Spring type safety valve in the commissioning, often used for different locations and its role is different, the degree of soft and hard. Hot water heating system such as the use of constant pressure pump supplies the control system of hydraulic electric contact pressure gauge, once the pressure relief valve will take off discharge pressure. If the working medium pressure is not very high and the use of a high degree of hardness of the spring safety valve, in fact, do not play the role of the protection of the safe operation of the system. Therefore, in the choice, according to the safety valve to determine the scope of the jump pressure to determine the level of spring.