A safety
relief valve is a pressure valve and its main function is to pop open to
avoid or eliminate chances of abnormally high pressure which exceed the
predetermined levels. At the same time they smoothly and continuously modulate
the fluid flow to prevent pressure from building up above a certain desired
value. It is normally closed until the pressure levels approaches the said
predetermined value when it pops open to relief off the system the building
pressure. As system pressure rises, the safety relief valve will relief the
flow through the output and when the pressure drops the valve then closes and
starts running smoothly.
As safety devices they are also designed
for fast action rather than for pressure modulation. Pressure is relieved by
allowing the pressurized fluid to flow through an auxiliary passage out of the
system. It protects pressure vessels and other equipments from damages or
rupturing due to high pressures by opening and relieving the fluid as it
reaches the predetermined pressure which is believed as undesired pressures.
When the set pressure is acquired the relief valve then becomes the path of
least resistance and the valve is forced to open and a portion of the fluid is
diverted through the auxiliary path. This diverted fluid is usually routed by a
piping system known as a relief header to a central gas flare where is usually
burned and the resulting gases released to the atmosphere.
After the fluid is diverted the fluid
pressure will then drop and this will lead to closing of the valve preventing
any more diversion of the fluid to the auxiliary path. In some cases the relief
valve has by-pass valves that are used to return all or part of the fluid
discharged by the pump or compressor back to the storage reservoir or to the
inlet of the pump or compressor. The bypass valve can either be internal or
external.
System too have safety relief valves that
protect them from being subjected to internal vacuum collapses; that is
pressure going below a desired point especially lower than the equipments
handling capacity. Here safety relief valves will open thus allowing air or
inert gases into the system so as to control the amount of the vacuum and this
will also increase pressure to the desired level as well. In most cases this
happens when the tanks are being emptied or when being rinsed with cold water
after a hot clean in place procedure has been applied. This might lead to
condensation of the tank and might lead to collapsing, thus a safety relief
valve plays a great role in preventing this.
Thus as we have seen, the safety relief
valve relieves pressure on all fluids including water or gases, by
automatically sensing the pressure rate and prevents it from reaching that
undesired or harmful range. Even though pressure safety valves are almost
similar to safety relief valves, one should not confuse between the two, in that,
pressure safety valves have a manual lever to open the valve in case of
emergency, but for the safety relief valves it is an automated system.
