# DEPARTMENT OF

ENVIRONMENTAL CONSERVATION

Performance Audits for COMS

Adopted by Reference in 18 AAC 50.030

April 1, 2002

Revised August 20, 2008Performance Audits for COMS April 1, 2002 Revised August 20, 2008 1 

### Alaska Department of En vironmental Conservation

Performance Audi ts for COMS

Performance audits. The following elements shall be included in performance audits for Continuous Opacity Mon itoring Systems (COMS), unless the department gi ves written approval for unit-specific audit procedures.

1 Optical Alignment Assessment. The status of the optical alignment of the monitor components shall be checked and recorded according to the proced ures specified by the monitor manufacturer. Realign as necessary.

2 Zero and Upscale Response Assessment. The zero and upscale response errors shall be determined and recorded according to the calibra tion drift procedures of 8.1(4)(i) and (ii) in 40 C.F.R. 60, Appendix B, Pe rformance Specification 1 (PS-1), adopted by reference in 18 AAC 50.040(a). The error is defined as th e difference (in % opacity) between the correct

value and the observed valu e for the zero and high-le vel calibration checks.

3 Zero Compensation Assessment. The value of the zero compen sation applied at the time of the audit shall be calculated as equivalent op acity, corrected to stack exit conditions as necessary, according to the procedures specified by the manufacturer. Re cord the compensation applied to the effluent reco rded by the monitor system.

4 Calibration Error Check. Conduct a three-point calibration error test using three calibration attenuators that produc e outlet pathlength corrected, singl e-pass opacity values shown in ASTM D 6216-98, section 7.5, adopted by referen ce in 18 AAC 50.035(c). If the applicable limit is less than 10 percent opacity, use at tenuators as describe d in ASTM D 6216-98, section 7.5 for applicable standards of 10 to 19 percent opacity. Confirm the external audit device produces the proper zero value on the CO MS data recorder. Separately, insert each calibration attenuator (low, mi d, and high-level) into the ex ternal audit device. While inserting each attenuator, (1) ensure that the entire light beam passes through the attenuator; (2) minimize interference from reflected light; and (3) leave the attenu ator in place for at least two times the shortest recording interval on the COMS data reco rder. Make a total of five nonconsecutive readings fo r each attenuator. At the end of the te st, correlate each

attenuator insertion to the co rresponding value from the data recorder. Subtract the singlepass calibration attenuator values corrected to the stack exit conditions from the COMS responses. Calculate the arithmetic mean diff erence, standard deviation, and confidence

coefficient of the five measurements valu e using equations 1-3, 1-4, and 1-5 of PS-1.

Calculate the calibration error as the sum of the absolute value of the mean difference and the 95 percent confidence coefficient for each of the th ree test attenuators using equation 1- 6 of PS-1. Report the calibration error test resu lts for each of th e three attenuators.Performance Audits for COMS April 1, 2002 Revised August 20, 2008 2 5 Zero Alignment Assessment. Compare the COMS simulated zero to the actual clear path zero of the installation. The assessment may be c onducted in conjunction wi th, but prior to, other performance audit elements.

A. Primary Zero A lignment Method. The primary zero alignmen t shall be performed under clear path conditions. This may be accomplished if the proc ess is not operating and the monitor pathlength is free of particulate ma tter or the monitor may be removed from its installation and set up under clear path conditi ons. The absence of particulate matter shall be demonstrated prior to conduc ting the test at the installed site. No adjustment to the

monitor is allowed other than the establishment of the proper monitor pathlength and correct optical alignment of the monitor components. Record the monitor resp onse to a clear path

condition and to the mon itor's simulated zero condition as pe rcent opacity corrected to stack exit conditions as necessary. Fo r monitors with automatic zero compensation, disconnect or disable the zero compensation mechanism or r ecord the amount of corr ection applied to the monitor's simulated zero condition. The response difference in percent opacity to the clear path and simulated ze ro conditions shall be reco rded as the zero alignm ent error. Adjust the

monitor's simulated zero device to provide the same response as the cl ear path condition. Restore the COMS to its operating mode.

B. Alternate Zero Alignment Method. Monitors capable of allo wing the installation of an external, removable zero-jig ma y use the equipment for an alternative zero alignment provided that the zero-jig settin g is established for the monito r pathlength and recorded for the specific COMS by comparison of the COMS responses to the installed zero-jig and to the clear path condition. The zero-jig is shown to be capable of produc ing a consistent zero response when it is repe atedly (i.e., three consecutive in stallations and removals prior to conducting the final zero alig nment check) installed on th e COMS. The zero-jig setting shall be permanently set at the time of the initi al COMS zeroing to the clear path zero value and protected when not in use to ensure that the setting equivale nt to zero opacity does not change. The zero- jig setting shall be chec ked and recorded prior to initiating the zero alignment. Emission unit owners and operat ors that employ a zero-jig shall perform a primary zero alignment audit once every three years.

C. Failure Criteria for Zero Alignment. The zero alignment is acceptable if the error at the simulated zero check is less or equal than 2% opacity prior to adjustment (i.e. if the zero alignment error is 0% the analyzer does no t need servicing solely based on this test).