According to the ratio of the maximum opening height of the valve disc to the diameter of the flow passage of the safety valve, the safety valve can be divided into two types: Spring micro opening closed high-pressure safety valve and spring full opening safety valve.

1. Spring micro opening closed high pressure safety valve: the opening height of the micro opening safety valve is less than 1 / 4 of the diameter of the flow channel, usually 1 / 40-1 / 20 of the diameter of the flow channel. The action process of the micro opening safety valve is proportional action type, which is mainly used in liquid occasions and sometimes in gas occasions with small discharge.

2. Spring full open safety valve. The opening height of the full open safety valve is greater than or equal to 1 / 4 of the flow path diameter. The discharge area of the full open safety valve is the minimum sectional area of the valve seat throat. Its action process is a two-stage action type, which can be fully opened only with the help of a lifting mechanism. The fully opened safety valve is mainly used in the occasion of gas medium.

3. The opening height of medium lift safety valve is between micro lift and full lift. That is to say, it can be made into two-stage action or proportional action.