ASME PCC-1 — Guidelines for Pressure Boundary Bolted Flange Joint Assembly

ASME BPVC Section VIII UG-134 / OSHA 1910.169(b)

ASME Section VIII requires the pressure relief device on a vessel to be set at or below the vessel's maximum allowable working pressure (MAWP). A PRV set above MAWP provides no overpressure protection, risking catastrophic vessel failure. The PRV set pressure must never exceed the MAWP stamped on the nameplate.

ASME CSD-1 — Controls and Safety Devices for Automatically Fired Boilers

A 4,000 MBH (4 MMBtu/hr) boiler falls under ASME CSD-1, not NFPA 85: NFPA 85's scope begins at 12,500,000 Btu/hr of fuel input, while ASME CSD-1 governs automatically fired boilers below that threshold. CSD-1 requires a proof-of-closure (valve-proving) interlock on the main fuel safety shutoff valves at this input, in addition to a proven pre-purge before ignition. The missing proof-of-closure interlock is the real violation: it confirms the main gas valves have physically closed after a shutdown signal, and without it a leaking or stuck-open valve could let raw gas accumulate in the combustion chamber, creating an explosion hazard on the next ignition attempt. Post-purge is good engineering practice on many burners but is not a universally mandatory life-safety interlock the way pre-purge proving and proof-of-closure are, so its absence is not the governing deficiency here. The fuel train must be corrected and the boiler locked out until the CSD-1-required interlocks are verified operational.

ASME CSD-1 — Controls and Safety Devices for Automatically Fired Boilers (governs boilers ≤12.5 MMBtu/hr)

ASME CSD-1 requires a high-gas-pressure switch to prevent burner operation when gas supply pressure exceeds the maximum rated pressure. Overpressure can cause excessive firing rate, flame impingement, and damage to the combustion chamber. The switch must be wired in the safety interlock circuit.