1 reply to this topic

[rxnarang]

Alan,

Here are the definitions from API 520 Part I- 7th Edition:

1.2.1.2 pressure relief valve:
A pressure relief device
designed to open and relieve excess pressure and to reclose
and prevent the further flow of fluid after normal conditions
have been restored.
a. A relief valve
is a 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 is used primarily with incompressible
fluids.
b. A safety valve
is a spring loaded pressure relief valve actuated
by the static pressure upstream of the valve and
characterized by rapid opening or pop action. A safety valve
is normally used with compressible fluids.
c. A safety relief valve
is a spring loaded pressure relief valve
that may be used as either a safety or relief valve depending
on the application.
d. A conventional pressure relief valve
is a spring loaded
pressure relief valve whose operational characteristics are
directly affected by changes in the back pressure.
e. A balanced pressure relief valve
is a spring loaded pressure
relief valve that incorporates a bellows or other means
for minimizing the effect of back pressure on the operational
characteristics of the valve
f. A pilot operated pressure relief valve
is a pressure relief
valve in which the major relieving device or main valve is
combined with and controlled by a self actuated auxiliary pressure relief valve ( pilot)