Safety Valve, Relief Valve?

Pretty much the same meaning....

"The safety valve theory was a theory about how to deal with unemployment which gave rise to the Homestead Act of 1862 in the United States. Given the concentration of immigrants (and population) on the Eastern coast, it was hypothesized that making free land available in the West, would relieve the pressure for employment in the East. By analogy with steam pressure (= the need for work), the enactment of a free land law, it was believed, would act as a safety valve."

"A safety valve is a valve mechanism which automatically releases a substance from a boiler, pressure vessel, or other system, when the pressure or temperature exceeds preset limits.

It is one of a set of pressure safety valves (PSV) or pressure relief valves (PRV), which also includes relief valves, safety relief valves, pilot-operated relief valves, low pressure safety valves, and vacuum pressure safety valves."

"

Vacuum Relief Valve

Prevents internal vacuum conditions that could collapse storage tanks - especially copper. "

As far as anyone knows, the function is the same. Welcome to the world of language. Some other redundant terms are pressure relief valve and pressure safety valve. That said, some valves (and fusible plugs) can relieve on the basis of temperature.

One thing to watch for is whether or not the relief device will close again if the pressure or temperature decreases to a safe level.

While the three animals may be one and the same device, watch out for the weasle word "safety". Pretty much anything with that word attached will have to comply with some pretty strict standards, and have a certificate to prove it.

safety valve, relief valve and the safety relief valve are all different with one thing in common - they are all automatic pressure actuated relief devices.

relief valve is used for liquids, safety valve for steam, gas or vapor and safety relief could be configured as a safety valve or relief valve.

i got score 1 for off topic, i would suggest that person to read fm global data sheet on pressure relief devices

I'm going to take a guess and assume you're asking about a hot water water tank (water heater) although many other systems utilize these type of valves. as Mr Tornado correctly points out mostly they are different terms for the same (or similar) things on a hot water tank they can also be called a PT valve. PT- pressure and Temperature. if the valve sees that either of these parameters have exceeded design the valve opens to vent the excess. the vent is usually plumbed with a "tee" at it's end to prevent a thrusting situation as the excess blasts through the pipe. ( you don't need a tank turning into a rocket!

There is difference in pop up.Safety valve pop up is immediate,relief valve pop up is slow.

As per API 521 ,

Relief Valve is normally used with incompressible fluids.

Safety Valve is used with with compressible fluids

Safety Relief valve is spring loaded pressure relief valve that can be used either as a safety valve or relief valve depending upon application