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. - 1 -
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. - 2 -
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). Sample Point 12 Distance from inside wall Correction With Reference 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. 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 leakcheck 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 crosssectional 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 ±90-3 -
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. Width Length 175 In the case of rectangular ducts, an equivalent diameter, D e is used in the siting and traverse point considerations. For a rectangular duct, use the following equation to determine the equivalent diameter, De. De = 2LW (L+W) 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. - 4 -
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. - 5 -
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. - 6 -
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 Port Length 4.5" Sample Ports Percent of Diameter Distance from inside Wall Distance with Reference 24" 12.5% 3.0 7.5 37.5% 9.0 13.5 62.5% 15.0 19.5 87.5% 21.0 25.5 36" 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 leakcheck 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 crosssectional 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 - 7 -
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. - 8 -