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Simplifying Complexity.
Delivering Safety.

Mercury analysis in natural gas

Mercury analysis in natural gas


Working with a leading trace contaminant analyser OEM to develop a hazardous area solution for a Mercury analyser



Trace levels of Mercury (Hg) can be present in natural gas wells and natural gas production streams, depending upon factors such as the local geology, and may be present in either elemental form or in compounds such as chlorides. Measuring Hg content is important for natural gas producers as, even in trace amounts, it can damage gas processing equipment, various metal parts, and gas pipelines due to steady Hg accumulation over time.


Project Brief

Work with the customer to develop a hazardous area enclosure solution for a Mercury analyser for installation in Zone1 and Class I Div.1 areas.


  • Although the analyser requires only a small sample flow of natural gas, the enclosure would still be classed as having an internal source of release (ISOR - the potential for a release of hazardous gas inside the protected enclosure itself). This requires additional safety features and a more complex certification process under hazardous area standards, including EN 60079-2 in Europe and NFPA496 in North America.


  • Expo's engineers worked with the client to design a bespoke Ex p enclosure that would meet the stringent requirements of systems with an ISOR.
  • The enclosure was compartmentalised to separate the gas sample components from the main electronics area
  • The purge system was configured as a continuous flow (CF) X purge system to provide a suitable dilution flow to ensure that, in the event of any sample leak, the maximum concentration would remain below 25% of the lower explosive limit (LEL)
  • The system also series purged the electronics compartment before the gas sampling area
  • In line with the requirements to isolate the power automatically in the event of purge gas failure, a minipurge interface unit was installed
  • Expo's consultancy team developed the certification plan along with a Notified Body to deliver the required certification. 


Expo Products and Services
  • Custom enclosure service
  • Expo Minipurge Type X
  • Minipurge interface unit (MIU)
  • Design services
  • Certification consultancy

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