ISOKINETIC AIR EMISSION TESTING Method 1 Reference- 1 -
EPA Method 1 Field Procedures Step Instruction 100 Is the stack or
duct circular or square/rectangle? If square/rectangular go to step
170. 105 Determine the diameter of the stack from one of the
following methods.
a. Review drawings of stack b. If the stack has been tested
previously, determine diameter from previous test. c. Measure the
inside diameter with a rigid tube or pipe from the sampling ports
on
two axis and average the diameter. Be sure to subtract the distance
from the inside wall to the end of the sample port, this is your
reference value.
d. Measure the circumference and calculate the inside diameter,
less the wall thickness times two.
110 Measure the distance from the sampling ports downstream to the
nearest disturbance. A disturbance is a bend in the ductwork,
transition from square to round duct shape, a fan, or some other
disturbance such as the stack exit, that may cause the flow not be
uniform.
120 Measure the distance from the sampling ports upstream to the
nearest disturbance. 125 Determine the duct diameters upstream from
the flow disturbance. Determine the duct
diameters downstream from the flow disturbance. 130 Reference the
chart below to determine the minimum number of required sample
points.
135 Example: Stack diameter 18”, distance from ports to downstream
disturbance is 24” and distance from ports to upstream disturbance
72”. Duct diameters upstream from flow disturbance (Distance B) is
24 / 18 = 1.3. Duct diameters upstream from flow disturbance
(Distance A) is 72 / 18 = 4.0.
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140 Distance B requires 20 sample points and Distance A requires 24
sample points. The number of required sample points will be 24
since Distance A requires more sample points.
145 Locate the sample points using the following chart.
Stacks having diameters greater than 0.61 m (24 in.), no traverse
points shall be within 2.5 centimeters (1.00 in.) of the stack
walls; and for stack diameters equal to or less than 0.61 m (24
in.), no traverse points shall be located within 1.3 cm (0.50 in.)
of the stack walls. When any of the traverse points as located fall
within 2.5 cm (1.0 in.) of the stack walls, relocate them away from
the stack walls to: (1) a distance of 2.5 cm (1.0 in.); or (2) a
distance equal to the nozzle inside diameter, whichever is larger.
These relocated traverse points (on each end of a diameter) shall
be the “adjusted” traverse points.
Whenever two successive traverse points are combined to form a
single adjusted traverse point, treat the adjusted point as two
separate traverse points, both in the sampling and/or velocity
measurement procedure, and in recording of the data.
Stacks With Diameters Equal To or Less Than 0.61 m (24 in.). Follow
the procedure in Section 11.3.1.1, noting only that any “adjusted”
points should be relocated away from the stack walls to: (1) a
distance of 1.3 cm (0.50 in.); or (2) a distance equal to the
nozzle inside diameter, whichever is larger.
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150 Example: Using the information from the example in Step 135 and
assuming the distance from the inside wall to the end of the sample
port as 5 inches (reference), the sample point on a diameter
(traverse) would be the following. (% diameter X diameter +
reference value).
155 Use wrappings of glass electrical tape, or other suitable means
to clearly mark each
sample point on the probe. During testing begin at point 1 and
progressively move to the next point when finished at that point.
Repeat until all points on the traverse have been sampled. Move to
the other sampling point and repeat the process.
160 In most stationary sources, the direction of stack gas flow is
essentially parallel to the stack walls. However, cyclonic flow may
exist (1) after such devices as cyclones and inertial demisters
following venturi scrubbers, or (2) in stacks having tangential
inlets or other duct configurations which tend to induce swirling;
in these instances, the presence or absence of cyclonic flow at the
sampling location must be determined. The following techniques are
acceptable for this determination.
Level and zero the manometer. Connect a Type S pitot tube to the
manometer and leak- check system. Position the Type S pitot tube at
each traverse point, in succession, so that the planes of the face
openings of the pitot tube are perpendicular to the stack cross-
sectional plane; when the Type S pitot tube is in this position, it
is at “0° reference.” Note the differential pressure (Δp) reading
at each traverse point. If a null (zero) pitot reading is obtained
at 0° reference at a given traverse point, an acceptable flow
condition exists at that point. If the pitot reading is not zero at
0° reference, rotate the pitot tube (up to ±90°
Sample Point
(inches) Correction (inches)
With Reference (inches)
1 2.1 0.38 0.5 5.5 2 6.7 1.21
6.21 3 11.8 2.12 7.12 4
17.7 3.19 8.19 5 25 4.50
9.50 6 35.6 6.41 11.41 7
64.4 11.59 16.59 8 75 13.50
18.50 9 82.3 14.81 19.81
10 88.2 15.88 20.88 11 93.3 16.79
21.79 12 97.9 17.62 17.50
22.50
Stack diameter is 18 inches, reference 5 inches, distance from
ports to downstream disturbance is 24” and distance from ports to
upstream disturbance 72”. Duct diameters upstream from flow
disturbance (Distance B) is 24 / 18 = 1.3. Duct diameters upstream
from flow disturbance (Distance A) is 72 / 18 = 4.0. Total sample
points are 24, 12 per diameter (traverse).
Note: Sample points 1 & 12 must be relocated. The stack
diameter is less than 24 inches, thus no sample point should be
closer than 0.5” from the inside wall, see step 145.
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yaw angle), until a null reading is obtained. Carefully determine
and record the value of the rotation angle (α) to the nearest
degree. After the null technique has been applied at each traverse
point, calculate the average of the absolute values of α; assign α
values of 0° to those points for which no rotation was required,
and include these in the overall average. If the average value of α
is greater than 20°, the overall flow condition in the stack is
unacceptable, and alternative methodology, subject to the approval
of the Administrator, must be used to perform accurate sample and
velocity traverses.
Square / Rectangular Ducts & Stacks 170 Determine the duct or
stack dimensions, width and length from one of the following
methods. a. Review drawings of stack b. If the stack has been
tested previously, determine dimensions from previous test. c.
Measure the inside dimensions, width and length.
175 In the case of rectangular ducts, an equivalent diameter, De is
used in the siting and traverse point considerations. For a
rectangular duct, use the following equation to determine the
equivalent diameter, De.
Where: L = length of the duct W = width of the duct
180 Measure the distance from the sampling ports downstream to the
nearest disturbance. A
disturbance is a bend in the ductwork, transition from square to
round duct shape, a fan, or some other disturbance such as the
stack exit, that may cause the flow not be uniform.
185 Measure the distance from the sampling ports upstream to the
nearest disturbance. 190 Determine the duct diameters upstream from
the flow disturbance. Determine the duct
diameters downstream from the flow disturbance. If the duct or
stack is rectangular, use the equivalent diameter De in calculating
the duct diameters.
Width
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195 Reference the chart below to determine the minimum number of
required sample points.
200 Example: Stack is 24” wide by 36” long (rectangular), distance
from ports to downstream disturbance is 75” and distance from ports
to upstream disturbance 190”. Equivalent diameter is 28.8”. Assume
that there are 4 sample ports on the 36” side of the duct. Duct
diameters upstream from flow disturbance (Distance B) is 75 / 28.8
= 2.6. Duct diameters upstream from flow disturbance (Distance A)
is 190 / 28.8 = 6.6.
205 Distance B requires 12 sample points and Distance A requires 16
sample points. The number of required sample points will be 16,
since Distance A requires more sample points.
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210 Locate the sample points using the following chart for square
and rectangular stacks and ducts.
Stacks having diameters greater than 0.61 m (24 in.), no traverse
points shall be within 2.5 centimeters (1.00 in.) of the stack
walls; and for stack diameters equal to or less than 0.61 m (24
in.), no traverse points shall be located within 1.3 cm (0.50 in.)
of the stack walls. When any of the traverse points as located fall
within 2.5 cm (1.0 in.) of the stack walls, relocate them away from
the stack walls to: (1) a distance of 2.5 cm (1.0 in.); or (2) a
distance equal to the nozzle inside diameter, whichever is larger.
These relocated traverse points (on each end of a diameter) shall
be the “adjusted” traverse points.
Whenever two successive traverse points are combined to form a
single adjusted traverse point, treat the adjusted point as two
separate traverse points, both in the sampling and/or velocity
measurement procedure, and in recording of the data.
Stacks With Diameters Equal To or Less Than 0.61 m (24 in.). Follow
the procedure in Section 11.3.1.1, noting only that any “adjusted”
points should be relocated away from the stack walls to: (1) a
distance of 1.3 cm (0.50 in.); or (2) a distance equal to the
nozzle inside diameter, whichever is larger.
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215 Example: Using the information from the example in Step 200 and
assuming the distance from the inside wall to the end of the sample
port as 4.5 inches (reference). , the sample point on a diameter
(traverse) would be the following. (% diameter X diameter +
reference value).
Sample Point Placement in Rectangular
Stack
220 Use wrappings of glass electrical tape, or other suitable means
to clearly mark each sample point on the probe. During testing
begin at point 1 and progressively move to the next point when
finished at that point. Repeat until all points on the traverse
have been sampled. Move to the other sampling point and repeat the
process.
225 In most stationary sources, the direction of stack gas flow is
essentially parallel to the
stack walls. However, cyclonic flow may exist (1) after such
devices as cyclones and inertial demisters following venturi
scrubbers, or (2) in stacks having tangential inlets or other duct
configurations which tend to induce swirling; in these instances,
the presence or absence of cyclonic flow at the sampling location
must be determined. The following techniques are acceptable for
this determination.
Level and zero the manometer. Connect a Type S pitot tube to the
manometer and leak- check system. Position the Type S pitot tube at
each traverse point, in succession, so that the planes of the face
openings of the pitot tube are perpendicular to the stack cross-
sectional plane; when the Type S pitot tube is in this position, it
is at “0° reference.” Note the differential pressure (Δp) reading
at each traverse point. If a null (zero) pitot reading is obtained
at 0° reference at a given traverse point, an acceptable flow
condition exists at that point. If the pitot reading is not zero at
0° reference, rotate the pitot tube (up to ±90° yaw angle), until a
null reading is obtained. Carefully determine and record the value
of
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