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
------- |