Safety valves are used in boilers, pipelines or pressure vessels. When the pressure exceeds the set value, the pressure is reduced by discharging the medium to protect the safety of the equipment. When the pressure returns to normal, the valve will automatically close.

1. Micro-opening safety valve

The valve disc opening height of the micro-opening safety valve is 1/40 to 1/20 of the valve seat throat diameter, and the valve disc opening height is proportional to the pressure. The opening height is lower at low pressure and higher at high pressure, and the valve disc gradually opens. As the pressure decreases, the valve disc gradually returns to the seat. This type of safety valve is suitable for liquid media, low-pressure gas and steam, and has a small displacement. Under normal circumstances, liquids are incompressible, and a small amount of discharge can effectively reduce the pressure.

Discharge area: equal to the cylindrical or conical channel area formed after the valve seat and valve disc are opened.

Displacement coefficient: When the opening height is 1/40, the displacement coefficient is 0.14~0.16; when it is 1/20, the displacement coefficient is 0.07~0.08.

Model: A21H/Y, A41H/Y, A47H/Y.

2. Full-open safety valve

The opening height of the valve disc of the full-open safety valve is 1/4 of the valve seat throat diameter, and the discharge area is equal to the flow area. The valve disc is equipped with a recoil disc. When the pressure reaches the set value, the recoil disc pushes the valve disc to open quickly and achieve large-displacement discharge. This design enables the full-open safety valve to quickly reduce pressure and ensure equipment safety.

Displacement coefficient: 0.7~0.8, which is 5~10 times that of the micro-open safety valve.

Valve seat reduction: two gears smaller than the nominal diameter, for example, PN16, valve diameter DN50, valve seat diameter d=32, outlet diameter DN65, one gear larger than the inlet diameter.

Structural features: The pressure of the discharge medium acts on the recoil disc, prompting the valve disc to open quickly. The valve disc is opened in a sudden jump manner, returns to the seat instantly, and has high discharge efficiency.

Model: A42H/Y, bellows WA42H/Y, A44H/Y, A48H/Y.

3. Main differences

Valve flap opening height: The opening height of the micro-opening safety valve is relatively small (1/40~1/20), while that of the full-opening safety valve is relatively large (1/4).

Displacement coefficient: The full-opening safety valve has a large displacement coefficient and is suitable for handling compressible media such as steam and gas; the micro-opening safety valve has a small displacement coefficient and is suitable for incompressible media such as liquid.

Structural design: The full-opening safety valve is equipped with a recoil disc, which can be fully opened quickly, while the micro-opening safety valve flap opens gradually and has a small displacement.

4.Conclusion

There are obvious differences between the micro-opening safety valve and the full-opening safety valve in terms of structure, discharge volume and applicable media. The micro-opening type is suitable for low-pressure liquids and steam, and has a small displacement; the full-opening type is suitable for high-pressure gas and steam, and can provide a larger displacement and rapid pressure reduction.