Boiler Design – issue 4765

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, all I can say is the the UTS is in the plastic range, and there is no elasticity in the elastic range. When I started work, high tensile bolts were not in general use, and when you unbolted things, the same bolts were used to bolt them up again. It soon became clear to me, that used bolts would stretch a little bit more every time they were done up again, and the stretching would accelerate, to the point it was clearly obvious, and the tightness of the bolt could not be made to the original, and it would eventually fail trying to even reach any sort of tightness at all. The UTS tells you the point that a material is most likely to fail. When I did my testing on the Tesometer, you could feel the stretching takin place, as the effort used to turn the handle was getting les as it was approaching the UTS.

Regards Nick.

[noel shelleyParticipant @noelshelley55608]

I take a dim view of being referred as a LUDDITE or the use of other derogatory terms ! May be this thread has run it’s course and should be closed ?  Noel.

[Paul KempParticipant @paulkemp46892]

Magic numbers, my thoughts;

We want to build a boiler.  We know it’s physical dimensions and the pressure we want to operate.  The absolute minimum theoretical shell thickness considering pressure alone will be that thickness that produces a circumferential stress in the cylinder that is equal to the UTS of the material we want to use (ignoring distortion as it has to distort before failure if it is a ductile material).  Using that thickness to build the boiler will result in certain failure when it exceeds operating pressure.  But wait, we are required for the first pressure test on the shell to pressurise it to twice working pressure, we can’t do that, it will fail, so actually to guarantee a pass we need to use a thickness of our material that will resist a pressure of 2xWP +1.  I suggest +1 because we want the absolute minimum thickness at which we can pass the 2xWP test with certainty.  We already have 2 magic numbers, my arbitrary +1 because I wanted to be certain it wouldn’t fail at 2WP and in fact the multiplyer of 2 for the test pressure, who decided 2 was the optimum number?  Whatever, we now have a minimum strength thickness for our boiler that will resist a 2xWP test.  It is already twice as strong as it needs to be based on material strength alone to be operated once at its design working pressure.

We now need to consider the other properties of the material we wish to use outside its basic UTS (or YP), it’s resistance to corrosion, creep, ductile properties, susceptibility to fatigue, behaviour at elevated temperature at the same time as considering how long we want it to last, how many pressure cycles will it go through in its design service life, what external stresses or other stress raisers is it subjected to? For each of these considerations we can assign a correction factor (magic number) or limiting factor through modelling or calculation to define the minimum operating thickness.  We don’t have the luxury of being able to ask Mr Greenly to explain how he arrived at his magic number of 8 but as it provides a result that is close to the alternative proposal I am assuming there was some science behind it, suggested by the results of the two methods being close to each other.

Personally I like magic numbers, I wouldn’t be happy with a plane, train, boat, bridge etc having a magic number of 1 for design strength and with systems that have a poor FMEA, ie single point of failure.

The sole advantage proposed for the YPM appears to me to be ensuring there is no distortion when the 2xWP test is applied and the material remains in its annealed state.  But as the results in terms of thickness correlate quite closely between the UTS and YPM is there a fundamental issue?

I can’t comment on the Aussie code, I don’t have it and thus haven’t read it.

On Lez’s point re RIDDOR, I am very familiar with it and Duncan is correct the definition of workplace is a very grey area and as various individuals have found to their cost the fact they were operating in a volunteer environment for no financial reward is no defence and Courts have ruled in favour of HSE in some instances even where the public were not present.  I mentioned RIDDOR as one example of why an incident would be reportable.  That is a separate discussion though and a distraction from the YPM debate.

As for holding the hobby back, I have no issue with modern manufacturing methods or using available technology to assist design.  The EU accept stainless steel for boilers, the UK should review this.  My criteria for change is it needs to bring clear and tangible benefit over what we had before.  With the small difference in results even ignoring Luker’s points I am on the fence.  If a notified body (that is after all who will approve our design) accepts this is the future direction then I will happily comply.

Paul.

[lezsmithParticipant @lezsmith]

Hi Luker,
With reference to your post, the YP method presented, clearly states that it was for use with “Copper” therefore your point about not using it for other materials is clearly as stated in the proposal.

You go on to say “Design a shell to the minimum thickness” is NOT what was stated in the proposal, it clearly states the calculated value is the minimum thickness required to resist permanent deformation during the 2x working pressure testing, the proposal goes on to state an appropriate safety value MUST be added to account for operational conditions the boiler will encounter, rather than an arbitrary 8x used in the current UTS method.

You state “Practically, this example brings the YP design method much closer to failure than the UT method. And that’s not what we want…”
How can this be true if the points in previous posts above and in the examples given, the minimum copper thickness is generally thicker?

As you said, I also don’t want to get into a debate here on the correct application of numerical methods, therefore I will refer this question to my old professor of Engineering at MIT, hopefully some undergraduate can take this on as research for his/her degree.

 

 

[lezsmithParticipant @lezsmith]

Hi Paul,

First off, thank you for a very good post, no insults just interesting commentary 🙂

Taking your last comment first, fair point on RIDOR, it clearly states workplace, but as you point out “how to define a workplace is debatable”, if I employ a gardener to cut my grass is my personal home now a workplace?

However, an interesting fact was raised “where do I find the RIDOR reports” just doing some research I’m trying to find all the reported “Model Boiler failures” but I’m not able to find any, clearly their have been some, at least 2 as mentioned in the above posts, so where are the records?

I’m not going to comment on the YP vs UTS anymore, we put the presentation and methodology together not as you must abide by this, it was meant to be here is an alternative that does NOT use magic numbers and follows other standards such as the AMBSC that have used the Yield point of annealed copper as the reference rather than the UTS. Our hope is it would provide an alternative by using well defined values that can be referenced in easily obtained literature.

If you are ok with your boiler deforming during the 2xWP test no problem as the builder and perhaps the designer that is your prerogative, just because we provided another tool for the workshop it does not mean you have to use it, but at least it is available and like most tools covers a specific function (defines a minimum copper thickness that will not deform under the 2xWP test) the reality is 99% of boilers will use copper that is significantly thicker than this minimum value, and so they should, they need to increase the thickness by adding a safety margin based on the environmental situation the boiler will be used, then the normal next step is to find what thickness is commercially available, this could be slightly thinner than the calculated value, however with the YP method it is very easy to work backwards to find the calculated safety value for the thinner copper, allowing the builder/designer to consider if the decrease in the safety value is ok or not.

 

 

[MEinThailandParticipant @meinthailand]

Lezsmith and all, just to clarify the following statement in your post:-

“an appropriate safety value MUST be added to account for operational conditions the boiler will encounter, rather than an arbitrary 8x used in the current UTS method.”

I just want to reiterate and emphasise once again that the so-called safety factors in the UTS method are not Safety Factors at all.

They can best be considered as Conversion Factors, used to convert the strength properties of the material used in the UTS calculation (hard drawn copper) into the actual properties of the material when a boiler has been silver soldered, ie annealed copper.

To refer to the UTS ‘safety factors’ as actual Safety Factors is misleading and could lead copper boiler builders into thinking that they have a large safety factor (e.g. 8) in their boiler when in fact they do not, due to the reduction in strength of copper during the silver soldering process.

 

 

 

 

[MEinThailand]

On MEinThailand Said:

Lezsmith and all, just to clarify the following statement in your post:-

“an appropriate safety value MUST be added to account for operational conditions the boiler will encounter, rather than an arbitrary 8x used in the current UTS method.”

I just want to reiterate and emphasise once again that the so-called safety factors in the UTS method are not Safety Factors at all.

They can best be considered as Conversion Factors, used to convert the strength properties of the material used in the UTS calculation (hard drawn copper) into the actual properties of the material when a boiler has been silver soldered, ie annealed copper.

To refer to the UTS ‘safety factors’ as actual Safety Factors is misleading and could lead copper boiler builders into thinking that they have a large safety factor (e.g. 8) in their boiler when in fact they do not, due to the reduction in strength of copper during the silver soldering process.

 

 

 

 

Ref my own post I would like to choose better words.

I said:-

They can best be considered as Conversion Factors, used to convert the strength properties of the material used in the UTS calculation (hard drawn copper) into the actual properties of the material when a boiler has been silver soldered, ie annealed copper.

A better choice of words would be:-

They can best be considered as Compensating Factors, used to compensate for the fact that the strength properties of the material used in the UTS calculation (hard drawn copper) is much reduced to the properties of the material when a boiler has been silver soldered, ie annealed copper. (Approximately by 1/6 depending upon the source of information for the properties of the materials.)

[MEinThailand]

On MEinThailand Said:

On MEinThailand Said:

Lezsmith and all, just to clarify the following statement in your post:-

“an appropriate safety value MUST be added to account for operational conditions the boiler will encounter, rather than an arbitrary 8x used in the current UTS method.”

I just want to reiterate and emphasise once again that the so-called safety factors in the UTS method are not Safety Factors at all.

…

To refer to the UTS ‘safety factors’ as actual Safety Factors is misleading and could lead copper boiler builders into thinking that they have a large safety factor (e.g. 8) in their boiler when in fact they do not, due to the reduction in strength of copper during the silver soldering process.

 

 

 

 

…A better choice of words would be:-

They can best be considered as Compensating Factors, used to compensate for the fact that the strength properties of the material used in the UTS calculation (hard drawn copper) is much reduced to the properties of the material when a boiler has been silver soldered, ie annealed copper. (Approximately by 1/6 depending upon the source of information for the properties of the materials.)

I fear inventing ‘Compensation factor’ as an alternative to ‘Safety Factor’ only muddies the water!

Though there are variations Safety Factor is long established in engineering,  see Wikipedia’s ‘Factor of Safety‘  In my view, this whole debate is about understanding Safety Factor.

Simply put, the underlying YP and UTS formula were derived scientifically. At root, the burst pressure of a cylinder depends on the outside diameter, how thick the wall is, and the strength of the material.   Easy enough on paper, unfortunately the real world is complicated!  Especially “strength of material”.

Material strength can be expressed imperfectly with Yield Point or Ultimate Tensile Strength.  Both can be measured and used to give reasonable answers in calculations,  but material strength is best explained with a graph.   More!  The formula assume a perfect cylinder and ignore all the external factors, which matter.   For example, material strength varies with temperature, construction matters (joints, end-caps and penetrations),  and so do the operating conditions.   Metal fatigue!

In practice, the underlying formula is used to derive the minimum thickness of a pressurised cylinder,  and then an arbitrary safety factor is applied.  How big is the safety factor?   My machine design book says:  ‘To compensate for the fact that not all the assumptions involved in a rational analysis are true, the machine designer must choose a safety factor which in his judgement will permit satisfactory machine operation.’    

Safety Factors are usually a multiplier decided in light of practical experience, often radically increasing strength above formula!   SF’s are often embedded in codes of practice, likely updated after a catastrophic collapse.

I pointed out in post #800663 that the Safety Factors in the YP and UTS formula dominate the answer.  In my view the difference between YP and UTS is academic in this application because both are heavily weighted by the Safety Factor and produce similar results.  Not worth arguing about.

Unfortunately, the size of boiler Safety Factors are lost in the mists of time!  But they are based on practical experience – boilers built to them giving a good service life without going bang.   Practical experience increases the Safety Factor to cover unknowns like material differences.  The strength of Copper depends on which alloy is used, how it was worked during the build process, and then on how hard, hot, and often the boiler is cycled.   Safety Factors are not an exact science.

Worth challenging current standards because they’re excessively high compared with a good design built by a skilled worker using well-chosen material.   But they cover weak designs, built by semi-skilled workers from scrap!

I suggest YP versus UTS isn’t the most important factor.    Both formula only apply to the cylinder and assume it has perfect ends, which is unreal.  Actual boilers have a smoke-box, tubes, holes punched in the shell for drainage, safety valves & the regulator, and a firebox full of stays.  MEInThailand recognises the problem, noting silvering soldering can reduce strength by up to 1/6.    Multiplying by a SF fixes that, but the SF is arbitrary…

My gut feel is that FEM offers a better way of challenging the status quo. The whole boiler can be modelled, not just the cylinder, the software calculates stresses throughout the whole structure, and shows where they concentrate.   Not a trivial job though.

I welcome articles like this and the resulting discussion.

Dave

 

 

[JasonBModerator @jasonb]

 the strength properties of the material used in the UTS calculation (hard drawn copper) is much reduced to the properties of the material when a boiler has been silver soldered, ie annealed copper. (Approximately by 1/6 depending upon the source of information for the properties of the materials.)

 

MEInThailand recognises the problem, noting silvering soldering can reduce strength by up to 1/6.

 

Be careful using “by 1/6″ as 24,000 reduced by (1/6 * 24,000) =20,000

When it is reduced to 1/6th the original value 24,000/6 = 4000

 

 

[Nigel Graham 2Participant @nigelgraham2]

Lezsmith –

Some posts back but re your:

…reported “Model Boiler failures” but I’m not able to find any, clearly their have been some, at least 2 as mentioned in the above posts, so where are the records?

If that includes the one I had described a while previously, that was decades before any such reporting was devised; and indeed before the test system we now use.

Possibly the other was also before the RIDDOR rule, but only two serious failures in service, although still two too many, shows just how thankfully rare they are; making me wonder the point of this entire thread. We all want to build and operate safe engines but let’s not give ourselves opening for making the hobby no longer feasible.

 

I can offer a third failure in service, and its lessons.

It was not catastrophic, by sheer luck. The locomotive, a doubled-up (so 7-1/4″ g.) version of LBSC’s Juliet, struggled to draw its loaded train into the station, with the driver reporting water in the visible part of the ashpan.

Assuming a tube leak we took the engine out of service and examined it. A leak had developed in the inside firebox wall, and quietly extinguished the fire. The boiler was steel and it proved possible to grind the damage out and patch-weld it, and after very careful, thorough testing return the locomotive to service for just two remaining events. Then it was withdrawn for a new boiler, now copper, by a professional boiler-maker although at cost as he was retiring and was also a club member!

The lessons, after I cut the old boiler up for full examination:

– Design fault: Lower gauge-glass bush too low so possibly the crown-plate occasionally ran dry. (No fusible plug.)

– Operational faults not recognised for years, leading to serious scale and corrosion. The water-legs were nearly choked by calcite and iron-oxide, sufficient to distort the plates. The locomotive had run for years before water-treatment became normal in model-engineering circles, and ours is a hard water area. Although the boiler was usually blown down at the end of running, a single blow-down valve is insufficient for proper cleaning.

– Deep crown-plate corrosion, perhaps liked to the times when mimium water indication might actually have meant a dry plate. (I did not think to measure this properly in the post-mortem.)  Some sectioned pits on the water side had floors ~0.03″ thick. Fire side moderately eroded.

– The rest of the boiler’s internal surface was rusty but evenly and not deeply, nor particularly scaled.

– Materials source and approvals: not relevant! The boiler had been assembled by a professional welder outside the club, although he did not understand locomotive boilers and had no reason to query the gauge-glass bush height. The materials were probably industrial off-cuts not knowingly certified for anything, let alone pressure-vessels; but no-one worried about that in the 1970s. The barrel was of standard steel pipe, the plates likely ordinary hot-rolled mild-steel. I think the tubes were of copper. This shows paper does not protect anything physically: you can quote all the numbers and codes you like but oxygen still attacks iron, and calcium-carbonate still precipitates from solution in water.

[Paul KempParticipant @paulkemp46892]

Boiler failures;

A few years ago now, prompted by 2 then issues I embarked on the same quest as Lez.  The first issue was publication of an article in local media by a clearly uninformed journalist trying to create hysteria over model steam boats running on a park pond – the article implied the local residents were at severe risk from these “floating bombs”of an event on the scale of Hiroshima that would injure and maim many!  The second was a debate running on a forum at the same time over the ineffectiveness of the club boiler testing regime.

There was a time when miniature railways were going to be covered by fairground legislation, this was in response to a realisation that they really had no regulatory oversight, this approach didn’t last long so the next attempt was to put them under the office of railway regulation – I had to report a non injury derailment at our local club 5” track to them and got a very bemused inspector who once he understood the scale of the incident told me to “go away” and not long after the small gauges were transferred to the HSE, HS2020 being the latest iteration of guidance / code of practice for passenger carrying miniature railways.

So I searched the above three sources for evidence of miniature boiler failures and drew a blank.  I then thought about media reports, found plenty of reports for derailments but none mentioning boiler failures.

Considering the reason for wanting to identify documented failures now, for the information to be valid we have to define what a boiler failure actually is that will support the argument of poor design.  To my mind there are four categories of failure;

Poor design, this would include either inadequate or improper material specification, joint methods, stress relief detail and poorly supported flat surfaces (stays).

Poor manufacture, this would include a boiler that had an adequate design but was poorly manufactured or materials other than those specified had been used.

Poor operation, this would include internal scaling, running with low water level, defective safety valves, sight glass(s), pressure gauge etc. (Kirklees light railway report – that was an incident with a boiler but attributed to its operation not its design).  This is where I would place Nigel’s steel boiler example, had water treatment been used and regular descales carried out and a proper inspection (see below category as additional factor) been carried out in previous boiler tests to verify the lower gauge fitting position it would have lived longer – whether it should have been re certified for its last 2 operations after ‘repair’ is also a moot point.

Poor maintenance and inspection, Operator not following routine to prevent scale or descaling, aging boiler not recognised as approaching life expiry, corrosion, erosion of threads securing fittings etc.

I have witnessed 2 boiler “failures” so far in my 50 odd years of exposure to models and miniatures.  Both unspectacular incidents with a root cause of poor manufacture.  The first was a 5” gauge Britania with a commercial boiler that suffered a small separation of the wrapper from the backhead over about 15mm result a jet of steam back into the cab, cause lack of silver solder penetration through the joint, there being a only a small fillet of solder on the outside.  The second was a smokebox tube plate to tube failure, one tube developed a leak at its joint with the tube plate, resulting in nothing immediately obvious externally but the boiler a refused to steam and lost pressure, cause as the first a lack of penetration of silver solder through the joint relying on a small fillet on the outside – which cracked.  Neither incident to my knowledge was reported anywhere (they were not my boilers so can’t comment for sure).

I am sure there will be other examples of unspectacular failures that have gone unreported.  Is this important?  Depends on your view point I guess, if my examples had been reported then maybe the boiler manufacturer would have been forced to improve quality control, they may also have been lumped into a boiler failure general category that could be erroneously used to justify this case – “look how many failures there have been, we must improve shell thickness calculations!”  We can only consider here examples of faulty design directly leading to a failure as justification for the argument.

So, have there been examples of catastrophic failure of miniature boilers due to poor design?  So far no one on this thread has found a documented report from an official body or been able to relate first hand experience of a boiler failure attributable to poor design.  Is it likely there have been many incidents that have been kept secret?  Personally I think not.  I also think that any catastrophic failure is very likely to result in some form of injury so an alternative in locating incidents to consider may be to ask RSA who seem to be the main underwriter for the boiler explosion insurance?  I used to attend the Northern Fed AGM at which there would be a broad non identifiable summary of any new claims arising and claims settled in the previous year.  I never heard a boiler failure mentioned.  So I assume there were none but to confirm, maybe ask?

My conclusion to my original motivation for the questions on the safety of miniature boilers construction and testing was it was “safe” and low risk.  The argument that just because there are no reported or documented incidents doesn’t mean they are low risk doesn’t stack up.  There can only be reports if there have been incidents, thus a lack of reports (either from official bodies or in the media) can be considered as some evidence to support the safety case.  Any catch all “boiler failures” statistic would need to be broken down to relevant figures of failures attributable to poor design and then further examined for incidence of inadequate shell thickness to be meaningful to the current discussion.  If there had been significant incidents in the blame culture we now live under there would have been insurance claims.  Insurance companies are heavy commercial gamblers and any increased risk results in increased premiums or conditions.  The boiler explosion element of my insurance is one of the cheaper elements, what drives up my premiums are theft and damage cover!

Paul.

[lezsmithParticipant @lezsmith]

Hi Paul,

Wow where to start excellent post. Starting with RIDOR, I reached out to them for comment and received a very generic response “We do not publish details of events as they contain personal identifiable information”.

So clearly, they have some details but will not disclose them to the public.

However, even before RIDOR there were regulations to control the reporting of Boiler failures.

The Boiler Explosions Act 1882 defined the original reporting of Boiler failures. It was repealed by the Health and Safety at Work etc. Act 1974, which established a comprehensive framework for workplace safety. The 1882 Act primarily focused on regulating boiler explosions and investigations after such incidents.

Whilst model engineering does not have the same legal reporting structure, searching for larger boiler failures turns up well over 100 incidents e.g. https://en.wikipedia.org/wiki/List_of_boiler_explosions.

So, I’m sorry but I just cannot believe there are so few model boiler failures, for example this was stupidity on the part of the operator but where is it documented? Other than YouTube.

This one is very sad a very nice model destroyed but it looks strange almost like it was planned?

The only place I can see these two incidents documented is on YouTube?

Just doing a basic search on YouTube I found several such videos, again no official reports or media coverage outside of YouTube.

This is not a dig against model boiler builders, it just does not make sense when people say “there have been no reported failures therefore it must be ok”.

What I had hoped for with this thread is the collective wisdom and years of experience would contribute to making the proposal better, both Alan and I debated the safety number but we could not come up with a scientific rational to justify any values, I had hoped this forum would have said something like “The Hoop formula seems reasonable, but what about the safety factors and yield value looks a bit low”.

I would have very much appreciated the whole community debate and propose a set of safety values for different environmental conditions resulting in a table that could be used with the YP method to determine the minimum boiler shell thickness.

I would have also appreciated an honest debate about the Yield value of copper, and perhaps add specific grades of copper with relevant Yield and Tensile strength values to the proposal.

It is very saddening to see comments that does not move the argument forward it just causes friction and bad feelings. Paul please do not get me wrong I was not referring to your latest post, I do not agree with some of your statements for the reasons I have outlined above, but I thought it was a good response that moved the conversation forward.

[lezsmithParticipant @lezsmith]

Please ignore “https://youtu.be/0IVgfQdq7Lg”. It looked suspicious I just found out it was a pyrotechnic stunt.

[noel shelleyParticipant @noelshelley55608]

From 807004 by lezsmith.

WE DO NOT PUBLISH DETAILS .

SO CLEARLY, THEY HAVE SOME DETAILS.   Really ? I see no evidence to back up this assumption. A standard non committal answer from an official body.  Noel.

[JasonBModerator @jasonb]

With mention of “tweaking the safety valve” and nothing after the failure how do you know the boiler failed due to the tube wall thickness being too low for the design pressure?

Could have been anything that failed from a fitting, joint, endplate (no stays visible), etc

It is unlikely that any failures in the home would get reported unless there was a serious injury or death.

Unfortunately it is idiots like that who will have failures but they will also not bother to read up on what wall thickness to use, preferring to build their boilers from any bit of scrap that comes cheap enough.

Why would you want to add various grades of copper to your proposal when there is only one preferred grade for boiler barrels?

[lezsmithParticipant @lezsmith]

Hi Noel,

Sorry I should have been more clear, one of the replys above stated they had an incident and it was reported to RIDOR.

Therefore my statement stands, clearly they have some details but will not share them with the public.

[lezsmithParticipant @lezsmith]

Hi Jason,

I did not state or imply how the boiler failed, this discussion is related to reporting of a boiler failure irrispective of the way the boiler failed.

I agree the actual cause of the failure is unknown, however that is on no significance to the discussion on the reporting of an incident.

I agree with your 3rd point, infact my argument has been and still is “boiler failures do occur but are never reported” therefore no one can say “there have not been any reported boiler failures therefore the design must be ok”.

C101 (Oxygen-Free Electronic Copper – OFE): 99.99% pure, very low oxygen content, excellent for high-end electronics.  
C102 (Oxygen-Free Copper – OF): >99.95% pure, suitable for applications needing high conductivity and ductility.  
C110 (Electrolytic Tough Pitch Copper – ETP): >99.9% pure, good conductivity, widely used in electrical applications.  
Commercially Pure Copper: Contains 0.7% impurities, soft and ductile.  
Free-Machining Copper: Contains elements like sulfur or tellurium to improve machinability. 

Please feel free to state what grade of copper is the “preferred grade for boiler barrels”, and if that grade is not locally available are you saying they can not use any other grade ?

 

[JasonBModerator @jasonb]

None of the above. C106 is the preferred grade for plate and tube.

Deviating from that I would suggest anyone speak with their club boiler inspector or whoever will be testing it.

 

I was under the impression that the discussion (thread) was about the YP method as per your article. As has been said there is very little evidence of boilers failing due to the tube being too thin, those that do go pop tend to be due to other reasons but that is outside the scope of your article as it only covers the min thickness for the tube. One only has to look at that image of failed boilers that I posted to see that the tube can take many times it’s calculated WP before it fails.

[lezsmithParticipant @lezsmith]

Hi Jason,

Interesting the AMBSC section 2.2 states accepted grades of copper are:

Fair point the overall topic is the use of YP, however if you followed the thread their are several topics being discussed, one being “there is very little evidence of boilers failing due to the tube being too thin” I’m stating that their is no data to substantiate this claim, lack of data does not indicate lack of issues, it could just as easily mean no one bothered to report them or their is no way for the public to know.

[JasonBModerator @jasonb]

Nothing funny about it C106 and 122 can be taken as equivalent, just depends who’s designation the particular country uses. Anything else as I said check with who is going to sign it off. No point in wasting money and time on a meterial the inspector may not be happy with.

As 99% of the membership here are UK base I tend to stick with what is accepted here. Including our test code.

[Charles LamontParticipant @charleslamont71117]

In full size practice in the UK, copper locomotive inner fireboxes and stays are made of C107 arsenical copper, which, among other qualities, retains more strength at elevated temperatures (yes, that is vague – anyone wanting to know more can look it up!)

[lezsmithParticipant @lezsmith]

Hi Jason,

Thank you for the info, I’m not being funny about the grades of copper, to be honest most of my engineering work revolved around rolled steel joists and re-bar so I’m not as familiar with copper.

I see Alloy 122 in the AMBSC chart and happy to take your word that C106 is the same, however it still leaves a big difference in that the AMBSC also accepts 102, 110 and 120. I’m trying to understand where the Australian, UK and USA standards overlap (if they overlap at all), here in Thailand the local codes tend to follow the USA standards and living and working in the USA I tend to be more familiar with ANSI.

I’m assuming you refer to BS-EN-1254 and BS-EN-1057, if that is not correct please point me to the appropriate standards you use.

[lezsmithParticipant @lezsmith]

Jason,

One more question you might be able to help me:

You stated “Deviating from that I would suggest anyone speak with their club boiler inspector or whoever will be testing it.”  I 100% concur, sound advice.

But that raised the following question in my head “What standard do club boiler inspector’s use”?

Doing a bit of research I found a few different standards.

These appear to be the ones most referenced

https://fmes.org.uk/wp-content/uploads/2021/04/Boiler-Test-Code-2018-Volume-1.pdf

https://fmes.org.uk/wp-content/uploads/2021/04/Boiler-Test-Code-2018-Volume-2.pdf

Again assuming 2021 is the latest updates?

https://knowledge.bsigroup.com/products/shell-boilers-inspection-during-construction-documentation-and-marking-of-pressure-parts-of-the-boiler-1

https://assets.publishing.service.gov.uk/media/63e25c96e90e076266ed429c/Improving_boiler_standards_and_efficiency_consultation.pdf

I see your reply on a model engin maker forum (April 28, 2013) on a similar topic.

Perhaps you can shed some light on the current state of model boiler legislation in the uk,  and what club boiler inspecters reference as the current standard.

 

[JasonBModerator @jasonb]

As I said C106 is preferred for tubes and sheet/plate as that is what is being discussed here. Not having the Australian code I don’t know if they suggest which parts can be done with what grade.

As you can’t generally get get sections in that grade in the UK then for things like foundation rings you would use say C101.

The UK code is rather limited in technical details and the refs you link to are more related to testing. But the inspectors are generally people with a lot of experience in making and running model boilers particularly copper and will have picked up over time what is acceptable and what isn’t. There are a few here who are inspectors maybe they will comment further. As I have suggested before you would be better contacting the bodies that issue the test codes if you want change, they may well also be able to answer your questions.

If that was the thread on MEM that I was thinking of you would also have seen many others suggesting C106 be used, boiler designers included in those active in the thread.

[lezsmithParticipant @lezsmith]

This is very worrying: “But the inspectors are generally people with a lot of experience in making and running model boilers particularly copper and will have picked up over time what is acceptable and what isn’t.”
If I’m reading this correctly what you are saying is “The UK code is not very good therefore individual boiler inspectors make up their own code”.

That does not sound good, clearly a very experienced inspector with years of experience will make good informed decisions and is likely to guide the boiler maker, but what about new boiler inspectors who rely on a published specification that they can use as a reference. As the older generation retires who takes their place?

Hopefully there are some boiler inspectors reading this and can comment.

Regarding your statement “None of the above. C106 is the preferred grade for plate and tube” I’m trying to understand where you obtained that data as it appears by your statement “Deviating from that I would suggest anyone speak with their club boiler inspector or whoever will be testing it.” that it is stated somewhere in some code that is the grade of copper you must use in the UK.

Please let me know the reference to the code you are using.

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