LAB 2.pdf

Introduction The APM 421 Calibrator has been designed to calibrate the flow rate of Respirable Dust Samplers (RDS) in the field. The figure below shows the different components that are provided with the APM 421 calibrator. Sabet site = “TOP LOADING CALIBRATOR AIR INLET COUPLER Each APM 421 Cal...

Introduction The APM 421 Calibrator has been designed to calibrate the flow rate of Respirable Dust Samplers (RDS) in the field. The figure below shows the different components that are provided with the APM 421 calibrator. Sabet site = “TOP LOADING CALIBRATOR AIR INLET COUPLER Each APM 421 Calibrator is tested against an NABL traceable primary standard roots meter and the entire system is supplied in a convenient carrying case. The system gets coupled to the air inlet pipe of the respirable dust sampler and allows the user to verify the accuracy of the flow metering system of the sampler by comparison with a calibrated orifice. For instruments exposed to the rigors of field use flow rate calibration should be verified at least once in six months and after any major repairs have been carried out. Perforated plates provided with the APM 421 enable the user to simulate different amounts of dust loads on the filter and enable multi-point calibration to be performed. CE: Crannad with NK Preparing the Sampler & Calibrator The steps given below will enable you to setup the calibrator as shown here: * Open the Top cover of the RDS and examine the condition of the filter clamp down gasket. Check that there is no filter in place and close the top cover taking care to tighten the wing nuts uniformly. * Unscrew the Yellow Cap over the Air Inlet Pipe and | (as Srannad with OKI mount the Air Inlet Coupler over the threaded portion of the inet pipe Place a perforated plate over the face of the coupler and mount the Top loading Calibrator over it and Trmly tighten the Knurled ring of the calibrator Suitable O rings have been provided on the face of the coupler and the calibrator to ensure that there is No leakage. Place the Differential Pressure Meter along side the , Tront plate of the instrument as shown above. ‘AC Connect the nozzle provided on the side of the ( d Calibrator to the —ve inlet of the Differential Pressure Meter. The +ve inlet must be left free at atmospheric ) pressure, * Check the water level in the Manometer of the RDS. tf necessary top up the level with distilled water until the Zero mark. * The sampler and calibrator are now ready, Performing a Calibration Check 1. Power ON the Respirable Dust Sampler. Allow the blower speed to stabilize and note the flow rate indicated by the Orifice meter of the instrument. Press the power ON button on the Differential Pressure meter of the Calibrator. The instrument will show the pressure developed across the calibrated orifice of the APM 421. Check that the units for pressure measurement are in mmH,2O. Use the Calibration Curve provided with the system to determine the actual flow rate measured by the top loading calibrator. 3. Switch OFF the RDS, loosen the knurled ring and replace the perforated plate placed below the top loading calibrator. Repeat steps 1 and 2 above to check the flow rate calibration at the new flow rate. N 1 es Srannad with OKI The RDS is usually operated at a flow rate of 1m°/min so it is recommended that an audit check at this flow rate be performed every month. Normally plate No. 3 will give you a flow rate in this range. If the flow rate calibration error exceeds 5% perform a multi point calibration and determine a correction factor. In genéral it is recommended that a multi point calibration be performed at least once a year. Barometric Pressure and Temperature correction Each APM 421 Calibrator is tested against a traceable primary standard roots meter maintained at Envirotech and a calibration certificate is provided with each system. The calibration certificate states the ambient temperature and pressure conditions prevailing in our test laboratory when the calibrator was tested. Field conditions when the Calibrator is used to check the flow rate of an RDS can sometimes be substantially different from these. Central Pollution Control Board (CPCB) recommends that a pressure correction be applied if field conditions differ from the lab conditions by more than 4%. Similarly a temperature correction should be applied if the prevailing temperature differs by more than 15 °C from the lab conditions. A digital barometric pressure indicator is optionally supplied by Envirotech (at an extra cost) to determine the atmospheric pressure prevailing at the site where a calibration check is being performed. The section below gives a sample calculation that may be used as a guide to perform a Pressure / Temperature correction: LAB CONDITIONS FIELD CONDITIONS Pressure (P1) 986.6mbar | Pressure (P2) 1026 mbar Temp (11) 273+25 degk Temp (T2) 273+40 degK Air Volume (V1) 0.87 m’ | AirVolume (V2) sm” | (as Grannod with OKI As per Gas Laws (P1xV1)/T1 = (P2xV2)/T2....-..eeeeee eee (1) Rearranging equation 1 we have: V2 = (P1xV1xT2)((T1xP2) —......-eeeeeee eee (2) | (as Grannod with OKI V2 = (986.6x0.87x313)/(298x1026) V2 = 0.879 m’®. Remember to use consistent units and convert temperature readings to degrees Kelvin. if Pressure / temperature correction needs to be applied the test procedure remains as described earlier. You take readings of differential pressure and determine the flow rate from the calibration curve provided with the APM 421. Apply the temp / pressure correction using gas laws as indicated above to work out the “TRUE Flow Rate’ at site conditions.