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25 June 2014

Safety tips for working with high-pressure gas systems

Kneser_LFG-hi-pressIn the past few years I have been working with many more high-pressure gas systems, rather than the low-pressure systems typically found in the landfill and biogas industries. High pressure systems present different and additional hazards, so I thought I’d offer information on these hazards, and a few tips on how to deal with these systems safely.

Why the increase in high pressure gas systems?

The increasing popularity of high BTU pipeline gas projects and compressed natural gas fuel processing skids and fueling stations are two key reasons we’re seeing more high pressure gas systems and their associated hazards. Another big reason is the recent NFPA 56 regulations, which require nitrogen purging of piping systems at many of the beneficial-use facilities we work on.

Typical operating pressures for the systems vary depending upon the application. A few examples include:

• BioCNG fueling station – 4,500 pounds per square inch (PSI)

• Nitrogen purging – 2,200 PSI

• LFG to CNG processing facilities – 500 PSI

What are the hazards of high pressure gas systems?

There are three main types of hazards associated with working on high pressure biogas and nitrogen systems. Here’s a brief overview and a few pointers for dealing with the risk.

Pressure – Pressure causes the most injuries in the compressed gas industry – probably because it can’t be seen. The biggest injury risk comes from working on pressurized fittings. Never tighten a pressurized fitting to try to stop a leak! Also, be sure to exercise caution if you are using sampling equipment on high pressure fittings. Wear hearing protection when releasing pressure from fittings. Don skin protection when handling fittings and regulators releasing gas on high pressure systems to avoid risk of injury from freezing temperatures.

Asphyxiation – We in the landfill industry are quite used to dealing with methane’s asphyxiation risks. However, at high pressures, even small volumes of methane can expand quickly and fill an enclosed area. Nitrogen is also an asphyxiant with similar breathing hazards to methane. A few additional factors to keep in mind:

• In most high pressure systems, methane does not have an odor until a mercaptan or other odorant is injected.

• Unlike biogas, methane is lighter than air and will rise to the ceiling in enclosed spaces.

• Nitrogen is heavier than air and can collect in low areas.

What does this mean? Do not open valves or small sample ports without proper ventilation or the ability to route vented gases to a safe area. Also, be sure to use appropriate gas monitoring equipment to ensure a safe working atmosphere.

Fire – Methane is flammable between 5 percent and 15 percent by volume in air, at low or high pressure. At 3,600 PSI, nearly 300 times as much energy from methane fits into a container as that contained at atmospheric pressure. In addition to pressure relief devices (PRDs), there may be a high temperature relief device that would typically release all gas in a vessel at 212-220oF.

So, make sure you are aware of safety relief valve vents and vent direction and ensure they are located and directed away from personnel access points. Another tip – do not open valves or small sample ports without proper ventilation or the ability to route vented gases to a safe area.

Health and safety tips

Aside from the specific pointers mentioned, be sure to start by making sure you fully understand the process and materials for each application, and any site conditions that may affect your specific working environment. Prior to working on high pressure systems, perform a Job Safety Analysis, identify all potential hazards, develop a site-specific Health & Safety Plan, and make sure you have good communications with administrative and support personnel.

Using the right staff for the job at hand is key – only qualified, trained staff should work on pressurized high pressure gas systems. And, finally, make sure staff is equipped with the right personal protection equipment, including a 4-gas meter, safety glasses, hard hat, steel toe boots, hearing protection, and heavy gloves.

Do you have any questions about working safely on high pressure gas systems?


Categories: Air Quality, Alternative Energy, Biogas and Landfill Gas
Posted By Kyle Kneser, PE at 11:25 AM  |  No Comments on Safety tips for working with high-pressure gas systems

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