NIST Traceability Offered for H2S Measurement in Natural Gas

SpectraSensors (USA) in collaboration with Air Liquide has developed the first National Institute of Standards and Technology (NIST) traceable analyser for measuring impurities such as hydrogen sulfide (H2S) in natural gas pipelines. Both companies realised it would require a major commitment of time and money to build a traceability path back to NIST.

“SpectraSensors showed us we could differentiate ourselves if we could solve this problem and their analyser would have a strong case in any dispute,” says Air Liquide Chief Technical Officer, Dr. Stephen Miller.

 “First, we determine the concentration and the accuracy of the mixture by mass alone using NIST primary references and stringent statistical methods,” adds Dr. Miller. “Then, we analyse that same cylinder in the laboratory using instruments calibrated with NIST SRM’s (standard reference materials). When these two independent processes agree with one another, we have high confidence in the certified H2S concentration, and we have the required unbroken chain of comparisons within our measurements all the way back to NIST.”

The bottom line for everyone in the measurement business is that NIST is the standard, NIST traceability ends all debates.

The analyser is calibrated at the SpectraSensors factory using the new, dual-certified NIST traceable H2S calibration standards from Air Liquide. Termed the SSRM (SpectraSensors Reference Material) since it is a unique product developed for SpectraSensors, the blend is diluted in hydrocarbon streams through a dynamic blending station that uses mass flow controllers (MFCs). Both the SSRM and the MFCs are verified with NIST traceable flow references.

A customer can also validate an analyser in the field, using an Air Liquide NIST traceable bottle.