ASME CSD-1 — Controls and Safety Devices for Automatically Fired Boilers
What it means on the job
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.
Tested in 1 CraftIQ puzzle
- code-checkBoiler Fuel Train Missing Interlocks
Related ASME sections
ASME BPVC Section VIII / OSHA 1910.169
This passes code requirements. The tank has proper ASME Section VIII certification with National Board registration as required by OSHA 1910.169. The PRV is correctly set at the MAWP of 200 psig, satisfying ASME Section VIII UG-134 which requires the relief device to be set at or below the MAWP. The automatic condensate drain and pressure gauge are operational requirements for reliable compressed air service. The annual external inspection meets the minimum inspection frequency required by most jurisdictional authorities. Note that internal inspections may also be required at intervals determined by the jurisdiction and the tank's corrosion history.
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 (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.
ASME PCC-1 — Guidelines for Pressure Boundary Bolted Flange Joint Assembly
Flange bolts must be tightened in a star (cross) pattern to ensure even gasket compression. Circular tightening causes uneven loading, gasket distortion, and leaks.
CraftIQ explanations are original educational commentary written in trade language and verified against the cited standards. Always confirm requirements against the code edition adopted by your jurisdiction — this is training material, not a substitute for the code book or your AHJ.