Safety valve & relief valve

tmech03 · Jan 10, 2008, 04:07 AM

Safety Valve - generally it is used for gas or steam applications, and it is characterize by rapid, full opening action.
Relief Valve - liquid applications, opens in proportion to the increase of system pressure over the opening pressure

I hope you can understand now.

rdhanson · Jan 14, 2008, 01:46 PM

I agreee with tmech03's assessment. Also:

Safety valves are often rated by a standards agency. They are designed to open even after long periods of inactivity. They often will not reseat once opened.

Relief valves will typically operate many thousands of times without failure. However, they are not designed for long periods of inactivity.

msk · Feb 6, 2008, 02:59 AM

I agree with the above answers.There is a little to add to it. Safety valves are always mounted on vessels to protect them against pressure build up (even if discharge valves are closed accidently) whereas relief valves are installed on pipe lines to relieve excess pressure and are normally installed across pumps. A good example can be seen in pressure cookers, the center valve is a relief valve whereas it has a safety valve in case relief valve fails.

cfarnum · Jun 20, 2008, 08:45 AM

Quote:

Originally Posted by meherbabu

What is the difference between safety valve and relief valve

There is no difference they are one in the same. If pressure gets to high relief valve/safety valve opens, which prevents an explosion. So it is a safety device. that's how they became to be known as one.

nasr_elshafei · Dec 18, 2009, 08:38 AM

I agree with them , safety vavles in normal operation is closed
but you can find some relief is open in normal operation specially which are in discharge of pumps it works as minimumflow & make stability for pressure

akshaydesai87 · Dec 27, 2010, 01:01 AM

There IS a difference between safety valve and a Relief valve! A safety valve is supposed to relief pressures from unsafe to safe ranges. Whereas Relief valves are supposed to MAINTAIN the pressure.... Consequently the requirement is addressed by the design which enables a SAFETY valve to POP OPEN at a certain pressure, but sit back closed on a pressure significantly lower... For instance, a Saftey valve may pop open at 13.3 bars and sit down on a pressure of 12.7 bars. This difference is called Blow down and it ensures that the valve is not kept open......

premkumar381 · Feb 5, 2011, 04:57 AM

Safety valve is for safety. Relief valve is for relief.

premkumar381 · Feb 5, 2011, 05:00 AM

Quote:

Originally Posted by akshaydesai87

There IS a difference between safety valve and a Relief valve! A safety valve is supposed to relief pressures from unsafe to safe ranges. Whereas Relief valves are supposed to MAINTAIN the pressure.... Consequently the requirement is addressed by the design which enables a SAFETY valve to POP OPEN at a certain pressure, but sit back closed on a pressure significantly lower... For instance, a Saftey valve may pop open at 13.3 bars and sit down on a pressure of 12.7 bars. This difference is called Blow down and it ensures that the valve is not kept open......

superb............................

dinuka.de.silva · Mar 4, 2011, 09:15 PM

Safety valve allows for pressure accumilation even while dumping excessive pressure. It can be simply described from an example. As in a container which is filled at a constant rate of water and a valve at a level which open at when the water amount reaches its level. The amount of valve open can be adjusted (like in a safety valve). Now when the water reaches the valve level valve opens and dumps the excess but at the same time water fills and safety valve regarding to the example do the same, when a pressure reaches valve opening pressure it opens and dumps the excessive pressure allowing for a pressure accumilation. And safety valve is designed to allow to pressure drop of 3% of the pressure of the containing pressure before closing. So it opens when the pressure reaches its limit, allows for pressure build up, and dumps excessive pressure and closes when pressure drops below designed opening pressure.

Relief valve is designed to open and dump pressure without letting to exceed (or reduce like in a safety valve) its designed pressure.

Safety valve & relief valve

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