Safety technical operation procedures for safety valves

1) Adjustment of opening pressure ① before leaving the factory, the opening pressure of the safety valve shall be adjusted one by one to the setting value required by the user If the user puts forward the working pressure level of spring, it should be adjusted according to the lower limit value of the pressure level ② before installing the safety valve on the protected equipment or before installation, the user must readjust it on the installation site to ensure that the set pressure value of the safety valve meets the requirements ③ within the range of spring working pressure level indicated on the nameplate, the opening pressure can be adjusted by rotating the adjusting screw to change the spring compression ④ Before rotating the adjusting screw, the inlet pressure of the valve shall be reduced below 90% of the opening pressure to prevent the valve disc from being driven to rotate when rotating the adjusting screw, so as to damage the sealing surface ⑤ in order to ensure the accuracy of the opening pressure value, the medium conditions during adjustment, such as medium type and temperature, shall be close to the actual operation conditions as much as possible With the change of medium type, especially when the accumulation state of medium is different (for example, from liquid phase to gas phase), the opening pressure often changes When the working temperature increases, the opening pressure generally decreases Therefore, when it is adjusted at room temperature and used at high temperature, the set pressure at room temperature shall be slightly higher than the required opening pressure The degree to which it is related to the valve structure and material selection shall be based on the manufacturer's instructions 6 When the conventional safety valve is used to fix additional back pressure, the setting value should be less than the required back pressure when the opening pressure is adjusted after testing ② Before installing the safety valve on the protected equipment or before installation, the user must readjust it at the installation site to ensure that the set pressure value of the safety valve meets the requirements ③ within the range of spring working pressure level indicated on the nameplate, the opening pressure can be adjusted by rotating the adjusting screw to change the spring compression (2) adjustment of discharge pressure and reseating pressure ① to adjust the discharge pressure and reseating pressure of the valve, the action test of the valve reaching the full opening height must be carried out, so it can only be carried out on the large capacity test device or after the safety valve is installed on the protected equipment The adjustment method depends on the valve structure ② for the structure with recoil plate and valve seat adjusting ring, the valve seat adjusting ring is used for adjustment Screw out the fixing screw of the adjusting ring, extend a thin iron bar or other tools from the exposed screw hole, and then move the teeth on the adjusting ring to make the adjusting ring rotate left and right When the adjusting ring rotates counterclockwise to the left, its position increases, and the discharge pressure and the reseating pressure decrease On the contrary, when the adjusting ring is rotated clockwise, its position will decrease, and the discharge pressure and reseating pressure will increase For each adjustment, the adjustment: the rotation range of the ring should not be too large (generally, the number of teeth can be turned) After each adjustment, screw on the fixing screw so that its end is located in the groove between the two teeth of the adjusting ring, which can not only prevent the adjusting ring from turning, but also do not generate radial pressure on the adjusting ring For the sake of safety, the inlet pressure of the safety valve shall be properly reduced (generally lower than 90% of the opening pressure) before the adjusting ring is moved to prevent the valve from suddenly opening during the adjustment, causing accidents ① Before leaving the factory, the opening pressure of the safety valve shall be adjusted one by one to the setting value required by the user If the user puts forward the working pressure level of spring, it should be adjusted according to the lower limit value of the pressure level ③ for the structure with up and down regulating rings (one regulating ring on the guide sleeve and one regulating ring on the valve seat), the adjustment is more complicated The valve seat adjusting ring is used to change the size of the channel between the disc and the adjusting ring, so as to change the accumulation of pressure in the chamber between the disc and the adjusting ring when the valve is initially opened When the valve seat adjusting ring is raised, the degree of pressure accumulation increases, so that the valve proportional opening stage is reduced and the sudden rapid opening is achieved quickly Therefore, raising the valve seat adjusting ring can reduce the discharge pressure It should be noted that the seat adjusting ring can not be raised too close to the disc In this way, the leakage at the sealing surface may cause the valve to open prematurely and suddenly, but because the medium pressure at this time is not enough to keep the valve disc in the open position, the valve disc will close immediately, so the valve will jump frequently Valve seat adjustment: the ring is mainly used to reduce the valve proportion, the opening stage and adjust the discharge pressure, but also has an impact on the reseating pressure The upper pitch ring is used to change the angle of the flow medium after reflection at the lower side of the valve disc, so as to change the magnitude of the fluid force, so as to adjust the reseating pressure When the upper pitch ring is raised, the turning angle decreases, and the fluid force decreases accordingly, so that the reseating pressure increases On the contrary, when the upper adjusting ring is lowered, the reseating pressure is reduced Of course, when the upper regulating ring changes the reseating pressure, it also affects the discharge pressure That is to say, raising the upper regulating ring will increase the discharge pressure, and lowering the upper regulating ring will reduce the discharge pressure, but the effect is not as obvious as the reseating pressure (3) after the adjustment of lead seal safety valve, lead seal shall be applied to prevent any change of the adjusted condition When repairing the safety valve, the position of adjusting screw and adjusting ring shall be recorded before disassembling the valve, so as to facilitate the adjustment after finishing Lead sealing shall be applied again after readjustment