W-1 W.0 EVALUATI ON OF RCA DATA
W.1 WHAT IS THE PURPOSE OF AN RCA? A response correlation audit (RCA) is a periodic evalua tion of PM CEMS responses to determine if the responses are consistent with the correlation equa tion developed for the PM CEMS. RCAs are used to evaluate the long-ter m stability of the correla

tion. If the PM CEMS satisfies the per for man ce c rit eri a fo r an RC A, i t ca n be ass um ed t hat th e co rre lat io n eq uat io n i s s ti ll val id . If the PM CEMS fails an RCA, that indicates that the correlation cannot be used to provide an accurate measurement of PM emissions. RCA failures can r esult from changes in emission characteristics or change s in the operation of the emission source, control device, or PM CEMS. In the case of a

n RCA failure, the correlation equation must be revised. Other c orrective actions ma y al so be ne ce ss ar y.
W.2 HOW DO I PERFORM AN RCA? The procedure for conducting an RCA is the same as the procedure used to conduct an initial correl ation test

for a PM CEMS. The onl y di ffere nce betw een an RCA

and a co rrelati on test is that a minimum of 12 test runs must be performed for an RCA, instead of the 15 runs required for the correlation test. Refer to Sections 10.3(8) and 10.4(5) of Procedure 2 for the gene ral procedu res and p erforma

nce cri teria for RCAs. For details on the tes ting re quireme

nts for RCA s, refer to Section 8.6 of PS-11, which specifies the procedur es for performing corre lation tests. The main requirements for conducting an RCA include

# Recording PM CEMS responses simultaneously with sampling for PM using the reference method specified in the a pplicable regulation (use of paired r eference method sampling trains is recommended);

# Coordina

ting pro cess ope

rations, refer

ence me thod sampl ing, an

d PM CEMS operation; and

# Perform

ing a min imum of 12 te st runs. Section 8.6(3) of PS-11 allows you to discard the results of up to five test runs without explanation. You can reject additional test runs if the basis for rejecting them is specified in the test method, PS-11, or the QA plan for the source. Also note that it is not necessary to conduct the RCA over the three levels of PM concentration describe d in Section 8.6(4) of PS-11.W-2

W.3 WHAT ARE THE PERFORMANCE CRITERIA F OR AN RCA?
Section 10 .4(5) of

Procedu re 2 spec ifies thr

ee perf ormance criteri a for an

RCA. Firs t, the PM CEMS response value

for any RCA test ru

n can be no gre ater tha

n the gr eatest PM CEMS response value used to develop the correlation. F or example, if the correlation equation is based on PM CEMS re sponses that rang ed from 5 .1 mA to 35. 7 mA, the ma ximum allowa

ble PM CEMS response for an RCA is 35.7 mA. If the PM CEMS response exceeds 35.7 mA for a ny RCA test run, the results of that run must be discarded.
The sec ond crite

rion, whic

h is speci fied in Se ction 10.4 (5)(ii) , is that nine of the 1 2 PM CEMS responses must be within the range of response va lues used to develop the correlation. For the example c ited abov e, this mea ns that the

PM CEMS resp onse for

up nine of

the 12 tes t runs must be within the range of 5.1 mA to 35.7 mA. Otherwise, additional RCA test runs must be conducted.
The fina l criter ion, which is speci fied in Se ction 10.4 (5)(iii) , is that the measure d PM concentrations for at least 75 percent of the te st runs for an RCA must be within a band defined by the PM concentra

tion calculated from the correlation equation, plus or minus 25 perce nt of the numeric al emission limit. For any test run, this crite

rion can be expres sed as fo llows: í - 0. 25E L # y RCA # í + 0.25EL (Equation W-1)
where í = PM conce

ntration c alculate d from the correl ation equ

ation usin g the PM CEMS response (

xvalue) recorded during the RCA test run EL = value of emission limit (concentration) y RCA = PM concentration ( yvalue) measured during the RCA test run. For example, assume that the emission limit is 34 mg/dscm, and the correlation equation develope d for a PM C EMS is í = 1.14 x+ 2.68
where

x = PM CEMS response. Substituting the emission limit and correlation equation into Equation W-1, each test run of the RCA must then satisfy the following expression:

1.14x+ 2.68 - (0.25 × 34) # y RCA # 1.14x+ 2.68 + (0.25 × 34)
This expr essio n can b e simp lifi ed to t he fol lowi ng:
1.14x+ 2.68 - 8.5 # y RCA # 1.14x+ 2.68 + 8.5W-3 1.14x- 5.82 # y RCA # 1.14x+ 11.18 If the PM CEMS response value ( x ) during an RCA run was 18.2 mA, the PM concentration would have to fall within the following range for the RCA run to be counted toward the 75 percent criterion: (1.14 × 18.2) - 5.82 # y RCA # (1.14 × 18.2) + 11.18
20.75 - 5.82 # y RCA # 20.75 + 11.18
14.9 # y RCA # 31.9 For this example, y RCA , the PM concentration for the RCA test run, would have to be within the range of 14.9 mg/dscm to 31.9 mg/dscm for the run to be counted toward the criterion that 75 percent of the test run values fall within the band defined by the correlation equation plus or minus 25 pe

rcent of the emissi on limit.
W.4 EXAMPLE PROBLEM: HOW DO I EVALUATE THE RESUL TS OF AN RCA? The correlation equation developed during the initial correlation test for a PM CEMS installation is linear and is expr

essed as follows: í = 0.65 x- 1.00
The PM CEMS r

esponse d ata used to develo p the cor relation equation range d from 4.9 mA to 32.2 mA. The emission limit is 22.6 mg/dscm. To demonstrate that the installation meets the criteri a for the

RCA, 13 tes t runs wer

e performed. The

RCA test da

ta are s ummarized

in Table W-1.
The firs t step in de

termining if the tes t results s atisfy

the RCA cr

iteria is to compar

e the PM CEMS response value s to the maxim um respon se value

used to de

velop the correl ation. I

n this example, the maximum al lowable P M CEMS resp onse valu e is 32.2 mA . A revie

w of the d

ata indicates that the PM CEMS response for Run 7 was 33.6 mA, which exceeds the maximum allowable value. Therefore, Run 7 must be discarde d. All other runs satisfy the c riterion for maximum PM CEMS response.
The next ste

p is to dete

rmine if t he PM CEMS re sponse va lues for at least n ine test r uns fall within the

range of value s used to de

termine t he corr elation, which is 4. 9 mA to 32.2mA for thi s example. After discarding Run 7, the PM CEMS responses for the remaining 12 runs range from 7.2 to 31.9 mA and satisfy this criterion.W-4 Table W-1. Results of R CA Test R

uns

Run PM CEMS

respon se, mA Meas ured PM Concentration, mg/dscm 1 7.2 7.6 2 10.9 7.4 3 10.2 2.8 4 26.8 23.5 5 27.7 14.2 6 31.9 22.7 7 33.6 25.1 8 12.6 8.0 9 16.8 8.5 10 17.3 6.2 11 19.2 14.6 12 23.3 10.9 13 28.4 18.1

The third step is to determine the number of test runs for which the measure d PM concentrations are within the band defined by the correlation equation plus or minus 25 percent of the numerica l emission limit, as shown by Equation W-1. Substituting the emission limit and correlation equation , Equation

W-1 can be

simplified

as follow s:
0.65 x- 1.00 - (0.25 × 22.6) # y RCA # 0.65 x- 1.00 + (0.25 × 22.6)

0.65 x- 6.65 # y RCA # 0.65 x+ 4.65 Substituting the PM CEMS response values for x , the allowable range for ea ch test run can be calculated and compared to the PM concentra tion for that run. The results of these calculations are summarized in Table W-2 and illustrated graphically in Figure W-1.

Table W-2. Comparison of PM Concentration to Allowable Concentrations for RCA

Run No. a PM CEMS response

value ( x ), mA Meas ured PM concentration (

y RCA ), mg/dscm Allowable range for y RCA Is y RCA within range? Minimum Maximum 1 7.2 7.6 -1.97 9.33 Yes 2 10.9 7.4 0.44 11.74 Yes 3 10.2 2.8 -0.02 11.28 Yes 4 26.8 23.5 10.77 22.07 NoTable W-2. (continue d)

Run No. a PM CEMS response

value ( x ), mA Meas ured PM concentration (

y RCA ), mg/dscm Allowable range for y RCA Is y RCA within range? Minimum Maximum

W-5 5 27.7 14.2 11.36 22.66 Yes 6 31.9 22.7 14.09 25.39 Yes 8 12.6 8 1.54 12.84 Yes 9 16.8 8.5 4.27 15.57 Yes 10 17.3 6.2 4.6 15.9 Yes 11 19.2 14.6 5.83 17.13 Yes 12 23.3 10.9 8.5 19.8 Yes 13 28.4 18.1 11.81 23.11 Yes

a Note that Run 7 ha s been discarded because it failed criterion 1.

As indica ted in Tab le W-2, of

the rema ining 12 R

CA test run s (follow

ing rem oval of Ru

n 7), all but Run 4 meet the criterion that the measured PM concentration is within the band defined by the correlation equation plus or minus 25 percent of the emission limit. For Run 4, the measured PM conce

ntration was 23.5 mg

/dscm, an d the allo wable ra

nge is 10 .77 mg/ds cm to 22.07 mg/dscm. In Fig

ure W-1, the correlation equation is represented by the solid line, and the dashed lines represent the ± 25 percent band. Run 4 (26.8 mA a nd 23.5 mg/dscm) lies outside of this band. Figure

W-1. Gr aphical representa tion of exam

ple RCA t est res ults.

+25%EL

! 25%EL

" = RCA data poi ntW-6

In summary , 11 of the 12 test runs (or 91.7 percent of the runs) wer e within the band defined by the correlation equation plus or minus 25 percent of the emission limit. Because more than 75 percent of the test runs were within the allowable ra nge, the third criterion has been satisfied. Therefore, the PM CEMS satisfied the three RCA performance criteria, and no changes to the correlation equation are required.
W.5 WHAT MUST I DO IF I FAI L AN RCA? Section 10.6 of Procedure 2 specifies a series of c orrective actions that must be taken following the failu re of an RCA. The f

irst step f ollowing a failed RCA, as not

ed in Sect ion 10.6(1 ), is to combine the RCA data with the data used to develop the current cor relation and develop a new correlation equation using the combined data (orig inal correlation test data plus RCA data). The new correlation equation must be developed using the pr ocedures specified in Section 12.3 of PS-11. If the correlation equa tion developed from the combined data meets the criteria spe cified in Section 13.2 of PS-11, the revised correlation equation should be used. No further testing or corrective action is needed.
If the combined data do not mee t the criteria specified in Section 12.3 of PS-11, a revised correlation equation must be developed using only the results from the RCA. If this revised correlation equation meets the criteria specifie d in Section 13.2 of PS-11, the revised correlation equation should be u sed, and

additiona l testing or corr ective a ction is un

necessa ry . Howeve

r, it is still advisable to investigate why the c orrelation changed. One possible explanation for such a shift in the correlation is a change in control device or process operation. For example, a difference in fuel properties could cha nge the characteristics of the e xhaust stream, thereby altering how the PM CEMS responds to sampled emissions. In such ca ses, it may be more appropriate to develop and use separate c orrelations for the different operating conditions and calcula te emissions based on the cor relation that cor responds to the spe cific op erating

condition s. If neither the cor

relation equation developed from the combined data nor the c orrelation equation develope d from onl

y th e RCA data

satisfie s Section 1 3.2 of PS-1 1, other c orrect ive actions must be taken. First, the PM CEMS must be inspected and repaired as neede d. If this inspection indicate s that the P M CEMS is ope rating properl y, i t may be nece ssary

to reloc ate the PM

CEMS and perform a new correlation test. An a lternative to relocating the PM CEMS is to install a new PM CEMS that uses a measurement technology that is more appropriate for the source opera ting parameters and

emissions c

haract eristics . As explained above , it is also p ossible tha t a singl e correlation is inadequate for chara cterizing different source or control de vice operating conditions, and it may be nece ssary to develop multiple corr elations. If none of these mea sures corrects the problem, the final option is to petition the permitting authority for alternative moni torin g.
W.6 EXAMPL

E PROBL

EM: HOW DO I DEVEL OP A NEW CORRELATION FOLL OWING A FAI

LED RCA?
A succe ssful cor

relation test is per

formed on a hazar

dous wast e incine rator. T he incine rator mus t meet an emission limit of 22.6 mg/dscm. The correlation test consisted of 15 runs. Table W-3W-7 Figure W-2. Initi al correlation te st data and r esulting

correl ation equat

ion. summarize s the data

from the c orrela

tion test. F igure W- 2 shows a p lot of the c orrela tion test data. Th e corre lation co efficie nt for the data is 0. 93, and th e linear correl ation equ

ation is í = 0.792x- 2.01 Table W-3. Summary of Initial Correlation Test Results

Run No. PM CEMS

Respon se, mA Meas ured PM Concentration, mg/dscm 1 5.2 3.2 2 7.8 2.9 3 8.2 6.1 4 10.4 5.2 5 14.8 6.8 6 14.1 12.6 7 19.2 9.2 8 20.3 18.8 9 19.5 12.1 10 26.4 15.1 11 21.9 16.4 12 28.7 17.8 13 29.3 23.2 14 33.5 23.9 15 31.8 27.2W-8

A year after the PM CEMS is brought on line, an RCA is performed. The RCA consisted of 12 test ru ns. The r esults of t he RCA ar

e summari zed in Tabl e W-4. The PM CEMS resp onse values f or the RCA r

ange f rom 7.2 to 3 1.9 mA. All

of these values f all within t

he rang e of PM CEMS values used to develop the correlation (5.2 to 33.5 mA). Therefore , the RCA data meet the first two criteria specified in Section 10.4(5)(i) and (ii) f or the allowable data range.

Table W-4. Results of RCA

Run PM CEMS

response Meas ured PM concentration, mg/dscm Allowable range for y RCA , mg/dscm Is y RCA within

allowable range? x y RCA Minimum Maximum RCA-1 7.2 5.7 -1.95 9.35 Yes RCA-2 10.9 6.2 0.98 12.28 Yes RCA-3 10.2 2.4 0.42 11.72 Yes RCA-4 26.8 12.5 13.57 24.87 No RCA-5 27.7 11.9 14.29 25.59 No RCA-6 31.9 14.8 17.61 28.91 No RCA-7 28.2 9.9 14.68 25.98 No RCA-8 12.6 6.7 2.32 13.62 Yes RCA-9 16.8 7.1 5.65 16.95 Yes RCA-10 17.3 5.2 6.05 17.35 No RCA-11 19.2 8.7 7.55 18.85 Yes RCA-12 23.3 9.2 10.8 22.1 No

To determine if the RCA meets the requirements of Section 10.4(5)(iii) of Proce dure 2, the band defined by t he corr elation li ne plus or minus 25 pe

rcent of the emissi on limit ca

n be simplif

ied to the fo llow ing:
0.792 x- 7.66 # y RCA # 0.792 x+ 3.64 Table W-4 shows the applicable range for each run of the RCA based on the above expression. Wh en th e v al ue s f

or th e P M C EM S r es po ns es fo r t he RC A a re co mp ar ed to th es e r an ge s, on ly 6 of the 12 runs (50 percent) fall within the acce ptable band. Figure W-3 shows a plot of the correlation line and the lines that define the plus or minus 25 percent band a round the correlation line. As indicated in the figure, six of the data points for the RCA (indicated by the  sym

bols) fall below the band. As specif ied in Sec tion 10.6( 1) of Proc edure 2, the next ste p is to comb ine the da

ta used to develop the correlation and the RCA data and determine if the resulting correlation satisfies the criteria of Section 13.2 of PS-11. A plot of the combined data is shown in Figure W-4.W-9 Figure W-4. Plot of combined correlation test data and RCA data.

Figure W-3. Results of RCA. ! 25%EL +25%EL

" = RCA data pointW-10 Figure W-5. Plot of correlation curve for RCA data only. When the c orrela

tion is per

formed u sing the

combined

data, none of the f

ive corr elation mo dels meet the criteria of PS-11. The correlation coef ficients are all less than 0.85, and three of the five models fail to meet the criterion for a tolerance inter val half range of 25 perc ent. Table W-5 shows the outcome o f the cor

relation analy sis for the five mode ls.

Table W-5. Results of Correlation Analysis for Combined Correlation Test and RCA Data

Model Equation Correlation coefficient Confidence

interva l half range Tolerance

interva l half range Acceptance Criteria for PS -11 $ 0.85 # 10% # 25% Linear í = 0.638x - 1.22 0.813 6.81 % 26.3 % Polynomial í = 0.0135 x 2 + 0.111 x + 2.94 0.816 9.11 % 26.6 % Logar ithmi c í = 9.92Ln( x ) -17.12 0.765 7.54 % 29.1 % Exponential í = 2.70e 0.0636 x 0.844 5.63 % 22.7 % Power í = 0.477 x 1.042 0.838 5.72 % 23.1 %

When the c orrela

tions deve loped fr

om the com

bined dat a do not me et the cr

iteria sp ecified

in PS-11, Sec tion 10.6( 2) of Proc edure 2 r equires developi ng a ne w corre lation usin

g only the data from the RCA test runs. A plot of the RCA data and the new linear correla tion equation developed from these data are shown in Fig ure W-5. The results of the analy sis for the five correl ation mode ls are su mmarized i

n Table W- 6. The line ar and po lynomial cor relation models both satisfy the corre lation criteria of PS-11 and either equation can be used to dete rmine compliance with th e emission limit.W-11 Table W-6. Results of C orrelat ion Analysis fo r RCA Da ta Only

Model Equation Correlation coefficient Confidence

interva l half range Tolerance

interva l half range Acceptance Criteria for PS -11 $ 0.85 # 10% # 25% Linear í = 0.889 x + 0.386 0.888 4.61 % 13.6 % Polynomial í = 0.0131 x 2 - 0.123 x + 5.06 0.900 5.96 % 13.5 % Logar ithmi c í = 6.24Ln( x ) - 9.53 0.826 5.64 % 16.6 % Exponential í = 2.92e 0.0496 x 0.809 6.25 % 19.3 % Power í = 0.726 x 0.819 0.772 6.77 % 21.0 %