3 replies to this topic

[gvdlans]

Well you do not give a lot of details...

In general, you need overpressure protection (such as a relief valve) if there is a possibility that you overpressure your system. If I were to design your system, I would make sure that the line can withstand the maximum pressure in the cilinder. In that case there is no possibility to overpressure the line and therefore, no relief valve is required. The maximum pressure that a line (piping or tubing?) can withstand is a function of its internal diameter, wall thickness, material and temperature.

[Art Montemayor]

New Guy:

The way I understand your description of the configuration you are presumably planning or using, I would say: No, you don't need "a safety relief valve hooked up to the line between the cylinder and the regulator".

I understand you to be concerned with the protection of the equipment upstream of the gas regulator. This upstream equipment would be the high pressure gas cylinder - filled with whatever gas it is that you are regulating downstream. I base myself on the norms and standards used for HP gas cylinders in the USA and the familiarity I have with European standards. If you are somewhere else where there are no standards, then you have to define your situation better. HP gas cylinders in the USA and Europe carry their own safety relief devices incorporated in the cylinder valve used on the cylinder. This device varies with the service and use in question and usually is a rupture disc that may include a fuseable plug (that melts in case of an external fire). This description applies to Acetylene cylinders - which don't exactly fit the description of "compressed gases" because the Acetylene exists inside its cylinder in the dissolved state, within a liquid charge of Acetone.

So, in effect, you are automatically protected for over-pressure withing the HP cylinder. Normally, I'm more concerned about what happens downstream of the HP gas cylinder and how that part of the process is protected - even if it operates at relatively lower pressures. But you don't seem to be concerned about that part, so I can't comment further.

I recommend you read up on the pressure relief systems (if you are in the USA) for HP gas cylinders by reading and studying "The Handbook of Compressed Gases" as published by the CGA (Compressed Gas Association, Inc). It explains the relief systems in great detail and explanations.

I hope this information helps you out.

Art Montemayor
Spring, TX