Exploding boilers?

[paul]

Now I realise I've only been a member of this forum for a few weeks but (probably as a result of my newbie questions) I've seen plenty written about the dangers of incorrectly made or tested boilers. It begs two questions....

1. Does anyone personally know of any actual damage caused by a defective boiler?

2 Are the moving bits of a badly made/designed xxx rpm engine not more dangerous?

Apologies in advance if you have a nasty scar as a result of one of the above but I honestly have no idea how likely either are or whether the 'regulations' are more EU/nanny state/politically correct stuff gone mad.

[chris vine]

Ha Ha,

You have hit a nail fairly squarely on the head.

I think that moving bits, especially wheels on railways and fingers between buffers cause far more injuries than boilers BUT if a largish boiler goes off catastrophically and someone is too close then the damage will be more serious.

The fantastic thing is how few boilers really have gone bang over the last 100 years. Most of them which fail, do so very unspectaculary, usually putting the fire out by a leaking firebox. Copper, in particular, because it does not really corrode is most likely to leak at a stay or a seam rather then split asunder along the whole length of the barrel.

I have enjoyed reading old Model Engineer magazines from all eras and I can only remember reading about 3 real boiler explosions and there were two common threads inall of them. First was that they were not properly constructed, eg soft solder/ unflanged plates/ no stays (on a boat on a pond in a london park). Secondly, in each case the sentence before the one which read "and then there was a loud bang and flying bits of metal" (or equally sensational equivalent) was always along the lines of "the locomotive/traction engine/boat had never gone better before"!!! Clearly the water was dangerously low and the engine was getting a good dose of superheated steam.....

None of this is intended to make anyone careless with a steam boiler or not to recognise the awsome pent up energy of course. Just watch out if your engine suddenly seems to become turbocharged.....

Chris.

[greasemonkey]

Hi All
I'd like to think that the reason there havent been many boiler accidents is because the regulations for testing have prevented those dangerous examples being used!!! There was a reported case of a traction engine boiler suffering a collpased firebox tube plate fortunately whilst steam was being raised, caused by the owner letting the water level run low!!
Personally, as I am the person nearest the boiler when driving, if it hasnt been tested I dont want to know.

Andy

[alanstepney]

Over the years I have tried to get as much information on model boiler "explosions" as possible.
The last one I found that caused any injury (and then only very minor) happened in 1923 or 1928 (cant recall which) with a model steam launch, being used on the Serpentine in London.

As greasemonkey said, the regulations, which have gradually been imposed over the years, have helped prevent most accidents.
Over time, boiler pressures and size of models (and boilers) has increased, thus adding to the risk.
New and improved rules, plus better techniques and more information have kept boilers safe.

It is worth remembering, or working out, exactly how much energy there is in a boiler.
Whilst a dramatic failure might be rare, if it happened to the boiler you were right next to, it could ruin your day!

[burnettsj]

Hi - this is my first post - but I have heard of one potentially nasty incident which I thought would be useful to mention.

A 7.25" Duchess (apparently it's a big red thing - which didn't come from Swindon) was running around a track hauling a heavy load. Engine was working hard, blowing off hard (4 safety valves on a duchess), no injectors (or other water feed on) and maintaining half a glass of water for a considerable period/distance. Anyone notice anything wrong?

Eventually the driver decided to put an injector on, cue firebox crown collapsing, and the fire being ejected out of the firebox (through the fire hole) and onto the driver's lap. Luckily in this case the driver was wearing a heavy knee length coat and was saved from serious injury.

The reason for this incident, was that the gauge glass was blocked up with scale and not showing the correct water level. With the engine working hard, the water level was dropping (undetected by the gauge). When the injector was put on, the boiler was nearly empty. When the water entered the boiler it immediately flashed to steam, generating higher than design pressure and causing the boiler to fail.

I've also have experience of boilers failing irreparable due to leaking after being scaled up, but not as dangerously as the story above.

The morale of the story then:
- Keep the boiler descaled (depends of boiler use and water quality)
- If you suspect that the boiler contains little/no water DON'T put any water in, but just kill the fire.

Stephen

[the_viffer]

I am aware of a catastrophic boiler failure. I was not present but I have it on the authority of the boiler owner and have heard of it from others in the coterie. I understand the debris is still in existence.

A brand new commercially built "Springbok" boiler was undergoing a steam test by the owner and his friends.

Unfortunately pressure build up was slow. The reason for this was eventually determined to be that the boiler was empty. Someone then actuated the hand pump resulting in collapse of the crown.

Very much to my surprise no one was hurt either during or after the incident. The owner of the boiler and the person who worked the pump remain, so far as I know, friends.

[ron]

With regards to gauge glasses, normal industrial practice was to blow them down once a shift, so I blow down model ones every time I use the boiler, it surprises me that a lot of small model boilers only have one glass and no blowout valves in event of the glass being broken, also having a lot of experience of real boilers and very little of model boilers it surprises me they have no low level whistle or some other form of audible warning, it might lead you to believe that the hazard from small boilers is slight compared to full size.
My only bad experience of a model boiler was when the centre of the relief valve blew out at 60psi, it was quite spectacular, but not really dangerous unless my head had been right over it when it happened, it emptied the contents of the boiler onto the ceiling of my workshop in about 5 seconds.
Ron

[havoc]

In order to get a spectacular explosion of a boiler, it has to have a certain size. A gauge 1 boiler will just not explode, only make a loud hiss and a cloud of steam. This has to do with crack lenghts and volume of water that can flash into steam. Maybe this starts to become a problem with the larger 7"1/4 boilers. But this is a very safe hobby. So a lot of this regulation is over the top for the boiler it applies to.

So splitting the regulation and test according to volume/pressure makes sense.

CE marking isn't a big deal. If you make something yourself, you can do it yourself. It will be harder to make the CE mark according to the rules that to adhere to the rules for putting it on.

[burnettsj]

With regard to low water level alarms - I am not aware of any full size steam locos with alarms. True that they have fusible plugs - but these are boiler protection features.

Full size procedure is to check water level (by "blowing" the gauge glass down) before lighting up. The water level should return to the same level. This should also be done once in steam - before moving off shed. And I would recommend this practice to all model owners.

With regard to shut off valves, in small sizes they are likely to seize open unless regularly operated, and are difficult to access with lots of hot water and steam in the vicinity.

I have had experience of three gauge glass failing - once was when it was hit by a shovel (not me ).

Generally they don't go bang, but start to fizz and you then get a nice hot jet of water across the cab and lots of steam. Water loss can easily be overcome by putting the injectors on, and then drop / kill the fire. Replacing the gauge glass with the engine hot is fun though.

Here's a handy hint that I have been taught, if you need to kill the fire and don't know how co/can't drop the fire - put a rag down the chimney and turn the blower on.

[ron]

All industrial boilers have an audible LL alarm, XLL alarm and trip that stops the fans and fire, testable by the insurance inspector [HL as well], you have to take into account most if not all full size locos were designed in an era when safety wasn't given the same consideration as it is now, mind you I suppose a fusible plug concentrates the mind
The valve in full size the gauge glasses I'm referring to is not the isolation cock it's the blow out valve that automatically shuts off in event of the glass being broken.
Ron

[chris vine]

I like Bennetsj's tip about putting a rag down the chimney and turning on the blower to kill the fire. That's a good one to remember.......

C

[paul]

Havoc, pardon my ingnorance but what's the definition of Gauge 1?

[houstonceng]

Havoc

I think you may be wrong about Gauge 1 boilers not exploding due to amount of water contained. Some time back, there was an article in the ME about "coke-can boilers" tested to destruction. Seems that a fair amount of damage could be caused.

The various "gurus" like LBSC, Jim Ewins and Martin Evans all, at some time or other, remarked on the volume of steam that could be produced suddenly when a previously uncovered (ie no water on it) firebox crown was suddenly dowsed in water as the loco changed it's attitude on an embankment or someone pumped in some cold water. The safety valves may not be able to disipate the steam volume quickly enough leading to - - -

Let's put it this way, I'm with Alan and another few of the contibutors. I'm not about to experiment with my life and well-being.

Andy

Remember. Anyone can solve an engineering problem with a hammer, but an engineer will pre-calculate to ensure that the "bonker" is the correct size.

[greasemonkey]

Hi All
It would be intresting to see how a low/high water level alarm would work on a locomotive boiler given that its moves and the water would surge about?
In my experince of locomotive gauge glasses there is only a restricter in the gauge glass water passages. A valve that would seal the passage could be dangerous for obvious reasons.

Andy

[houstonceng]

Greasemonkey said, "A valve that would seal the passage could be dangerous for obvious reasons"

But that's exactly what you have in full size. Three cocks. Two to shut off the glass from the boiler and one to vent it to atmosphere. Correct use of all three to "blow-down the gauge" was part of the "proficiency test" and two of them could isolate a broken glass from t'boiler.

There again, most full size had two glasses.

Have you seen the "electronic low water" system described in Martin Evans's book on Loco Design ? I've seen something similar on a loco at Guildford. Why couldn't that be used with a suitable delay to cover surge ?

Andy

[the_viffer]

greasemonkey said:

Hi All
It would be intresting to see how a low/high water level alarm would work on a locomotive boiler given that its moves and the water would surge about?
In my experince of locomotive gauge glasses there is only a restricter in the gauge glass water passages. A valve that would seal the passage could be dangerous for obvious reasons.

Andy

Maxitrak sell I believe a water level detector that clips outside the glass. Not tried it...

I believe that some gauge glasses have a ball that gets pushed onto a seating if the glass break thereby substantially sealing the fitting and enough to allow the cocks to be closed.

I know I shouldn't be but I'm often surprised at how cold the steam coming out of blow downs and safety's is.

On the subject of safety valves I had to give up steaming one of my locos on my rubber wheeled test stand as if the boiler blew off for a decent period I'd get an electric shock when I touched the stand or loco.

[steammadman]

I have been "messing" about with steam boilers of one type/size or another since i was 13 yrs
old,iam now near 70, i have seen gauge glasses blow, safety valve's blow out of their flanges,
due to bad threads, flanges blow almost out ,due to bad soft soldering,but, i have only ever heard of one boiler going "BANG",and that,thank god was in America,and lets face it they have got to do things better.
BUT i have only ever heard of one person being ingered or scolded, i think that speaks volumes of the skills and common sense among MODEL ENGINEERS.

[greasemonkey]

Yes, you have the isolation cocks to isolate the gauge glass, after the blow out, or when the loco is left unatttended for a long period ie overnight, but the 'blow out valve' or 'restrictor valve' doesnt usually seal the passage only restricts the flow of steam and water!
Ive seen Maxitraks little electronic gizmo what is Martin Evans solution and what was fitted to the engine at Guildford?

Andy

Andy

[GWRdriver]

i have only ever heard of one boiler going BANG, and that, thank god was in America,and lets face it they have got to do things better.

Please elaborate. I occasionally speak to various live steam groups on model boiler design, construction, and safety and I'd be very interested to hear the details of this accident. I like to keep abreast of such things. In my 40 years of live steam activity I have never heard of a single reported personal injury which was attributable to an accidental, unscheduled, or catastrophic release of steam or water from a model boiler, much less an ocurrence of "Bang."

There were of course the fatalities caused by the explosion of the full size traction engine boiler at an Ohio fair a few years ago but we don't include that in model statistics, just as you probably do not (and should not) include the deaths of the grandfather and grandson due to the failure of the boiler inspection hatch in that tragic marine launch accident some years ago.

So far, after 1000's of hours at track, I have only ever seen flue failures and broken gauge glasses, nothing else. That, combined with what so far as we know is a perfect safety record (pending your documentation of the incident you mention), makes me wonder what we have got to do better?

[dinmoremanor]

Having been on the footplate of a loco recenty, full size obviously!! and had a gauge glass failure, to be honest it was quite a fright!!!!!! What a bang, made my ears go funny for a while and we only had a 140 psi on the clock!!!! Would have been quite spectacular at 225! There was next to nothing left of the glass in the protector, it was reduced to a fine dust with the explosion, a very quick dive for the shut off was made I can tell you!!! Really made me wonder just what the bang would be like if one of my 5" gauge loco's went pop! I wouldn't want to find out thats for sure.