Stack PT Schemes  

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The aim of the Gas Measurement and Gas Cylinder Proficiency Testing Scheme is to assess the performance of test houses in sampling and measuring stack gases, using test atmospheres traceable to National Standards.

The scheme involves the measurement of combustion gases (NO, NO2, SO2, CO, O2, VOCs & CO2) directly from cylinders and from NPL’s stack simulator facility, at concentrations and conditions typical of plant falling under the Industrial Emissions Directive (IED). The cylinder component gives information on instrument calibration, performance and NOx converter efficiency, while measurements from the artificial stack give additional information on sampling. Testing is performed at NPL.

Testing is performed at NPL.

Concentrations for Gas Measurement Proficiency Testing:

Test

NOx
(ppm)

VOC
(ppm)

SO2
(ppm)

CO
(ppm)

O2
(%)

H2O
(%)

Max Range

270

10

200

100

17

20





Maximum concentrations for Gas Measurement component

Description: Gases & Gas Analysis

 

Minimum concentration

Maximum concentration

SO2

50 ppm

1000 ppm

C3H8 + 10%O2 in nitrogen

1 ppm

50 ppm

NO

5 ppm

500 ppm

CO

10 ppm

1000 ppm

O2

2 %

21%

CO2

1%

20%

NO and NO2 in nitrogen
For testing NOx converters

NOx 50 ppm
NO 40 ppm

NOx 500 ppm
NO 400 ppm


                                                                   Range of concentrations for cylinder component

The NPL stack simulator is able to reproduce a wide range of simulated stack gases under controlled conditions. The simulator is a recirculating system which recreates a cross section of a 1.5 m duct. Four standard five-inch ports are available for fixed sampling probes or cross stack instruments. Assigned values are calculated by measurement of the gases within the simulator using the standard reference methods or proven equivalent. Standard deviation for proficiency testing is derived by reference to the relevant CEN standards to which participants are accredited.

All components of the Gas Measurement and Gas Cylinder PT Scheme are accredited to ISO EN 17043.

Participants will be able to make measurements using 2 analysers for each pollutant for both the Gas Measurement and Cylinder components, thus allowing them to test different measurement technologies and calibration techniques.