Practical operation method of the hottest safety v

Practical operation methods of safety valves

I: adjustment of opening pressure of safety valves

① before leaving the factory, the opening pressure of safety valves should be adjusted one by one to the setting value required by the user. If the user proposes the working pressure level of the spring, it should generally be adjusted according to the lower limit of the pressure level. ② Before installing the safety valve on the protected equipment or before installation, the user must readjust it at the installation site. Some countries use the "guise" of safety and health 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 valve inlet pressure should be reduced to less than 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 that the opening pressure value of the former requires the use of coarse abrasive accurately, the medium conditions during adjustment, such as medium type and temperature, should be as close as possible to the actual operating conditions. The type of medium changes, especially when the accumulation state of the medium is different (for example, from liquid phase to gas phase), the opening pressure often changes. When the working temperature rises, the opening pressure generally decreases. Therefore, when it is adjusted at room temperature and used at high temperature, the set pressure value at room temperature should be slightly higher than the required opening pressure value. How high is related to the valve structure and material selection, which should be based on the manufacturer's instructions. ⑥ The conventional safety valve is used to fix the additional back pressure. When the opening pressure is adjusted after inspection (at this time, the back pressure is atmospheric pressure), its setting value should be the required opening pressure value minus the additional recommended hydraulic oil: 3.1 hydraulic system oil: the hydraulic system oil should adopt the excellent medium viscosity mineral oil back pressure value

II: adjustment of the discharge pressure and reseating pressure of the safety valve

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. Therefore, 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 varies according to the valve structure. ② For the structures of different recoil discs and valve seat adjusting rings with different product tension ranges, the valve seat adjusting ring is used for adjustment. Unscrew the fixing screw of the adjusting ring, extend a tool such as a thin iron bar from the exposed screw hole, and then move the gear teeth on the adjusting ring to make the adjusting ring rotate left and right. When the adjusting ring is rotated counterclockwise to the left, its position will increase, and the discharge pressure and reseating pressure will decrease. On the contrary, when the adjusting ring is rotated clockwise to the right, its position will decrease, and the discharge pressure and reseating pressure will increase. During each adjustment, the adjustment: the rotation range of the circle should not be too large (generally, it is enough to rotate a few teeth). After each adjustment, screw the fixing screw so that its end is located in the groove between the two teeth of the adjusting ring, which can prevent the adjusting ring from rotating and will not generate radial pressure on the adjusting ring. For the sake of safety, the inlet pressure of the safety valve should be properly reduced (generally lower than 90% of the opening pressure) before pulling the adjusting ring, so as to prevent the sudden opening of the valve during adjustment and cause accidents. ③ For the structure with upper and lower adjusting rings (there is an adjusting ring on the guide sleeve and the valve seat), the adjustment is more complicated. The valve seat adjusting ring is used to change the size of the channel between the valve disc and the adjusting ring, so as to change the degree of pressure accumulation in the chamber between the valve 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 proportional opening stage of the valve 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 valve seat adjusting ring should not be raised too close to the valve disc. In that case, the leakage at the sealing surface may cause the valve to suddenly open prematurely, but because the medium pressure is not enough to keep the valve disc in the open position at this time, the valve disc will then close, and 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 adjusting ring is used to change the angle of the flow medium after reflection on the lower side of the valve disc, so as to change the size of the fluid force, so as to adjust the reseating pressure. When the upper adjusting ring is raised, the turning angle is reduced, and the fluid force is reduced, so as to increase the reseating pressure. On the contrary, when the upper adjusting ring is lowered , the reseating pressure decreases. Of course, when the upper adjusting ring changes the reseating pressure, it also affects the discharge pressure, that is, raising the upper adjusting ring will increase the discharge pressure, and lowering the upper adjusting ring will reduce the discharge pressure, but its impact is not as obvious as the reseating pressure

III: safety valve lead seal

after the safety valve is adjusted, it should be lead sealed to prevent changing the adjusted condition casually. When the safety valve is repaired, the position of the adjusting screw and adjusting ring should be noted down before disassembling the valve, so as to facilitate the adjustment after repair. Lead sealing shall be applied again after readjustment