The physical strength of the boiler structures against internal pressure spikes.
Large utility boilers are susceptible to structural failure caused by excessive negative pressure (implosions). NFPA 85 outlines control system requirements, master fuel trip (MFT) sequences, and fan control loops to mitigate these pressure excursions. 3. Multiple Burner Boilers
: Revised boiler enclosure purge requirements for scenarios where no fans remain in service. ANSI Webstore Core Requirements of NFPA 85 This code applies to units with a fuel input of 12.5 million Btu/hr (3.7 MW) or greater and covers: National Board of Boiler and Pressure Vessel Free access NFPA codes and standards
For field use (where “install” matters), you need a downloaded, offline PDF.
While NFPA 85 is updated every few years, the introduced several foundational shifts in automation, safety integrity, and system design that remain relevant for legacy industrial systems. 1. Unified Structure
