Boilers & Accidents

As my colleague just pointed out, this is not a boiler "tragedy". It is the E type superheater head that has burst and you can see all the superheater elements as a "corona".
Rest of the boiler seems intact.

 

Does say the crown sheet collapsed, and that 3 enginemen were killed, that's a tragedy in my book....

 

I think the person making the video started really showing their lack of understanding around the two minute mark ...

A catastrophic failure of the superheater would potentially result in a major blowback in the cab - which is a tragedy for those concerned, but nothing to do with the crown sheet, or low water, or the completely debunked (but widely touted) theory put forward that adding water to an overheated crown sheet causes a sudden pressure rise.

Tom

 

Obviously any boiler explosion is a sad occurrence, but one thing always strikes me in photos of them - There always look to be a Hell of a lot more bits come out than went in in the first place...

Richard.

 

Could well be the case, I just looked att the front and did not think about the blowback.

 

The gauge glass of the S160s was a standard American fitting supplied by Nathan, which was a typical reflex design. The lower connection was direct into the backhead, via a taper thread rather than a flanged fitting as was common in the UK. The upper connection was by way of a similar fitting mounted higher up in the centre of the backhead but connected by a pipe, as you mention. I suspect it was intended that this indirect connection helped to mitigate surging. In another common design of US water gauge, the gauge was attached to a "bottle" to which the try cocks were fitted.

Screw down valves seem to have been usual in the States, and may be easier to keep steam tight than a taper cock. When a screw down valve is opened, it should be backed off from the limit of travel so it is free to turn so there is no doubt as to its position - although I suspect many people's domestic water stop cock is hard up against its limit. The blow down cock on UK water gauges is in my limited experience rather non-intuitive in its position as it is usually (?) in line with the discharge pipe (vertical) when closed, whereas one might consider that it should be at 90 degrees to give a visual clue.

I attach an image of the backhead of the S160 as built - the layout of the water gauge is fairly clear. The valve handle to the upper fitting is behind the regulator/throttle handle and acts on the lengthy rod via a universal joint. The gauge glass is obscured by the gauge lamp. The try cocks are next to the regulator quadrant and empty into the trough shown.

The locos were fitted with fusible plugs - see attach extract from the ALCO spec (we have previously been through the efficacy of fusible plugs at length on here).

With these examples of "if it can go wrong it will", I am always reminded of the HMS Thetis disaster, which contributed the Thetis Clip to successor submarines.

 

Thanks for this lot, particularly the fusible plug matter, I was under the impression that they had none. However, I'm still playing 'Spot the Guage Glass' it makes a Fowler ploughing engine seem unambiguous, but regarding the screw down valves, there is no means of having a 'Quick Look' to confirm there position, whereas a plug cock is visually fairly obvious, I like to keep handles pointing 'Down' as gravity cannot then interfere with things, but in any case if ALL valve handles are in a vertical plane when in 'Working Condition' then there SHOULD be no confusion. As an illustration from My own experience, at one time I had the worst of all worlds, an Odd drain valve on the glass, and a driver who wouldn't stay on His own side of the cab and mind His own business. Although it was His interference that caused a problem it was Yours truly Who had to sort it.

 

Three S160 accident reports all involving the boiler/firebox and gauges:

https://www.railwaysarchive.co.uk/documents/MoT_Honeybourne1943.pdf
https://www.railwaysarchive.co.uk/documents/MoT_Thurston1944.pdf
https://www.railwaysarchive.co.uk/documents/MoT_Sudbury1944.pdf

 

Thanks for those, Mr Moore was very 'Matter of Fact' in his reporting and does make the same point that I have regarding the 'Visibility' of plug cocks being open or closed. Must say that I'm amazed at how lightweight the construction of the firebox is on these boilers.

 

Gauge glass cocks are not usually taper plug cocks. At least, I've never come across one. In times past they were asbestos packed but modern ones are sleeve packed.

The cocks on gauge glasses are by convention in the vertical position in there normal position. This applies to all such glasses, not just loco boilers. I'm fairly certain that it is pretty standard throughout the world.
On Westinghouse brake systems the normal position of any cock is in line with the pipework. This applies whether it is meant to be normally open or closed.

 

Are the S160s that are operational in Britain still fitted with the original guage glasses?

 

Some time back I restored a Traction engine that had unpacked taper plug cocks on the water glass, they were murder to try and keep working and after a couple of seasons I changed to 'Modern' PTFE sleeved fittings from Chanter Biomed, which are everything that the plug cocks were not. The only downside is appearence, but that comes secondary to injuries to crewmembers.

 

Diagram of Nathan water columns.

Bob.

 

It was later discovered in Italy post-war (and after some 20 more firebox collapses) that the cause was a design fault in that the firebox crown stays had a coarse thread relative to the thickness of the crown sheet. This allowed scale to penetrate the threads leading to overheating, the metal going 'plastic', and finally the crown sheet collapsing.

There is more about this in P. M. Kalla-Bishop's book 'Locomotives At War' published by D. Bradford Barton Ltd as ISBN 0 85153 373 6.

Edit. After re-reading the 3rd incident report by J. Moore on the Sudbury Hill explosion of an S160 from which it would appear that the water gauge was not at fault, perhaps it was a case of him just being unable to comprehend that the boilers on these locos had a design fault as he had not had such a situation presented to him before. It is clear that there in an element of puzzlement in his report as to why it happened.

 

Sorry, but can't see a practical method of doing that.

 

I will have to make you a sketch

Sent from my SM-A105FN using Tapatalk

 

I can't seem to find any mention now but I have a recollection that Dean experimented with a remote lever to close the gauge glass valves in the 1890s. Possibly on Badminton's or Dukes?

 

Quite a number of GWR classes had a lever on the outside of the cab about that time. I assume they went once reliable automatic shut off valves were fitted.

 

IIRC, that lever was connected to the standard GWR gauge frame.
Its purpose was to allow the fireman to isolate the gauge from outside a steam-filled footplate in the event of a gauge glass breaking. They fell into disuse as the quality of gauge glasses improved.

 

I recall reading decades ago in a footplate reminiscences book (was it the Harold Gasson one? - it was years ago I read it). Anyway, said young fireman got onto the footplate of a GWR engine, and once they were well underway, the driver asked if he were carrying a spare gauge glass. He answered yes, at which point the driver took out a large spanner and smashed the existing glass! Cue a cab full of steam and a young fireman having to get the glass changed while under way ... It was a kind of test of competence.

Tom