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December, 2000 - Cylinder Pressure Relief Devices

One or more of four types of pressure relief devices are used in most cylinders of compressed gases: (1) pressure relief valves, (2) frangible disks (caps attached to the back of valves which contain a small disk designed to burst at a specifies pressure), (3) frangible disks backed with fusible metal designed to melt at a specified temperature and (4) "fuse plugs" (threaded plugs resembling bolts, with a fusible metal core, designed to melt at specified temperature.

Pressure relief valves (commonly used on LPG gas cylinders) and fuse plugs (acetylene cylinders) may begin to function by leaking gas slowly. Frangible disks ("backed" or "unbacked") function by releasing the entire cylinder contents very quickly.

Never tamper with a relief device in any way. If a relief valve or fuse plug is releasing gas, do not try to "repair" it. Doing so risks creating an ignition, or may mask a potentially dangerous condition.

Move the cylinder outdoors if you can do so safely, mark it with a warning sign and instruct others to stay away. If you cannot safely move the cylinder, open doors and windows to increase natural ventilation and immediately leave the area. If you picked up your cylinder personally, do not try to return it -- call your supplier to replace the cylinder.

Important:

This information is offered by the National Welding Supply Association and your local distributor as general guidance only and may not explain all relevant safety precautions or hazards

Mike Lopez, NWSA Safety
Consultant

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