- Open the pressure adjustment
① Before the safety valve leaves the factory, its opening pressure should be adjusted one by one to the setting value required by the user. If the user puts forward the working pressure level of the spring, it should generally 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 re-adjust the installation site to ensure that the setting 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 the adjusting screw to change the compression amount of the spring.
④Before 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, resulting in damage to the sealing surface.
⑤In order to ensure the accuracy of the opening pressure value, the medium conditions, such as the medium type and temperature, should be adjusted 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 the liquid phase to the gas phase), the opening pressure often changes. When the operating temperature rises, the opening pressure is generally reduced. Therefore, when it is adjusted at room temperature for high temperature, the setting pressure value at room temperature should be slightly higher than the required opening pressure value. The degree to which it is high is related to the valve structure and material selection, and should be based on the manufacturer’s instructions.
⑥The conventional safety valve is used to fix the additional back pressure, when the opening pressure is adjusted after the test (at this time the back pressure is atmospheric pressure), the setting value should be the required opening pressure value minus the additional back pressure value.
- Adjustment of discharge pressure and return pressure
(1) To adjust the valve discharge pressure and return pressure, the valve must be tested to reach the full open height, so 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 disk and a seat adjusting ring, the seat adjusting ring is used to adjust. Unscrew the adjusting ring fixing screw and extend a tool such as a thin iron bar through the exposed screw hole to move the teeth on the adjusting ring and make the adjusting ring rotate left and right. When the adjusting ring is rotated counterclockwise to the left, its position is raised, and the discharge pressure and return pressure will be reduced. On the contrary, when the adjusting ring is rotated clockwise to the right, its position is reduced, and the discharge pressure and return pressure will be increased. When adjusting each time, adjust: the amplitude of rotation of the circle should not be too large (generally the number of teeth can be rotated). 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 adjustment ring, which can prevent the adjustment ring from rotating, and does not produce radial pressure on the adjustment ring. For safety reasons, before the adjustment ring is flipped, the inlet pressure of the safety valve should be properly reduced (generally, it should be less than 90% of the opening pressure) to prevent the valve from suddenly opening during adjustment, causing an accident.
(3) For the structure with an upper and lower adjustment ring (there is an adjustment ring on the guide sleeve and the seat), the adjustment is more complicated. The seat adjusting ring is used to change the size of the passage between the disc and the adjusting ring, thereby changing the degree to which pressure accumulates in the chamber between the disc and the adjusting ring when the valve is initially opened. When the seat adjusting ring is raised, the degree of pressure accumulation is increased, so that the proportional opening stage of the valve is reduced and the sudden rapid opening is achieved more quickly. Therefore, raising the seat adjusting ring can reduce the discharge pressure. It should be noted that the seat adjusting ring should not be raised too close to the disc. 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 is then closed, and the valve frequency occurs.
The upper adjusting ring is used to change the Angle of turning after the flow medium is reflected in the lower side of the valve disc, so as to change the size of the fluid force, so as to adjust the return seat pressure. When the upper adjusting ring is raised, the bending Angle decreases, the fluid force decreases, and the return pressure increases. Conversely, when the upper adjustment ring is lowered, the return pressure is reduced. Of course, when the upper adjustment ring changes the seating pressure, it also affects the discharge pressure, that is, increasing the upper adjustment ring increases the discharge pressure, and reducing the upper adjustment ring reduces the discharge pressure, but its impact is not as obvious as the seating pressure.
- Lead seal
After the adjustment of the safety valve, it should be sealed to prevent random changes in the adjusted situation. When the safety valve is repaired, the position of the adjusting screw and the adjusting ring should be noted before removing the valve to facilitate the adjustment work after the dressing. It should be sealed again after readjustment.
