If the medium remained in the cavity after the cryogenic gate valve is closed, the residue will gradually absorb the heat in the air and re-gasify. After the gasification, it will expand violently up to 600 times and generate extremely high pressure on the valve, which is called 'abnormal boost'.

When the unusual occurrence happens, the wedge will be pressed firmly onto the seat and can’t be opened. The high pressure will push the gasket of the flange out or damage the packing. It may also deform the body and bonnet, significantly reducing its sealing performance. What’s worse is that the valve breaks down and causes economic loss.

In order to prevent the misfortune of abnormal pressure increase, we take following measures:

1. Set an orifice, also known as pressure-balancing orifice or exhaust orifice, that is, a small hole drilled on the inlet side of the flexible gate or double gate serves as a pressure-balancing hole in the inner cavity of the valve and the inlet side. When the pressure in the valve cavity increases, the gas can be discharged through the small hole. This method is relatively simple and has been widely adopted. Once an orifice is added to the valve, there should be an arrow dedicating the direction of the flow.

2. Set an outlet pipe on the valve or install a safety valve to discharge abnormal high pressure. Generally, a safety valve is installed on the cover. When the pressure rises to a certain value, the safety valve opens and balances the pressure to ensure the safety of the body.  Or an exhaust valve can also be installed in the lower part of the valve body to drain the residual medium in the cavity, preventing abnormal boost.

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