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NOTE: This method does not include all of the specifications (e.g., equipment and supplies) and procedures (e.g., sampling) essential to its performance. Some material is incorporated by reference from other methods in this part. Therefore, to obtain reliable results, persons using this method should also have a thorough knowledge of at least the following additional test methods: Method 1, Method 2, and Method 2A.
Necessary equipment for performing flow Method 2Content [ show/hide ].
1.1 This method is applicable for the determination of the volumetric flow rates of gas streams in small pipes and ducts. It can be applied to intermittent or variable gas flows only with particular caution.
1.2 Data Quality Objectives. Adherence to the requirements of this method will enhance the quality of the data obtained from air pollutant sampling methods.
2.1 All the gas flow in the pipe or duct is directed through a rotameter, orifice plate or similar device to measure flow rate or pressure drop. The device has been previously calibrated in a manner that insures its proper calibration for the gas being measured. Absolute temperature and pressure measurements are made to allow correction of volumetric flow rates to standard conditions.
5.1 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 appropriate safety and health practices and determine the applicability of regulatory limitations prior to performing this test method.
Specifications for the apparatus are given below. Any other apparatus that has been demonstrated (subject to approval of the Administrator) to be capable of meeting the specifications will be considered acceptable.
A rotameter, orifice plate, or other volume rate or pressure drop measuring device capable of measuring the stack flow rate to within ±5 percent. The metering device shall be equipped with a temperature gauge accurate to within ±2 percent of the minimum absolute stack temperature and a pressure gauge (accurate to within ±5 mm Hg). The capacity of the metering device shall be sufficient for the expected maximum and minimum flow rates at the stack gas conditions. The magnitude and variability of stack gas flow rate, molecular weight, temperature, pressure, dew point, and corrosive characteristics, and pipe or duct size are factors to consider in choosing a suitable metering device.
Same as Method 2, Section 6.5.
Capable of measurement to within 1 second.
Same as Method 2A, Sections 8.1 and 8.2, respectively.
At least once an hour, record the metering device flow rate or pressure drop reading, and the metering device temperature and pressure. Make a minimum of 12 equally spaced readings of each parameter during the test period. Record the barometric pressure at the beginning and end of the test period. Record the data on a table similar to that shown in Figure 2D-1.
Use volume rate devices with particular caution. calibration will be affected by variation in stack gas temperature, pressure and molecular weight. Use the procedure in Section 8.2.1 with the addition of the following: Record all the metering device parameters on a time interval frequency sufficient to adequately profile each process cyclical or non-continuous event. A multi-channel continuous recorder may be used.
Same as Method 2A, Section 10.0, with the following exception:
Same as Method 2A, Section 10.1, except calibrate the metering device with the principle stack gas to be measured (examples: air, nitrogen) against a standard reference meter. A calibrated console meter is an acceptable reference meter. Ideally, calibrate the metering device in the field with the actual gas to be metered. For metering devices that have a volume rate readout, calculate the test metering device calibration coefficient, Ym, for each run shown in Equation 2D-2 Section 12.3.
Refer to the manufacturer's instructions to calculate the Vm corresponding to each Vr.
Use the procedure and specifications in Method 2A, Section 10.2. Perform the calibration at a temperature that approximates field test conditions.
Calibrate the barometer to be used in the field test with a mercury barometer prior to the field test.
Sample collection and analysis are concurrent for this method (see Section 8.0).
Pbar = Barometric pressure, mm Hg (in. Hg).
Pm = Test meter average static pressure, mm Hg (in. Hg).
Qr = Reference meter volume flow rate reading, m3/min (ft3/min).
Qm = Test meter volume flow rate reading, m3/min (ft3/min).
Tr = Absolute reference meter average temperature, K (R).
Tm = Absolute test meter average temperature, K (R).
K1 = 0.3855 K/mm Hg for metric units = 17.65 R/in. Hg for English units.
Calculation for testing metering device calibration coefficient, Ym.
1. Spink, L.K. Principles and Practice of flowmeter Engineering. The Foxboro Company. Foxboro, MA. 1967.
2. Benedict, R.P. Fundamentals of temperature, Pressure, and flow Measurements. John Wiley & Sons, Inc. New York, NY. 1969.
3. Orifice metering of Natural Gas. American Gas Association. Arlington, VA. Report No. 3. March 1978. 88 pp.
Figure 2D-1. Volume flow rate measurement data.