|
|
Post by serannelo on Jul 4, 2019 16:28:10 GMT
Greeting to all, I have been lurking for several years and enjoying the interactions and exchanges of useful ME information.
I am contemplating a model of which there appears to be no published design in 5" gauge and therefore no boiler per se.
However if I found a boiler (published design) that was close to diameter, firebox shape (Belpaire) and had the dome in approx right position, would it be acceptable to ask for the manufacturer to make it say 2" longer and orientate the two safety valve bosses across the top of the outer wrapper above the firebox instead of along the centre line. Maybe one or two back head bushes may need to move as well. Further would a boiler inspector then refuse to test and certify as the comleted boiler would no longer be exactly as published? For clarity we are talking of extending/modifying a Horwich Crab boiler to go on a Hughes 2-8-0 Dreadnought tender loco.
I am aware I may be head above parapet but other may have questions in a similar vein.
Thanks in advance
Serannelo
|
|
|
|
Post by springcrocus on Jul 4, 2019 18:32:11 GMT
I was under the impression that if a professional builds your boiler, he can do what he wants because he has the requisite skill to alter designs safely. He would also issue the boiler certificate and renewals don't need to consider design, that was done for the first certificate.
For a self-build, I think you would find it difficult to convince any inspector to verify your alterations and issue the first certificate. This is assuming a UK build.
Alternatively, ask Julian (who will probably tell you I'm talking a load of tosh, and may well be right).
Regards, Steve
|
|
|
|
Post by Deleted on Jul 4, 2019 19:48:42 GMT
I would agree with Steve, if you are getting the boiler professionally made you will be fine. The builder will make the caculations and build accordingly, no need for you to worry about any changes, the builder won't/shouldn't do anything to make the boiler unsafe and will tell you if something you ask him/her to change can't be done.
Pete
|
|
|
|
Post by serannelo on Jul 4, 2019 22:36:58 GMT
Thank you for the helpful replies. I will be having the boiler professionally built and wanted a flavour of possible pitfalls but the replies make perfect sense.
Just need to light up the autocad and start laying things out.
Thanks for the help.
|
|
|
|
Post by ettingtonliam on Jul 5, 2019 6:17:46 GMT
Umm - how does extending the barrel by 2" alter any of the stresses in the boiler?
Would a boiler inspector really refuse to test a boiler because a couple of bushes had been moved?
|
|
|
|
Post by simplyloco on Jul 5, 2019 7:30:01 GMT
According to the Code, moving the bushes is not allowed!
The Inspector shall satisfy himself:
c. That the boiler is constructed in accordance with the design
drawings.
Extract from the current Boiler Code regarding unpublished designs.
The constructor of a boiler to other than a recognised design
available through the model engineering trade and/or press shall
produce design drawings and demonstrate to the satisfaction of
the Inspector, either by calculation or by well-proven example, that
the design and materials used have adequate strength.
And on Inspector competence. How many do we know who would not qualify for such a role?
An Inspector acting as a competent person who carries out an
examination under the Written Scheme of Examination shall
have such sound practical and theoretical knowledge and
actual experience of the type of system which is to be
examined as will enable defects or weaknesses to be detected
which is the purpose of the examination to discover and their
importance in relation to the integrity and safety of the system
to be assessed. The individual should know his own limitations and should not
act outside his level of qualification or knowledge.
|
|
|
|
Post by David on Jul 5, 2019 12:20:11 GMT
As long as you still had the same number of stays in the crown, the same positions, what difference would it make to have the safety valve bushes go cross-wise rather than fore-aft?
If the design has crown girder stays they might be in the way.
Paying someone else to do it sounds like it will avoid a lot of grief.
|
|
|
|
Post by ettingtonliam on Jul 5, 2019 18:25:38 GMT
So, to be clear, a 'professional boiler maker' could, if he chose, take the standard crab boiler design, extend the barrel by 2 ", move the bushes as described, neither of which would alter the stresses in the boiler, and on completion test it and issue a certificate which would not be questioned by the purchaser's club? The same boiler, if built by the owner would, without question be rejected out of hand by any club boiler inspector because it didn't comply with the published design?
I'm sorry if this has been covered before, but how does a 'professional boiler maker' establish his bona fides to make such changes? How, for that matter did LBSC, Martin Evans, Keith Wilson, Ken Swan, David Piddington, Don Young, WJ Hughes etc etc establish their competence as boiler designers?
Would a boiler to LBSC's basic design, but incorporating bronze bushes for the fittings instead of threading into the copper shell, and possibly silver soldered stays instead of soft solder caulking, if built by the owner, be rejected out of hand because it wasn't in accordance with the published design? Are there recorded instances of this having happened?
|
|
|
|
Post by simplyloco on Jul 5, 2019 18:43:37 GMT
The Code doesn't recognise 'professional boiler makers': it merely refers to the constructor of a 'non-standard' boiler who has to produce the necessary drawings and calculations (or well proven examples) to satisfy the inspector. Our original poster's builder will have to provide this.
Trouble is, how many boiler inspectors do you know who understand the mathematics of stress and strain in boilers...? Not many Benny!
John
|
|
|
|
Post by springcrocus on Jul 5, 2019 18:47:09 GMT
At the end of the day, the whole question of boiler safety comes down to public liability insurance. To be covered by a club's insurance, the insurance companies insist that a certain level of competence has been shown in constructing a boiler. Uncle Tom Cobbley et al can only show this competence by having inspections during construction and tests at completion.
With regard to professional boiler makers, I don't know whether they have to demonstrate competence via certification (boiler maker's guild member, City & Guilds certificates etc) but they will carry their own public liability insurance, and possibly profession indemnity insurance. From the point of view of club insurers, the risk of a claim arising from a boiler made by a professional can be offset by, basically, passing the buck.
There are good, bad, and average levels of competency in all trades and insurers know this. They balance their risks accordingly and this is reflected in premiums. It all comes down to money in the end.
Regards, Steve
|
|
|
|
Post by ettingtonliam on Jul 5, 2019 19:34:27 GMT
The Code doesn't recognise 'professional boiler makers': it merely refers to the constructor of a 'non-standard' boiler who has to produce the necessary drawings and calculations (or well proven examples) to satisfy the inspector. Our original poster's builder will have to provide this. Trouble is, how many boiler inspectors do you know who understand the mathematics of stress and strain in boilers...? Not many Benny! John I'd be disappointed if there were boiler inspectors out there who did not know that extending the boiler barrel by 2", and no other changes will not alter the stress in any boiler component in any way. Different if we were talking about the firebox zone where the staying would need examining. |
|
|
|
Post by David on Jul 5, 2019 22:01:44 GMT
I can't really tell from here but it seems buying boilers is becoming the norm over there so the boiler builders know the problems of the the designs and have come up with the own ways around them, having built so many. It's the person who wants to do it themselves that gets let down by the rules which is exactly the person who should be supported by them!
I think you've described the benefit of the Australian code. As long as our govts and insurance companies believe it is written and maintained by competent people it allows the rest of us to design what we need and not be beholden to 50 year old designs which have known design problems, that either make construction difficult or make the boiler not as good as it could be over its lifetime.
That doesn't help you of course but I'm wondering why your leading lights don't recognise a way of doing things that is both more flexible for new designs so it's not only 'the few' who are able to come up with them and allows those troublesome old designs to be updated by any builder by giving them and the inspectors clear, prescriptive rules on how to do so.
|
|
|
|
Post by ettingtonliam on Jul 6, 2019 1:13:36 GMT
The Code doesn't recognise 'professional boiler makers': it merely refers to the constructor of a 'non-standard' boiler who has to produce the necessary drawings and calculations (or well proven examples) to satisfy the inspector. Our original poster's builder will have to provide this. Trouble is, how many boiler inspectors do you know who understand the mathematics of stress and strain in boilers...? Not many Benny! John But from what was being said earlier, the OP's builder won't have to produce drawings and calcs to satisfy an inspector. He is his own inspector, tests and certifies it himself. Its a self builder who has to jump through the hoops to attempt to satisfy a third party club inspector. |
|
|
|
Post by Deleted on Jul 6, 2019 9:31:56 GMT
Having had my own boiler professionally made recently I can only add my experience/understanding. For a recognised professional, moving bushes, changing design is not an issue. My own boiler has numerous extra bushes, has a lot more crown stays, has no longitudinal stays (useless for a long barrel) but follows OZ code for added butt straps that increase the associated tube plates from 3mm to 6 mm thickness. Some other strengthing aids that are not seen in model boilers but are in full size. Construction is a mixture of Tig and silver soldering, both tested by iirc Reading university for strength. Cad drawings were produced for the crown stay positions, some may recall my boiler has 6 rows instead of the publised 4. There are probably other changes that I can't recall just now. The paperwork is about 11 pages of details including the hydraulic cert where the boiler held 200PSI, code states for 30 mins, mine was left for 2 hours as is Paul's preferred practice.
You don't need to worry about changes if done by a recognised professional, he/she will unsure everything is to code or beyond. Southern Boiler works are part of the group of 6 of the main well known names for boiler making in the UK, I don't have the details with me but do recall Western Steam is one of the others in the group.
Pete
|
|
|
|
Post by ettingtonliam on Jul 6, 2019 10:50:30 GMT
I'm sure that Paul, Western Steam, Southern Boiler are beyond reproach in these matters, but what defines 'a recognised professional'? Is there a body which issues accreditation for boiler makers?
|
|
|
|
Post by Deleted on Jul 6, 2019 12:14:18 GMT
I'm sure that Paul, Western Steam, Southern Boiler are beyond reproach in these matters, but what defines 'a recognised professional'? Is there a body which issues accreditation for boiler makers? I can give the list of boilermakers that Southern Boiler Works LTD is part of and is covered in their 'Declaration of Compliance' cert along with the warranty and 'Authenticity of this document' details. The listed group forms the APCBM(ME), don't ask me what the initials stand for... I can't show the document as I haven't sought permission to do so. Swindon Copper Boilers J.M. Ellis (Model Engineers) Kingswood Boilers LTD Dragon Boilers Western Steam Model Engineers Southern Boiler Works LTD Miller Boilers All boilers built by these will carry the identification code number 5080 |
|
|
|
Post by cplmickey on Jul 10, 2019 8:25:18 GMT
That's a really useful list. Is there an equivalent for steel boiler makers by any chance? I think I'm right in saying that all of the above only make copper boilers. Ian
|
|
|
|
Post by Deleted on Jul 10, 2019 8:58:58 GMT
That's a really useful list. Is there an equivalent for steel boiler makers by any chance? I think I'm right in saying that all of the above only make copper boilers. Ian I would say they are most likely just copper but don't know for certain.. one of them might know of a steel boiler maker though... Pete |
|
|
|
Post by serannelo on Jul 14, 2019 20:55:19 GMT
Thank you to everyone who replied and added to this thread. It leaves much to think about before I do anything else. This question (thread)has probably run its course now, so again thanks for all of the input. Hopefully I can contribute in some small way to others in this well respected forum. Bye for now.
|
|
