Reference method for measuring asbestos emissions from asbestos mining and milling operations: part I

Part I - Sampling - Method S-1

Sampling of Stacks and Ducts in Asbestos Milling Operations

• S-1.1 Scope
• S-1.2 Procedures

S-1.1 Scope

This method is applicable to the sampling of stacks or ducts in asbestos milling operations which are a source of particulate emissions to the atmosphere.

S-1.2 Procedures

Sampling shall be carried out according to the standard sampling procedures indicated in Report EPS 1 -AP-74-1, Standard Reference Methods for Source Testing: Measurement of Emissions of Particulates from Stationary Sources. The following procedures, S-1.2.1 to S-1.2.5, refer to methods described in this report. Procedure S-1.2.6 incorporates certain modifications to the standard method and shall be used in place of Method E in the above report.

S-1.2.1 Determination of Sampling Site and Traverse Points

Method A. Report EPS 1-AP-74-1.

S-1.2.2 Determination of Stack Gas Velocity and Volumetric Flow Rate

Method B. Report EPS 1-AP-74-1.

S-1.2.3 Determination of Molecular Weight by Gas Analysis

Method C. Report EPS 1-AP-74-1.

S-1.2.4 Determination of Moisture Content

Method D. Report EPS 1-AP-74-1.

S-1.2.5 Calibration Procedure for S-Type Pitot Tube, Dry Gas Meter, Orifice Meter, and Rotameter

Method F. Report EPS 1-AP-74-1.

S-1.2.6 Sampling for Particulate Asbestos Emissions

S-1.2.6.1 Principle

Particulate matter including asbestos particles, is withdrawn isokinetically from a number of sampling points in the stack. Sampling isokinetically means that the linear velocity of the gas entering the sampling nozzle is equal to that of the undisturbed gas stream at the sample point.

S-1.2.6.2 Apparatus

Sampling Train (Figure S-1-1).

Figure S-1-1: Asbestos Stack-Sampling Train (In-Stack Filter)

Figure S-1-2: Sectioned Filter

Nozzle. A stainless steel nozzle with a sharp tapered leading edge is required.

Probe. A Pyrex probe encased in stainless steel is required. This probe must have a heating system capable of maintaining the temperature of gas at the exit end in excess of 250°F during sampling to prevent condensation.

S-Type Pitot Tube. An S-type pitot tube or equivalent is attached to the probe to monitor stack-gas velocity.

Temperature Gauge. A thermocouple or equivalent, capable of measuring stack temperatures to within 1.5% of the minimum absolute stack temperature, is attached to the pilot tube.

Filter Holder. An in-line filter holder designed for filters 47 mm in diameter is required. It must be able to withstand temperatures up to 200°F and must include a stainless steel filter support pad and a suitable gasket.

Filter. A cellulose membrane filter 47 mm in diameter, with 0.8 μm nominal pore size, is required. When supported in the filter holder there is an effective filtering area of about 960 mm². The effective filtration area is marked with a grid of eight angular 45° sectors which are each divided into an inner (A_i) and outer (A_o) radial area The ratio A_i:A_o is 1:3. Each angular sector is identified by a printed number on its outer edge. A 'T' is printed to identify the top of the filter. Diagrams of the sectioned filter and a typical filter sector are given in Figure S-1-2.

lmpingers. Four Greenburg-Smith impingers are connected in series. The first, third, and fourth impingers are modified by replacing the tips and impaction plate of the standard design with a ½-in. I.D. glass tube extending to within ½ in. of the bottom of the flask. The second impinger has the standard tip and impaction plate.

Leakless Vacuum Pump. A vacuum pump capable of maintaining an isokinetic sampling rate and continuously withdrawing a portion of the stack gases through the sampling train is used. The pump is connected to the outlet of the last impinger by a vacuum line containing a gauge to measure the pump intake vacuum to within 0.5 in. Hg and a coarse adjust valve to regulate the sample flow. A bypass valve is connected across the vacuum pump to allow fine control of the sample flow.

Dry Gas Meter. A dry gas meter calibrated to within ± 1 % and equipped with inlet and outlet temperature indicators is used to determine sample volume. The dry gas meter follows the vacuum pump in the sampling train.

Orifice Meter. A calibrated orifice meter is used to measure the sampling flow rate. The orifice meter is connected to the outlet of the dry gas meter.

Differential Pressure Gauges. Inclined manometers, or equivalent, capable of measuring pitot tube velocity pressure and the pressure drop across the orifice meter to within 0.025 in. H₂O are required.

Barometer. A barometer capable of measuring atmospheric pressure to within ± 0.1 in. Hg should be used.

Sample Recovery and Analysis

Trip Balance. A balance with a 300-g capacity, capable of measuring to within ± 0.05g is required.

Miscellaneous. A wash botttle, sample-storage containers, and a 250-ml graduated cylinder are also required.

S-1.2.6.3 Reagents

Sampling Train. Indicating-type, 6-16 mesh silica gel, dried at 350°F for 2 h, is required together with deionized or distilled water, and crushed ice.

Sample Recovery and Analysis. Deionized or distilled water is required.

S-1.2.6.4 Procedure

Sampling Train

Preliminary. Select the sampling site and minimum number of sampling points according to the procedures described in Method S-1.2.1. Determine the stack pressure, temperature, moisture, and range of velocity pressures, and use this information to calculate the required isokinetic sampling flow rate during subsequent stack-sampling tests. Determine the nozzle size required for isokinetic sampling using this data. Recommended minimum nozzle size is ¼ in. I.D.

Preparation of Collection Train. The filter holder is loaded in the laboratory. A separate preloaded filter holder must be prepared for each sample. Place the filter in the holder so that the "T" on the filter corresponds with an external marking on the holder. Seal the ends of the loaded filter holder with plastic plugs and place in a suitable container with the filter face in the upright position. The preloaded filter holder should be carefully conveyed to the sampling site.

Place 100 ml of deionized or distilled water in each of the first two impingers and weigh. Weigh the third impinger and leave empty. Place approximately 200 g of silica gel in the fourth impinger and weigh. Record these initial weights on the moisture analysis data sheet, Figure S-1-3.

Figure S-1-3: Moisture Analysis Data Sheet

At the sampling site, attach a loaded filter to the probe and then attach the nozzle to the holder. Align the nozzle so that the "T" on the filter will be at the top of the filter holder with respect to the nozzle tip. Attach the probe to the sampling train so that the final configuration is as indicated in Figure S-1-1. Check the sampling unit for leaks by plugging the nozzle inlet with a rubber stopper and pulling a 15 in. Hg vacuum. If the needle on the dry gas meter moves, a leakage rate not in excess of 0.02 ft³/min at a vacuum of 15 in. Hg is acceptable. After leak checking, adjust the heater to provide a minimum gas temperature of 250°F at the probe outlet. Adjust the temperature in the heated area ahead of the impingers to 225°F. Place crushed ice around the impingers. Add more ice during the run to keep the temperature of the gases leaving the last impinger as low as possible, preferably at 70°F or less. Temperatures above 70°F may result in damage to the dry gas meter from either condensation or excessive heat.

Particulate Train Operation. To begin sampling, position the sampling nozzle at the first sampling point (traverse point). Point the nozzle directly into the approaching gas stream and secure the entire apparatus to the support system. Immediately start the vacuum pump and adjust the sampling flow rate to isokinetic conditions. Sample for at least 2 min at each sampling point; sampling time must be the same for each point. Maintain isokinetic sampling throughout the sampling period by making the necessary adjustments in the sampling flow rate as stack conditions change, or as the buildup of particulate matter on the filter affects the flow. Nomographs are available, or can be constructed, which aid in the rapid adjustment of the sampling rate without other computations. For each run, record the data required on the data sheet in Figure S-1-4. Record instrument readings at intervals consistent with the test duration established for each point. For example, if testing for a minimum of 2 min per point, record readings every minute and whenever flow adjustments are necessary. The time between readings should not exceed 2 min. When the traverse is completed, turn off the vacuum pump and record the final instrument readings. Transfer the sampling apparatus to the other sampling port and repeat the sampling procedure. When the second traverse is completed, remove the sampling apparatus from the stack and handle in accordance with the sample recovery procedure described below.

Figure S-1-4: Data Sheet - Stack Sampling

Sample Recovery

At the sampling site, disconnect the probe from the sampling train. Carefully disconnect the filter holder from the probe and avoid jarring or knocking the unit. Once removed, hold the filter holder in a horizontal position so that the exposed filter surface is facing upward at all times and carefully disconnect the nozzle. Seal the filter holder with plastic plugs and place upright in a container for transfer to the analytical laboratory.

Sample Analysis

Filter. The filter is analysed for asbestos content according to the analytical procedure (A-1) in Part II. For each filter sample obtained, a minimum of four alternate sectors must be analysed (1, 3, 5, and 7, or 2, 4, 6, and 8). The result for the filter sample is the average of the results for the four or more sectors analysed.

Impingers. Determine the final weights of all four impingers and their contents to the nearest 0.5 g and record on the moisture analysis data sheet (Figure S-1-3). Total moisture (V_lc) is the total volume of liquid collected in all impingers.

S-1.2.6.5 Calculations

Average Dry Gas Meter Temperature and Average Orifice Pressure Drop. Refer to data sheet (Figure S-1-4).

Dry Gas Volume. Correct the sample volume measured to reference conditions (77°F and 29.92 in. Hg), using Equation S-1-1.

Equation S-1-1

where

• (V_m)_ref = sample volume corrected to reference conditions, ft³
• V_m = volume of gas measured by dry gas meter at meter conditions, ft³
• T_ref = absolute temperature at reference conditions, 537 °R
• T_m = average dry gas meter temperature, °R
• P_bar = barometric pressure, in. Hg
• ΔH = average pressure drop across orifice (see Figure S-1-4), in. H₂O
• 13.6 = conversion factor, in. H₂O/in. Hg
• P_ref = absolute pressure at reference conditions, 29.92 in. Hg

Volume of Water Vapour. Convert the volume of water condensed during the stack test to a volume of water vapour at reference conditions using Equation S-1-2.

Equation S-1-2

where

• (V_w)_ref = volume of water vapour in gas sample at reference conditions, ft³
• V_lc = total volume of liquid collected in impingers (see Figure S-1-3), ml
• ρ_H2O = density of water, 0.9982 g/ ml
• M_H2O = molecular weight of water, 18 lb/lb-mole
• R = ideal gas constant, 21.83 in. Hg ft³/lb-mole °R
• T_ref = absolute temperature at reference conditions, 537 °R
• P_ref = absolute pressure at reference conditions, 29.92 in. Hg
• 453.6 = conversion factor, g/lb

Moisture Content. Calculate the moisture content of the stack gas using Equation S-1-3.

Equation S-1-3

where

• B_wo = proportion by volume of water vapour in the gas stream
• (V_w)_ref = volume of water vapour in the gas sample at reference conditions (see Equation S-1-2), ft³
• (V_m)_ref = volume of gas through dry gas meter at reference conditions, ft³

Acceptable Results. The percent isokinetic variation (%I), calculated for each sample point using Equation S-1-4, should fall within the range 90% < %I < 110%.

Equation S-1-4

where

• I = ratio of the sampling velocity through the nozzle to stack gas velocity
• V_m = volume of gas sampled through gas meter at meter conditions for each point sampled, ft³
• t = sampling time for each point sampled, min
• B_wo = proportion by volume of water vapour in the gas stream (see Equation S-1-3)
• P_s = absolute stack-gas pressure, in. Hg
• T_s = absolute stack-gas temperature for each point sampled, °R
• T_mi = dry gas meter, absolute inlet temperature for each point sampled, °R
• T_mo = dry gas meter, absolute outlet temperature for each point sampled, °R
• P_bar = barometric pressure at the sampling site, in. Hg
• U_s = stack gas velocity at each point sampled, ft/s
• N_d = inside diameter of sampling nozzle, in.
• ΔH = pressure drop across orifice meter for each point sampled, in. H₂O
• 0.3272 = conversion factor, (s/min) (ft²/in.²) (π)
• 13.6 = conversion factor, in. H₂O/in. Hg