《Sample and Velocity Traverses for Stationary Sources With Small Stacks or Ducts EPA Method .doc》由会员分享，可在线阅读，更多相关《Sample and Velocity Traverses for Stationary Sources With Small Stacks or Ducts EPA Method .doc（33页珍藏版）》请在三一文库上搜索。
1、Sample and Velocity Traverses for Stationary Sources With Small Stacks or Ducts EPA Method 1Method 1Sample and Velocity Traverses for Stationary Sources Note: This method does not include all of the specifications ( e.g., equipment and supplies) and procedures ( e.g., sampling) essential to its perf
2、ormance. Some material is incorporated by reference from other methods in this part. Therefore, to obtain reliable results, persons using this method should have a thorough knowledge of at least the following additional test method: Method 2. 1.0 Scope and Application 1.1 Measured Parameters. The pu
3、rpose of the method is to provide guidance for the selection of sampling ports and traverse points at which sampling for air pollutants will be performed pursuant to regulations set forth in this part. Two procedures are presented: a simplified procedure, and an alternative procedure (see Section 11
4、.5). The magnitude of cyclonic flow of effluent gas in a stack or duct is the only parameter quantitatively measured in the simplified procedure. 1.2 Applicability. This method is applicable to gas streams flowing in ducts, stacks, and flues. This method cannot be used when: (1) the flow is cyclonic
5、 or swirling; or (2) a stack is smaller than 0.30 meter (12 in.) in diameter, or 0.071 m2 (113 in.2 ) in cross-sectional area. The simplified procedure cannot be used when the measurement site is less than two stack or duct diameters downstream or less than a half diameter upstream from a flow distu
6、rbance. 1.3 Data Quality Objectives. Adherence to the requirements of this method will enhance the quality of the data obtained from air pollutant sampling methods. Note: The requirements of this method must be considered before construction of a new facility from which emissions are to be measured;
7、 failure to do so may require subsequent alterations to the stack or deviation from the standard procedure. Cases involving variants are subject to approval by the Administrator. 2.0 Summary of Method 2.1 This method is designed to aid in the representative measurement of pollutant emissions and/or
8、total volumetric flow rate from a stationary source. A measurement site where the effluent stream is flowing in a known direction is selected, and the cross-section of the stack is divided into a number of equal areas. Traverse points are then located within each of these equal areas. 3.0 Definition
9、sReserved 4.0 InterferencesReserved 5.0 Safety 5.1 Disclaimer. This method may involve hazardous materials, operations, and equipment. This test method may not address all of the safety problems associated with its use. It is the responsibility of the user of this test method to establish appropriat
10、e safety and health practices and determine the applicability of regulatory limitations prior to performing this test method. 6.0 Equipment and Supplies. 6.1 Apparatus. The apparatus described below is required only when utilizing the alternative site selection procedure described in Section 11.5 of
11、 this method. 6.1.1 Directional Probe. Any directional probe, such as United Sensor Type DA Three-Dimensional Directional Probe, capable of measuring both the pitch and yaw angles of gas flows is acceptable. Before using the probe, assign an identification number to the directional probe, and perman
12、ently mark or engrave the number on the body of the probe. The pressure holes of directional probes are susceptible to plugging when used in particulate-laden gas streams. Therefore, a procedure for cleaning the pressure holes by “back-purging” with pressurized air is required. 6.1.2 Differential Pr
13、essure Gauges. Inclined manometers, U-tube manometers, or other differential pressure gauges ( e.g., magnehelic gauges) that meet the specifications described in Method 2, Section 6.2. Note: If the differential pressure gauge produces both negative and positive readings, then both negative and posit
14、ive pressure readings shall be calibrated at a minimum of three points as specified in Method 2, Section 6.2. 7.0 Reagents and StandardsReserved 8.0 Sample Collection, Preservation, Storage, and TransportReserved 9.0 Quality ControlReserved 10.0 Calibration and StandardizationReserved 11.0 Procedure
15、 11.1 Selection of Measurement Site. 11.1.1 Sampling and/or velocity measurements are performed at a site located at least eight stack or duct diameters downstream and two diameters upstream from any flow disturbance such as a bend, expansion, or contraction in the stack, or from a visible flame. If
16、 necessary, an alternative location may be selected, at a position at least two stack or duct diameters downstream and a half diameter upstream from any flow disturbance. 11.1.2 An alternative procedure is available for determining the acceptability of a measurement location not meeting the criteria
17、 above. This procedure described in Section 11.5 allows for the determination of gas flow angles at the sampling points and comparison of the measured results with acceptability criteria. 11.2 Determining the Number of Traverse Points. 11.2.1 Particulate Traverses. 11.2.1.1 When the eight- and two-d
18、iameter criterion can be met, the minimum number of traverse points shall be: (1) twelve, for circular or rectangular stacks with diameters (or equivalent diameters) greater than 0.61 meter (24 in.); (2) eight, for circular stacks with diameters between 0.30 and 0.61 meter (12 and 24 in.); and (3) n
19、ine, for rectangular stacks with equivalent diameters between 0.30 and 0.61 meter (12 and 24 in.). 11.2.1.2 When the eight- and two-diameter criterion cannot be met, the minimum number of traverse points is determined from Figure 11. Before referring to the figure, however, determine the distances f
20、rom the measurement site to the nearest upstream and downstream disturbances, and divide each distance by the stack diameter or equivalent diameter, to determine the distance in terms of the number of duct diameters. Then, determine from Figure 11 the minimum number of traverse points that correspon
21、ds: (1) to the number of duct diameters upstream; and (2) to the number of diameters downstream. Select the higher of the two minimum numbers of traverse points, or a greater value, so that for circular stacks the number is a multiple of 4, and for rectangular stacks, the number is one of those show
22、n in Table 11. 11.2.2 Velocity (Non-Particulate) Traverses. When velocity or volumetric flow rate is to be determined (but not particulate matter), the same procedure as that used for particulate traverses (Section 11.2.1) is followed, except that Figure 12 may be used instead of Figure 11. 11.3 Cro
23、ss-Sectional Layout and Location of Traverse Points. 11.3.1 Circular Stacks. 11.3.1.1 Locate the traverse points on two perpendicular diameters according to Table 12 and the example shown in Figure 13. Any equation (see examples in References 2 and 3 in Section 16.0) that gives the same values as th
24、ose in Table 12 may be used in lieu of Table 12. 11.3.1.2 For particulate traverses, one of the diameters must coincide with the plane containing the greatest expected concentration variation ( e.g., after bends); one diameter shall be congruent to the direction of the bend. This requirement becomes
25、 less critical as the distance from the disturbance increases; therefore, other diameter locations may be used, subject to the approval of the Administrator. 11.3.1.3 In addition, for elliptical stacks having unequal perpendicular diameters, separate traverse points shall be calculated and located a
26、long each diameter. To determine the cross-sectional area of the elliptical stack, use the following equation: Square Area=D1 D2 0.7854 Where: D1=Stack diameter 1 D2=Stack diameter 2 11.3.1.4 In addition, for stacks having diameters greater than 0.61 m (24 in.), no traverse points shall be within 2.
27、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. To meet these criteria, observe the procedures given below. 11.3.2 Stacks With Diameters Greater Than 0.61 m (2
28、4 in.). 11.3.2.1 When any of the traverse points as located in Section 11.3.1 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 t
29、raverse points (on each end of a diameter) shall be the “adjusted” traverse points. 11.3.2.2 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 proce
30、dure, and in recording of the data. 11.3.3 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 t
31、he nozzle inside diameter, whichever is larger. 11.3.4 Rectangular Stacks. 11.3.4.1 Determine the number of traverse points as explained in Sections 11.1 and 11.2 of this method. From Table 11, determine the grid configuration. Divide the stack cross-section into as many equal rectangular elemental
32、areas as traverse points, and then locate a traverse point at the centroid of each equal area according to the example in Figure 14. 11.3.4.2 To use more than the minimum number of traverse points, expand the “minimum number of traverse points” matrix (see Table 11) by adding the extra traverse poin
33、ts along one or the other or both legs of the matrix; the final matrix need not be balanced. For example, if a 4 3 “minimum number of points” matrix were expanded to 36 points, the final matrix could be 9 4 or 12 3, and would not necessarily have to be 6 6. After constructing the final matrix, divid
34、e the stack cross-section into as many equal rectangular, elemental areas as traverse points, and locate a traverse point at the centroid of each equal area. 11.3.4.3 The situation of traverse points being too close to the stack walls is not expected to arise with rectangular stacks. If this problem
35、 should ever arise, the Administrator must be contacted for resolution of the matter. 11.4 Verification of Absence of Cyclonic Flow. 11.4.1 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
36、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
37、 acceptable for this determination. 11.4.2 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
38、cross-sectional plane; when the Type S pitot tube is in this position, it is at “0 reference.” Note the differential pressure (p) 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
39、 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 the rotation angle () to the nearest degree. After the null technique has been applied at each traverse point, calculate the averag
40、e of the absolute values of ; assign values of 0 to those points for which no rotation was required, and include these in the overall average. If the average value of is greater than 20, the overall flow condition in the stack is unacceptable, and alternative methodology, subject to the approval of
41、the Administrator, must be used to perform accurate sample and velocity traverses. 11.5 The alternative site selection procedure may be used to determine the rotation angles in lieu of the procedure outlined in Section 11.4. 11.5.1 Alternative Measurement Site Selection Procedure. This alternative a
42、pplies to sources where measurement locations are less than 2 equivalent or duct diameters downstream or less than one-half duct diameter upstream from a flow disturbance. The alternative should be limited to ducts larger than 24 in. in diameter where blockage and wall effects are minimal. A directi
43、onal flow-sensing probe is used to measure pitch and yaw angles of the gas flow at 40 or more traverse points; the resultant angle is calculated and compared with acceptable criteria for mean and standard deviation. Note: Both the pitch and yaw angles are measured from a line passing through the tra
44、verse point and parallel to the stack axis. The pitch angle is the angle of the gas flow component in the plane that INCLUDES the traverse line and is parallel to the stack axis. The yaw angle is the angle of the gas flow component in the plane PERPENDICULAR to the traverse line at the traverse poin
45、t and is measured from the line passing through the traverse point and parallel to the stack axis. 11.5.2 Traverse Points. Use a minimum of 40 traverse points for circular ducts and 42 points for rectangular ducts for the gas flow angle determinations. Follow the procedure outlined in Section 11.3 a
46、nd Table 11 or 12 for the location and layout of the traverse points. If the measurement location is determined to be acceptable according to the criteria in this alternative procedure, use the same traverse point number and locations for sampling and velocity measurements. 11.5.3 Measurement Proced
47、ure. 11.5.3.1 Prepare the directional probe and differential pressure gauges as recommended by the manufacturer. Capillary tubing or surge tanks may be used to dampen pressure fluctuations. It is recommended, but not required, that a pretest leak check be conducted. To perform a leak check, pressuri
48、ze or use suction on the impact opening until a reading of at least 7.6 cm (3 in.) H2O registers on the differential pressure gauge, then plug the impact opening. The pressure of a leak-free system will remain stable for at least 15 seconds. 11.5.3.2 Level and zero the manometers. Since the manometer l