1. drain hole

Safety valve body design should seek to reduce the impact of media deposits of dirt. Steam and liquid use of safety valves should be below the seat sealing surface of the lowest part of the set of liquid drain hole.

Nominal diameter greater than 65mm safety valve, the diameter of the vent hole is not less than 9.5mm; nominal diameter less than or equal to 65mm safety valve, the diameter of the vent hole is not less than 6.5mm.

GB/T 12243-2021 ‘spring direct-loaded safety valve’ Article 4.4.5 also provides that: in order to prevent the accumulation of liquid line below the sealing surface of the valve seat in the part of the drain bolt hole.

Safety valves for steam and liquids should be installed in such a way that fluid does not accumulate on the downstream side of the valve, as this will affect the performance of the valve and cause erosion of the spring and internal parts. Many safety valves are provided with a drain connection hole in the valve body. If this drain is not used in actual application, or if this drain hole is not provided on the safety valve, a tear hole should be provided in the piping as close as possible to the safety valve outlet.

2.Drain hole

For bellows type safety valve, its bonnet should be provided with a drain hole to ensure that the bellows inner cavity is connected to the atmosphere, for combustible or corrosive media, the drain hole is connected to the safety site with a pipe to prevent the bellows from breaking the media leakage caused by the danger.

Balanced bellows safety valve will be shipped with a temporary dust-proof plastic plug on the relief hole (vent hole), the plug must be removed during normal operation, otherwise it may lead to pressure build-up in the bonnet and thus cause the bellows to expand and fail. This can also occur if the vent hole is artificially blocked.

Installation of a vent elbow with a dust cover will prevent contaminants from entering the valve cavity to ensure normal operation of the safety valve.

3.Adjustment screw

The adjustment screw of the safety valve is usually located in the upper part or the side of the safety valve, the specific position depends on the model of the safety valve. Usually the adjustment screw is marked with an arrow in the direction of adjustment. Tightening the adjustment screw will increase the opening pressure of the safety valve, and vice versa will decrease the opening pressure value of the safety valve.

In order to prevent the mechanism for adjusting the spring compression (e.g., the adjusting screw) from loosening and from arbitrarily changing the already adjusted state, safety valves must be equipped with an anti-loosening device.