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The Effect of Low Feedwater!

Posted by chuk williams 
The Effect of Low Feedwater!
October 13, 2020 12:59PM

A few weeks ago, someone on this Forum mentioned a locomotive boiler explosion-the attached photo shows quite clearly what happens! The outer shell is partially gone, leaving the boiler tube/staybolt spaghetti. I wonder how far down the track the front end of the boiler was found?


Re: The Effect of Low Feedwater!
October 13, 2020 01:58PM
NASA expert identifies mysterious extraterrestrial object as old ... eye rolling smiley

Just kidding...
Re: The Effect of Low Feedwater!
October 14, 2020 09:20AM
Hey Chuk,

And this is good graphic evidence explaining Bonneville's fear of Stanley type boilers.

Actually, I think any sort of drum that is directly heated by the furnace should be avoided at all costs. It would arguably be better to fit the drum in a Bosolver or Ofeldt off to the side rather than directly above the burner.

Even when the storage volume is unheated, it's awfully easy to make the argument that it would be better to fabricate it in the form of a coil rather than a drum. It isn't that I think drums are naturally explosion prone --- it's just that I've seen what kind of damage a 60 mph collision can do to even well-constructed steel components ... at 200 mph you can understand the concern.

In any case, the coil is inherently safer because any point of failure is limited in size by simple geometry and the escaping flow will be forced to pass through the coil and hiss out, whereas a drum has a much greater potential to fail explosively. I was actually leaning against Bill Ryan's go-kart when the coil failed at 1,000 psi --- it sounded like a large leak in a tire and was so innocuous that it took a second or so for me to realize what happened.


Re: The Effect of Low Feedwater!
October 14, 2020 10:17AM
It’s not a mater of drum verses coil type boilers so much as it is the over all design and components used. In 1998 the ASME lowered the design factors from four times operating pressure to three and one half times. Because material quality is so much better today. Why was not the safety valve large enough to handle the volume generated, Why was the water allowed to get so low. Why was there not automatic feed water control. Where was the operating engineer.

The ASME code is not law. The ASME is a privet club of registered engineers, they sale there codes. States pay to use parts or all of any part of their codes.

The railroad most likely designed to there own code. Every state has different laws. In New York all pressure vessels fall under the law, in Mass the boiler laws only cover stationary boilers Cars Boats Cranes heavy equipment are not covered.

Most Stanley boilers built with rolled in tubes when over heated, the tubes all leak water out and Stanley also had a low water alarm.

Re: The Effect of Low Feedwater!
October 30, 2020 06:55PM
I think the investigation for that accident concluded the gauge glasses weren't reading properly due to scale buildup in the boiler and associated fittings. Sudden introduction of feed water on a red hot crown sheet sounded the death nell. Superheater tubes sure make of a interesting steampunk octopus.
Re: The Effect of Low Feedwater!
November 03, 2020 03:43AM
It's an amazing photo. Given that the main barrel of the boiler seems to be intact how on earth did the tubes come out like that? I presume the front cover plate of the boiler blew off, pulling the tubes with it but then parted from them leaving them spread as they are. It seems that many boiler explosions have a similar cause. I recall a traction engine explosion not so long ago had the same explanation.

Re: The Effect of Low Feedwater!
November 29, 2020 07:02PM
In most of the pictures that I've seen of locomotive boiler explosions, it's the crown sheet that fails--but not always--and the bulk of the energy is directed downward thru the firebox and out thru the grate. Interesting that this one blew the smoke box off, and that the boiler stayed on the frame.

There are records of boilers breaking free of the frames and going as much as a half mile. A Southern Pacific cab-forward did precisely that near Salinas around 1940. Except in that case, with the firebox up front the boiler was launched backward.
Re: The Effect of Low Feedwater!
November 30, 2020 05:08PM
Looking at the picture a bit more closely it appears that much of what was vomited out of the boiler was the superheater, where you see the looped tube ends. It doesn't appear that any of the barrel courses of the boiler let go, but I suppose a tube sheet could have, which could have explained the forward pressure discharge. When a crown sheet blows, the boiler is usually catapulted end over end off the frame. Would be interesting to know the date of the explosion. They are not usually the result of overpressure.

Some locomotives had large fusible plugs that would drop out of place in the crown sheet in the event of overheating. The steam would extinguish the fire. All of that depended on good boiler maintenance, including frequent washing and inspections, to minimize calcium build up and equipment malfunction. Seems like this one was overdue.
Re: The Effect of Low Feedwater!
December 03, 2020 01:23PM
Burt, So the increase of pressure didn`t blow it apart but the weakening of the steal because of heat increase?
Re: The Effect of Low Feedwater!
December 25, 2020 02:19PM
Locomotives of that era usually had three safety valves--one set at a pound or two above nominal boiler pressure, another one set 2 psi over that, and a third set 4 psi over the first. I can only imagine the din if all three are going. So, it's unlikely that a locomotive boiler would blow because of simple overpressure. It's almost like the front tube sheet failed.

As locomotives grew in size prior to WWII, builders began using different alloys in their boilers to lighten the machines. Some worked better than others. In some cases, cracking was so bad that boilers had to be replaced with ones made of different alloys. Perhaps this is one that prompted the changes?
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