Safety valves play a critical role in protecting pressure systems from overpressure conditions. When pressure rises beyond a safe limit, a safety valve automatically opens to release excess pressure, helping prevent equipment damage, system failure, or serious accidents. Because pressure systems vary widely across industries, safety valves come in several types, each designed for specific operating conditions and media.
1. Spring-Loaded Safety Valve
The spring-loaded safety valve is the most widely used type across industrial applications.
A calibrated spring keeps the valve closed under normal pressure. When system pressure exceeds the set point, the force overcomes the spring and the valve opens. Once pressure returns to a safe level, the valve closes automatically.
Key characteristics:Simple structure.Reliable and cost-effective.Fast response to overpressure
Typical applications:Steam boilers, pressure vessels, compressed air systems, oil and gas pipelines, marine auxiliary systems.
2. Pilot-Operated Safety Valve
Pilot-operated safety valves use system pressure to control the opening and closing of the main valve through a smaller pilot valve.
When pressure reaches the set point, the pilot valve opens first, causing a pressure imbalance that opens the main valve. This design allows accurate pressure control with minimal leakage under normal conditions.
Key characteristics:High set-pressure accuracy.Suitable for high-pressure systems.Reduced seat leakage
Typical applications:High-pressure gas systems, refineries, power plants, large-capacity pressure vessels.
3. Balanced Bellows Safety Valve
Balanced bellows safety valves are designed to reduce the influence of back pressure on valve performance.
A metal bellows isolates the spring and bonnet area from downstream pressure. This helps maintain a stable set pressure even when back pressure fluctuates.
Key characteristics:Stable operation under variable back pressure.Improved sealing performance.Reduced effect of downstream conditions
Typical applications:Chemical processing, steam systems with long discharge piping, marine exhaust and vent systems.
4. Conventional Safety Valve
A conventional safety valve relies directly on system pressure acting on the valve disc to open the valve.
While simple and durable, its performance can be affected by back pressure in the discharge line. For this reason, it is best used where back pressure is low or stable.
Key characteristics:Simple design.Easy maintenance.Lower cost
Typical applications:Low-pressure boilers, water systems, non-critical pressure relief applications.
5. Safety Relief Valve
A safety relief valve combines the functions of a safety valve and a relief valve in one design.
It can handle both compressible fluids, such as gas or steam, and incompressible fluids, such as liquids. The valve opens gradually or rapidly depending on the pressure rise.
Key characteristics:Versatile performance.Suitable for mixed media.Smooth pressure release
Typical applications:Oil and gas systems, chemical plants, marine fuel and lubrication systems.
6. Low-Lift and Full-Lift Safety Valves
Safety valves are also classified by how far the disc lifts during operation.
A low-lift safety valve opens only a small distance and is suitable for liquid services.
A full-lift safety valve opens fully almost instantly and is ideal for gas or steam.
Typical applications
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①Low-lift: liquid pipelines, hydraulic systems
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②Full-lift: steam boilers, gas systems, pressure vessels
Why Choosing the Right Safety Valve Matters
Each safety valve type responds differently to pressure, media, temperature, and back pressure. Using the wrong type can lead to unstable operation, leakage, or insufficient pressure relief. Proper selection improves system safety, extends equipment life, and ensures compliance with international standards.
Post time: Dec-18-2025