs to be taken into account as well. Additionally, drying of the instrument air is critical to prevent freezing in the process control systems which cause failures t o occur. Most gas processing/treating facilities, offshore platforms, and larger sites (such as compressor stations) with grid electricity or on

- site electrical generation have instrument air systems for pneumatic services. Where grid electricity is avai lable and sufficient air demand exists

, instrument air systems should be evaluated.

Where grid electricity is available

, electric

- powered controllers and actuators can be used rather than pneumatic systems

– which eliminates emissions. However, the availability of electric

- powered controllers safe for use in flammable gas service and capable of meeting all process control needs is somewhat limited. Low power electrical controllers and actuators capable of running on a solar & battery electrical supply system are beginning to appear on the market. Currently

, the price on these controllers is several times that of an equivalent pneumatic controller plus the additional cost for an array of solar panels and batteries for reliab le electrical power. Since they are fairly new

, the span of available controllers is limited and their reliability and safety performance is not yet proven. Additionally, questions regarding the “fail safe” capabilities of these controllers and actuators have been raised. The manufacture of new batteries, and the subsequent generation of used batteries as a waste

, should be taken into consideration when determining the potential emission benefits of solar

- electric controllers and actuators.

Lower Emitt ing Pneumatic Controllers

The historical approach for mitigating emissions from pneumatic controllers has been to replace continuous high

- bleed controllers with intermittent

- vent, often called no

- bleed controllers due to their near zero emissio ns between de

- actuation vents, or continuous low

- bleed controllers. This remains as a viable strategy for sharply reducing emissions from pneumatic controllers and should remain as a primary option. Again, t here are process control applications where a l ower emitting controller is not available or where the process demands require a continuous high

- bleed type and the option to continue use should be preserved.API

– March 24, 2014

ICF/EDF Paper: Economic Analysis of Methane Emission Reduction Opportunities in the U.S. Onsh ore Oil and Natural Gas Industries

The ICF/EPA paper prominently notes two important caveats which need to be kept in mind:

 The 2011 EPA inventory is the best starting point for analysis, but it is based on many assumptions and some older data sources. Although the inventory is improving with new data, it is designed to be a planning and reporting document and is imperfect, especially at the detailed level, for a granular analysis of this type.

 Emission mitigation cost and performance are highly site specific and variable. The values used here are estimated average values.

This study adjusted the EPA’s 2011 inventory based on the GHGRP data and UT Phase 1 studies along with some of the author’s assumptions and opinions which introduces significant uncertainty in addition to the GHGRP and UT Phase 1 study data uncertainty discussed above

. The authors then “grew” the inventory to a 2018 projection using a series of projections and assumptions which adds additional uncertainty. Additionally, the auth ors “adjusted” the emissions projections, both in the 2011 baseline and 2018 projection, for individual source types which adds uncertainty at the individual source type level. The limitations the authors note

, the additional uncertainties introduced by t he adjustments made to the 2011 baseline

, the assumptions and methodologies used in “growing” the inventory to 2018 , and the adjustments to individual source type emissions need to be considered carefully in use of this papers conclusions

.
In determining the mitigation costs for a particular practice, technology, or action the authors adjusted
EPA ’s and the State of Colorado ’s economic analyses based on their opinions and assumptions which adds uncertainty on top of the inherent uncertainty in the EPA and Colorado analyses.

Pneumatic Controllers in the ICF/EDF Study

The ICF/EDF study used the GHGRP data (discussed above) to adjust the 2011 inventory data for pneumatic controllers with the end result of a 41% increase in the 2011 baseline. Using the GH GRP data
, the authors subdivided the population of pneumatic controllers into the three categories of continuous high

- bleed, continuous low

- bleed, and intermittent controllers; established the population of devices in each category, and used the GHGRP data to assign emission factors to each category. Using a series of assumptions the authors then subdivided the population of intermittent controllers into “dump valve intermittent controllers ” and “ non‐dump valve intermittent controllers ” with assumed differ ent emission factors for each. Additionally, based on the API/ANGA survey report issued in September 2012, the authors added 23,000 pneumatic controllers to the number derived from the GHGRP data to account for pneumatic controllers at Gathering and Boost ing stations which are not covered under the GHGRP. These additional controllers were subdivided into the three categories based on the GHGRP population split.

The paper makes two recommendations for emission mitigation from pneumatic controllers:

 Repl ace high bleed controllers with low bleed controllers

 Replace high‐emitting intermittent controllers (not dump valves) with low bleed controllersAPI

– March 24, 2014

Given the uncertainty in the US Inventory, the uncertainty in the GHGRP data for pneumatic controller
counts and emissions, and the additional uncertainty added by the authors assumptions these recommendations need to be viewed with a significant degree of skepticism.

As previously discussed

, replacement of continuous high

- bleed controllers with lower emissio n controllers is a well demonstrated approach to mitigating emissions from pneumatic controllers. However, the author’s conclusion that the replacement should be done with a continuous low

- bleed controller rather than an intermittent

- vent controller is likely not a valid recommendation overall

. Replacement of a continuous high

- bleed controller with either an intermittent

- vent or continuous low

- bleed controller , where the process can tolerate the delay in response inherent to a low

- bleed controller, is a more appropriate recommendation.

The author’s recommendation to replace “high

- emitting intermittent controllers (not dump valves) with low bleed controllers” would likely result in higher emissions overall. As previously discussed, the GHGRP data (used by the authors to establish emission factors) for intermittent

- vent controllers is very likely significantly overstated which would make the author’s recommenda tion suspect from an emission reduction perspective. Also, the ability of the process to properly function with the slow response time inherent to a continuous low

- bleed controller must be taken into account. There are cases where the slow response time can be tolerated and a continuous low

- bleed device would be a lower emission selection. Again, these instances demand a case

- by

- case evaluation and determination.

Conclusion

Overall, choices of specific controller types to replace continuous high

- bleed controllers need to be made by the operators, after evaluation and analysis of the demands of the process system and the likely emission outcome based on actual knowledge of the process and controllers rather than a series of uncertain assumptions. Also, a s previously noted, there are cases where the use of high

- bleed continuous controller s are necessary and cannot be replaced with another type.

Recommended Charge Que stions for Peer Reviewers

1. Are assertions made in the paper supported by the underlying facts and data? 2. Are assumptions made in the paper clearly noted? Do these assumptions seem valid and balanced? 3. Do the data sources and studies that the paper relies up on appear credible and complete?
4. Was sufficient QA/QC conducted with regard to the data sources and studies that the paper relies on to determine their applicability and validity?
5. Does the paper adequately discuss the constraints inherent in a low

- bleed co ntinuous controller’s delay in initiating a control action and the consequent constraints on where they can be used? 6. Does the paper reflect an understanding of the limited instances where replacement of an intermittent controller with a low

- bleed continuou s controller is a lower emission option?
7. Does the paper present a realistic evaluation of actual emission reduction potential from additional regulation of pneumatic controllers ? 8. Are the conclusions reached by the authors supported by the information and data that was relied upon?

# Pneumatic Controllers

# Common Misconceptions

2 

#  

# Intermittent controllers emit at a higher rate than low 

# bleed (Subpart W)

 

# Low bleed controllers are the best overall choice

 

# Emissions also occur at the valve actuator

 

# Controller terminology is standardized and commonly understood

 

# That snap

- acting, on/off, no

- bleed, & intermittent are synonymous terms

 

# That throttling, continuous bleed, and proportional are synonymous terms

# Goals

 

# Seek common understanding of pneumatic controllers

 

# Types of pneumatic controllers

 

# How they operate

 

# Expected emission profiles.

 

# Seek common understanding of key principles

 

# The choice of controller types for a particular application is dictated by the process needs/demands while ensuring safe and reliable operation

 

# For most applications, intermittent controllers are the lower 

# emission option than continuous bleed controllers

 

# If the process can tolerate the inherent delay in response associated with a low

- bleed continuous controller, a low

- bleed continuous controller may, in limited situations, be a lower emission option

3

# Process Control Systems

4 

##  

# A process control system/loop must have:

 

# A way to sense the state of a process variable (Float, pressure transducer, etc.)

 

# A way to change the state of the sensed process variable (Pneumatic Supply Gas, Controller, Actuator, and Valve)

 

# Process variables most commonly controlled in upstream Oil & Gas are:

 

# Fluid level (often found on separators, tanks, treaters , etc.)

 

# Pressure (includes pressure regulating, back pressure regulating, and over
pressure limiting)

 

# Temperature (includes tank heaters, indirect process heaters, direct process heaters, and fan control)

 

# Differential pressure (often used as a surrogate for flow, generally used for constant flow processes)

 

# Position (includes devices that sense plunger arrival in a well and signal end

devices to allow after flow and/or to shut off the flow to allow the plunger to drop)

 

# Safety

– Unique Category ( includes control of emergency shut

- down valves that shut when manually tripped or an unsafe condition is sensed )

# Simple Control Loop Example

- Wrong

5

# Simple Control Loop Example

- Right

6

A control loop has the following components:

• Pneumatic supply gas

• Pneumatic controller

• Process variable /

measurement

• Valve actuator

• Control valve

# Simple P rocess Control Loop Concepts

7 

#  

# The sensor, control valve and actuator do not bleed or vent gas

 

# All emissions occur at the controller

 

# The amount of gas needed for a full actuation cycle 

# depends on the pressure and volume of the control loop

 

# The full actuation volume is the volume of the valve actuator + the tubing from the controller to the actuator

– corrected to standard conditions for the actuation pressure.

 

# For a continuous bleed controller the speed of actuation is limited by the rate that gas can pass through the restrictive orifice. ( Limits utility of low bleed devices)

# Example: 3

- Phase Separator Control Schematic

8

# Pneumatic Controllers

 

# Pneumatic controllers convert an input signal to a pneumatic pressure output using gas pressure

 

# Input signals: Mechanical (e.g. float arm (level)), ( bordon tube (pressure)), (bi

- metal rod (temperature), etc )); Electrical (e.g. pressure transducer)

 

# Two types of pneumatic controllers:

 

# Intermittent vent (physical barrier between supply gas and output)

 

# Continuous bleed (no physical barrier)

 

# Two types of service

 

# On/Off

 

# Throttling

 

# Protection/Shut

- in Devices

– unique category

9

# Controller Description

10 

#  

# Large number of controller manufacturers and models

 

# Large number of field configurations

 

# All typically control a valve via a valve actuator

 

# From an emissions standpoint, process controllers can be classified into 4 buckets

Type of Service

On/Off Throttling Type of Controller 

## Intermittent Vents on de

- actuation with

emissions near zero between de

- actuation cycles Vents some gas pressure when valve needs to move towards closed

Continuous Bleeds continuously, rate slows

while process is “on”, but average rate is ~constant Bleeds continuously, rate varies with actuation, but average rate is ~constant

# On/Off Controller Action

– Snap acting vs. Proportional

11  

## On/Off C ontrollers can be configured to operate in a “snap

- acting” or proportional mode. These modes are often confused with the on/off and throttling services but are not 

## interchangeable with them.

 

## Snap

- acting is not the same as On/off service

 

## Proportional acting is not the same as Throttling service

 

## On/Off Snap acting (like an on/off light switch)

 

## Snap acting controllers wait until a set point is reached and then send a full supply pressure signal to the valve actuator which fully opens the valve.

 

## When the low set point is reached, a snap acting controller will fully vent the actuation volume and return 

## the valve to fully closed.

 

## On/Off Proportional (like a light switch with a dimmer)

 

## A proportional controller will send a partial pressure signal to a valve actuator as the control variable reaches the actuation set point. If the control variable continues to increase, the controller will increase the pressure signal to the valve actuator until the variable ceases increasing.

 

## When a control variable approaches the de

- actuation set point a proportional controller will vent a portion of the pressure signal from the actuator. As the control variable continues to decrease the 

## controller will decrease the vent rate until the actuator loop is fully depressured.

 

## This is different than a throttling action and can be thought of as a soft open/close action

 

## Snap acting vs Proportional action does not normally have a large impact on emissions.

 

## For an intermittent

- vent controller, a proportional action may vent somewhat less gas on de

- actuation than a snap
- acting controller in the same service.

 

## For a continuous bleed controller emissions would be essentially the same between proportional and snap
- acting settings

# Intermittent Controllers

– How they operate

12 

#  

# On/Off service

 

# Operate against a set point (s) (e.g. liquid level Hi/Lo)

 

# Send a pressure signal (gas) when a set point (e.g. liquid level) is reached (e.g. pressure
- to

- open dump valve ) to fully open valve

 

# Vent pressure (gas) to fully return valve to prior position (e.g. normally closed with spring

- for

- return dump valve)

 

# Throttling service (like cruise control in your car)

 

# Operate against a desired set point (e.g. pressure)

 

# Send a pressure signal (gas) to increase output signal (pressure to
open

– partially open valve)

 

# Vent pressure (gas) to decrease output signal (partially close valve)

 

# Hold a valve in an intermediate position

# Intermittent Controllers

– Design & Operation

13 

#  

# Typically a pilot (small 3

- way valve) operated design

Pilot Ball


## Upper Seat

Output Port

Thrust Pin Supply Port

• To actuate, the thrust pin displaces the upper ball allowing 

## supply gas to flow to the output port and valve actuator

• To de

- actuate, the thrust pin moves down, the upper ball reseats and the exhaust port is opened de

- pressuring the actuator and tubing

• In throttling service the diaphragm senses force/feedback with the output signal proportional to the mechanical force on the thrust pin. The upper ball controls supply gas and has spring assist to help seating and the lower ball vents gas. The pilot seeks to maintain equilibrium by increasing or decreasing pressure. Supply air does not flow when balanced. 

# Exhaust Port Not Shown Images courtesy of Norriseal

Diaphragm Lower Ball Assist Spring

# Intermittent Controllers

– Emissions #1

14 

#  

# Two components to emissions in normal operation

 

# Vent on de

- actuation

– Almost all emissions from an intermittent controller are from venting the internal volume from the valve actuator to return the valve to its prior position and return the control loop to an idle (non

- emitting) mode.

 

# Seepage/Leakage past pilot ball/seat

– Normally minor

 

# De

- actuation vent volume depends on:

 

# Size/volume of valve actuator & l ength of valve actuator travel

– Actuation Volume

 

# Service

• 

# On/Off

- Pressure of output gas (function of supply pressure and controller);

• 

# Throttling

– Differential pressure from adjustments to maintain set

- point

 

# Length and diameter of tubing from controller to actuator

# Intermittent Controllers

– Emissions #2

15 

#  

# Emissions from intermittent controllers are “event based”

 

# An event is an occurrence of cycling the control valve actuator

 

# Nearly zero emissions between events

 

# Gas volume emitted per unit of time depends on frequency of cycles and de

- actuation volume per cycle

 

# Total vented gas is a function of the number of times that the valve operates, not the length of time the controller is in operation

 

# Normal continuous seepage/leakage depends on:

 

# Material of balls and seats; Elastomer seats claim zero leakage

 

# Pressure of supply gas

 

# Gas gravity; Natural gas volume is ~1.3 X air volume

 

# Designed for near

- zero emissions when not de

- actuating a control loo p

# Emission Profile

16 

# On/Off Snap Acting

Throttling More frequent de

- actuations with less volume each



# Note: data is not actual; constructed for illustration purposes only Seep/Leak Rate examples Kimray : (Air) Snap: 0.407 scf

/day Throttle: 0.610 scf

/day

Norriseal : (Gas) 

# Snap: 0.2 scf

/ hr Throttle: 0.007 scf

/ hr Envirosave : 0.0 scf

/ hr

# Cycle Frequency Challenges

17 

#  

# Events do not tend to occur on a predictable schedule

 

# A pressure regulator is actuated when downstream demand changes (not predictable)

 

# A level controller is actuated when liquids accumulate (a function of the process inlet stream which is not completely predictable for a short time frame)

 

# Two identical controllers and end

- devices can have significantly 

# different emissions depending on the particular process configuration, process variable controlled and demands that change the number of cycles

 

# There is no reliable way to convert an event

- based emission into a time

- based emission rate unless the frequency of events (actuations) 

# is known or determined.

 

# Currently, there is insufficient high

- quality measurement data, coupled with the relevant process data, to support an average emission factor reflective of the population of intermittent controller types, services, and conditions.

# Continuous Bleed Controllers Design & Operation

18 

# • As the block/flapper is pushed closer to the nozzle the output signal to the actuator increases

• As the block/flapper moves away from the nozzle the output signal decreases

• Maximum emissions are controlled by the restriction orifice Typically a nozzle & flapper arrangement

# Continuous Bleed Controllers

– How they operate

19 

##  

# On/Off service

 

# Operate against a single set point (e.g. pressure)

 

# Fully close the nozzle (with flapper) and send a 100% output pressure signal (gas) when a set point (e.g. pressure) is reached

 

# Continuously bleed gas at a rate determined by critical orifice/restriction size; gas pressure; gas gravity and degree of nozzle closure by block/flapper

- except when nozzle is fully closed

 

# Throttling service

 

# Operate against a desired set point (e.g. pressure)

 

# Partially close nozzle and send a pressure signal (gas) to increase output signal (partially open valve)

 

# Partially open nozzle to decrease output signal (partially close valve)

 

# Continuously bleed gas at a rate determined by critical orifice/restriction size; gas pressure; gas gravity and degree of nozzle restriction

 

# Continuous “low bleed” <6scf/ hr ; “high bleed” >6scf/ hr (regulatory)

 

# Low bleed rates are achieved by using small diameter orifices (0.012

– 0.009 inches). These small diameters increase the risk of debris plugging and 

# significantly limit the speed of control action/response which limits the situations they can be used.

# Continuous Bleed Controllers

- Emissions

20 

#  

# Emissions in normal operation

 

# Bleeds to atmosphere continuously except for 100% output (flapper fully closes nozzle)

 

# Rate of bleed decreases during actuation and increases on de

actuation

• 

# De

- actuation exhausts the actuation volume plus returns controller to 

# normal bleed rate

 

# Bleed rate depends on

 

# Restrictive orifice size

 

# Pressure of supply gas

 

# Gravity of supply gas

 

# Lower bleed during actuation depends on degree that flapper closes nozzle vs. maximum rate through restrictive orifice

 

# Exhaust during de

- actuation balances lower rate during actuation

# Continuous Bleed Controllers Emission Profile

21



# Note: data is not actual; constructed for illustration purposes only Zero output emission rate (steady

- state) determined by restrictive orifice size, gas pressure, and gas properties

The average emission rate over time will be ~equal to the amount of gas through the restrictive orifice

# Protection/Shut

- in Devices/Controllers

22 

##  

# Not a source of material emissions

 

# Used to protect against abnormal 

# conditions

 

# e.g. Overpressure/under

- pressure (Hi/Lo pilots); Hi/Hi liquid level in tanks/vessels;
 

# Typically do not emit unless abnormal condition occurs

 

# Example: Hi/Lo pressure pilot

 

# Normally operates at 100% output holding a “fail closed” valve open
 

# If overpressure or under

- pressure occurs then output bleeds to 

# atmosphere and valve closes

 

# Not controlling a “process variable”

 

# Seldom open and emit

Image and information courtesy of FISHER

# Intermittent or Continuous

– Choice?

23 

#  

# Although intermittent vent controllers are the lowest emitting selection in most applications, due to not bleeding gas between 

# actuation cycles, in certain cases a low bleed continuous type controller may be a lower emission selection.

 

# This is only the case where “over

- shooting” the high parameter set point can be safely and operationally tolerated.

 

# Each application must be analysed to determine whether a low

bleed continuous controller is a better emission choice and whether the application can tolerate the “overshoot” inherent in the slow response time of a low bleed continuous controller.

 

# All of the different types and services of controllers have 

# scenarios where they are the lowest emission options and operators need the flexibility to deploy the appropriate technology while taking into account the overriding drivers of operational and process safety, stability, and reliability.

# Intermittent or Continuous

– Temp. Control Example

24  

## Comparing a typical temperature control loop using 

## an intermittent controller to a low

- bleed continuous controller the intermittent is the lower emission choice

 

## Temperature control loops sense temperature and control fuel flow to a heater to turn it on or off. Very common and basically every field heater (dehydrator, tank heater, heater

- treater , production 

## unit, etc.) has a temperature control loop. Also used to control air coolers and other processes

 

## Since the fuel valve is small and in low pressure service, the actuator used to move the valve is equally small volume. For instance an actuator for a fuel control valve is about 1.1 cubic inch volume which will yield emissions ~100 times smaller per 

## cycle than the 110 cubic inch level controller example used in background slide.



# • It would require ~378 cycles/ hr (or about one cycle every 9.5 seconds) to reach hourly emissions of 6 scf

/ hr (regulatory low

- bleed continuous). This is not going to

occur.

• In this application, an intermittent type controller is the obvious low emission choice and fits the process control demand very well. 

# Image Courtesy of Kimray

# Emission Factors and Population Counts

25 

##  

# Subpart W (GHGRP) emission data for pneumatic controllers

 

# The current emission factor (EF) for intermittent controllers is 

# almost certainly an order of magnitude too high.

 

# Given how intermittent controllers and continuous controllers operate this is almost certainly not valid across the spectrum of controllers and services.

 

# For 2011 and 2012 the “counts” of pneumatic controllers in each category were estimated rather than counted. The 2013 emission data requires an actual count.

 

# National inventory emission data for pneumatic controllers

 

# The National Inventory uses a single estimate of the number of pneumatic devices and a single emission factor to calculate a potential methane emission for pneumatic controllers (called devices).

 

# Reductions in emissions attributable to Natural Gas Star voluntary taken and reported actions and regulatory required reductions (if required) are subtracted 

# from these potential emission estimates.

 

# It is not clear what the genesis is for the pneumatic controller population estimate or emission factor.

# Known Studies/Projects

26  

# UT Phase 1 Study sampled 305 controllers.

 

# UT Phase 2 study, with improved methodologies, is underway and due to be 

# published later this year

 

# GRI/EPA 1996 study

 

# Canadian Association of Petroleum Producers published pneumatic device emission factors (CAPP, 2002 and CAPP, 2003)

 

# Recent British Columbia study ( Prasino ) published

 

# Pioneer Natural Resources is planning to publish the results of a measurement study in the near future.

Important to remember the following:

 

# All studies need to be QA/ QC’d to judge whether the type of controller and service was correctly identified

 

# All studies need to be QA/ QC’d to judge whether the appropriate methodologies, sampling populations, and sampling times were used to adequately measure emissions from controllers

 

# All studies need to be QA/ QC’d to judge whether the data collected was appropriately analyzed and attributed

# Conclusions

27 

##  

# Operators need the flexibility to deploy the appropriate technology while taking 

# into account the overriding drivers of operational and process safety, stability, and reliability.

 

# Different types and services of controllers have scenarios where they are the lowest emission options

 

# Intermittent controllers will be the low emission choice in most applications

 

# In a small number of cases, where the process can tolerate control delay , low

- bleed continuous controllers may be the low emission choice.

 

# The current views regarding the emission rate from intermittent controllers are almost certainly not correct.

 

# Although measurement studies are being done and published, care needs to 

# be taken to QA/QC the results before simply accepting them. Sufficient good quality study and measurement data is not yet available to characterize the population of controllers and applications.

 

# Due to the methodologies and emission factors the GHGRP and National Inventory data for pneumatic controllers needs to be carefully understood before using it for either population counts of different types of controllers or 

# emissions estimates.

# Background

28

# Intermittent Controllers

– Emissions Example

29  

# Typical example only. In practice the parameters and actuations per unit of time will vary.

 

# The seepage/leakage of gas (minor) while in the idle mode is additional to the volume shown

 

# In 2012 the average US gas well produced 1.3 bbls /day of 

# oil/condensate (Source: DI)

 

# In 2012 the average US oil well produced 9.4 bbls /day of oil (Source: DI)

 

# In 2012 the average US well produced 5.6 bbls /day of oil (Source: Basic 

# Petroleum Databook

)

 

# At 25 psig and 5.6 bbls /day the gas emitted for an average intermittent oil dump controller would be between 1.4 SCF/ hr and 0.4 SCF/ hr ; The GHGRP factor is 13.5 SCF/ hr

# Intermittent Controllers

– Emission Variability

30 

#  

# What can go wrong to increase emissions

 

# Debris/deposits on vent pilot plug: Material on the vent pilot can allow the controller to exhaust gas during the activation cycle.

 

# Debris/deposits on the supply pilot plug. Material on the supply pilot can cause the introduction of gas while the vent is open

.  

# Broken spring (when equipped) The spring holds the supply pilot

plug on its seat and without this spring the controller has similar emissions as a continuous bleed controller. This particular malfunction generally calls attention to itself quickly because the end

device being actuated doesn’t operate.

 

# Broken diaphragm (where installed). Many intermittent vent 

# controllers have diaphragms for various reasons. A detailed analysis of a particular device would be required to determine the results of the failure on the emitted gas.

 

# Other

- leaking tubing/tubing

- fittings, etc (equipment leaks not controller emissions)

# Continuous Bleed Controller

- Schematic

31 

# Schematic Courtesy of FISHER

# Continuous Bleed Controllers Emission Variability

32 

#  

# What operational factors impact emissions rate

 

# Supply Gas Pressure and Gravity

 

# What can go wrong to change emissions

 

# The orifice can partially plug which lowers bleed rate

 

# A continuous controller that will still operate an end device has its emissions capped by the restriction orifice

 

# A leak within the controller upstream of the restriction orifice can increase total emissions.

 

# Other (e.g. leaking tubing/tubing

- fittings, o - rings )