Hot-Water Heaters: Cold-Blooded Killers

08/10/2015 | By Eric Woodroof, Ph.D., CEM, CRM

Be alert to the warning signs of dangerous heaters

Shortly after noon, in the busy school cafeteria of the Star Elementary School in Spencer, OK, children were having lunch. Without warning, an 80-gallon water heater in the adjacent kitchen exploded, launching itself skyward. The concrete wall between the kitchen and cafeteria collapsed. The children seated near the wall were crushed by concrete and steel propelled by the blast. Six children and one teacher were killed, and 36 others injured.

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To those trained to see them, warning signs at the school were apparent before this 1982 tragedy. These signs must still be watched today. A “trouble-free” hot-water heater in your building can release energy equivalent to 100 sticks of dynamite. However, many FMs and building owners may not recognize dangerous signs.

I was on a boiler audit with safety expert John Puskar, who wrote a great book on combustion safety and “post explosion root-cause analysis.” John taught me important things to notice for safety’s sake (which goes hand-in-hand with energy efficiency). I have asked him to contribute to this article on water heater testing, repair and preventive maintenance.

Find out how IoT devices enable predictive maintenance

Shedding light on the causes of the Star Elementary blast is a good place to start.

How Did the Explosion Occur?

Cafeteria workers arriving at the school at 7 a.m. on the tragic day noticed that the domestic hot water was much hotter than normal. They called the custodian, shut down the gas unit to await a technician’s arrival.

The technician’s fix was to replace the gas valve and relight the water heater. He returned within the hour and noted that the water heater seemed to be working normally. The cafeteria workers soon noticed that the water temperature was again much too hot and getting hotter. They placed another call for service, which went unanswered before the explosion ripped through the school at lunchtime.

Jim Greenawalt, the state of Oklahoma’s Chief Boiler Inspector at the time, was on the scene 15 minutes after the catastrophe. Greenawalt’s initial investigation found problems with burner controls and a safety relief valve that showed evidence of tampering.

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At the time, Oklahoma’s boiler inspection law covered high-pressure steam boilers but not smaller equipment such as water heaters. This was not a situation unique to Oklahoma. Most states do not provide much in the way of inspections for certain classes of combustion equipment even when located in places of public assembly like schools.  

The full investigation revealed that the safety relief valve, a pressure temperature unit, had been altered improperly. The valve’s temperature probe had been cut down to fit an elbow. This action disabled the unit’s temperature relief capability.

A defective gas valve also contributed by not shutting off the water heater’s burner. This was the cause of the employees’ complaints about the water’s extreme heat. Without the safety relief valve, the pressure could not be relieved. When this happens, the water in the tank starts storing an enormous amount of energy. As temperature increases, a tank begins to tear. At the instant of failure, the water expands its volume 1,700 times, creating a pressure pulse that can blow out walls.

The FM’s Responsibility

Without a state requirement at the time for inspection of the heater, the Spencer school system was responsible to determine what constitutes adequate inspection, maintenance and repair. This is an often-overlooked responsibility. Most facility managers do not understand that they are responsible for proper inspections and maintenance of combustion equipment.

Read also: 4 Biggest Building Maintenance Challenges and Solutions

Tragedies can be avoided. Read John Puskar’s practical steps to avoid explosions, which can occur even with small water heating units.  

Eric A. Woodroof, Ph.D., is the Chairman of the Board for the Certified Carbon Reduction Manager program and a board member of the Certified Energy Manager Program since 1999. In August 2014, he was named to the Association of Energy Engineers Energy Managers Hall of Fame.


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