How does the safety valve adjust the pressure?

How does the safety valve adjust the pressure?

Tianjin Tanggu Water-Seal Valve Co., Ltd (TWS Valve Co., Ltd)
Tianjin，CHINA
21th，August，2023
Web:www.water-sealvalve.com

Adjustment of safety valve opening pressure (set pressure):
Within the specified working pressure range, the opening pressure can be adjusted by rotating the adjusting screw to change the spring preload compression. Remove the valve cap, loosen the lock nut, and then adjust the adjusting screw. First, increase the inlet pressure to make the valve take off once.
If the opening pressure is low, tighten the adjusting screw clockwise; if the opening pressure is high, loosen it counterclockwise. After adjusting to the required opening pressure, tighten the lock nut and install the cover cap.
If the required opening pressure exceeds the working pressure range of the spring, it is necessary to replace another spring with a suitable working pressure range, and then adjust it. After the spring is replaced, the corresponding data on the nameplate should be changed.
When adjusting the opening pressure of the safety valve, the following points should be paid attention to:
When the medium pressure is close to the cracking pressure (up to 90% of the cracking pressure), the adjusting screw should not be rotated, so as to prevent the disc from rotating and damaging the sealing surface.
In order to ensure that the opening pressure value is accurate, the medium conditions used for adjustment, such as medium type and medium temperature, should be as close as possible to the actual working conditions. When the type of medium changes, especially when changing from liquid phase to gas phase, the opening pressure often changes. When the working temperature increases, the cracking pressure decreases. Therefore, when it is adjusted at room temperature and used at high temperature, the set pressure value at room temperature should be slightly greater than the opening pressure value of the ball.
Adjustment of relief valve discharge pressure and reseating pressure:
After the opening pressure is adjusted, if the discharge pressure or reseating pressure does not meet the requirements, you can use the adjusting ring on the valve seat to adjust. Unscrew the fixing screw of the adjusting ring, and insert a thin iron bar or other tool from the exposed screw hole, and then the gear teeth on the adjusting ring can be moved to make the adjusting ring turn left and right.
When the adjusting ring is turned counterclockwise to the right, its position will increase, and the discharge pressure and reseating pressure will decrease; on the contrary, when the adjusting ring is turned clockwise to the left, its position will decrease, and the discharge pressure and reseating pressure will decrease. Seat pressure will be increased. During each adjustment, the range of rotation of the adjusting ring should not be too large (generally within 5 teeth).
After each adjustment, the fixing screw should be tightened so that the end of the screw is located in the groove between the two teeth of the adjustment ring to prevent the adjustment ring from rotating, but no lateral pressure should be exerted on the adjustment ring. Then perform an action test. For the sake of safety, before turning the adjustment ring, the inlet pressure of the safety valve should be properly reduced (generally lower than 90% of the opening pressure), so as to prevent the valve from suddenly opening during adjustment and accidents.
Note that it is only possible to carry out the safety valve discharge pressure and reseating pressure test when the flow rate of the gas source is large enough to make the valve not open (that is, when the rated discharge capacity of the safety valve is reached).
However, the capacity of the test bench usually used to verify the opening pressure of the safety valve is very small. At this time, the valve cannot be fully opened, and its reseating pressure is also false. When calibrating the opening pressure on such a test bench, in order to make the take-off action obvious, the adjustment ring is usually adjusted to a relatively high position, but this is not suitable under the actual operating conditions of the valve, and the position of the adjustment ring should be readjusted.
lead seal
After all the safety valves have been adjusted, they should be sealed with lead to prevent the adjusted conditions from being changed arbitrarily. When the safety valve leaves the factory, it is usually adjusted with normal temperature air according to the upper limit (ie high pressure) value of the working pressure level, except for special specified circumstances.
Therefore, users generally need to readjust according to actual working conditions. Then seal it again.

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