# Presentation: 080328

## PART 75SPAN & RANGE 

- Manuel J Oliva
- Clean Air Markets Division
- U.S. Environmental Protection Agency

**Notes:**
Sam, Sarah suggested this would be a good presentation for the Division.

## Instrument Span & Range

_**Question**_**:**
**Aren’t Span and Range the Same?**

_**Answer**_**:**
**Under Part 75 Span and Range can **
**be equal in value, but are not the same.**
**However, the range value must always **
**be ******** the span value.**

## Span & Range Defined

**Range:  Instrument Full-Scale **
**“****What the instrument is set up to measure”**
**Span:  Highest concentration or flow rate that a monitor component is required to be capable of measuring.  (§72.2)**
**“****What the rules require to be measured, Quality assured portion of the range”**
**“****Rules of the Game” - Appendix A, §2**
**Affected Parameters: SO****2****, NO****X****, CO****2****, O****2**** and Flow Rate**

**Notes:**
1. Kenon was gracious enough to provide initial allocation data.

## Example of Span & Range

**Case 1:  Span = Range**

**Case 2:  Span < Range**

**0 ppm**

**500 ppm**

**Span**

**0 ppm**

**500 ppm**

**Span**

**400 ppm**

## Range Settings

**Select a range so majority of readings obtained during typical unit operation are kept within 20 to 80 percent of instrument full scale range (to extent practicable)**
**Importance:  Avoid signal to noise problems at low end of range, and inaccuracies or exceedance at high end of range.  Accuracy of measured values is objective**
**Exceptions:  (SO****2****) low sulfur fuel, (SO****2****/NO****X****) emission controls and two span values, (SO****2****/NO****X****) dual span unit**

**Notes:**
1. Cement kilns in NY provided with 8,085 tons.

## Span Settings

**Span Settings:  Dependant on pollutant **
**Importance:  Concentrations of calibration gases used for daily QA and linearity checks, as well as daily control limits for gas and flow monitors are expressed as % span**
**“****Simple” rule of thumb, range and span values  can be equal**

## Setting the Span - SO2 Monitors

**Define MPC**
**Maximum Potential Concentration (MPC) is based on analysis of highest sulfur fuel burned (max % sulfur and min GCV, or max % sulfur/GCV ratio) or historical CEMS data**
**Define MEC if Appropriate**
**Maximum Expected Concentration (MEC) is based on expected % SO****2**** removal, fuel analysis or historical CEMS data**
**MEC is appropriate for units with SO****2**** controls or both high-sulfur and low-sulfur fuels, including blends**

## Setting the Span - SO2 Monitors(Continued)

**High Span* = MPC × 1.00 to MPC × 1.25**
**Rounded to nearest 100 ppm (or 10 ppm if SO****2**** ******** 500 ppm)**
**Full Scale Range ******** Span Value**
**Low Span = 1.00 × MEC to 1.25 × MEC  (If Required)**
**Rounded to nearest 10 ppm (or 100 ppm as appropriate)**
**Low Span Required if MEC < 20% of High Range (Controls or low sulfur fuels)**
**Use the Low Span when SO****2**** readings are expected to be below 20% of High Full-Scale Range**

***  If unit has SO****2**** control it  can forgo high span and report a “default high range value”**
**    ****of 200% of MPC during hours when low range is exceeded.  Full scale of low range **
**    ****cannot exceed five times MEC.**

## Setting the Span - NOX Monitors

- Setting the Span - NOX Monitors

**Define MPC**
**Maximum Potential Concentration (MPC) is based on the fuel (or blend) that gives highest uncontrolled NO****X**** emissions.  Options include:  fuel based defaults, boiler type defaults, NO****X**** emission test results, historical CEMS data or manufacturer data**
**Define MEC if Appropriate**
**Maximum Expected Concentration (MEC) is based on expected NO****X**** removal efficiency, NO****X**** concentration testing, historical CEMS data, or permit limit**
**Determine a separate MEC for each fuel (or blend)**

## Setting the Span - NOX Monitors(Continued)

**High Span* = MPC × 1.00 to MPC × 1.25**
**Rounded to nearest 100 ppm (or 10 ppm if NO****X**** ******** 500 ppm)**
**Full Scale Range ******** Span Value**
**Low Span = 1.00 × MEC to 1.25 × MEC  (If Required)**
**Rounded to nearest 10 ppm (or 100 ppm as appropriate)**
**Low Span Required if MEC < 20% of High Range (If more than one MEC, use MEC closest to 20% of High Range)**
**Use the Low Span when NO****X**** readings are expected to be below 20% of High Full-Scale Range**

***  If unit has Add-On NO****X**** control it can forgo high span and report a “default high**
**    ****range value” of 200% of MPC during hours when low range is exceeded.  Full scale **
**    ****of low range cannot exceed five times MEC.**

## Setting the Span - CO2 & O2 Monitors

**Define MPC for CO****2**
**CO****2**** Maximum Potential Concentration (MPC) is 14% CO****2**** (boilers) or 6% CO****2**** (turbines) default values, or determine based on historical CEMS data**
**MPC is used only for substitute data purposes**
**Define Minimum Potential Concentration for O****2**
**O****2**** Minimum Potential Concentration is determine based on historical CEMS data**
**Minimum Potential Concentration is used only for substitute data purposes for units using flow monitors and O2 diluent monitors to determine Heat Input**

**Notes:**
Bullet 1 - Allocations are initially set to “cap” emissions to a certain level (I.e. 20% reduction in emissions).  Sources will generally reduce emissions under cap by controls or operational changes.  It is expected therefore that sources would be sellers in a mature program.

Bullet 2 - 3% reduction required not counting sources with zero emissions.  27% reduction assuming sources with zero emissions emitted at their allowance levels.  5% surplus with cement kilns and not subtracting out zero emissions sources.

## Setting the Span - CO2 & O2 Monitors  (Continued)

**O****2**** Span**
**Between 15% and 25% O****2**
**Below 15% O****2**** allowed with technical justification**
**CO****2**** Span**
**Between 14% and 20%  CO****2**** (for boilers)**
**Between 6% and 14%  CO****2**** (for turbines)**

## Setting the Span - Flow Monitors

**Define MPV**
**Maximum Potential Velocity (MPV) is based on equations in Appendix A (F-factors, heat input, diluent concentration and moisture concentration), or Highest values from traverse testing (Ref. Method 2)**
**Define MPF**
**Maximum Potential Flow Rate (MPF) is equal to MPV × stack area**
**Used only for substitute data purposes**

## Setting the Span - Flow Monitors(Continued)

**Calibration Span = MPV* × 1.00 to MPV* × 1.25**
**Rounded up to at least two significant figures**
**Flow Rate Span = 1.00 × MPF to 1.25 × MPF **
**Expressed in the units used for Part 75 reporting (scfh) **
**Rounded to nearest 1000 scfh**

***  MPV must be converted to the units of daily calibration **
**    ****(e.g. kscfm, inches of H****2****0, etc.)**

## Adjustments to Span and Range

**Perform at least annual evaluation of the span and range settings (Appendix A, §2.1.2.5)**

**DAHS**

## Summary Process Diagram

**RANGE**

**SPAN VALUE**

**20% to 80%**
**of Full Scale Range**
**(Majority of Data)**

**Single Span**
**(or High Span)**

**Based on maximum potential **
**concentration or flow rate**

**Low Span**
**(if Required)**

**Based on maximum expected concentration**

****** ****??**

## Optimal Range