Safety Valves are used for one reason — safety. Instead of controlling the pressure in a system, they’re designed to immediately release pressure in the event of an emergency or system failure. Unlike relief valves, safety valves open immediately and completely to avoid a disaster, rather than to control the pressure of a system.
What is Pressure Relief valves?
A pressure Relief Valve is a safety device designed to protect a pressurized vessel or system during an overpressure event.
An overpressure event refers to any condition which would cause pressure in a vessel or system to increase beyond the specified design pressure or maximum allowable working pressure (MAWP).
The primary purpose of a pressure Relief Valve is protection of life and property by venting fluid from an overpressurized vessel.
Many electronic, pneumatic and hydraulic systems exist today to control fluid system variables, such as pressure, temperature and flow. Each of these systems requires a power source of some type, such as electricity or compressed air in order to operate. A pressure Relief Valve must be capable of operating at all times, especially during a period of power failure when system controls are nonfunctional. The sole source of power for the pressure Relief Valve, therefore, is the process fluid.
How does a Pressure Relief Valve work?
The function und design of pressure relief valves differs depending on the main type or loading principle. Use the following icons to navigate to the respective main type page. There you will find the corresponding LESER pressure relief valves as well as further information, for example on the function and design of the main types.
Spring Loaded Pressure Relief Valve
The basic spring loaded pressure Relief Valve has been developed to meet the need for a simple, reliable, system actuated device to provide overpressure protection.
The image on the right shows the construction of a spring loaded pressure Relief Valve.
The Valve consists of a Valve inlet or nozzle mounted on the pressurized system, a disc held against the nozzle to prevent flow under normal system operating conditions, a spring to hold the disc closed, and a body/Bonnet to contain the operating elements. The spring load is adjustable to vary the pressure at which the Valve will open.
When a pressure Relief Valve begins to lift, the spring force increases. Thus system pressure must increase if lift is to continue. For this reason pressure Relief Valves are allowed an overpressure allowance to reach full lift. This allowable overpressure is generally 10% for Valves on unfired systems. This margin is relatively small and some means must be provided to assist in the lift effort.
Most pressure Relief Valves, therefore, have a secondary control chamber or huddling chamber to enhance lift. As the disc begins to lift, fluid enters the control chamber exposing a larger area of the disc to system pressure.
This causes an incremental change in force which overcompensates for the increase in spring force and causes the Valve to open at a rapid rate. At the same time, the direction of the fluid flow is reversed and the momentum effect resulting from the change in flow direction further enhances lift. These effects combine to allow the Valve to achieve maximum lift and maximum flow within the allowable overpressure limits. Because of the larger disc area exposed to system pressure after the Valve achieves lift, the Valve will not close until system pressure has been reduced to some level below the set pressure. The design of the control chamber determines where the closing point will occur.
The difference between the set pressure and the closing point pressure is called blowdown and is usually expressed as a percentage of set pressure.
Safety Valve vs. Relief Valve
While both terms refer to valves used to release pressure from a pressurized system, their technical definitions are a bit different. In general, the term relief valve refers to a valve within a pressurized system that is used to control pressure for the optimal functionality of the system. Relief valves are designed to help your facility avoid system failures, and protect equipment from overpressurized conditions.
The term safety valve, on the other hand, refers to pressure valves that are designed to protect people, property, and processes. In other words, the term safety valve refers to a failsafe, last resort valve that will release pressure to prevent a catastrophe, usually in the event that all other relief valves have failed to adequately control pressure within a system.
| Relief Valve | Safety Valve |
| A relief valve is a device used to limit the pressure in a system within a specific set level | A safety valve is a device designed to actuate automatically to release excess pressure |
| The opening of a relief valve is directly proportional to the increase in the vessel pressure | A safety valve opens almost immediately and fully in order to prevent overpressure condition |
| A relief valve opens when the pressure reached the specific set pressure limit and it is usually operated by an operator | The purpose of a safety valve is to protect people, property, and environment. It is used to release excess pressure without operator assistance |
| The setpoint of a relief valve is usually set at 10 percent above the working pressure limit | The setpoint of a safety valve is usually set at 3 percent above the working pressure limit |
| Relief valves are divided into pop-type, direct-operated, pilot-operated, and internal relief valves | Safety valves are divided into a wide range of types based on applications and performance in different areas |
Do Safety and Relief Valves Do the Same Thing?
The general purpose of both safety valves and relief valves are the same. Both are pressure relief valves, and they are designed to let off pressure in any situation where a system becomes overpressurized. That said, relief valves and safety valves do function slightly differently:
Relief Valves are designed to control pressure in a system, most often in fluid or compressed air systems. These valves open in proportion to the increase in system pressure. This means they don’t fly all the way open when the system is slightly overpressure. Instead, they open gradually, allowing the system to return to the preset pressure level. When that level is reached, the valve shuts again.
Zeco Europe is the best Safety Relief Valve suppliers which is also known as the pressure relief valve, automatically opens to relieve excessive pressure. The primary function of this valve is to lift and reseat it. It seals after releasing the surplus pressure to prevent further fluid loss. It has automatic pressure relief equipment that is actuated by static gas or vapour pressure upstream of the valve, allowing substances to be released automatically by rapid full opening action while preventing explosion.
Types of Safety Valves include:
• Angle safety valve
• Steam Safety Valve
• Thermal Safety Valve
• Conventional Safety valve
• Spring-loaded Pressure-relief Valves
• Dead-Weight Pressure-relief Valves
• Pilot operated pressure relief Valve
Safety Relief Valve
A safety Relief Valve is a pressure Relief Valve characterized by rapid opening or pop action, or by opening in proportion to the increase in pressure over the opening pressure, depending on the application and may be used either for liquid or compressible fluid.
Conventional Safety Relief Valve
A conventional safety Relief Valve is a pressure Relief Valve which has its spring housing vented to the discharge side of the Valve. The operational characteristics (opening pressure, closing pressure, and relieving capacity) are directly affected by changes of the back pressure on the Valve.
Balanced Safety Relief Valve
A balanced safety Relief Valve is a pressure Relief Valve which incorporates means of minimizing the effect of back pressure on the operational characteristics (opening pressure, closing pressure, and relieving capacity).
Pilot-Operated Pressure Relief Valve
A pilotoperated pressure Relief Valve is a pressure Relief Valve in which the major relieving device is combined with and is controlled by a self-actuated auxiliary pressure Relief Valve.
Power-Actuated Pressure Relief Valve
A poweractuated pressure Relief Valve is a pressure Relief Valve in which the major relieving device is combined with and controlled by a device requiring an external source of energy.
Temperature-Actuated Pressure Relief Valve
A temperature-actuated pressure Relief Valve is a pressure Relief Valve which may be actuated by external or internal temperature or by pressure on the inlet side.
Vacuum Relief Valve
A vacuum Relief Valve is a pressure relief device designed to admit fluid to prevent an excessive internal vacuum; it is designed to reclose and prevent further flow of fluid after normal conditions have been restored.
The advantages of Safety Check Valve include:
- • Prevents backflow
- • Prevents backflow
- • Can withstand high and low pressures
- • Self-actuated
- • Quick acting
- • Does not require power to function
- • Reduces unexpected valve failure
Applications of Safety Valves
- • Chemical, oil & gas
- • petrochemical
- • Food and beverage
- • air conditioning systems
- • Energy
- • LNG&LPG
- • Aircraft hydraulic systems
- • Irrigation System
- • fuel pump
- • heating boilers
We supply high-performance and trustworthy solution for your industrial requirements. We manufacture valves in a variety of sizes to meet the needs of our customers. Our valves is an excellent choice for any corrosive environment, as well as for low steam pressure and oil/gas/water media.
Body Material – Cast Iron and Steel Safety Valve (A216 WCB, WCC, LCB, LCC, WC6, WC9), Ductile Iron, Stainless Steel [SS316, SS304, SS316L, SS904L, CF8, CF8M, F304, F316, F31L, F51, F3, F55, F91] , WCB, WC6, SS304, SS316, DUPLEX STEEL Safety Valve.
Class – 150 – 2500
PN 10 – PN 450
Size – ½ – 24”
Ends- Butt welded, Socket welded, Flanged, Threaded
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