Check valve + safety relief test
Replace the tank check valve and proof-test the ASME safety relief valve.
This guide is general field reference for trained, qualified service technicians. It is not a substitute for the original equipment manufacturer's service manual, applicable codes (NEC, OSHA, ASME, local), or the judgment of a licensed professional. Procedures, torque values, pressures, refrigerants, and safety requirements vary by make, model, jurisdiction, and revision. Always verify against current OEM documentation and follow your employer's safety program. Working on compressed-air, electrical, pressure-vessel, and refrigerant systems can cause serious injury or death. By using this guide you accept all risk; AirCompDX and its authors disclaim all warranties and are not liable for any damage, injury, loss, or code violation arising from its use.
LOTO and bleed tank to 0 psi. ASME SRVs vent loudly — wear hearing protection during the lift test.
- Pipe wrenches
- Thread sealant
- Calibrated pressure gauge
- OEM check valve assembly
- ASME-stamped safety relief valve matched to tank MAWP and pump SCFM
- 1Diagnose check valve
If the pump kicks back through the head on stop (audible reverse rotation) or the unloader passes air continuously, the check valve is leaking.
- 2LOTO and bleed
Disconnect, LOTO, bleed tank to 0 psi.
- 3Replace check valve
Back off the discharge line union, unscrew the check valve from the tank port. Install the new check valve with sealant on male threads, arrow pointing into the tank.
- 4Inspect SRV
Confirm the ASME stamp on the SRV body — set pressure must match or exceed pump cut-out and never exceed tank MAWP.
- 5Manual lift test
After repressurizing to ~80% of SRV setpoint, lift the test ring for 1 second and release. The valve should reseat with no weep within 30 seconds.
- 6Set-pressure test
Annually, isolate the tank and slowly raise pressure with a calibrated gauge in line until the SRV pops. Within ±3% of set pressure = pass. Outside that = replace, do not adjust.