I have never seen the drawings for Britannia, but assuming that there is a D shaped combustion chamber like the LBSC/Martin Evans 9F wouldn't you need to keep the syphons in order to stay it?

My son bought an Evening Star "project" a while back and was advised by a boiler inspector to consider redesigning the boiler in order to abandon the combustion chamber completely as it cannot be tested before it becomes completely inaccessible. He said he would no longer accept the old solution of sloshing soft solder about inside the boiler in the hope of fixing a leak in the tubeplate, so the risk of building a scrap boiler was too great.

Perhaps I have misunderstood things, but there seem to me to be enough questions about older boiler designs under current inspection codes to justify a complete series in ME or even a book of revised drawings and instructions.

Brian

Seems to me that some boiler inspectors are making their own rules up. Boilers should be inspected exactly to the requirements of the Rule book. If the rules state no soft solder, fine, you cannot use it, but if nothing is mentioned about it you should be OK to use it. Imagine what our MOT tests would be like if testers deviated from the rules.

That is a good point, as whilst volume 2 says construction "should" (importantly not "shall&quot be silver soldered throughout but permits an exception for threaded and nutted stays, volume 1 makes no reference to soft solder at all. It does however require that the inspector checks all joints penetration of "silver" solder which could imply that a soft soldered joint, or one that has been repaired with soft solder, is not permitted. To me as a layman, it doesn't seem sufficiently definitive either way.

Incidentally, whilst volume 2 prohibits phosphorous-bearing brazing alloys for coal-fired boilers, volume 1 doesn't mention brazing. Does this imply that Sifbronze is no longer permitted on boilers over 3 bar-litres, or that it is permitted because it isn't mentioned?

Brian

"Just wondering – how did it become known as thermic syphon in boilers while it is thermosyphon in everything else?

Russell"

Could be because the guy who patented it in 1928 called it that. Google is your friend.

https://patents.google.com/patent/US1679051

I'm sure ME would welcome a serious series on boiler design, from simple pot boilers working up to proper loco boilers and traction engine ones.

It would be particularly wonderful if (a) it was about designing to meet the codes noting any major difference in Aus or Kiwi land, for example, and (b) there was one or more persons willing to check over and sign off new designs, possibly for a suitable fee, as a thrid party sense-check before they get ripped to pieces by nervous boiler inspectors.

That said, who would be a boiler inspector? Taking on a huge H&S responsibility for no reward as a volunteer and having to tell people what they often don't want to hear; is it any wonder that many err on the side of caution in the absence of really clear and explicit guidance. Perhaps there should not just be rule books, but plenty of 'worked examples' and case studies.

Neil

You're not going to get anyone to 'check over and sign off designs …for a suitable fee'. That would leave them open to being sued by Flywheel Schyster and Co if anything went wrong with a boiler, unless MyTimeMedia covered the personal liability insurance, and I suspect that's as likely as me winning a beauty contest.

Having said that, ME recently re-published an ancient LBSC design boiler which I'm fairly sure would have given most modern boiler inspectors conniptions. There was a health warning but why publish in the first place.

Neil, when I get back from holiday I'll send you a pm about Aussy standards and BS

Nicholson gained a US patent for his thermic syphon in 1928 and this is a link where some of its advantages are described. http://www.athra.asn.au/library/Thermic_Syphons.pdf

As to other locos tyhat used them Gresley designed the V4 2-6-2 in 1939 (his last design). The first member of this class, 'Bantam Cock' has a traditional copper firebox while the second had a boiler with an all welded steel firebox and thermic syphon. Why? Perhaps because it was felt that the increased efficiency would counter the lower heat conductance of a steel firebox compared to a copper one. Alternately Bulleid, who had been Gresley's assistant until he took up his position with the Southern, might have considered the case for the thermic syphon proved, but adding them to a copper firebox problematic so the welded steel firebox of the SR pacifics enabled their inclusion. It is difficult to determine exact reasons after this amount of time.

A final thought, while not professing to any expertise in boiler design or construction, the elimination of design features such as combustion chambers or syphons would surely make a boiler 'not to an accepted design' and raise more questions than it gives answers.

Edited By Nick Clarke 3 on 16/08/2018 11:42:31

Edited By Nick Clarke 3 on 16/08/2018 11:43:54

Edited By Nick Clarke 3 on 16/08/2018 11:53:28

Can I go back a few posts and pick up the point made by Brian G . I find it difficult to understand the inspectors comments viz :- " consider redesigning the boiler in order to abandon the combustion chamber completely as it cannot be tested before it becomes completely inaccessible "

Firstly if you are re-designing the boiler it is surely no longer a published design benefiting from " grandfather rights" You would need to get the altered design proven by calculation and as Duncan rightly points out who will sign it off? Not the boiler inspector I suspect!

Secondly having built a combustion tube boiler with cross stays for LBSC Uranus which is very similar size to a Brittania boiler in 3 1/2 G, one can either test the combustion chamber alone by blanking off both ends and pressurise from the combustion space outwards.

In my case I also fitted the end tube plate and the embryo firebox and throatplate, and it can then be tested up to full pressure by blanking off the firebox base, and the tubeplate ends and pressurising "inside out and upside down" so to speak. In my case I used an aluminium plate with a rubber gasket around the grate opening with a connection for the boiler test pump and a vent. I did it this way because all these joints were brazed with 750 deg silver solder and the remainder of the boiler is with 580 / 600 to avoid disturbing these joints at the later build stages. This will confirm the cross tube and the throatplate joints.

I agree that boiler inspectors take on a huge responsibility voluntarily on our behalf, and a proper set of standards for design and construction along the lines of the Australian code would at least give them all a standard to work to and avoid individual interpretation.

God forbid we should have an accident somewhere, then everything will be put on hold until we do get a code and a set of standards approved, which wont be a quick process; and the ensuing limbo will mean no one, not even the commercial builders will be in a position to build a boiler without knowing what the future standards will be. So perhaps the way forward is to be proactive and get it before the event.

Some recently suggested we should get ALL our designs signed off…

I'm sure a chartered engineer with appropriate experience and Professional Liability would do it happily – that's what their job is, after all. But I was thinking that boiler designers might take advantage of a reasonably costed service, suitable calcs have been published many times and an engineer would only be in trouble if they were negligent in choice of calculations and made mistakes in checking them. It's no different from designing your own extension and then getting an architect to check the drawings.

Come to think of it, surely every time a Boiler Tester advises on boiler construction then tests it, surely they are in the same situation – and all are happily protected by the club's insurance if they do the task with due care.

Neil

Edited By Neil Wyatt on 16/08/2018 19:04:22

I completely agree with your last message Duncan – specially the second paragraph.

I suspect that the inspector from Jons original message was simply suggesting the removal of the combustion chamber along with the cross tubes. That won't affect the boiler integrity surely?

Also 'design changes' to a published design?? I haven't seen a model boiler drawing for 3 1/2" gauge that doesn't have some kind of recommended modification.

Phil H

I realise that my question was parallel to the main topic, but …

Jeff Dayman suggests that the term Thermic Syphon is used because that was the term on the patent. Well a patent cannot be had for an idea (etc) which is already well known and in general use. So, it cannot be the same as 'thermosyphon'. So why can no-one tell me what the difference is, please?

Regards, Tim