As soon as mankind was able to boil water to create steam, the
necessity of the safety device became evident. As long as 2000 years
ago, the Chinese were using cauldrons with hinged lids to allow
(relatively) safer production of steam. At the beginning of the 14th
century, chemists used conical plugs and later, compressed springs to
act as safety devices on pressurised vessels.
Early in the 19th
century, boiler explosions on ships and locomotives frequently resulted
from faulty safety devices, which led to the development of the first
safety relief valves.
The first safety valve was invented by Denis Papin for his steam digester, an early pressure cooker rather than an engine.
A weight acting through a lever held down a circular plug valve in the
steam vessel. By using a "steelyard" lever a smaller weight was
required, also the pressure could easily be regulated by sliding the
same weight back and forth along the lever arm. Papin retained the same
design for his 1707 steam pump.
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.
Safety Valve is a one type
of valve that automatically actuates when the pressure of inlet side of
the valve increases to a predetermined pressure, to open the valve disc
and discharge the fluid ( steam or gas ) ; and when the pressure
decreases to the prescribed value, to close the valve disc again. Safety
valve is so-called a final safety device which controls the pressure
and discharges certain amount of fluid by itself without any electric
power support.
Safety Valve is mainly installed in a chemical
plant, electric power boiler, gas storage tank, preventing the pressure
vessels from exploding or damaging.
Pressure safety valves are
automatic or manual release devices designed to expel gas or liquid from
a mechanical system if the pressure rises above a set limit. Also known
as pressure relief valves, they are mechanical devices that function by
way of weights or springs, or electronic that has sophisticated sensors
to engage operation. There are three main types of pressure safety
valves used in both industry and commercial machines are thermal, flow
and shut-off valves.
Flow valves are different from thermal valves
in that they are very often considerably larger. Flow valves are sized
for situations when larger quantities of gas or liquids may need to be
quickly released to relive growing pressure. Flow valves are often used
for larger storage tanks or pipelines when a significant rupture could
cause much damage.
Edit by http://springcheckvalve.com
