Electrically fired Boilers?

A special section just for steam engines and boilers, as without these you may as well fit a sail.
Oilking
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Re: Electrically fired Boilers?

Post by Oilking » Wed Sep 02, 2020 6:32 pm

Allow me to share what come to call the “Aerospace Plumber”. The incident occurred in Longview, WA in the early 80’s. A young couple complained that they had recently started to get hot water when they first opened the cold water tap (clue #1). The apartment manager called the plumber and after a look at the situation installed a check valve on the tank inlet. No more hot water out of the cold problem solved, he thought?

Around midnight when the, couple was tucked in there bed, an eruption took place that lifted the roof off of the building, and pushed the wall against one side of the bed. Surprisingly the couple other than frightened and covered in sheetrock dust, had escaped injury. Parts of the tank were later found a couple hundred yards away on a ball park.

Clue #1: This was a recent occurrence. The plumber should have first checked for a stuck thermostat which will cause the water to over heat and expand back into the cold water line. As a public water works operator, I have seen plastic number wheels in a meter register melted as a result of hot water backing out of the house because of a stuck thermostat.

In addition to over looking the above, the plumber missed the fact that this was an old installation which did not have the relief valve on the tank. You guessed it, he installed the check valve between the tank and the relief valve. Duh, it’s not rocket science, or is it?

Dave

PS. In the Jan/Feb 2014 “Model Engineer” page 32 is a photo of the electric boiler used by the author, Bob Bramson, to test small ejectors and injectors.
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fredrosse
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Re: Electrically fired Boilers?

Post by fredrosse » Thu Sep 03, 2020 12:43 am

On Youtube one can see the rocket-ship character of a common 40 gallon domestic water heater (electric or gas fired) that is continuously heated with the safety valve connection plugged. Plenty of potential to destroy a house. One video I saw sent a mock house to destruction, launching the failed pressure vessel hundreds of feet in the air. The 100 PSI design pressure vessel failed at about 350 PSI.

USA rules require a temperature AND pressure relief valve mounted directly on all domestic and commercial hot water heater pressure vessels. All pressure vessel codes I have ever seen require a relief valve mounted directly on the pressure vessel which they protect, with no intervening valves, branch connections, etc.
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Lopez Mike
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Re: Electrically fired Boilers?

Post by Lopez Mike » Thu Sep 03, 2020 10:05 pm

This happened not that long ago in the Seattle area. No injuries or fatalities but half of the building was spread all over the neighborhood.

The history if this event was that the temperature/pressure valve had leaked at one time and some inspired soul had replaced it with a pipe plug. Years later the thermostat stuck on.
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