A safety valve is crucial in many critical applications such as petroleum refinery, chemical manufacturing, power generation, petrochemicals and natural gas processing, pharmaceuticals, cosmetics, food and beverages industries, and even nuclear plants. A safety valve is designed to act as a “fail-safe” system for an industrial process or other sensitive application. It safeguards processes and operations from hazards by opening and closing during certain conditions (such as high pressure build-up in a system).
Safety valves were first put into use over a century ago during the Industrial Revolution. They were used in steam boilers to help keep the heating equipment from exploding. The earliest model used weight to regulate steam pressure, and this design is still applied in modern-day pressure cookers. With advancements in technology, today’s safety valves are designed to protect critical operations from potential hazards.
One of the most important and popular safety valves in critical applications is the pressure relief valve. In many industries, the term “safety valve” encompasses three terms: relief valve, pressure relief valve (PRV), and pressure safety valve (PSV). Pressure relief valves are designed to control or limit the pressure within a given system so as to prevent its build-up, which could lead to the system exploding or causing serious hazards to the surrounding environment. The valves allow a substance to flow out of the system once a certain pressure is reached (minimum or maximum) and then close when the pressure returns to normal.
Pressure relief valves can be classified into two categories:
• Pilot-operated pressure relief valves: These valves are operated manually by opening them with a wheel, crank, or a similar tool. The operator opens the valve by hand to relieve pressure when a gauge reads that unacceptable pressure levels have been reached.
• Direct-operated pressure relief valves: These valves are operated automatically through a spring mechanism. They are programmed and controlled automatically using a computer program, remote device, control panel, or other similar devices. They open automatically when pressure rises above normal levels and shut automatically after it’s relieved.
Another common set of safety valves in critical applications are the safety relief valves used in gas and vapor operations. These valves often are customized to support whichever chemical, gas, or vapor they are dealing with, including natural gas, ammonia, and butane gas. Low pressure safety valves use the static pressure of a gas to relieve a system when the pressure within it becomes too low and near the atmospheric pressure.
Vacuum safety valves are another set of safety valves. They are used in tanks to prevent them from collapsing when being emptied, or during cold water rinsing of tanks after hot clean-in-place (CIP) or sterilization-in-place (SIP) procedures are carried out. They also are used on top of storage tanks to regulate emission losses resulting from hazardous or flammable petroleum products that release vapor.
Vacuum valves also comprise of breather valves, safety vents, and conservation vents. These valves are created to protect process systems, equipment, and tanks from collapsing due to excessive vacuum and pressure forces. Vacuum pressure safety valves automatically relieve static pressure on gas systems.