The flow direction of bellows globe valve is analyzed as follows:

Generally, when the nominal size DN ≤ 150 mm, it is low in and high out; when the nominal size DN ≥ 200 mm, it is high in and low out; at the same time, when the nominal size DN ≥ 200 mm, it is labor-saving to open, and the structure of external bypass valve or internal bypass valve is added.

2. The packing seal of the upper inlet and lower outlet type stop valve is under full pressure, while the lower inlet and upper outlet type stop valve is only under pressure on the sealing surface. For the large-diameter stop valve, if the pipe is under high pressure at the same time, the diameter of the stem must be thick. If it is thin, the stem will be bent. The upper in and lower out type has large opening torque and small closing torque.

3. Special reasons for high in and low out

(1) When the pressure side of the valve is high pressure, it needs to be high in and low out

(2) Two stop valves are connected in series on the bypass, and the second stop valve should be installed reversely

(3) Boiler vent stop valve

(4) Electromagnetic quick break valve

4. At present, in foreign countries, large diameter valves have been used to be made into upper inlet and lower outlet type, and they are usually designed as double disc (balance disc)

1. Avoid too large pressure difference when the valve is opened or closed.

2. Considering the rigidity of the valve, the high inlet and low outlet have a clear impact on the valve. Generally, the large diameter globe valve is not designed as a double disc, so it is difficult for the valve to hold the medium.