(1) Adjustment of opening pressure 

 1 Before the safety valve leaves the factory, the opening pressure should be adjusted to the fixed value required by the user. If the user proposes the working pressure level of the spring, it should generally be adjusted to the lower limit of the pressure level. 

 2 Before installing the safety valve to the protected equipment or before installation, the user must readjust it at the installation site to ensure that the fixed pressure value of the safety valve meets the requirements. 

 3 Within the range of the working pressure level of the spring indicated on the nameplate, the opening pressure can be adjusted by rotating and adjusting the screw to change the compression amount of the spring. 

 4 Before rotating the adjustment 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 the adjustment screw is rotated, resulting in damage to the sealing surface. 

 5 In order to ensure the accuracy of the opening pressure value, the adjusted medium conditions, such as medium type and temperature, should be as close to the actual operating conditions as possible. The type of medium changes, especially when the medium accumulation state is different. 

 (For example, from liquid phase to gas phase), the opening pressure often changes. When the working temperature rises, the opening pressure is generally reduced. Therefore, when adjusted at room temperature and used at high temperature, the fixed pressure value at room temperature should be slightly higher than the required opening pressure value. The degree to which it is related to the valve structure and material selection should be based on the description of the manufacturer. 

 6 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 set value should be the required opening pressure value minus the additional back pressure value. 

 (2) Adjustment of discharge pressure and return pressure 

 1 To adjust the valve discharge pressure and return pressure, an action test must be carried out to reach the full opening height of the valve. Therefore, it can only be carried out on a 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 structure with a recoil disc and a valve seat adjustment ring, the valve seat adjustment ring is used to adjust. Screw down the adjustment ring to fix the screw, and extend a tool such as a thin iron bar from the exposed screw hole, and you can move the teeth on the adjustment ring to make the adjustment ring rotate left and right. When the adjustment ring is rotated counterclockwise to the left, its position will increase, and the discharge pressure and return pressure will be reduced. Conversely, when the adjustment ring is rotated clockwise to the right, its position will be reduced, and the discharge pressure and return pressure will increase. During each adjustment, the adjustment: the amplitude of the circle rotation should not be too large (generally, it is enough to rotate several teeth). After each adjustment, the fixing screw should be screwed up so that the end is located in the groove between the two teeth of the adjustment ring, which not only prevents the adjustment ring from rotating, but also does not generate radial pressure on the adjustment ring. For the sake of safety, before moving the adjustment ring, the inlet pressure of the safety valve should be appropriately reduced (generally less than 90% of the opening pressure) to prevent the valve from suddenly opening and causing accidents during adjustment. 

 3 For the structure with upper and lower adjustment rings (there is an adjustment ring on the guide sleeve and the valve seat), the adjustment is more complicated. The seat adjustment ring is used to change the size of the channel between the disc and the adjustment ring, so as to change the degree of pressure accumulation in the chamber between the disc and the adjustment ring when the valve is initially opened. When the valve seat adjustment ring is raised, the degree of pressure accumulation increases, so that the proportion of the valve opening stage decreases and the sudden rapid opening is achieved relatively quickly. Therefore, raising the seat adjustment ring can reduce the emission pressure. It should be noted that the seat adjustment 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 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 immediately closes, so the valve jumps. 

 Valve seat adjustment: The coil is mainly used to reduce the proportion of valves, the opening stage and adjusting the discharge pressure, and also has an impact on the return pressure. 

 The upper adjustment ring is used to change the angle of the turning of the flowing medium after the reflection on the lower side of the disc, so as to change the size of the fluid force, so as to adjust the return pressure. When the upper adjustment ring is raised, the turning angle decreases, and the fluid force decreases, thus increasing the return pressure. On the contrary, when the upper adjustment ring is lowered, the return pressure is reduced. Of course, while changing the return pressure, the upper adjustment ring also affects the emission pressure, that is, raising the upper adjustment ring increases the emission pressure, and lowering the upper adjustment circle reduces the emission pressure, but its impact is not as obvious as the return pressure. 

 (3) Lead seal 

 After the safety valve is adjusted, it should be sealed with lead to prevent casual changes in the adjusted condition. When the safety valve is refurbished, the position of the adjustment screw and adjustment ring should be recorded before removing the valve to facilitate the adjustment after repair. After readjustment, it should be sealed again.