The safety valve is a special valve that prevents the medium pressure in the pipeline or equipment from exceeding the specified value by discharging the medium to the system when the medium pressure in the device or pipeline rises beyond the specified value under the action of external force. The safety valve is an automatic valve, mainly used in boilers, pressure vessels and pipelines. The control pressure does not exceed the specified value, which plays an important role in protecting personal safety and equipment operation. The relief valve must be pressure tested before use.

1. Weight lever safety valve weight lever safety valve USES the weight and lever to balance the force on the disc. According to the lever principle, it can use a heavy hammer with a small mass to obtain a large force by increasing the lever, and adjust the opening pressure of the safety valve by moving the position of the heavy hammer (or changing the weight of the heavy hammer).

The weight hammer lever type safety valve structure is simple, the adjustment is easy and quite accurate, the load which adds will not have the big increase because of the valve disc's elevation, is suitable for the high temperature occasion, used in the past quite generally, specially used in the boiler and the high temperature pressure vessel. But the heavy hammer lever safety valve structure is relatively bulky, the loading mechanism is easy to vibration, and often produces leakage because of vibration; Its return pressure is low, it is not easy to close and keep tight after opening.

2. Spring micro-open safety valve spring micro-open safety valve is the use of the force of the compression spring to balance the force on the disc. The amount of compression of the spiral coil spring can be adjusted by turning the adjusting nut on it so that the opening (setting) pressure of the relief valve can be adjusted as required. The spring-loaded micro-opening safety valve is light and compact in structure, high in sensitivity, unrestricted in installation position, and because of its low sensitivity to vibration, it can be used for mobile pressure vessels. The disadvantage of this safety valve is that the added load will change with the opening of the valve, that is, with the rise of the disc, the spring of the compression increase, the force on the disc also increases. This is detrimental to the rapid opening of the valve. In addition, the valve spring due to the long-term impact of high temperature will reduce the elasticity. When used on higher temperature containers, the thermal insulation or heat dissipation of springs is often considered, thus complicating the structure.

Pulse type safety valve pulse type safety valve consists of the main valve and auxiliary valve, through the auxiliary valve pulse action to drive the main valve action, its complex structure, usually only suitable for safe discharge of large amount of boiler and pressure vessels.

The spring type safety valve is commonly used in the above three types of safety valves.