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Safety Valves

The safety valve is a special valve that is in a normally closed state under the action of external force. When the medium pressure in the equipment or pipeline rises beyond the specified value, it discharges the medium to the outside of the system to prevent the medium pressure in the pipeline or equipment from exceeding the specified value. Safety valves belong to automatic valves, mainly used in boilers, pressure vessels and pipelines. The control pressure shall not exceed the specified value, which plays an important role in protecting personal safety and equipment operation.



Closed Spring Loaded Full Bore Type Safety Valve
Closed Spring Loaded Full Bore Type Safety Valve
Closed Spring Loaded Full Bore Type Safety Valve

MstnLand's series of closed spring loaded full bore type safety valve, A42Y-C type are used for the equipment and pipeline of air, petroleum gas, liquid, etc. medium what the working temperature a...

Closed Spring Loaded Low Lift Type Safety Valve
Closed Spring Loaded Low Lift Type Safety Valve
Closed Spring Loaded Low Lift Type Safety Valve

MstnLand's series of closed spring loaded low lift type safety valve, A41H type are used for the equipment and pipeline of petroleum gas, air, water, etc. medium what the working temperature are l...

High Temperature And High Pressure Safety Valve
High Temperature And High Pressure Safety Valve
High Temperature And High Pressure Safety Valve

MstnLand's series of high temperature and high pressure safety valves are used for the equipment and pipeline of steam, etc. medium what the working temperature with C type are less than 425℃ and...

Pilot Operated Safety Valve
Pilot Operated Safety Valve
Pilot Operated Safety Valve

MstnLand's series of pilot operated safety valve with newly-structured. It's mainly applied to such trades as petroleum & natural gas, chemistry, electric, metallurgy & burning gas. It...

Spring Full Bore Type Safety Valve With Radiator
Spring Full Bore Type Safety Valve With Radiator
Spring Full Bore Type Safety Valve With Radiator

MstnLand's series of spring full bore type safety valve with radiator, YA40Y-C type are used for the equipment and pipeline of air, N2,H2 mixed gas etc. medium what the working temperature are les...

Spring Full Bore Type With Lever Safety Valve
Spring Full Bore Type With Lever Safety Valve
Spring Full Bore Type With Lever Safety Valve

MstnLand's series of spring full bore type with lever safety valve, A28H type are used for the equipment and pipeline of air, N2, H2 mixed gas vapour etc. medium what the working temperature are l...

Spring Loaded Low Lift External Thread Type Safety Valve
Spring Loaded Low Lift External Thread Type Safety Valve
Spring Loaded Low Lift External Thread Type Safety Valve

MstnLand's series of spring loaded low lift external thread type safety valve, A21F, A21H-C type are used for the equipment and pipeline of air, ammonia, petroleum gas, etc. medium what the workin...

Spring Loaded Low Lift Type Safety Valve
Spring Loaded Low Lift Type Safety Valve
Spring Loaded Low Lift Type Safety Valve

MstnLand's series of spring loaded low lift type safety valve, A27H type are used for the equipment and pipeline of water, air, steam, etc. medium what the working temperature are less than 200℃....

Spring Loaded Low Lift Type With Lever Safety Valve
Spring Loaded Low Lift Type With Lever Safety Valve
Spring Loaded Low Lift Type With Lever Safety Valve

MstnLand's series of spring loaded low lift type with lever safety valve are used for the equipment and pipeline of steam, air, etc. medium what the working temperature are less than 350℃. Take f...

Stainless Steel Spring Loaded Full Bore Type Safety Valve With Handle
Stainless Steel Spring Loaded Full Bore Type Safety Valve With Handle
Stainless Steel Spring Loaded Full Bore Type Safety Valve With Handle

MstnLand's series of spring loaded full bore type with lever safety valve, A48Y type are used for the equipment and pipeline of steam, air, etc. medium what the working temperature are less than 3...

Twin Spring Type Safety Valve
Twin Spring Type Safety Valve
Twin Spring Type Safety Valve

MstnLand's series of twin spring type safety valves are used for the equipment and pipeline of steam, water, etc. medium what the working temperature are less than 350℃. Take for extra pressure p...


Safety Valve Types


There are two main types of safety valve structures: spring type and lever type. Spring type means that the sealing between the valve disc and the valve seat depends on the force of the spring. The lever type relies on the force of a lever and a heavy hammer. With the need of large capacity, there appears another kind of pulse safety valve, also known as pilot safety valve, which consists of main safety valve and auxiliary valve. When the medium pressure in the pipeline exceeds the specified pressure value, the auxiliary valve is opened first, the medium enters the main safety valve along the conduit, and the main safety valve is opened to reduce the increased medium pressure.

The discharge volume of the safety valve is determined by the diameter of the valve seat and the opening height of the valve disc. It can also be divided into two types: micro opening type and full opening type. In addition, there are closed and non-closed types depending on the requirements of use. The closed type means that the discharged medium does not leak out, and all of it is discharged along with the specified outlet. It is generally used for toxic and corrosive media. The non-closed type is generally used for non-toxic or non-corrosive media. According to its overall structure and loading mechanism, it can be divided into three types: heavy hammer lever type, spring type and pulse type. According to the different ways of medium discharge, safety valves can be divided into three types: fully enclosed, semi-closed and open. According to the ratio of the maximum opening height of the valve disc to the diameter of the safety valve flow passage, it can be divided into two types: spring slightly open closed high pressure safety valve and spring full open safety valve. According to the safety valve working principle, it can be divided into direct-acting safety valves and non-direct-acting safety valves. According to whether the pressure can be adjusted, it can be divided into fixed non-adjustable safety valve and adjustable safety valve. According to the working temperature, it can be divided into normal temperature safety valve and high temperature safety valve.


Safety Valve Selection


1. The safety valve of the steam boiler generally adopts full-open spring safety valve;

2. Safety valve for liquid medium generally use micro-opening spring safety valve;

3. Safety valves for air or other gaseous media generally use full-open spring safety valves;

4. The safety valve for LPG truck tanker or LPG railway tanker generally adopts full-opening built-in safety valve;

5. The safety valve for the outlet of the oil production well is generally a pilot-operated safety valve;

6. For the high-pressure bypass safety valve of steam power generation equipment, a pilot-operated safety valve with dual functions of safety and control is generally selected.

7. If the safety valve is required to do opening test regularly, the safety valve with a lifting wrench should be selected. When the medium pressure reaches more than 75% of the opening pressure, the valve disc can be slightly lifted from the valve seat with a lifting wrench to check the opening flexibility of the safety valve;

8. If the temperature of the medium is high, in order to reduce the temperature of the spring chamber, generally when the operating temperature of the closed safety valve exceeds 300 °C and the operating temperature of the open safety valve exceeds 350 °C, a safety valve with a radiator should be selected;

9. If the back pressure at the outlet of the safety valve changes, and the change exceeds 10% of the opening pressure, a bellows safety valve should be used;

10. If the medium is corrosive, the bellows safety valve should be used to prevent the failure of important parts due to the corrosion of the medium.


Safety Valve Installation


1. Mount the safety valve in a vertical position so that the valve body is self draining. If a body drain port is provided, make sure it is open when required by the ASME code. Do not plug any bonnet vent openings. The inlet piping should be as short as possible, with no elbows, and equal to or greater than the size of the pressure relief valve inlet connection. This will help to limit the inlet pressure drop to 3% or less when the valve is relieving. 

2. When discharge piping is connected to valve outlet, make sure it is self draining when a body drain port is not used. The safety valve should not be connected to any discharge pipe that contains pressure before the valve opens or to any pipe where the pressure build-up is greater than 10% of the set pressure when the valve is open and relieving. Discharge piping, other than a short tailpipe, must be supported by something other than the valve. For steam service, a drip pan elbow or flexible connection between the valve and the pipe should be used to prevent excessive pipe stress, due to thermal expansion, from being imposed on the valve body. 

3. For threaded valves, apply a small amount of pipe thread sealing compound to external threads only. Do not put any sealing compound on the first thread or any internal threads. To do so may cause the sealing compound to enter the valve and cause seat leakage. Use wrench flats provided to tighten the valve to the connecting pipe. Do not use the valve body or bonnet and do not over-tighten. To do so may cause valve leakage. 

4. For flanged valves, use new gaskets and tighten the mounting studs evenly. 



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