Safety Valve vs. Relief Valve
Safety Valve vs. Relief Valve
(OP)
I vaguely recall reading that there was a difference (by definition) between a "safety valve" and a "relief valve". I think most people use these terms interchangeably, but is there a difference?
Is one used for liquid service and the other for gas/vapor service?
Is one used for liquid service and the other for gas/vapor service?





RE: Safety Valve vs. Relief Valve
Safety valve: That part of the toilet that gets the feces out of the house before it runs out over the floor.
RE: Safety Valve vs. Relief Valve
RE: Safety Valve vs. Relief Valve
Mark Hutton
RE: Safety Valve vs. Relief Valve
Definitions extracted from the Pressure Relief Valve Handbook available from the link below are,
Safety Valve
A safety valve is a pressure relief vavle actuated by inlet static pressure and characterized by rapid opening or pop action. (It is normally used for steam and air services)
Relief Valve
A relief valve is a pressure relief device actuated by inlet static pressure having a gradual lift generally proportional to the increase in pressure over opening pressure. It may be provided with an enclosure spring housing suitable for closed discharge system application and is primarily used for liquid service.
Safety Relief Valve (Interesting!)
A safety relief valve is a pressure relief valve characterized by rapid opening or pop action, or by opening in proportion to the increase in pressure over the opening pressure, depending on the application and may be used either for liquid or compressible fluid.
http://www.tycovalves-na.com/ld/CROMC-0296-US.pdf
Moral of the story(IMHO): Confuse others when you are confused.
Regards,
RE: Safety Valve vs. Relief Valve
Now for a similar question: What is the difference between an Emergency Stop and a Rapid Stop? (Hint: there are several different Emergency Stops, but I have a problem deciding which is what).
Gunnar Englund
www.gke.org
RE: Safety Valve vs. Relief Valve
It's a question of application. A relief valve will, in many circuits, open occasionally, continually, or possibly continuously. It's a working part of the circuit.
The safety valve application should never open in normal use (apart from test). It's the final safeguard that stops things blowing apart and hurting people. If a safety valve keeps opening, something's wrong.
Maybe this should be in the 'Piping & Fluid Mechanics' forum - it's a valid technical thread.
Cheers - John
RE: Safety Valve vs. Relief Valve
In the world of rail airbrakes, where I actually have some standing, the emergency brake system bypasses most of the control features and devices from the brake system and uses only highly reliable, and mostly fail-safe components. The intent is to have a system with a high probability of applying the brakes when requested. While the brake force may be higher than a normal brake application that is secondary to the reliability need.
RE: Safety Valve vs. Relief Valve
A rapid stop is what happens if you did not notice you should have done an emergency stop. :)
JHG
RE: Safety Valve vs. Relief Valve
The idea is: halt all moving parts, regardless of what the control system may think it is doing.
Jay Maechtlen
http://home.covad.net/~jmaechtlen/