API-RP-576
API ICP Self Study Notes API ICP Self Study Notes
Type Characteristics Mediums Limitations Safety Valve. valve that is actuated by the static pressure upstream of the valve and characterized by rapid opening or pop action. normally used with compressible fluids (air, steam, gaseous) should not be used in/where; (1) corrosive services. (2) the escape of process fluid around. blowing valves. (3) in liquid service (4) impose any backpressure (5) as pressure control or bypass valves. Relief Valve. The valve opens normally in proportion to the pressure increase over the opening pressure. normally used for incompressible fluids should not be used in; (1) steam, air, gas, or other vapor services (2) impose any backpressure (3) as pressure control or bypass valves. Relief valves usually reach full lift at either 10% or 25% overpressure. Valves have closed bonnets to prevent the release of corrosive, toxic, flammable, or expensive fluids. Better degree of tightness than conventional valves. Fion Zhnag/ Charlie Chong
4.4.1 General. A relief valve is a direct spring-loaded pressure-relief valve actuated by the static pressure upstream of the valve. The valve opens normally in proportion to the pressure increase over the opening pressure. A relief valve begins to open when the static inlet pressure reaches its set pressure. When the static inlet pressure overcomes the spring force, the disk begins to lift off the seat, allowing flow of the liquid. The value of the closing pressure is lower than the set pressure and will be reached after the blowdown phase is complete. Relief valves usually reach full lift at either 10 % or 25 % overpressure, depending on the type of valve and trim. These valves have closed bonnets to prevent the release of corrosive, toxic, flammable, or expensive fluids. They can be supplied with lifting levers, balancing bellows, and soft seats as needed. Figure 2 illustrates one type of relief valve. The ASME BPVC requires that liquid service relief valves installed after January 1, 1986 have their capacity certified and stamped on the nameplate. Fion Zhnag/ Charlie Chong
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Type<br />
Characteristics<br />
Mediums<br />
Limitations<br />
Safety Valve.<br />
valve that is actuated<br />
by the static pressure<br />
upstream of the valve<br />
and characterized by<br />
rapid opening or pop<br />
action.<br />
normally used with<br />
compressible fluids<br />
(air, steam,<br />
gaseous)<br />
should not be used in/where;<br />
(1) corrosive services.<br />
(2) the escape of process fluid around.<br />
blowing valves.<br />
(3) in liquid service<br />
(4) impose any backpressure<br />
(5) as pressure control or bypass valves.<br />
Relief Valve.<br />
The valve opens<br />
normally in proportion<br />
to the pressure<br />
increase over the<br />
opening pressure.<br />
normally used for<br />
incompressible<br />
fluids<br />
should not be used in;<br />
(1) steam, air, gas, or other vapor services<br />
(2) impose any backpressure<br />
(3) as pressure control or bypass valves.<br />
Relief valves usually reach full lift at either 10% or 25% overpressure. Valves have closed<br />
bonnets to prevent the release of corrosive, toxic, flammable, or expensive fluids. Better<br />
degree of tightness than conventional valves.<br />
Fion Zhnag/ Charlie Chong
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