①Safety valveBefore leaving the factory, the opening pressure should be adjusted one by one to the set 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 to the protected equipment or before installation, the user must re-adjust at the installation site to ensure that the set pressure value of the safety valve meets the requirements.
③Within the working pressure range of the spring indicated on the nameplate, the opening pressure can be adjusted by rotating the adjustment screw to change the compression of the spring.
④Before 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, which may damage the sealing surface.
⑤In order to ensure the accuracy of the opening pressure value, 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 a liquid phase to a gas phase), the opening pressure often changes.When the working temperature increases, the opening pressure generally decreases.Therefore, when adjusting at room temperature for high temperature, the set pressure value at room temperature should be slightly higher than the required opening pressure value.How high it is is related to the valve structure and material selection, and should be based on the manufacturer's instructions.
⑥ RoutineSafety valveWhen used to fix additional back pressure, when the opening pressure is adjusted after inspection (the back pressure is atmospheric pressure at this time), the setting value should be the required opening pressure value minus the additional back pressure value.
① To adjust the valve discharge pressure and return pressure, the valve must be tested to reach the full opening height. Therefore, it can only be performed on a large-capacity test device or after the safety valve is installed on the protected equipment.The adjustment method varies according to the structure of the safety valve.
②For the structure with recoil disc and valve seat adjusting ring, the valve seat adjusting ring is used for adjustment.Unscrew the adjusting ring fixing screw, and extend a thin iron rod or the like from the exposed screw hole to move the teeth on the adjusting ring to rotate the adjusting ring left and right.When the adjusting ring is rotated counterclockwise to the left, its position increases, and both the discharge pressure and the return pressure will decrease.Conversely, when the adjusting ring is rotated clockwise to the right, its position is lowered, and both the discharge pressure and the return pressure will increase.During each adjustment, adjust: the amplitude of the circle rotation should not be too large (generally, it is sufficient to rotate a few teeth).After each adjustment, the fixing screw should be screwed on 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 not generate radial pressure on the adjusting ring.For safety reasons, before turning the adjusting 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 opening suddenly during adjustment and causing accidents.
③For structures with upper and lower adjusting rings (the guide sleeve and the valve seat each have an adjusting ring), the adjustment is more complicated.The valve seat adjustment ring is used to change the size of the passage between the valve disc and the adjustment ring, thereby changing the degree of pressure accumulation in the chamber between the valve disc and the adjustment 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 reached faster.Therefore, raising the valve seat adjustment ring can reduce the discharge pressure.It should be noted that the valve seat adjustment ring should not be raised too close to the valve clack.In that way, 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, the valve disc closes immediately, and the valve jumps frequently.Valve seat adjustment: "The ring is mainly used to reduce the valve ratio, the opening stage and adjust the discharge pressure, but also have an impact on the return pressure.
The upper adjusting ring is used to change the turning angle of the flowing medium after being reflected on the lower side of the valve disc, thereby changing the size of the fluid force, thereby adjusting the return pressure.When the upper adjusting ring is raised, the turning angle is reduced, and the fluid force is reduced accordingly, so that the return pressure is increased.Conversely, when the upper adjusting ring is lowered, the return pressure decreases.Of course, while the upper adjustment ring changes the seat pressure, it also affects the discharge pressure, that is, raising the upper adjustment ring increases the discharge pressure, and lowers the upper adjustment ring to reduce the discharge pressure, but the degree of influence is not as good as the return pressure. The seat pressure is so obvious.
Safety valveAfter the adjustment is completed, it should be sealed with lead to prevent the adjusted condition from being changed casually.When the safety valve is refurbished, the position of the adjusting screw and the adjusting ring should be noted before disassembling the valve to facilitate the adjustment work after the refurbishment.After re-adjustment, it should be sealed again.