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Common term and classification of safety valves

Aug 06, 2018

Common term and classification of safety valves

Safety valve is a safety valve that prevents medium pressure from exceeding the specified value.The safety valve is in the pipeline. When the working pressure of the medium exceeds the specified value, the valve will automatically open and discharge the excess media.When the working pressure is restored to the specified value, it is automatically closed.

A term commonly used for safety valves

1. Opening pressure: when the medium pressure rises to the specified pressure value, the valve disc will automatically open and the medium will spew out rapidly. At this point, the pressure at the inlet of the valve is called opening pressure.

2. Discharge pressure;After the valve disc is opened, if the medium pressure in the equipment pipeline continues to rise, the valve disc should be fully open to discharge the rated medium displacement, at which point the pressure at the valve inlet is called the discharge pressure.

3. Closing pressure: when the safety valve is opened and part of the medium is discharged, the pressure in the pipeline of the equipment gradually decreases. When reduced to a predetermined value less than the working pressure, the valve disc is closed, the opening height is zero, and the medium stops flowing out.The pressure at the inlet of the valve is called the closing pressure, also known as the return seat pressure.

4. Working pressure;The medium pressure in normal operation of equipment is called working pressure.The safety valve is now sealed.

5. Displacement: when the discharge medium valve disc is fully open, the discharge amount of the media measured from the outlet of the valve in unit time is called the displacement of the valve.

Type of safety valve

1. According to the structure of the safety valve, it can be divided

Drip hammer (lever) safety valve: use lever and hammer to balance disc pressure.The hammer relief valve adjusts the pressure by moving the weight or changing the weight of the weight of the weight.It has the advantage of simple structure.The disadvantage is that it is relatively heavy and has low seating capacity.The safety valve of this structure can only be used on fixed equipment.

This valve USES the force of the compression spring to balance and seal the disc.The spring relief valve adjusts the pressure by adjusting the compression of the spring.Its advantages lie in its small size, light weight, high sensitivity and free installation position.The disadvantage is that the force acting on the stem changes with the spring deformation.Attention must also be paid to the heat insulation and heat dissipation of springs.The spring force of a spring-loaded safety valve should not exceed 2000 kg.Because too large and too hard a spring is not suitable for precise operation.

The pulse safety valve is composed of the main valve and auxiliary valve.The main valve is connected with the auxiliary valve, and the main valve is driven by the pulse action of the auxiliary valve.Pulse relief valves are usually used on large caliber pipe lines.Because large - bore safety valves are not suitable for heavy hammer or spring type.The pulse relief valve consists of the main valve and the auxiliary valve.When the medium in the pipeline exceeds the rated value, the auxiliary valve first ACTS to drive the main valve action, discharge the excess media.

2. According to the ratio between the maximum opening height of the relief valve disc and the valve seat size, it can be divided into:

The opening height of the valve disc is 1/20~1/10 of the valve seat clearance.Due to the small opening height, the structure and geometry of this kind of valve are not as strict as that of the full opening type. The design, manufacture, maintenance and test are all convenient, but the efficiency is low.

The opening height of the disc is 1/4~1/3 of the valve seat bore.The fully actuated safety valve USES the expansion force of the gas medium to raise the disc sufficiently and discharge it.It USES the upper and lower adjustment rings of the disc and seat to form a pressure zone between the disc and the upper and lower valve nodal rings so that the disc rises to the required opening height and the required return seat pressure.This kind of structure has high sensitivity and is used frequently, but the position of upper and lower adjustment rings is difficult to adjust.

3. According to the structure of the safety valve body, it can be divided

Complete sealing: the discharge medium does not leak outwards, but all of them are released through the discharge tube.

Disciplines semi-closed: some of the discharge medium is discharged through the drain pipe and others leak out of the valve cover and stem.

Blank: when discharging the media, do not lead to the outside, directly from the disc to discharge.

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