Boiler Explosion

[DaveH]

Hello,

I am just wondering has there been many boiler explosions - talking model type size boilers, steel, copper, brass.

DaveH

[PTsideshow]

It really isn't an explosion in the TV/Movie seen of what people tend to think of today.
It is a BLEVE Boiling liquid expanding vapor explosion
And yes it does happen it can be just as catastrophic to those in the area at the time.

As liquid and the steam still expand to depending on what source you want to sight. 1,100 to 1,200 times the volume.short explanation wiki.
there are a number of models BLEVE that are where on u tube. mostly of running the boiler out of water and the seam or joints giving away. As in the full size ones, or at the local steam tractors events, we had one a couple years ago in Ohio that killed a number of people.

That is why the shows in the states run the engines on air. Can't get insurance coverage, and some of the outdoor shows don't carry insurance coverage on the operating  models boilers. And more full size shows are running into cost problems along with the inspection and licensing of equipment and operators.

[DaveH]

PT,

The safety valve - why doesn't this take care of the problem?

DaveH

[John Hill]

PT,

The safety valve - why doesn't this take care of the problem?

DaveH

There are a few possible reasons for the saftey valve to fail to do its job:-

One that first springs to mind is the case where the operator screws down or otherwise disables the valve in an attempt to operate at a higher pressure. 

There is also the possibility that the boiler is damaged or deteriorated such that it is no longer safe at the normal operating pressure,  I think that is what caused the recent traction engine explosion in the US.

Locomotives and maybe others have been destroyed when the water level has been low and part of the fire box has got overheated then movement of the locomotive has caused water to surge over the overheated metal where it instantly turned to steap and overwhelmed the safety valve.  I believe a locomotive was destroyed in Canada when the crew reversed it up a steep spur to alow a train to pass on the main line.  While they were waiting the crown plate overheated as most of the water was at the front of the loco,  when they went back onto more level track the water flowed back over the hot metal and the loco exploded.

[DaveH]

I knew there was an inherent good reason why I run my engines on compressed air.

 
DaveH

[John Hill]

Here is some interesting reading on the subject:-

http://www.nytimes.com/1860/11/08/news/steam-boiler-explosions.html

[kvom]

The library at my club has a picture book of RR accidents going back to the late 1800s.  In a couple of pictures you see the boiler completely blown off of the locomotive.  

The very first locomotive in England exploded because the driver disliked the sound of the safeties and disabled them.  He did not survive this "experiment."

[PTsideshow]

Other than the reason stated. The biggest reason for hobby boilers, to fail is the cheapness of the owners,  Not having the boilers properly tested and or x ray and other ultra sound testing which cost just as much for hobby as full size commercial boilers.
I quit going to shows Full size traction engine shows that don't have, show inspections and some form of certificate of operational worthyness. I know the full size people on some other steam sites will call me names, etc for daring to mention it. But people that own them are sure granpappy ran it right, along with my favorite statement that causes me to put some good distance between me and an boiler. "it's only a little rust on or around the stay bolts or hand holes or rivets or crown sheets."
But I will link to a couple of sites.
Five people died as a result of that accident, and in the process our hobby, whether we like it or not, changed forever.
The Brit's steam groups take on the accident
he is the indecent report with photo's of the stay etc.

Reducing the operating pressure doesn't guarantee anything other that it might let go this time, but it will at some point.
There are more than enough out there to give one pause.

[kwackers]

I was told that copper boilers are safer because when it goes it goes it goes in a somewhat less catastrophic manner. Is that true?

To put some perspective on it though - you're more likely to be killed in a traffic accident on the way to the show.

[PTsideshow]

And by the way just as to clarify I don't consider myself an expert in the hobby field as I have spent 40 years in and out of it. I hold and have held  A first Class Stationary Engineers License for 34 years(issues), which means I am qualified to operate and be in charge of Steam boilers, Engines & Turbines of unlimited pressure and horse power in the City of Detroit and registered  with the state of Michigan. Which is fast becoming an antique in itself, with the change over to flash steam generators. No license required, and the contract companies!

[PTsideshow]

I was told that copper boilers are safer because when it goes it goes it goes in a somewhat less catastrophic manner. Is that true?

To put some perspective on it though - you're more likely to be killed in a traffic accident on the way to the show.

I think on that it is the joints  that let go,since they were generally silver soldered. Before a rupture in the shell.

Not really safer if you are close and it goes scalding is a terrible way to be injured.

Boiled alive was a description used in a paper or more aptly put by a doctor, in a newspaper interview "Boiled ¾'s dead"  when Fords Rouge plant power house had a gas line explosion. That took out a high pressure steam line. The poor bastard lingered for almost a week be fore he died!
The doctor said all we could do was keep him pumped up with morphine and hope he didn't wake up! Because the one time he did, his screams could be heard all over the hospital.

If you read the statement by Semple from the British steam group in the link above I gave he states that they have the inspections etc. that it is rare that an accident like that could happen there.

I am sorry but here in the states with some of the A$$holes at these shows I have meet and their ignorance of the equipment and operations. "most common statement I'm told I don't need no damn license, My granpappy taught me when I was 6 years old!" that may be true but the fact remains, Granpap couldn't read the instructions and was taught by an illiterate farm hand! And what ever you were taught you have lost to many braincells for the remaining knowledge to be of any use.

To many people have too high and over inflated opinion of themselves, just because they have inherited a rusted and busted  traction engine  here in the states. A couple years ago one guy was upset as they wouldn't let him steam up an engine he had pulled out of a field a couple weeks before. The trip on the trailer had broken a rusted out area around some of the lap joints rivets. Granted it probably wouldn't have held 2psig (17 pounds pressure).

Since I'm in charge of the show physical set up and air supply at the N A M E S expo. I get at least two geniuses each show telling me we are wusses for not using steam.
I smile and tell them I don't discuss safety matters with idiots that don't have a clue what they are talking about!

First most of the venues used are owned or operated by the cities.

They have insurance regulations anybody using the arena has to follow.

Fire dept regulations and inspections.

Building department/electrical not to mention that the state or county can come in and do fire or other inspections at anytime.

Then there is the groups insurance carrier and the cost per attendee ticket that goes to insurance cost. Which is climbing every year, because of the sue happy people.

Then finally from what I have seen of some of the tin plate toy type boilers, I wouldn't want to have them running on steam!

So I may be over sensitive about this kind of thing, but with the rates the insurance are charging if you can find it. Won't be long be long before the traction engine crowd here is pulling construction compressors behind their engines. Even one more small/slight accident with a working antique engine and operating on steam will be a memory here in the states.

Or so I have been told, an Insurance guy at the last show!
 

[kwackers]

If you read the statement by Semple from the British steam group in the link above I gave he states that they have the inspections etc. that it is rare that an accident like that could happen there.

Can't say I'm aware of any accidents over here. I know model boilers have to undergo regular testing to get a certificate and if other clubs are anything to go by our tester "works to rule". For visitors if it doesn't have a current certificate it doesn't run.
I would expect that full sized boilers are even more well serviced in the rules and regs department...
I've never known anyone complain about this, I mean it's common sense - if your boiler can't pass a safety examination then it's plainly dangerous!

The only 'payout' I'm aware of from our club was to a woman in a white dress who got 'smuts' on it - which was a bit rich considering she'd been warned before getting onto the train of the danger but insisted and then when dirt did get on it to decide it was a problem!

[PTsideshow]

The biggest difference in between you and us, is you have had a longer history of both the full size and model hobbyist and certificates for the hobbies. Real organized model shows, started and were patterned after the big show outside London about 25 years ago by the founding members of the NAMES group. Here in Michigan it is the dia of the boiler and if you charge to the general public for rides determine the status of the boiler. Even a donation box will change the rules you operate under. Also there is a line between antique boilers and commercial boilers, and the inspection is very different but that is fast changing.

Then add into the fact that the culture of the viewing public is different and people and lawyers sue over things that most wouldn't even give a second thought. As you have pointed out.

So there is a new direction in the clubs attitude about inspections, and running outside or inside a building. Air inside and my be heading air outside. Mostly again being forced on them by the insurance carriers for the groups and the property owners that used to allow use of their land for the shows.

[GWRdriver]

I am just wondering has there been many boiler explosions - talking model type size boilers, steel, copper, brass. -Dave

Dave,
I could write a book on this but I will try to keep it short, to answer your question simply . . . no.  A friend of mine in the UK and I have between us roughly 80 years of experience building and operating miniature hobby steam boilers, and we have tried to make a study of reported miniature hobby boiler accidents, specifically explosions, meaning the virtually instantaneous catastrophic release of pressure resulting in personal injury.  What we found was that there have been NONE.  Let me repeat that, there have been NO reported catastrophic failures.  In fairness I have to qualify the findings by saying our research was limited to REPORTED occurrences and we cannot know how many, or if any, were not reported.  There have been several documented deaths in the "hobby" steam world, the best known are the Ohio traction accident and the steam launch accident in England, but while owned and operated by "amatuers" and "hobbyists" but both of those accidents involved full size power boilers, both riveted steel, which were originally designed and built for commercial use.  These should not be confused with miniature model hobby boilers - miniature boilers and full size industrial power boilers, whatever their size, are two different animals and each has its own science and technology.

My specific speciality is the miniature copper boiler, of which I have built over 100, half of which were my design, and I need to correct a couple of the assertions and assumpions which have been made.  First, copper was not chosen because it would release an explosion, or overpressure, in a less catastrophic manner.  It was chosen because it was a widely available, it was maleable material which could be easily beaten into the required shapes, it was high on the nobility scale and resistant to corrosion, it took solder extremely well, and it had sufficient tensile strength to meet the needs of modelers.  Until perhaps the 1930's most miniature hobby copper boilers were of riveted and soft soldered construction.  Another accidental but convenient "fail-safe" of copper is that it is such a fast conducter of heat that in normal operation one would have to work hard or be very careless to create a heating condition that would melt either copper or silver solder.  Unfortunately this does happen, and more regularly than we would like to admit.

The next assumption that needs to be corrected is that properly made and silver soldered miniature cooper boilers do NOT always fail, or even tend to fail, at the soldered seams, with two exceptions.  Controlled experiments in both England and Australia have shown that silver soldered test boilers, steamed to failure, invariably fail at the barrel (by splitting), not from a seam separation.  In these tests flues do collapse but don't fail.  This should not come as a surprise because while the tensile strength of copper is between 14kps and 25kps, depending upon operating temperature and degree of prior annealing, the tensile strength of 45% silver solder (the preferred alloy) varies between 60 and 70kpsi.  The failure will occur at the point of least resistance which is in the copper, not in a sound solder joint.  There has never been a reported incident of miniature boiler failure due to a split barrel and is one reason why seamless hard-drawn copper tube is always specified for minitaure boiler barrels and flues.  The exceptions mentioned are that in reported miniature locomotive boiler failures (not explosions), where there is a loss of pressure due to a failed component rendering the boiler inoperable, the failures generally occur in two areas:   By far the most frequently reported is in the flues, either by simple tube structural failure (collapse or perforation) or by failure of the silver solder seal at the flue ends.  The least frequent reported failure is the separation of the outer wrapper of the firebox water leg from the mud ring.  It should be noted that both of these failures occur in locations where the heat or corrosion is most concentrated and there is high likelihood of accidental overheating.

Now, to make a comment about full size industrial power boilered equipment., specifically US antique traction.  I agree with PT in so many words . . . the antique tractor hobby seems to be full of good ol' boys who resist any kind of testing or regulation program and rely on the other good ol' boys on the show committee or Fair Board to look the other way while they do business as usual.  I'm like PT, I will no longer go near one.  To some extent the same has been true of miniature locomotive boilers and US club operation but the spectre of liability is about to bring the wink & nod to an end.   Oddly enough, the thing that is currently of greatest concern to insurors of miniature railways, public or private, and clubs is not boilers, it's passenger personal injury liability.  The insurance companies couldn't care less about boilers . . . there's no exposure there . . . there's no incidence of boiler accident injury claim.  All the most recent claims have come from injured riders.

[DaveH]

GWRdriver,

Thank you very much.

What a fantastic informative answer.

I thank you again for taking the trouble to write.

I was going to make a boiler, then I thought may be not, now after reading your post I'm back on making one

Many thanks
DaveH

[Bernd]

GWRdriver,

Thank you very much for such an informative post. It is greatly appreciated coming from somebody in the know. 

Bernd

[GWRdriver]

Dave and BernD,
You are welcome.  Dave, if you follow all of the tried and proven guidelines for copper boiler construction and operation, available in books or on model engineering and live steaming web sites, there is no reason why you cannot build a perfectly safe and long-lived boiler.  Not everyone in every country agrees on every detail of copper boiler construction, the Australian regulations are more stringent than the US for instance, but generally speaking we are all on the same page which has resulted in a stellar record of safety.  The problem arises when someone decides to ignore the proven basics and do things on the cheap and quick, as aluded to by PT, although not exactly in the way and for the purposes he addresses.  I'll start you off with a few basic guidelines.

If you are subject to a testing or certification authority, contact them first - you may be exempt.  If not, begin a conversation with the official who will be repsonsible for certifying your boiler.
Use new copper material and seamless hard-drawn tube stock.  The thickness of materials will be determijed by the size and design you choose.
If you design your own, or need one not covered by an existing design, design formulas are available for everything about a small copper boiler.
Use copper and bronze for all the structural components.  Never use brass in a steam pressure vessel structure.
Keep everything as clean as possible. "Pickle" (deoxidize and degrease) all components before final assembly and soldering to remove all oxidation and oils.
Use silver solder of around 45% silver content.  Don't skimp on flux, it's cheap, use plenty.
Have sufficient heating equipment available.  It takes LOTS more heat than you suspect.  The typical DIY propane torch will not do.
And most importantly ask for guidance and advice from those who have done it, although as can be expected everyone will have a slightly different approach.

As you can imagine there are lots of additional design and construction details to be aware of but these are the very basics and this will get you started.

[Ronkh]

PT,

The safety valve - why doesn't this take care of the problem?

DaveH

There are a few possible reasons for the saftey valve to fail to do its job:-

One that first springs to mind is the case where the operator screws down or otherwise disables the valve in an attempt to operate at a higher pressure. 

There is also the possibility that the boiler is damaged or deteriorated such that it is no longer safe at the normal operating pressure,  I think that is what caused the recent traction engine explosion in the US.

Locomotives and maybe others have been destroyed when the water level has been low and part of the fire box has got overheated then movement of the locomotive has caused water to surge over the overheated metal where it instantly turned to steap and overwhelmed the safety valve.  I believe a locomotive was destroyed in Canada when the crew reversed it up a steep spur to alow a train to pass on the main line.  While they were waiting the crown plate overheated as most of the water was at the front of the loco,  when they went back onto more level track the water flowed back over the hot metal and the loco exploded.

This has been a facinating thread and I thank you all for it.
I have never made a boiler but I do have the material in which to do so and if or when I do, it will only be with the correct books and help from the right people. (I value my life and my kids too much to go headfirst on a subject I know almost sod all about).

I have a question regarding the above quote; could an explosion similar to this happen with a model? Whether home-made or a bought model, say a Mamod or any commercially bought boiler, when if for some reason the model was placed at an angle for a while and then brought to an even level?

Kind regards,

Ron.

[crabsign69]

i was gonna say everybody wrote something but nobody answered the question  until gwr came on board .  all round the darn thing with out a answer .
wtg  gwrdriver.    thank you for a answer   i like straight answers no b/s. 

[NickG]

Surprised nobody posted this, which is a good illustration of what can happen - remember this is a very small, relatively low pressure boiler, having said that, they had no idea what the pressure was at - watching it as I type ... idiots.

Nick

[DaveH]

Yawellnofine,

Any moronic idiot can do that. This is why bad things happen to stupid people.
 
DaveH

[GWRdriver]

Surprised nobody posted this, . . .

For some reason unknown to me some folks think that posting such things, which has no relation to or is in no way indicative of what is strived for and what is going on the in the mainstream live steam community, helps the safety situation.  Yes such things CAN happen, but they don't, for very good reason.  After viewing such a video there are some folks who would never be convinced we are not ALL like that.  The same goes for those who describe model boilers in terms such as bomb, missile, shrapnel, death, dismemberment, and other similarly extreme or even hysterical terms.  The problem I have with that is, one never knows who might be listening or reading your post or letter, perhaps an official or administrator, an inspector, a legislator, or or a parent, who is now aware of a serious threat to the health and safety of the public and which now must be stamped out.  Poof!  Out go the fires.  The amount of harm that can be done by these exaggerations far outweighs any potential benefits.

[PTsideshow]

i was gonna say everybody wrote something but nobody answered the question  until gwr came on board .  all round the darn thing with out a answer .
wtg  gwrdriver.    thank you for a answer   i like straight answers no b/s. 

I can only answer what I know and had dealing with. As GWR said I have heard all the same stories he has and it is always the cousin of the uncle twice removed. I can even begin to verify any of the ones that have wiped out large numbers or injured the same. Since I don't do model loco boilers no point commenting on model locomotives.
All I can say is you don't like my posts, Then don't read them! in the future.

And I have to agree with what GWR has said about people using words and descriptions of problems that only apply to Hollywood. And the hammer is going to drop as GWR says a lot sooner than later.

[DennisWA]

Regarding miniature boilers, I would also like to commend GWR Driver for a very clear answer.  My own researches last year in the realm of live steam (up to 7 1/4" gauge ) agree with his findings - I searched in the model engineering press plus I asked fellow live steamers, all men of long experience and high standing in terms of their construction and running record. They were all aware of failures as GWR Driver described, typically described as "a loud click followed by some escaping steam", but as GWR Driver says there were no reported incidents of "catastrophic failure".

On the subject of safety valves for miniature locomotive and traction engine boilers, the experts stress that (with the exception of the very smallest boilers) at least 2 safety valves be provided, designed to never allow the pressure in the boiler to exceed 110% of normal working pressure, no matter how hard the boiler is worked. A nomogram compiled by the late J.Greenly Steel is used to find the diameter of safety valve orifice for the combination of 1. a given working pressure and 2. the heating surface area of the boiler in question.  As an example, a boiler working at 70psi with a 500 square inch heating surface needs 1 safety valve with an orifice of 0.35" diameter, or 2 safety valves, each with an orifice of 0.25" diameter. Nothing in the construction of those safety valves should reduce this area. A good example is the classic ball-type safety valve with an adjusting nut with holes in it for the steam to pass through - these holes are often too small.

Like the vast majority of live steamers / model engineers, I am NOT a technical expert in this field. There are books by well-known designers and codes published by statutory bodies and national associations to provide guidance. Sticking to published and proven designs is always sensible. If in doubt certainly in the UK, RSA, Australia and New Zealand all clubs have boiler testers, who can provide good advice.

I am happy to help DaveH should he wish to construct a boiler.

Dennis

[Ronkh]

Hi ya,

Could someone/anyone please reply to my question regarding whether a model boiler-engine,etc, could blow regarding my previous question? I do not mean to come across as being arrogant or bossy but I feel it could be pertinant to beginners such as myself and other guys who wish to start in the steam world.

Again,

many kind regards,

Ron.

[mike os]

Surprised nobody posted this, which is a good illustration of what can happen - remember this is a very small, relatively low pressure boiler, having said that, they had no idea what the pressure was at - watching it as I type ... idiots.

Nick

what a bunch of total arseholes... some people deserve maiming....

[PTsideshow]

Here are some of the better known books on boiler building. During the computer upgrade the reviews have been misplaced.



Volume 1 and 2


paperback and hard cover





There are a number of others who's scan has also gone missing.

[PTsideshow]

Hi ya,

Could someone/anyone please reply to my question regarding whether a model boiler-engine,etc, could blow regarding my previous question? I do not mean to come across as being arrogant or bossy but I feel it could be pertinant to beginners such as myself and other guys who wish to start in the steam world.

Again,

many kind regards,

Ron.

If all the conditions are met it might be possible. But the commercial ones are designed with abuse to a point in mind. Small fuel/fire box larger water/steam space then the full can convert etc. A home made one, can also have a failure if all the conditions are met.
Again they don't go like in the TV or movies like with the car explosions, a car parked across the street was rear ended by a drunk, We slept through it and the lazy/slow fire. What woke me up was the 200 people on my front lawn making noise!

[DaveH]

Well thank you all, I have certainly learned a lot, and probably so have lots of others.

Your generosity in giving your knowledge and taking the time and effort to write and post it,  is sincerely appreciated.

Dennis thanks for your offer – accepted with thanks.

Ron(Ronkh) are you happy?

 
DaveH   

[GWRdriver]

Ron,
If I sort out your question correctly, it concerns the possibility of a separation of the boiler from the chassis of a model engine in the case of say, a failed crown sheet.  Please correct me if I've gone down the wrong track.  Thew answer is, always "possible", but hightly, greatly, unlikely.  I have only known of one separation of parts upon the occurrence of a model boiler failure.  Some years ago in the UK, the lower edge of a firebox wrapper seperated from the mud ring in a 5" gauge (1"scale) model locomotive while standing in steam.  The resultant release blew the nearest adjacent drive wheel off the end of its axle and of course sent ballast and dirt flying.  There was no serious injury reported but observers and examiners were perplexed at how a release of such relatively small scale could have the force to dislodge a drive wheel, especially when the spoked drive wheel would allow an ample pressure escape route.

So far as a boiler leaving its frame and becoming airborne, no such event has ever been reported in an engineered model although over the decades many crown sheets (or their stays) have failed without catastrophic results.  I specify "engineered" models apart from soldered brass tabletop toys which can blow at any time for a variety of reasons.  The only explanation I can offer as to why no separations have occurred is that model locomotive boilers, even those which strictly adhere to scale detailing, tend to have more relative strength of connection than full size locomotives at the firebox end, while at the same time would have many times less propulsive force acting in the event of a crown failure.  Not very scientific, but that's the opinion I have.

[DaveH]

GWRdriver,

I think, also Ron wants to know if the boiler is tilted say from the horizontal with a low water level, then tilted back it likely to cause a major problem.

DaveH

[GWRdriver]

Thanks Dave.  What will happen will depend upon several variables, among them he amount of water in the boiler, the depth and intensity of the fire, the state of the boiler (heat and pressure reading) before uncovering the crown, the number and size of safety valves, the length of time the crown is uncovered, and then of course the physical condition and design strength of the boiler.  Lets say there is a good fire, the kind normally wanted for continuous running hauling passengers, the boiler is at full operating temperature and pressure and water is low but not in the danger zone if in a level position.  What is most likely to occur if the crown sheet is uncovered and then quickly recovered is a momentary severe over-pressure which should be released by the safeties.  If the crown is left exposed for longer and is allowed to get very hot the safeties probably can't release enough pressure soon enough and the probability is a failure will occur at the weakest point in the area closest to the pressure source.

In the event of such a low water disaster-in-waiting the thing to do is stop the locomotive wherever it is, drop the fire immediately, and walk away (ie, wait) and allow the engine to cool.  At that point whatever damage there will be has been done and under no circumstances should an attempt be made to introduce cold water into a hot boiler, even a tiny amount.  This will produce an extreme over-pressure failure and a ruined boiler.

Of the books listed above my favorite is the KN Harris book, but what I know about model boilers and boiler building (by far not everyhting there is to know) has been learned from several sources including books, magazines, my mentors, trial and error, and just building them.  The photo is of a boiler for a 4.75" gauge (1"scale) tank loco I built for a fellow in Ohio a few years ago.

[DaveH]

GWRdriver,

I have the K N Harris book and the two by Turbal Cain.

So I have no excuses
 
DaveH

[Ronkh]

Thank you DaveH, GWDriver, PTsideshow and all very much indeed for your replies.

There is sooooo much to learn regarding steam. I have quite a few of the books mentioned, and I think it will be a fair while before attempting to make one once I've read and re-read them, plus taking in what has been posted on this site.

Kind regards,

Ron.

[NickG]

I perhaps should have put a few more words around the video I posted. I agree completely with what GWRdriver is saying but I posted it to get across a point. In the UK small model boilers under 1.5 bar-litres (I think, but will check so correct me if I'm wrong), do not need testing or inspecting or anything. So the video is a good example of what can happen, any tom dick or harry could make or buy such a boiler and put it on show infront of thousands of people. It doesn't necessarily have to be an idiot either. When I was about 9 or 10 my grandfather gave me the Mersey model steam engine he bought as a kid, but the boiler had a leak so he soft soldered one end up using a soldering iron heated up in the coal fire, this did the trick and it worked a treat. I was thinking the other day it'll soon be getting to the time where I pass the model on to my children, but then I had 2nd thought - it's made from brass, soft soldered (neither of which are considered good practice now), doesn't have any stays, who knows whether the safety valve works, never been tested etc etc the list goes on. Imagine if I gave it to my children and something happened similar to that video - unlikely I know, but unlikely isn't good enough for me - I think it'll have a new boiler before my sons go anywhere near it. My grandad wasn't an idiot, he was a skilled engineer but maybe just wasn't aware of what could happen? There are other certain parameters that are designed in with such commercial boilers for instance, the meths runs out before it can boil away all of the water but these things can be by passed in the wrong or naive hands. So I posted that video just to try to make people aware of what could happen. With anything over 1.5 bar litres the boilers are subject to all the regulations and inspections etc so I agree such an incident is so unlikely if you did a risk assessment like we do at work, the risk would be very low due to the probability being so low. The consequences remain high though.

Anyway, thanks GWRdriver for the information. It has been useful discussion for a few people I think.

[andyf]

This reminds me of the Sunday 50 years ago when the ballcock float in the toilet sprang a leak and got a bit of water inside. In the old days, they were made as two hemispheres of thin copper sheet joined with solder round the equator. Dad decided it would be easy to fix. Grasping the thing by its attached lever, he held it over the gas hob to boil the water away, waving it around to distribute the heat. All seemed to be going well, with a slow escape of steam from one point on the equator – there must have been a pinhole in the fillet of solder.

However, while rolling the thing around, Dad must have got that point hot enough to melt the solder for a moment, before it re-solidified and sealed the hole. Not realising this, he continued heating what was now a sealed thin copper sphere containing a spoonful of water.

The bang was deafening; it must have been audible a quarter mile away. Happily, there was no damage except to the float, which resembled two tulip petals. Shops didn’t open on Sundays back then, so the family was reduced to taking a bucket of water to the loo for flushing purposes until Dad returned from work on Monday evening with a new-fangled plastic float.

Ever since, I’ve been very respectful of any closed system containing boiling water.

Andy

[DaveH]

Andy,

 

I know I shouldn't laugh but it is funny.

DaveH

[David Jupp]

Further to NickG's post above - Under the Pressure Equipment Directive, steam generators under 2 L volume fall into the 'Sound Engineering Practice' category.  This means that there is no laid down requirement relating to design or manufacture, but it is expected that 'Sound Engineering Practice' (SEP) will be applied.   SEP is not defined, but it might include making use of accepted formulae, standards, guidelines etc.

Ignoring an established good practice would tend to suggest that SEP had not been applied.
It is down to the manufacturer to be able to demonstrate that SEP has been applied.
Note that PED does not cover operation or maintenance.

I recall that some time ago a 'code of practice' or something similar for model steam plant was drawn up by a working party involving the HSE in some way.  If that document is still current it would seem to be 'required reading' - see http://www.hse.gov.uk/pubns/etis12.htm