Sampler Flow Rate Audit

The calibration relationship between the flow rate (in actual L/min) indicated by the flow rate standard and the sampler’s flow rate measurement device should be established or verified in accordance with the sampler’s operation or instruction manual prior to the audit; however, no adjustments may be made to the sampler’s flow rate sensors or controls before the audit is performed. A suggested audit data recording form is shown in Figure 10-1. For automated data acquisition, a printout may be attached to this and subsequent audit data sheets. The example audit data sheet shown in Figure 1-1 should be styled to include additional information as necessary. In conducting the sampler flow rate audit (or any audit for that matter) the auditor should consult the manufacturer’s operations manual for sampler-specific procedures,

suggestions, and precautions.

The audit of the sampler’s flow rate consists of one measurement made at the sampler’s operational flow rate. The flow rate transfer standard used for the audit must not be the same flow rate standard used to verify or calibrate the sampler but may have been made traceable to the same primary standard for flow rate or volume. The sampler’s operation or instruction manual should provide specific instructions for using the instrument’s flow rate readout or display. The audit is performed by the operator or by personnel from the quality assurance (QA) unit of the reporting organization as follows:

1. Install a flow rate audit filter/cassette in the filter holder and energize the sampler. Filters used for flow rate audits should not be used further for sampling. If the network’s sampling schedule is on a daily basis or if loss of a sampling day cannot be accommodated, a flow rate audit may be conducted during a sampling event provided that

• The active sampling filter is removed and protected from contamination and damage by

storing it in a clean container between uses • A flow rate audit filter is used for the audit

• The active sampling period is not interrupted for more than 1 hour in order to achieve a minimum overall sampling period of 23 hours.

2.12.10.0 Performance Evaluation Procedures November 1998 Page 4 of 13

and vacuum pump to stabilize.

3. Record the sampler’s flow rate as the “sampler flow rate before audit” on an audit data sheet, such as the example given in Figure 10-1.

4. Complete the required information at the top of the sampler audit data sheet (Figure 10-1). 5. Remove the sampler inlet and install the flow rate adapter device (refer to Figure 6-2). 6. Connect the adapter to the flow rate transfer standard outlet with flexible tubing, being

careful not to crimp the tubing. Refer to Figure 8-3 for an example of the setup. If the transfer standard is electronic (such as an electronic micromanometer coupled to an orifice device), allow sufficient warmup time, based on one’s prior experience with the device, for readings to stabilize.

7. Recheck the flow rate indicated by the PM sampler’s data display or other readout device._2.5 Record this value and the corresponding flow rate indicated by the audit device.

8. Record at least three sampler and audit flow rate readings of the output data directly on the audit data sheet (Figure 10-1). If electronic recording devices are used for one or more of the parameters, be sure that the clocks are synchronized. If units other than actual flow are displayed by the audit device, the ambient temperature and barometric pressure will have to be independently determined and calculations will have to be made to express results at ambient conditions. See Section 10.2.1.1 for calculation methods. Record all results on the data sheet and average them. Also compare the audit flow rate with the designated flow rate, 16.67 L/min.

9. Calculate the average difference in flow rate in L/min and as a percentage of the audit flow rate. Record all data for eventual submission to the EPA Aerometric Information Retrieval System (AIRS) database.

10. Following the measurement with the flow rate standard, remove the adapter and reinstall the sampler inlet. From the sampler’s display, read the sampler’s operating flow rate again (in L/min) with the flow rate filter in place. Record this as the “sampler flow rate after audit” on the audit data sheet. Remove the flow rate audit filter. Do not use it for further sampling; it may be used several more times for flow rate audits of the same model sampler, provided it is carefully stored between uses to prevent contamination or damage. Stop using this filter when a buildup of particles on the filter surface is visible.

11. Replace the sample filter if it was removed in the midst of a sampling event. Otherwise, return the sampler to its pre-audit condition.

10.2.1.1 Flow Rate Audit Data Calculations

PM flow rate audit results should be reported at ambient conditions and should not be_2.5 corrected to standard conditions (e.g., 25 EC, 760 mmHg). However, for some types of audit devices, it may be necessary to correct the indicated audit flow rates to ambient conditions. Equation (10-1) may be used to make this correction. The following correction should be applied only if the audit device reports flow rate already corrected to standard conditions (e.g., mass flowmeters). Be sure to verify the standard conditions of temperature and pressure (T and P ,std std respectively) applicable to the audit device.

2.12.10.0 Performance Evaluation Procedures November 1998 Page 5 of 13

PM Sampler Audit Data Sheet2.5

Flow Rate, Temperature, and Pressure Audit

Site Name. Site Location.

Auditor’s Name. Observer’s Name.

Sampler Model:

IO-2001 Sampler ID: R-102

Flow Rate Audit Device Manufacturer, Model, Serial Number: Orifice device, S/N 104,

coupled to electronic digital micromanometer

Temperature Audit Device Manufacturer, Model, Serial Number: Thermistor

temperature probe, S/N T01562-53

Pressure Audit Device Manufacturer, Model, Serial Number: Hand-held aneroid barometer,

S/N 420292

Flow Rate Audit: Date of Test: 8/13/97

Sampler flow rate before audit 16.65 L/min Sampler flow rate after audit 16.72 L/min Sampler’s Indicated

Flow Rate, L/min

Audit Flow Rate, L/min Difference (Sampler - Audit), L/min Difference ÷ Audit Flow, % 16.72 16.59 16.65 16.51 16.74 16.61 16.70 Avg. 16.57 Avg. 0.13 0.8%

Temperature Audit: Date of Test: 8/13/97

Sampler’s Indicated T , a EEC Audit T , a EEC

Difference (Sampler - Audit), EEC

Inlet Filter Inlet Filter Inlet Filter

33.7 34.5 33.1 34.7

33.8 34.6 33.2 34.8

33.7 34.5 33.0 34.7

33.7 Avg. 34.5 Avg. 33.1 Avg. 34.7 Avg. 0.6 -0.2

Pressure Audit: Date of Test: 8/13/97

Sampler’s Indicated P , mmHga

Audit P ,a

mmHg

Difference (Sampler - Audit), mmHg

759 760

761 760

758 759

759 Avg. 760 Avg. -1

Notes: Attach additional sheets, if necessary. Show calculations on attached sheets.

2.12.10.0 Performance Evaluation Procedures November 1998 Page 6 of 13

Q = Q (T /P ) (P /T )_{a std a a std std} (10-1)

where

Q = flow rate at actual conditions, L/min_a

Q_std = flow rate reported at standard temperature and pressure (e.g., 25 EC, 298 K;

760 mmHg or 101 kPa), L/min

T_a = ambient temperature, K

P = ambient barometric pressure, mmHg or kPa_a

P , T_{std std} = standard barometric pressure and temperature, respectively.

Determine the percentage difference between the sampler-indicated flow rates and the audit- measured flow rates using Equation (10-2). Record the result on the audit data sheet. Any deviation greater than ±2 percent may require recalibration.

% difference = 100 × (Q (sampler) - Q (audit))/Q (audit) _{a a a} (10-2)