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Retubing a boiler

billdadswell

Joined: 1-01-97

Topics: 4

Replies: 7

Posted: Tue 4th May 2010, 5:16pm
Retubing a boiler

I am at the advanced stage of retubing a steel boiler with steel tubes. I have replaced all the tubes and used a Wicksteed E7 tube expander which has been loaned to me. This has expanded the tubes in the firebox and smokebox tubeplates but the problem I now have is that they have not expanded the tubes enough although they are tight in the plates. The expander has reached the end of its travel. I require a method of expanding the tubes a little more and do not particularly want to just use a taper drift to seal them. The tubes are 3/4" OD and of 16 SWG. The expander was a fairly loose fit in the tubes to start with. I would appreciate any suggestions for expanding the tubes a few thou more.
 

Replies To This Post

mikehenderson

Joined: 1-01-92

Topics: 1

Replies: 3

Posted: Wed 5th May 2010, 6:30pm

This boils down to two questions/comments. First, how close a fit were the tubes in the holes? Contrary to frequent opinion, I've never found it necessary to ream the holes, though I've seen it said that there should only be a thou or so clearance. I use a drilled hole and that at the smokebox end is drilled at least 1/16" large to allow for future removal when the tubes are a bit scaled. Secondly, tube expanders are sized not just on the o.d. of the tube but also on the thickness. If your expander was a bit loose to start with, it was possibly intended for 3/4" od 12 swg. If half of the travel is used up getting the expander to touch the inside of the tube initially then it will run out of travel before acheiving a good expansion.

As I see it you have two choices: beg, borrow or buy (ugh!) a suitable larger expander or make one. This latter isn't as difficult as it might seem and is something I've done in the past. For the amount of use it's going to get, you can use mild steel for the body and unhardened silver steel for the rollers. By using a slightly larger diameter roller, you can use the same mandrel which in my experience is the hardest part to make. It may even be possible , if you only need a few thou extra, to use your existing body and mandrel and slightly oversize rollers.

There is a final workaround which you might wish to try. If you have some thin steel shim it is possible to wrap a few layers of this around the existing expander and then slip the assembly into the tube. The shim will only last for one or two tubes but is cheap and easily replaced. Someone will shout me down for even suggesting this but it is a trick I have used in the past, if only in desperation.

What I will also do is have a look tomorrow at work and see if I have a suitable expander that you could borrow. Can't be certain as most of mine are based around 1" or 1 1/4! tubes as those are what I mostly use now but I know I still have some smaller ones in the box. Murphy's Law dictates that there won't be the size you want, of course!

To add a little post script: I used to be works manager for a firm whose workload was about 50% boiler repairs so the suggestions above come from experience!! Both making an expander and the shim idea will work, though the latter does indeed smack of being a bodge ;-)
 

billdadswell

Joined: 1-01-97

Topics: 4

Replies: 7

Posted: Tue 18th May 2010, 7:36pm

Dear Mike,
Many thanks for your reply and sorry to be so long getting back to you. I have spent four days at Harrogate and two at the Woking track recently and not visited the website until today. I am hopeful that a member of my club, Chingford, has a suitable expander I can borrow (he says he has one)otherwise I will go down the route of making one or trying the shim idea which I quite like the sound of.
I got round the problem of getting the old tubes out by dlilling and tapping an oversize hole in the smokebox tubeplate where there was ample space and plenty of metal and then plugging it once all the tubes were removed which was very easy.
Thanks again for taking the time to reply, it is much appreciated.
 

Alan

Joined: 1-01-70

Topics: 0

Replies: 1

Posted: Mon 14th Jun 2010, 4:01pm

Hello Bill, We did speak about this at Woking but I forgot to mention that you could clock up the taper of the inner part of the tube expander,if you put it in the three jaw,then try some decent steel like E.N 24(T)and machine this one so the tube expander just fits in what you have already done.
 

jandrsupply

Joined: 1-01-70

Topics: 0

Replies: 1

Posted: Thu 17th Oct 2013, 10:33am

Boiler re-tubing is an important process for extending the life of any boiler. Any boiler can be easily re-tubed depending upon its design. Regular boiler re-tubing saves the tubes from deteriorating and ensures that the tubes will last for long. Various heat transfer equipment along with heat exchanges, pre-heaters, condensers can be re-tubed. Any one trained in the job can re-tube the boiler; however, if one does not know about it, then they can call a professional to handle the task. They not only stock all types of tubes, but also offer the services. Call a commercial boiler repair and installation company for assistance.
 

brianlee

Joined: 1-01-92

Topics: 1

Replies: 14

Posted: Tue 26th Nov 2013, 11:51am

Hello Bill
As a boiler inspector with 44 years experience, I would not retube a boiler with 16 SWG mild steel tubes as in my experience mild steel tubes of 16 SWG will only last between 5 and 10 years. What happens is it is the top row will fail first.
would strongly reccomend that you use Copper Tubes as these should last about thirty years . Also the thermal conductivity of copper is about 20 times better than Mild steel. if u are using mild steel tubes, you must be very careful to put water treatment in your boiler. The reason is that Oxygen in the feed water corrodes mild steel very quickly. I am presently writing an article for the News on this subject.
Brian Lee
 

nicholasglover

Joined: 1-01-95

Topics: 0

Replies: 1

Posted: Thu 28th Nov 2013, 7:02pm

From my experiences, NEVER put copper tubes in a steel boiler! Due to the electrolytic effect between the 2 metals, the steel will waste away very quickly and mainly around the crown of the fire box. I have seen inside "all steel boilers" and steel boilers with copper tubes, and the differences are very interesting...... The wasting around the firebox on a boiler with copper tubes can be literally paper thin. I personally wouldn't put any copper in a steel boiler. It is alot easier, and cheaper to replace a set of steel tubes, than have to have a new inner firebox, or worse a whole new boiler!
 

WembleyLion

Joined: 1-01-87

Topics: 2

Replies: 34

Posted: Thu 28th Nov 2013, 8:45pm

Brian

Are you making this suggestion to use copper tubes in a steel shell as a professional, time served, boiler inspector or as a model engineering club boiler inspector?

John
 

Cadellin

Joined: 1-01-70

Topics: 0

Replies: 2

Posted: Thu 28th Nov 2013, 10:09pm

I personally would also steer clear of copper tubes in a steel boiler. I would however, regardless of boiler material, use water treatment. It is not difficult to get the right dosage in your boiler, and the quick testing kit available from Heritage Steam Supplies makes ensuring the right dosage much easier.

What many don't realise is that all the treatment does is prevent the scale from sticking to the boiler plates/tubes, so is beneficial in copper and steel boilers, though the formulation is often slightly different, certainly it is from HSS where I obtain my treatment from. Regular washing out removes the scale and it is that process that does most of the preservation of the boiler.

There are instances where intensely used 7.25" locomotives have now done 15 seasons on the same set of boiler tubes (Mr. P at BHLR) through effective boiler management.

As for tubes I would simply replace like for like from the original build. If you are replacing the tubeplate and/or inner firebox then you can look into different tube materials/configurations etc etc on consultation with the boiler inspector.

Dom
 

stoneleigh

Joined: 1-01-70

Topics: 1

Replies: 31

Posted: Sat 30th Nov 2013, 12:27pm

I know that water quality varies from one area to another, & respect your replies as a result of that, but I once worked for the B.R.(Southern) Boiler Inspectorate & know water varies from one area to another. I had a loco. which ran at least 14 years on a set of steel tubes & possibly longer with Tannin water treatment. So with good treatment I would have thought it possible to get 20 years with steel if well treated. Having said that, I know of a couple of locos. with copper tubes in a steel boiler which have given no trouble to date, unless I quiz the owner next time I see him I cannot confirm how long he's run for.However he is a very experienced Model Engineer. In my B.R. days, locos. based at Three Bridges & Horsham M.P.D.'s would often require re-tubing earlier because of the acidity in the water supply that their locos. used. (Some of the trackside tanks apparently even had their own fish (gudgeon) swimming around I gather, so may not have been town water supply! (I would add that this is for interest an aside only, & has nothing to do with the above matter)!
In the end always treat your water & the tubes should last well, unless they are cheap steel from doubtful sources, mine were fully certified at source.
 

pauledmonds

Joined: 1-01-70

Topics: 1

Replies: 3

Posted: Sat 30th Nov 2013, 10:47pm

I managed to get 9 years out of my steel tubes before one let go. I used treatment but I suspect a greater factor could have been the periods that it was dry stored between steamings. I suspect that condensation would not have helped - therefore I now store the loco with a full boiler in the summer and drain and dry out to the best of my ability for any long period of inactivity to reduce the possibility of condensation.
The new tubes have been in 3 years now and so far they still look good - let hope I can get more than 9 years this time.
Paul
 

WembleyLion

Joined: 1-01-87

Topics: 2

Replies: 34

Posted: Sun 1st Dec 2013, 10:03am

Brian, re; Copper tubes in steel shells

Your suggestion to use copper tubes in a steel shell flies in the face of information given to me by a National Vulcan boiler inspector of a great many years standing.

Norwich based boiler inspector Reg Dines (now deceased) was a well known, in East Anglia, and well respected ‘Model Engineers Friend’ in that he would inspect the larger scale steel boilers that were then outside the interest of model engineering clubs.
In 1984 when I asked Reg to inspect my steel Sweet William boiler his first words were “Does it have copper tubes?” “No” I replied, “Good” he said “because if it has I won’t test it”.
His reason was that in certain areas of the UK the water contains chemical and/or mineral elements that are known to instigate premature failure of boilers due to the rapid corrosion of the steel shells of boilers manufactured from mixed metals and as he had no control or knowledge of the feed water to be used or of any boiler treatment that might be dosed during the period of a test certificate he could not estimate the safe life of the boiler and therefore his refusal to examine any boiler so built.

For many years the Gloucester boiler makers Franklin and Bell exhibited on their stand at model engineering exhibitions plates cut from a copper tubed steel shelled boiler; from a 4” scale traction engine, I think.
I found the tube plate the most interesting; the non water side looked perfectly ok but the water side looked akin to the cratered surface of the moon. The plate was originally ½” thick and such was the state of the corrosion that the only way I can describe it is that each tube hole had been chamfered at 45degs for about half the thickness of the remaining (less than 3/8” thick) plate and it had then left in salt water for a few years. If I remember correctly the boiler was less than 5 years old; a very expensive mistake!!!


When I tubed my Sweet William boiler I was recommended by the tube supplier (Willingales Tubes, Stowmarket, Suffolk) to use 12 gauge tubes and I had no problems with the expanders.

John.
 
 
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