P.1 

OAR Box 1802 

Prepped by Charmelle Mathews 

Document Number: 

79) IV-E-73 

Docket Number: 

A-90-37 

Printed 11/4/200811:58:00 AM Sheet 79 of 117 
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Routine Turbine Overhaul 

Presented to: 

U.S. Environmental Protection Agency 

Office of Air Quality Planning and Standards 

Presented by: 

Member Companies of the 

Interstate Natural Gas Association of America (INGAA) 

Durham, NC 

November 5, 2001 
Topics 

Issue Summary 

Recent History of the Turbine Maintenance Issue 

U.S. Natural Gas Transmission System and Turbine Horsepower 

Turbine Overhaul Exchange 

Overhaul Exchange is Routine Maintenance under NSPS and 

NSR 

Impacts if Overhaul Exchange becomes a modification 

EPA Concern with "Life Extension" 

Recommendations 
Issue Summary 

The U.S. natural gas pipeline system relies on light-industrial and 

aero-derivative gas fired turbines to power gas compressors 

For the past 30+ years, the routine maintenance of light industrial 

and aero-derivative combustion turbines has involved exchange of 

turbine components in a central overhaul facility 

Overhaul exchange does not increase capacity or emissions 

Recently, some EPA Regions and state air agencies have taken the 

position that exchange of overhauled turbine components requires 

re-permitting ^^v^^w ^ 

The efficiency and reliability of interstate natural gas pipelines in 

delivering energy resources to consumers, commercial facilities and 

electric generating plants will be adversely affected if each turbine 

overhaul exchange triggers re-permitting T^TTT- ~? 
Recent History of the 

Turbine Maintenance Issue (1) 

March 1, 1990 Letter from GE to Region 9 

"As discussed... engine change-out should not be considered an 'upgrade' situation possibly subject to 

New Source Review." 

October 8, 1998 Letter on NSR from AGA/INGAA to Docket No.A-90-37 

"We urge EPA to clarify that... 'routine changes would include natural gas transmission turbine 

component changes or temporary replacement of turbines for the purposes of maintenance of the original 

engine." 

March 24, 1999 Letter from Solar Turbines Inc. to OAQPS 

"...the component replacement does nothing to increase the operating life of the gas turbine beyond that 

of a properly maintained gas turbine that never utilized replacement components 

September 9, 1999 Letter from Washington Department of Ecology to Region 10 

Re: Gas Fired Turbine Engine Replacement at Natural Gas Pipeline Compressor Stations 

"Ecology desires a solution that does not require a PSD permit to be rescinded and reissued every four 

years for each compressor station." 
Recent History of the 

Turbine Maintenance Issue (2) 

November 9, 1999 Meeting of INGAA Member Companies with OAQPS 

Recommendation: "Use of replacement gas producer and/or power turbine components as part of the 

overhaul process also is exempt from the definition of "modification" under PSD or NSPS 

December 3, 1999 Letter from INGAA to OAQPS 

"We are concerned that the Agency is attempting to merge its policy concerns about the useful life of gas 

turbines with the Agency's technical findings concerning routine maintenance..." 

July 27, 2001 Letter from INGAA on NSR 90 Day Review 

"Efficient Overhaul Procedures are Critical to the operation of Gas Pipelines." 

August 2, 2001 Presentation to NSR Inter-Agency Task Force 

Recommendation: "Determine that 'routine maintenance' for light industrial and aeroderivative turbines 

includes use of central overhaul facilities and component exchanges." 

October 25, 2001 Tour by EPA Representatives of Solar Overhaul Facility and 

Mitchell Energy Plant 

"Domestic fleet - 5,800 engines...Approximately 600 overhauls per year executed by exchange." 
U.S. Natural Gas Transmission System 

Natural gas is moved from source areas to consumers by a 

national system of pipelines 

» 278,000 miles of transmission lines, in all lower 48 states 

» 22.8 TCF per year in 2000 

» Compressor stations are located approximately every 70 miles 

along pipelines 

Interstate pipelines are regulated by FERC 

» Each compressor station must comply with FERC certificated 

horsepower P ^ -^-, 

Demand is expected to reach 30+ TCF in 2015 * u h< 

System is near capacity in West, Northeast, and Southeast 

12.3 BCF/day capacity 

» In 1999 and 2000, 60 pipeline construction projects have added ' /s j ^ 

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V 
Turbines Provide Horsepower for the 

U.S. Gas Transmission System 

More than 1,100 natural gas-fired turbines at gas transmission 

compressor stations provide 40+% of horsepower* ^ k^\* ^ 

Most are simple-cycle, aero-derivative or light industrial turbines \A yz-, 

• Average size is approximately 6,300 horsepower (4.7 MW), \ T^O 

Median size is approximately 4,400 horsepower (3.3 MW) / } ^ s k\ 

• Principal manufacturers: $<wl52L(L 

» Solar Turbines (56%), General Electric (25%),

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» Also Rolls Royce, Allison, Dresser-Clark, Westinghouse 

• Routine, periodic overhaul is required to provide safe & reliable turbine 

operation and maintain permitted emission limits 

» Loss of turbine availability will result in curtailment of natural gas 

supplies in critical markets 

'Based on 1998 survey of 57 of 165 gas transmission companies 
Turbine Exchange Overhauls 

The design time between overhauls (TBO) for most light industrial 

and aero-derivative turbines is about 30,000 hours, 3 to 4 years 

Unlike larger turbines that cannot be truck-transported, light 

industrial and aero-derivative turbines are designed to be 

overhauled at specialized central facilities 

Currently, about six weeks' loss of turbine availability is avoided by 

installation of identical overhauled components when turbine 

components are removed and sent to the overhaul facility 

The exchanged turbine has the same model number, capacity 

rating, operating characteristics and emissions limits as the replaced 

turbine 
Example: Solar Turbines (1) 

5,800 Solar Turbine installations in U.S. 

» Gas compression service >1,000 units 

All Solar turbines must be removed and sent for overhaul at a 

specialized facility; units cannot be overhauled in the field 

» Overhaul results in return to Original Operating Specifications 

» 600 overhauls by exchange in 2000, 320 fromXTS" 

» 80% of overhauls are exchange program, others are "customer propertyin-shop" U A *U~ ^ J ^

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Overhaul Exchange Results in:

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» Minimized down time (~2 days v. 6 weeks) 

» Use of highly specialized personnel and equipment 

» Rigorous inspection specifications and QA 

» Vertical assembly/disassembly 

» Verification of performance and emissions in test cells 
Example: Solar Turbines (2) 

"Uprates" occur infrequently with overhaul 

» May occur at time of overhaul if customer buys it 

» Requires uprate to entire turbomachinery system 

» Subject to contractual terms, increased cost 

» Model number and capacity rating change 

» Uprates trigger permit review 

"Upgrades" may occur during overhaul 

Solar does not support historical parts inventory 

Replacement parts meet current production standards 

Same fit/form/function 

Unit retains model rating operating specifications 

Emissions are the same 

£~kr<^<H-
Overhaul Exchange is Routine 

Maintenance Under NSPS and NSR (1) 

For the past 30 years, in almost all cases owner/operators and 

air agencies have regarded overhaul exchange as routine 

maintenance 

The Turbine NSPS Support Document states that replacements 

that occur at overhaul will not be considered a modification: 

"The following physical or operational changes will not be considered as 

modifications to existing gas turbines: 

a. Changes determined to be routine maintenance, repair, or 

replacement in kind. This will include repair or replacement of stator 

blades, turbine nozzles, turbine buckets, fuel nozzles, combustion 

chambers, seals, and shaft packings. (Vol. I, page 5-6) 

The NSPS Support Document notes that, because of these 

exemptions, the "impact of the modification provision on existing 

gas turbines should be very slight." (Vol. I, page 5-6) 
Overhaul Exchange is Routine 

Maintenance Under NSPS and NSR (2) 

NSPS regulations 60.14(e)(1) state that the Administrator shall 

determine which activities are "routine" for a particular source category 

» At the time EPA issued the NSPS for turbines, EPA declined to include a more 

specific finding about turbine maintenance and argued in the NSPS Support 

Document that the general NSPS definition was sufficient (Vol. II, pages 2-9 through 

2-11) 

NSR and NSPS have similar exemptions for routine maintenance 

Exchange overhaul meets EPA tests for "routine" for the purposes of 

NSR: 

» Nature, Extent, Purpose, Frequency, Cost 

» It is industry practice that a typical facility will frequently 

conduct overhaul exchange on a routine basis 
Overhaul Exchange is Well Below 

Reconstruction Threshold 

50% Threshold defined under NSPS regulations 

40 CFR 60.15(b): "Reconstruction means the replacement of components of an 

existing facility to such an extent that: (1) the fixed capital cost of the new components 

exceeds 50 percent of the fixed capital cost that would be required to construct a 

comparable entirely new facility..." 

Turbine NSPS support document states: 

Although substantial portions of turbines are replaced during normal overhauls, 

"such routine maintenance should be exempted from the regulatory consequences of 

becoming a reconstructed turbine, subject to the '50 percent rule' discussed in 5.1.2." 

(Vol. I, Page 5-6) 

Overhaul costs are typically below 25% of the total cost 

of a new turbine installation 
Impacts if Overhaul Exchange 

Becomes a Modification 

States and Regions would have to address a large 

increase in the number of permit actions 

Decrease in turbine availability due to permitting and 

"customer-property-in-shop" overhauls 

Decreased turbine availability will result in 

» curtailment of natural gas supply 

» increased use of reciprocating IC engines where reserve 

horsepower is available 

Example: single turbine boost station for dedicated line to 

an electric utility 

» overhaul would cause curtailment, shift to back-up fuel if 

available 
Example: El Paso Compressor Stations 

• Region 9 actions on Part 71 permits in Indian lands 

indicate that overhaul exchange requires test for PSD 

significance 

• Navajo Station 

» Solar Taurus unavailable for 74 days, April 29-July 12, 2001 

» 60 MMSCF/day impact on system capacity 

» Reciprocating IC engines used to make up horsepower 

• Window Rock Station 

» Solar Centaur unavailable for 57 days, July 18 - Sept. 13, 2000 

» 57 MMSCF/day impact on system capacity 

» System capacity decreased 
EPA Concern With "Life Extension" 

There is no increase in turbine lifetime with exchange 

compared to customer-property-in-shop overhaul 

» Components are overhauled to the original operating specification 

Turbines in natural gas transmission are replaced 

because of economic factors, not mechanical 

deterioration 

» Because more efficient turbines are available 

» Because cost of operation and overhaul increases 

» Because pipeline system requires new horsepower solution 

Pipelines continually evaluate horsepower replacement 

» In the past 25 years El Paso has replaced 89 units, 150,000 hp, at 10 V° ^ *y 

stations, including 13 turbines \sv 

» Last year, El Paso replaced 69 units, 133,000 hp, including 5 GE Frame 

3 turbines 

V 
Recommendation 

EPA's air regulations and guidance should facilitate, not 

discourage, overhaul exchange as a highly efficient system for 

maximizing turbine availability while safeguarding the operating 

performance, emissions, and reliability of turbines 

EPA should issue a determination under NSPS GG that "routine 

maintenance" for light industrial and aero-derivative turbines 

includes overhaul exchange 

EPA should extend the NSPS routine maintenance definition to 

NSR for gas pipeline sources 

EPA's policy objective to define an endpoint for a turbine's useful 

life should be addressed in the larger context of the agency's 

reform of the NSR regulations 

The Agency's finding regarding routine maintenance for turbines 

should be based on fact-finding regarding routine practices, and 

not a policy prescription 
NSR Applicability at Gas 

Transmission Stations 

Scoping Meeting with EPA and the Natural 

Gas Transmission Industry 

November 5. 2001 

Purpose: To discuss options with industry 

representatives on how NSR should apply 

to periodic turbine overhauls at gas 

compressor stations. 
What's at issue? 

Certain maintenance practices at gas transmission 

stations could be considered a "physical change/5 or a 

life extension project, and subject to New Source 

Review. 

The natural gas delivery industry does not want their 

maintenance projects delayed by NSR permitting, and 

believes their periodic overhauls should be exempt 

from NSR by way of being "routine." 
What's at issue? (cont.) 

In the absence of specific EPA guidance, 

overhauls at gas pumping stations have typically 

been treated as routine; however, recently this 

approach has been challenged in a few cases. 

Over the summer, industry members raised this as 

an example of EPA delays in issuing NSR 

guidance, and INGAA later met with 90-day 

Review Team to spell out their concerns. 

INGAA wants an "routine" exclusion from NSR, 

barring uprates, and regulatory certainty. 
Industry Description 

Natural gas-fired turbines used at compressor stations 

to move natural gas around the country 

- Turbine sizes: 2K to 20K hp (1 to 15 MW) 

- 1 to 4 turbines per station 

- 1400 turbines in service in US 

- Simple cycle, aeroderivative models; some lightweight 

industrial turbines (25-30% efficient) 

Stations also have backup gas-fired reciprocating 

engines, emitting twice as much as same sized turbines 

FERC requires uninterrupted service at interstate 

pumping stations 

Stations are located in both Attainment and NA areas 
Current Maintenance Options 

Overhauls are done periodically to replace worn parts on 

turbines. 

Planned overhauls are preferred over waiting until 

sustaining significant equipment damage, and they 

- Restore lost output, and 

- Restore fuel efficiency. 

Overhauls can be performed: 

- On site (done mainly w/larger turbines, &for minor repairs) 

- In shop (repaired/tested in shop for -30 days, then returned) 

- Through exchange 
Exchange Practices 

Exchange program has existed since 1960's. 

Gas producer and power turbine sections ("hot side") 

designed for modular replacement. 

Swapped out every 3OK hours (4 yrs), or sooner/later 

depending on startups and intermediate maintenance. 

Essentially a new turbine is provided at each exchange 

Downtime savings is the major incentive. 

> 24-36 hr (exchange) vs 30 days (onsite/in-shop) 

Overhauls cost 6% to 17% of turbine "package" 

replacement. 

> Roughly $200K for small units and $1M for larger turbines 

> About 40 to 50% of turbine replacement cost 

Not intended to increase rated efficiency or output. 
Emissions/Controls 

Turbine NSPS (c.1979) requires 150 ppm NOx. 

Older turbines (installed in 70's and 80's) operate at 

75-150 ppm. 

SMALL EXAMPLE: Solar Centaur (3.3MW), gas-fired 

• Uncontrolled @ 130ppm: 88 tpy NOx 

• With Water injection @ 42 ppm: 30 tpy NOx 

• Cost effectiveness of WI: $2,000/ton 

(NOTE: based on site visit, water controls are rarely installed on 

Solar 9s units Cost ofDLN "Solonox " Conversion ?) 

LARGE EXAMPLE: GE LM 1600 (13MW), gas-fired 

• Uncontrolled @ 133ppm: 296 tpy NOx 

• With Steam injection @ 25 ppm: 51 tpy NOx 

• Cost effectiveness of SI: $l,500/ton 
Past EPA Decisions 

> Gas Turbine NSPS Support Document (1977) 

> Suggests periodic overhauls are routine for the purposes 

of40CFRPart60 

> "... substantial portions of a turbine may be replaced as a 

matter of routine maintenance during normal overhauls. " 

> Alludes to "useful lifetime" of 30 years. 

> Region 2 Letter to New Jersey DEP (1999) 

> Provides plan to track serial numbers of pool of 

overhauled turbines, while subjecting new & uprated 

units to PSD/NSR. 
Key EPA Issues 

PALs may be problem if SIP jurisdiction does not allow. 

How can we justify a source getting a new turbine every 4 

years and not considering it a modification? 

Gas transmission industry is demand driven. Seldom are 

there ACTUAL emission increases following an overhaul. 

Concerns with "routine" determination may run counter to 

opinions on enforcement initiatives and other cases. 

- Where do these repeated overhauls cross the line into 

life-extension projects? 

How would this decision impact other industries? We 

learned on our site visit that the turbine exchange program 

is not limited to the gas pumping industry. 
Key EPA Issues (cont.) 

With the majority of the fleet being uncontrolled, requiring 

NSR on grandfathered units could yield 5 OK to 100K tons 

of NOx reduction. 

Should a 10-15% maintenance expediture every 4 years 

qualify as "routine"?... WEPCO directs us to consider 

Cost, Frequency, Nature and Extent when determining 

routine. 

Can we track non-routine repairs if performed via 

exchange? How can we be sure that power "uprates" and 

efficiency boosts are not performed during swap-outs? 

Should we treat repairs made on site differently than if 

performed through exchange? 
Possible Options 

1) Treat each overhaul as a physical change. 

2) Track overhauls at a given site and apply NSR once 

the "useful lifetime" is reached. 

3) Option #1, but provide Actual-to-Actual emissions 

test, plus demand growth. 

4) Explore use of PALs and State/local agency 

intervention where air quality is jeopardized. 

5) Set $/hp (per unit, per year) maintenance cap. All 

maintenance beneath cap is routine, all above would 

be evaluated. Years could be averaged (<5 yrs max?) 
Possible Options (cont.) 

6) List serial numbers for compressor units owned 

by a company. Swap-outs do not trigger NSR if 

unit comes from within pool. (Region 2 

approach) 

7) Treat overhauls as "Routine" as long as do not 

result in power uprates. Uprates are a physical 

change and NSR is triggered where there is an 

actual emissions increase. 

8) Provide routine determination for all nonuprated maintenance, but phase in NSR for older 

fleet to get predetermined control (25-42 ppm) 

via sector based rule. 

\ 
Next Steps 

TODAY: 

List pros/cons with each listed Option, and any 

other option raised today. 

Select 3 most viable options. 

Commit to reconvening group. 

NEXT 4 WEEKS: 

Study further each selected option to evaluate 

workability. 

Establish data gathering needs; determine 

deadlines. 

- The NEPD/90-day NSR Study report will list 

this as a prioritized initiative. 
Next Steps (cont.) 

NEXT 3 MONTHS: 

- Select option. 

- Put out guidance on selection. 

NEXT 12 MONTHS: 

- Formalize through rulemaking?