In order to ensure that safety valves work efficiently and accurately, it is critical to understand how their opening pressure (setting pressure) is adjusted. In industrial environments, this procedure is especially critical to maintaining safe operation of equipment.
The adjustment procedure is briefly described:
Within the specified operating pressure range of the safety valve, we can make precise adjustments to the opening pressure by rotating the adjusting screw to change the amount of preload compression on the spring.
Preparation: First, remove the valve cover cap and loosen the lock nut.
Preliminary adjustment: Gradually increase the inlet pressure to make the valve jump once to confirm its function.
If the opening pressure is low, turn the adjusting screw clockwise to increase the pressure.
If opening pressure is high, turn adjusting screw counterclockwise to reduce pressure.
LOCKING ADJUSTMENT: When the desired opening pressure is reached, be sure to tighten the lock nut and reinstall the cap.
SPRING REPLACEMENT: If the desired opening pressure is outside the current spring’s operating pressure range, replace the spring with a suitable one and update the relevant data on the nameplate.
Precautions during adjustment:
Avoid damage: When the medium pressure is close to 90% or more of the opening pressure, avoid rotating the adjusting screw to prevent damage to the sealing surface as the valve flap rotates with it.
Accurate adjustment: In order to ensure the accuracy of the opening pressure value, the adjustment should try to simulate the actual working conditions, including the type of media and temperature. The opening pressure may change when the medium changes from liquid to gas. At the same time, an increase in operating temperature will result in a decrease in opening pressure. Therefore, when adjusted at room temperature and used in a high-temperature environment, the set pressure value should be increased appropriately.
Adjustment of discharge and return seat pressure:
After the opening pressure is adjusted, if the discharge or return seat pressure does not meet the requirements, it can be realized by adjusting the adjusting ring on the valve seat.
Counterclockwise rotation: When the adjusting ring is rotated counterclockwise to the right, its position is elevated and both the discharge and seat back pressures are reduced.
Clockwise rotation: When the adjusting ring is rotated clockwise to the left, its position is lowered and both discharge and seat pressures are increased.
The adjustment ring should not be rotated too far during each adjustment (no more than 5 teeth is recommended). After adjustment is complete, be sure to tighten the set screw and make sure it is in the groove between the two teeth of the adjusting ring to prevent the ring from rotating, but to avoid creating lateral pressure on the ring.
SAFETY NOTE: Before adjusting the adjusting ring, the inlet pressure should be appropriately reduced (usually below 90% of the opening pressure) to prevent accidents caused by sudden opening of the valve.
Testing and Calibration:
When performing safety valve vent and seat-back pressure tests, it is necessary to ensure that the flow rate of the gas source is sufficient to fully open the valve (i.e., to reach the rated discharge of the safety valve). However, the small capacity of the test stand normally used to calibrate the opening pressure of safety valves may not allow the valve to reach full opening, so its seat-back pressure may be inaccurate. In this case, the adjustment ring should be adjusted taking into account actual operating conditions and readjusted if necessary.
Seal protection:
After the safety valve has been adjusted, it should be sealed to prevent arbitrary changes. When shipped from the factory, safety valves are normally adjusted to the upper limit of the operating pressure stage (i.e., high pressure) unless otherwise specified. Therefore, the user should readjust to actual operating conditions and seal again for safety.
By following the above guidelines, the user can easily adjust the opening, venting, and seating back pressures of the safety valve to ensure safe operation of the equipment.
How do I adjust the pressure of a safety valve?
