The Forgotten Boiler That Suddenly Isn't
National Board Governmental and International Affairs Represenative,
Former National Board consultant
Summary: The following article is a part of National Board Classic Series and it was published in the National Board BULLETIN. (3 printed pages)
This article outlines the hazards associated with reactivating an idle boiler. In the case below, a closed school was re-opened several years later to serve as a government facility.
Though disaster was averted when the failing boiler was reactivated without inspection, several safety tips listed at the bottom of this article should prove useful for proper boiler maintenance, not only as boiler personnel prepare for winter, but all year round.
The old elementary school in which the subject boiler was installed had been closed down for several years, and the boiler had been removed from the active inspection list by the jurisdiction.
But recently the run-down school building had been reactivated for other uses, and the neglected water-tube boiler was started up and placed in service without inspection or proper servicing to ensure that all controls and safety devices required by the jurisdiction were installed and tested for proper operation.
This forgotten boiler was suddenly brought to the attention of everyone when firefighters were summoned to the school to find the boiler "glowing cherry red" and smoke throughout the building. The boiler system was shut down, thus limiting damage to the boiler itself.
Reviewing this incident, the following was found:
- The boiler was equipped with only one low-water fuel shutoff (combination low-water fuel shutoff and water feeder).
- The piping to the low-water fuel shutoff was plugged.
- Both safety shutoff valves in the main fuel gas train had failed in the open position. These are normally closed valves which must be energized to open, and when examined all power had been shut off.
- One of the safety shutoff gas valves was an obsolete diaphragm, weight-loaded valve, actuated by an electrical solenoid.
The boiler had been seriously overheated causing the steam drum to grow lengthwise about 8 inches, parting the insulation. This caused the "cherry red glow," a fireman reported.
The boiler experienced a runaway firing condition due to stuck safety shutoff gas valves, and the boiler was dry due to a malfunctioning low-water fuel shutoff and plugged piping. The resulting intense heat melted all the tubes in the boiler.
This incident was preventable, had the boiler been properly serviced and inspected before being placed in service.
Had the boiler been inspected first, the inspector would have recommended that all controls and safety devices required by regulation be installed, and the plugged low-water fuel shutoff piping would have been replaced. The fuel train would have been upgraded to meet current requirements.
It is true that the work required to bring this boiler into compliance with safety standards would have been quite expensive, estimated between $2,500 and $3,000. However, compared to the repairs or more likely replacement, which will cost approximately $45,000 to $50,000, such preventive maintenance would have been a bargain - not to mention preventing hazards to people and property.
This incident again shows the need for thorough inspections by qualified inspectors. Had the jurisdiction been notified prior to placing the boiler in service, this forgotten boiler would not have been remembered so suddenly, dangerously and expensively.
SAFETY TIPS FOR REACTIVATING IDLE BOILERS
|1. Exterior shell and/or insulation. Look for indications of overheating.
|2. Leaks. Look for water on the floor. Check for water or steam escaping from any part of a pressurized system including the boiler, valves or piping.
|3. Flue gas leaks. Look for black dust (soot) around sheet-metal joints. Check any part of boiler enclosure and breaching, especially in the connection to the stack, and check the boiler exhaust system integrity.
|4. Controls. Look for open panels, covers and signs of rewiring on floor or bottom of panels. Check for jumper wires and locked shutoffs.
|5. Safety Devices. Test all operating controls and safety devices for proper operation. Observe at least three cycles of automatic operation before independent operation.
|6. Electrical. Ensure that covers are installed on overlimit switches, temperature sensors, and controls.
|7. Safety valves. Ensure that a safety valve is installed with full-sized discharge piping properly supported and directed to a point of safe discharge. Safety valve set pressure must be equal to or less than boiler maximum allowable working pressure. Safety valve relieving capacity must be equal to or greater than boiler output.
|8. Fuel sources. Check for the ability to shut off the fuel source to the vessel.
|9. Gages. Make sure temperature and pressure gages are operational and are located for proper monitoring.
|10. Hazards. Remove all fire hazards from the boiler room and do not use the boiler room for storage.
|11. Air openings. Check combustion air openings for obstructions.
|12. Proper piping. Check for proper supports and allowance for expansion and contraction.
|13. Operating certificate. Observe certificate, noting last date of inspection and expiration date, as well as when next inspection is required.
Editor's note: Some ASME Boiler and Pressure Vessel Code requirements may have changed because of advances in material technology and/or actual experience. The reader is cautioned to refer to the latest edition of the ASME Boiler and Pressure Vessel Code for current requirements.