United States Environmental Protection Agency Office of Air Quality Planning and Standards Research Triangle Park NC 27711 EPA-450/3-82-016a August 1982 Air Proposed Revisions to Reduce Number of Traverse Points in Method ! - Background Information Document ------- EPA-450/3-82-016a Proposed Revision to Reduce Number of Traverse Points in Method I— Background Information Document Emission Measurement Branch Emission Standards and Engineering Division U.S. ENVIRONMENTAL PROTECTION AGENCY Office of Air, Noise, and Radiation Office of Air Quality Planning and Standards Research Triangle Park, North Carolina 27711 August 1982 ------- This report has been reviewed by the Emission Standards and Engineering Division of the Office of Air Quality Planning and Standards, EPA, and approved for publication. Mention of trade names or commercial products is not intended to constitute endorsement or recommendation for use. Copies of this report are available through the Library Services Office (MD-35), U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711; or, for a fee, from the National Technical Information Services, 5285 Port Royal Road, Springfield, Virginia 22161. Publication No. EPA-450/3-82-027 ------- CONTENTS Introduction 1 Fluidyne Report 1 TRW Report 3 Entropy Reports 4 Emission Measurement Branch Report 6 British Coal Utilisation Research Association 7 References 8 ------- BACKGROUND INFORMATION FOR PROPOSED REVISIONS TO REDUCE NUMBER OF TRAVERSE POINTS IN METHOD 1 INTRODUCTION On December 23, 1971, the Environmental Protection Agency (EPA) published in the Federal Register (36 FR 2kQl6) Method 1, which specifies the minimum number of traverse points required for velocity and particulate matter sampling from stationary sources. This method was later revised and published on August 18, 1977 (^2 FR klJ5k). During 1976, 1977, and 1980, several published reportsl-° indicated that the number of traverse points could be reduced from those specified by Method 1. The results of these studies served as the basis for revising Method 1 to utilize a lesser number of traverse points. These studies and a 1961 study7 are summarized below. FLUIDYNE REPORTl Fluidyne Engineering Corporation conducted its study under EPA Contract No. 68-02-12UU. In this study, 27 velocity and U particulate profiles were obtained from a literature survey, laboratory-scale modeling, and field testing. The data were fitted by polynomial equations, and various traverse schemes were then compared against the value determined by integrating the polynomials over the cross-sectional area of the duct. The results of the study are summarized in Tables 1, 2, and 3. Table 1 summarizes the velocity relative errors based on 21 rectangular ducts, and Table 2 lists data from 6 circular stacks. Table 3 summarizes the particulate mass rate relative errors for four rectangular ducts. ------- TABLE 1. VELOCITY RELATIVE ERRORS FROM 21 RECTANGULAR DUCTS1*2 Matrix 1x1 2x2 3x3 k x 3 U x U 5 x U 5x5 6 x 5 6x6 8x6 No. of traverse points 1 k 9 12 16 20 25 30 36 1+8 Average relative error, a percent lU.90 It. 01 0.92 O.TO O.U7 O.UO 0.33 0.29 0.25 0.21 95% tolerance region for average relative error, ^ percent ±50.59 +12. UO + 2.39 + 1-95 +_ 1.51* +. 1.29 +_ 1.11 +_ 1.07 +_ 0.85 +_ 0.82 Average of absolute relative errors. Considered signs in calculations. TABLE 2. VELOCITY RELATIVE ERRORS FROM SIX CIRCULAR STACKS1 No. of traverse points No. of stacks having maximum error less than: One diameter U 8 12 16 Total3- 8 16 2U 32 6.0% 6 6 6 6 k.0% 5 6 6 6 2.0% I 5 5 5 1.0% 1 3 U k a Two perpendicular diameters. ------- TABLE 3. PARTICULATE MASS RATE ERRORS FROM FOUR RECTANGULAR DUCTS1 Matrix 1x1 2x2 3x3 1+ x 3 1+ x U 5 x U 5 x 5 6 x 5 6x6 8x6 No. of traverse points 1 U 9 12 16 20 25 30 36 U8 Average relative error, a percent 12.51 8.37 2.1U 1.58 1.02 0.82 0.58 O.U8 0.38 0.20 95% tolerance region for average relative error, ^ percent +39-35 ±27.33 _+ 6.81 +_ k.96 jf 2.85 +_ 2.21 _+ 1.60 _+ 1.27 +_ 1.07 + 0.58 Average of absolute relative errors. b Considered signs in calculations. TRW REPORTS This study was conducted by TRW Systems Group under EPA Contract No. 68-02-1U12. As part of this project, 18 velocity traverses were examined. A curve fitting technique was used to generate the data, which were then compared to those obtained from a 25- by 21-point matrix. The report concluded that there was no notable increase in accuracy for matrices in excess of 16 traverse points and that the average velocity error for the l6-point traverse was l.U percent with an expected standard deviation of less than 2 percent. ------- ENTROPY REPORTS1*^ Two studies were conducted by Entropy Environmentalists, Inc., under EPA Contract No. 68-01-3172. One study dealt with velocity, and the other 'dealt with particulate traverses. For the velocity study, data from some 150 circular ducts and more than 120 rectangular stacks were evaluated. In the analysis, however, each traverse line was considered to be a separate test. Each traverse line was fitted to a curve, and the various number of traverse points were compared to 2k points. The results of this study are summarized in Table k. The particulate study was similar to that of the Fluidyne study except the basis for comparison was the 7- by 7-point matrix. The results are summarized in Table 5« TABLE k. VELOCITY ERRORS FROM 150 CIRCULAR STACKS AND 120 RECTANGULAR DUCTS1* No. of traverse points on a line 2 U 6 8 12 16 20 2k Average relative error, percent8- Circular 7.19 2.76 1.27 1.28 0.08 0.09 0.02 _ Rectangular 1.90 0.50 - 0.53 0.16 0.09 - _ Average of absolute errors. Note: Tolerance regions not calculated because of insufficient information in report. ------- TABLE 5. PARTICULATE MASS RATE ERRORS FROM 10 RECTANGULAR DUCTS5 Matrix 3x3 k x 3 U x h 5 x U 5x5 6x5 6x6 7x6 12 x U 7x7 traverse points 9 12 16 20 25 30 36 U2 U8 U9 Average relative error, a percent 3.00 3.11 2.60 3.05 1.89 1.30 1.51 1.1*5 1.30 _ 95% tolerance region for average relative error,13 percent +8.68 ±7.60 ^7.68 +9.61 ±5-12 +U.13 +k.29 +_5.00 _+3.8l _ Average of absolute relative errors. Considered signs in calculations. ------- EMISSION MEASUREMENT BRANCH REPORT6 The Emission Measurement Branch (EMB) of EPA conducted a study to determine- the least number of sampling points for particulate mass flow rate in circular stacks. Three different particulate profiles were studied, and various numbers of traverse points on a line were compared to a 2l*-point traverse. The results are summarized in Table 6. TABLE 6. PARTICULATE MASS RATE ERRORS FROM THREE TYPES DISTRIBUTIONS IN CIRCULAR STACKS6 No. of traverse points on a line 2 1* 6 8 10 12 Ik 16 18 20 22 21* Percentage error U-shaped +0.1* +0.1* -0.1* +0.1* 0 +0.1* +3.1 +0.1* 0 +0.1* +0.1* _ Skewed +18.0 +37.8 + 3.6 0 + 0.9 + U.5 + 0.9 0 0 + 1.8 0 _ Parabolic -0.8 +0.4 +0.1+ +O.U 0 0 0 0 0 0 -0.1* _ ------- BRITISH COAL UTILISATION RESEARCH ASSOCIATION! A report on a study performed by the British Coal Utilisation Resesarch Association (BCURA) is included here because it covers a wide range of conditions in rectangular ducts, including steep gradients of solids flow. The bias due to sampling a limited number of points was calculated from different mass flow profiles found in a number of plants. The results are summarized in Table J. TABLE 7. MAGNITUDE OF BIAS DUE TO SAMPLING AT A FINITE NUMBER OF SAMPLING POINTS No. of sampling points 1 u 8 9 95% confidence limits of bias expressed as percentage of true value +U2 +13 +_ 5.0 + 3.9 DISCUSSION AND CONCLUSIONS The summaries of the data from the various reports clearly show that the number of traverse points can be reduced from the 48 points specified in Method 1 with no significant loss in measurement accuracy on an average. The average accuracy improves dramatically up to about eight or nine points, then improves very slowly beyond a total of nine traverse points. For example, Table 1 shows that the average absolute relative error for velocity measurements decreases rapidly from lU.90 to 0.92 when the number of traverse points goes ------- from 1 to 9, while the error changes from 0.92 to 0.21 percent when the number of traverse points is increased from 9 to kB, This effect is graphically illustrated in Figure 1 for the data presented in Tables 1 and 3. The 95 percent tolerance region for nine particulate or velocity traverse points are conservatively estimated to be +10 percent. To reduce the tolerance region to +5 percent, the number of traverse points must be increased to 16 for velocity and 2k for particulate mass flow rate measurements. The effect of the 95 percent tolerance region against the number of traverse points is graphically illustrated in Figure 2. Since none of the studies considered the effect of the number of traverse points on accuracy in relation to the number of equivalent diameters from points of disturbances, an arbitrary decision was made to leave unchanged the present 8-diameter-downstream and 2-diameter-upstream criteria and to limit the decrease of the number of sampling points to the 2 to k diameters downstream and 0.5 to 1 diameter upstream. The proposed revisions to Method 1 are given in Figures 3 and U. REFERENCES 1. Hanson, H.A., R.J. Davini, J.K. Morgan, and A.A. Iversen. Particulate Sampling Strategies for Large Power Plants Including Nonuniform Flow. U.S. Environmental Protection Agency. Research Triangle Park, N.C. Publication No. EPA-600/2-76-170. June 1976. 350 p. 2. Knapp, K.T. The Number of Sampling Points Needed for Representative Source Sampling. In: Proceedings of the Fourth National Conference on Energy ------- and the Environment, Theodore, L., et al. (ed.). Dayton, Dayton Section of the American Institute of Chemical Engineers. October 3-7, 1976. p. 563-568. 3. Brooks, E.F., and R.L. Williams. Flow and Gas Sampling Manual. U.S. Environmental Protection Agency. Research Triangle Park, N.C. Publication No. EPA-600/2-76-203. July 1976. 93 p. U. Entropy Environmentalists, Inc. Determination of the Optimum Number of Traverse Points: An Analysis of Method 1 Criteria. EPA Contract No. 68-01-3172. April 1977. 23 p. 5. Entropy Environmentalists, Inc. Traverse Point Study. EPA Contract No. 68-01-3172. June 1977. 19 p- 6. Brown, J., and K. Yu. Test Report: Particulate Sampling Strategy in Circular Ducts. Emission Measurement Branch, Emission Standards and Engineering Division, U.S. Environmental Protection Agency. Research Triangle Park, N.C. 277H. July 31, 1980. 12 p. 7. Hawksley, P.G.W., S. Badzioch, and J.H. Blackett. Measurement of Solids in Flue Gases. Leatherhead, England, The British Coal Utilisation Research Association, 1961. p. 129-133. ------- AVERAGE RELATIVE ERROR, PERCENT o en o en ,« I 1 1 f \ i \ \ \ i \ \ L ', 1 \ \ \ [I) \ \ \ \ V 'v \ \ ^ ^ \ 1 ^ n I?- ~l i i F^rp i =±^ T L •~-i -- -[ -< i >- ~t 0 Q = -I ^ 1 1 1 I VELOCITY (FROM TABLE 1) PARTI CULATE (FROM TABLE i j- •< -A h ! i 1 — — _ h i -lJJ~i— = •~~i = 1 3) = i 0 50 10 20 30 40 NUMBER OF TRAVERSE POINTS Figure 1. Average relative error vs. number of traverse points. 10 ------- +60 +50 +40 o i—i CD o: .1- +30 Q- _« in +20 +10 0 0 9 VELOCITY (FROM TABLE 1) S PARTICULATE (FROM TABLE 3) A PARTICULATE (FROM TABLE 5) 40 50 10 20 30 NUMBER OF TRAVERSE POINTS Figure 2. 95 percent tolerance region vs. number of traverse points. 11 ------- 0:5 50 to O n. to cc LU O CC LU m 20 3 S ? 10 DUCT DIAMETERS UPSTREAM FROM FLOW DISTURBANCE^(DISTANCE A) 1.0 • 1.5 2.0 2.5 I T T ^ T A i j — f I 4 'DISTURBANCE MEASUREMENT r~ " SITE; DISTURBANCE x» 1 STACK DIAMETER > 0.61 m (24 in.) * FROM POINT OF ANY TYPE OF DISTURBANCE (BEND, EXPANSION. CONTRACTION. ETC.) STACK DIAMETER = 0.30 TO 0.61 m (12-24 in! i J 4 5 6 7 89 . * DUCT DIAMETERS DOWNSTREAM FROM FLOW DISTURBANCE (DISTANCE B) Figure 3. Minimum number of traverse points for paniculate traverses. 10 ------- DUCT DIAMETERS UPSTREAM FROM FLOW DISTURBANCE (DISTANCE A) 0.5 1.0 1.5 • 2.0 2.5 5U i- 40 H i O a. LU tn oc UJ > 30 oc u. O oc m § 20 i 5 S ? 10 s 0 I — — :_ I I i . I \ T A — - B — i 7 'DISTURBANCE MEASUREMENT -- SITE * DISTURBANCE Iv . V?" 1 — - — • STAC.K niAMFTPO -^ n ci ~ It* :„ 1 • 1 • ^M^« STACK DIAMETER "= 0.30 TO 0.61 m (12-24 in.) I I I I 2345 6 7 8 9 DUCT DIAMETERS DOWNSTREAM FROM FLOW DISTURBANCE"(DISTANCE B) 10 Figure 4. Minimum number of traverse points for velocity (nonparticulate) traverses.. ------- TECHNICAL REPORT DATA (Please read Instructions on the reverse before completing) . REPORT NO. EPA-450/3-82-016a 2. 3. RECIPIENT'S ACCESSION NO. 4. TITLE AND SUBTITLE Proposed Revisions to Reduce Number of Traverse Points in Method 1 - Background Information Document 5. REPORT DATE August 1982 6. PERFORMING ORGANIZATION CODE 7. AUTHOR(S) Roger T. Shigehara 8. PERFORMING ORGANIZATION REPORT NO. 9. PERFORMING ORGANIZATION NAME AND ADDRESS Emission Measurement Branch (MD-19) Emission Standards and Engineering Division U.S. Environmental Protection Agency Research Triangle Park, N.C. 27711 10. PROGRAM ELEMENT NO. 11. CONTRACT/GRANT NO. 12. SPONSORING AGENCY NAME AND ADDRESS Office of Air Quality Planning and Standards (MD-10) Office of Air, Noise, and Radiation U.S. Environmental Protection Agency Research Triangle Park, N.C. 27711 13. TYPE OF REPORT AND PERIOD COVERED 14. SPONSORING AGENCY CODE EPA/200/04 15. SUPPLEMENTARY NOTES 16. ABSTRACT This document summarizes the data from several studies on the number of traverse points specified by EPA Method 1. This summary is used as the basis for revising Method 1 to utilize a lesser number of traverse points. 17. KEY WORDS AND DOCUMENT ANALYSIS DESCRIPTORS b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group Sampling Tests Stationary Sources 13B 18. DISTRIBUTION STATEMENT Unlimited 19. SECURITY CLASS (This Report) Unclassified 21. NO. OF PAGES 16 20. SECURITY CLASS (This page) Unclassified 22. PRICE EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION is OBSOLETE ------- |