Safety Valve Set Pressure Adjustment: Step by Step Guide
The set pressure is the inlet pressure at which the valve begins to open. The following sequence describes the standard adjustment procedure in text diagram form, from preparation through final sealing.The main safety valve product names of China safety valve Network include:Explosion Wave Proof Safety Valve,F2-250/400 Main Safety Valve,Fan Engine Safety Valve,Freezer-used Safety Valve,Gas Specific Fall Lift Safety Valve,GA49H-DN20 Pulse Safety Valve,High Temperature and Pressure Fall Lift Safety Valve,Hydraulic Safety Valve,Impulse Safety Valve,Impulse Spring Safety Valve,JIS Safety Valve,Main Safety Valve,Overflow Valve,Oil Refining Specific Safety Valve,Pulse Safety Valve,Pilot Safety Valve,Pressure Safety Valve.
Step 1. Confirm the valve data. Record the model, size, spring range, required set pressure, and allowable tolerance from the nameplate and the purchase specification. Confirm that the installed spring is suitable for the required set pressure. A spring operating near the end of its range will produce unstable opening and poor repeatability.
Step 2. Isolate and depressurize. Remove the valve from service, depressurize the inlet and outlet, and drain any trapped media. For steam service, allow the valve to cool. Never loosen the bonnet or adjusting screw while pressure remains in the system.
Step 3. Mount on the test bench. Install the valve on a calibrated test stand with a pressure gauge whose range is appropriate for the set pressure and whose calibration is current. Vent the outlet to a safe discharge path. Confirm that the test bench can supply enough flow to fully lift the valve.
Step 4. Release the locking device. Remove the lead seal and loosen the locknut on the adjusting screw. On some designs a cap or cover must be removed first. Keep the adjusting screw in its original position until the test begins.
Step 5. Adjust the spring compression. Turning the adjusting screw clockwise compresses the spring and raises the set pressure. Turning it counterclockwise reduces compression and lowers the set pressure. Make adjustments in small increments, no more than one quarter turn at a time. Large changes make it difficult to identify the exact opening point.
Step 6. Test the opening pressure. Raise inlet pressure slowly until the valve opens. Record the opening pressure. Reduce pressure and allow the valve to reseat. Repeat the test at least three times. All three openings must fall within the allowable tolerance, typically plus or minus 3 percent for pressures above 1 bar and plus or minus 0.1 bar for lower pressures. Stable repeatability matters more than a single correct reading.
Step 7. Check blowdown and reseating. After the set pressure is stable, observe the reseating pressure. If it is outside the specified blowdown range, adjust the blowdown ring according to the manufacturer instructions. Do not use the adjusting screw to correct blowdown.
Step 8. Lock and seal. Hold the adjusting screw in position and tighten the locknut firmly without altering the setting. Refit the cap and install a new lead seal. Record the final set pressure, reseating pressure, test date, and technician name.
Step 9. Apply hot correction if required. For high temperature service, the cold set pressure on the bench may need correction so that the valve opens at the required pressure when hot. Follow the manufacturer correction curve or the applicable code requirement.
Summary. Safety valve set pressure adjustment requires a calibrated bench, a suitable spring, small incremental screw changes, three consecutive opening tests within tolerance, correct blowdown adjustment, and proper locking and sealing. Online adjustment under pressure is unsafe and is not permitted. Correct procedure ensures reliable overpressure protection and repeatable valve performance.
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