Traditional Boiler Rivets Vs Welded Rivets.

I have a question concerning Boiler rivets. On a visit to a steam railway recently i found myself looking at a boiler that was from an engine that was having it's ten year overall. I noticed that the boiler stays were welded and also the stays looked like, they were some kind of high grade stainless steel, if that is the correct term. Also the engine had recently been dismantald and the boiler looked to me in a fare condition. I ask do modern welded boiler stays have more prolonged life, compared to traditional boiler stays. I am just curious, i have been reading Dominic Wells book on How Steam Locomotives work. Thanks in advance.

 

I'd be rather surprised if they were stainless steel, although freshly machined mild steel can have a high sheen to it as well.

Dunno about stay longevity of welded compared to screwed and rivetted - but fitting welded will be a damn sight quicker and easier, although it's a lot easier to fit and replace a traditional screwed one with just hand tools in the middle of no where by someone who isn't a coded welder...

 

Thank's, I did not know about screw in boiler stays. It has dawned on me that i was looking at a boiler, with new stays. The stays i was looking at had a very small diameter hole in the core of each of the boiler stays. Nice job if you like drilling ,reaming and tapping threads.

 

The small hole down the middle is a tell-tale to make it obvious if you've had a stay break - water/steam will be seen coming out of the hole if the stay's broken, indicating you need to think about replacement.
It's a bit easier than having to frequently go around hammering them to check.

 

Thanks , I have come across a Publication from the Office Of Rail Regulation. The Management of Steam Locomotive Boilers, Rail safety publication 6, It's an interesting read.

 

Most likely they were monel - see https://en.wikipedia.org/wiki/Monel. Very good for corrosion resistance, but very difficult to drill out.
Rob

 

Not if they were welded, as was stated by the original poster.

 

S&DJR 88's Boiler at Minehead, WSR spring Gala. There are some good vidio clips on Loco boiler construction on you-tube. I also now know that stays are made of mild steel.

 

I'm pretty sure they aren't welded and are monel.

Rob

 

Things on here don't seem right to me. Welded stays will probably have tell-tale holes drilled in them. Monel probably won't. (or at least it's something I've never seen.)
88's boiler won't have welded stays as it has a copper box.

 

see http://www.wsr.org.uk/2015/11/103.jpg

Rob

 

If the loco has a copper inner box it is unlikely the stays are welded in place as you may be thinking as the stays will all be threaded and screwed into both outer and inner plates, however they could be seal welded to the outer wrapper, which will be steel. This type of weld is not to provide structural support as that will be provided by the stays being screwed into both plates, rather it is purely to prevent egress of steam/water through the stay threads instead of a riveted stay head which would required caulking following riveting.

 

It's fairly rare for stays to leak on the outer wrapper, though, once caulked. Makes them much harder to remove when needed. And, if you're going to weld on the steel side, why screw, as well? Might as well make it a full weld, rather than a seal weld. Having said that, I've never seen this done with a copper box, though.

 

I agree Steve, just trying to shed some light on why stays may appear welded.

 

88's firebox stays are screwed not welded

Rob

 

That explains what i was looking at at the spring gala. Also i did not know that screwed stays existed. I am reading a book called The Design, construction and working of Locomotive Boilers. By Alan J Haigh . I am going through a bit of a learning process, concerning the workings and construction of of steam boilers.

 

Nick, Fixation will have only a small influence on the life of the stay, material choice and service being the predominant factors at play.

Rob, Are you sure about Monel? I ask purely on the grounds of price as Monel is not cheap and is a pig to machine. Stays are generally lifetime expired items over the course of a ticket, in my understanding, so would one not be inclined to use Carbon steel?

 

I've read in the past of Monel metal being used to make stays. One modern example is as quoted on the website of the Bulleid Society re. the rebuilding of Sir Archibald Sinclair (scroll down to the entry for March, 2008):

"Recent work has concentrated on the boiler with the machining in house of over forty new crown stays, each nearly three feet in length, for the firebox and their insertion, knocking over and caulking. This was the last area for re-staying in the firebox. Over seven hundred and fifty new stays, both steel and monel metal . . . "
http://www.bulleidsociety.org/34059/34059_Restoration_3.html

In the case of the Bluebell's engine, Birch Grove, the new stays are made of arsenical copper - so it seems that a variety of metals can be used, with their pros and cons weighed up against the detail design of the boiler and the likely working conditions.

Talking of which, in one respect our boilers have a much tougher life than they did in routine mainline service; our boilers go through a complete stone cold to boiling hot to stone cold cycle on a regular basis - in the past, many engines would never really cool down until they had a boiler wash-out. In the case the BR, Eastern Region, the developed a system in the 1950s in which the boiler wasn't totally drained, and then hit with jets of really cold water, but cold water was added gradually, whilst the hot water was piped across to another engine which had already had a wash-out, so as to warm its boiler up over a number of hours, before a fire was even lit.

I'd be interested to know, if anyone here has the knowledge, how did boiler and stay life compare when engines were working maybe 18 or 20 hours a day, and 6 or 7 days a week, as compared to 8 or 9 hours, and (at times) only 1 or 2 days a week as some engines do in preservation?

 

I came across another reference to Monel metal stays, and a reason for their usage, on the Great Central's website, with regards to their Class 2 2-6-0, 46521:

"After restoration, the locomotive was steamed and entered service on the SVR in July, 1974 and provided service until being withdrawn on 24th August, 1984. The engine was overhauled and again entered service on the SVR in the Autumn of 1991, running until being withdrawn with wasted firebox roof stays on 18th December, 2000."

So the stays failed after nine years in service. Further on, the same page says:

" . . . the locomotive was originally fitted with Monel metal (a form of nickel steel) stays, as the material never seems to wear or corrode (as we saw above, it tends to be the copper around the stay that gives in first!). But Monel is a very expensive material and steel is a substitute frequently used for this application. However, steel does wear and corrode and we didn’t want to be doing the job again, especially bearing mind that all of the material around the stays had been renewed. So, we took the plunge and had new Monel metal stays fitted, although the material costs alone were almost £8,000!"
http://www.gcrailway.co.uk/the-railway/locomotives/46521-2/

So it appears that the main reason for using Monel may be that you won't have to stop an engine part-way through her 10 year boiler ticket, just because some stays have gone - though that is just my reading of it! But it does remind me of the way, if you have work done on the engine of a car which involves separating the engine from the gearbox, the mechanics will invariably strongly suggest that you have the clutch replaced, and won't add much to the overall bill. If you don't though, and you have to have the clutch replaced a bit later on because it's worn out, the cost of labour will dwarf the cost of the clutch, making for a very expensive job.

And how much would it cost to have replacement stays fitted, part way through a 10 year ticket, as compared to the cost of using more expensive stays to start with, but on which you could rely to go through ten years without problems?