Selecting the appropriate safety valve type is critical for protecting pressure vessels and ensuring personnel safety. The choice depends on the medium, operating conditions, and discharge requirements. Below are eight essential guidelines for safety valve selection, helping engineers make informed decisions.The main safety valve product names of China Safety Valve Network include:Impulse Safety Valve,Impulse Spring Safety Valve,JIS Safety Valve,Main Safety Valve,Overflow ValveOil Refining Specific Safety Valve,Pulse Safety Valve,Pilot Safety Valve,Pressure Safety Valve,Quick Switching Safety Valve,

1. Based on Discharge Medium

For Gas or Steam Service: Select Full-Lift Safety Valves
Full-lift safety valves achieve a disc lift of at least 1/4 of the nozzle bore diameter, providing maximum discharge capacity for compressible fluids. They are ideal for rapid pressure relief in gas and steam systems.

For Liquid Service: Choose Either Full-Lift or Conventional Lift Valves
Liquids are incompressible, so conventional lift valves (with lift typically 1/20 to 1/40 of bore diameter) offer smooth, stable operation. Full-lift valves can also be used but may generate higher reaction forces.

For Steam or Air Service: Valves with Test Levers Are Recommended
Safety valves equipped with a test lever allow manual lifting to verify disc mobility and prevent sticking. This is particularly useful in steam boilers and compressed air systems where regular testing is required.

2. Based on Operating Conditions

For High-Pressure High-Temperature Gas: Select Valves with Cooling Fins
When set pressure exceeds 3 MPa and temperature surpasses 235°C, hot gas can directly impinge on the spring, causing relaxation or failure. Cooling fins dissipate heat, protecting spring integrity.

Vented vs. Closed Bonnets Based on Leakage Acceptability

• Open bonnet (vented) valves are suitable when discharge to atmosphere is permitted, offering simplicity and easy adjustment.

• Closed bonnet valves must be used when leakage to atmosphere is unacceptable (e.g., toxic, flammable, or valuable media), directing discharge to a closed system.

For Highly Hazardous Media: Specify Bellows-Sealed Safety Valves
Bellows isolates the spring from the process fluid, preventing corrosion and eliminating leakage through the stem. Essential for toxic, corrosive, or extremely dangerous services.

3. Based on Backpressure and System Requirements

For High Backpressure Applications: Use Balanced-Bellows or Pilot-Operated Valves
Backpressure affects set pressure and capacity. Balanced-bellows valves compensate for backpressure, while pilot-operated valves provide precise control and are ideal for high backpressure or demanding processes.

Critical Installations May Require Dual Redundant Safety Valves
In essential services, two safety valves are installed in parallel, with mechanical interlocks on isolation valves. This ensures that at least one valve is always operational during maintenance or repair, maintaining required relief capacity.

4. Conclusion

Proper safety valve selection involves evaluating the medium phase, pressure/temperature, leakage tolerance, backpressure, and system criticality. Correct choice enhances safety, extends valve life, and reduces maintenance. Always reference applicable standards (e.g., ASME VIII, API 520, EN 4126) and consult manufacturer data for optimal selection.

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