ASME BPVC Section VIII / OSHA 1910.169

ASME BPVC Section I PG-71.2

ASME BPVC Section I strictly prohibits any intervening stop valve between a boiler and its pressure relief valve. A closed block valve renders the PRV inoperable, allowing boiler pressure to exceed the maximum allowable working pressure (MAWP) and potentially causing a catastrophic boiler explosion.

ASME BPVC Section IV / ASME B31.1

This fails code. ASME Boiler and Pressure Vessel Code Section IV (Heating Boilers) and ASME B31.1 require a safety relief valve on the low-pressure side of every pressure reducing valve station. The safety valve must be set at or below the MAWP of the downstream equipment (30 PSI in this case). If the PRV fails open, full upstream pressure (150 PSI) would reach equipment rated for only 30 PSI — a catastrophic overpressure event. This is one of the most critical safety lessons taught at every UA local.

ASME BPVC Section IX / ASME B31.1

Per ASME Section IX, a welder qualified on 6-inch pipe is qualified for pipe diameters from 2-7/8 inches and larger (for pipe over 2-7/8" OD test coupons). The 4-inch pipe falls within this range. Since the WPS covers both sizes and the same welding processes are used, this is code-compliant.

ASME BPVC Section VIII Div. 1 / OSHA 1910.169

All pressure vessels including compressed air receivers must bear an ASME Section VIII nameplate with National Board (NB) registration number, MAWP, manufacturer data, and serial number. An unregistered vessel cannot be legally operated and may not have been properly designed, fabricated, or tested per ASME code.

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.