Weeping tubes in smokebox

[houstonceng]

A friend's 3 inch Burrell traction engine - copper boiler - has developed leaks around two of the tubes (tube to tube plate joint) in the smokebox.

It's a very small weep at 30psi hydraulic test, but has caused no problems under steam. Of course, it will fail a full boiler test at 135psi hydraulic (1.5 we) so must be repaired or scrapped.

Various people have suggested expanding the tubes. One suggested using a tapered plug and a hammer, another a proper tube expander as used to expand tubes in steel boilers. I can see problems with this as the tube plate in a copper silver soldered boiler isn't usually thick enough for expanded tubes and he may have a problem with the tihe silver solder that would resist the expander.

Another suggestion was to use loctite and draw that into the gap using a small vacuum (circa 10psi) in the boiler.

I thought about caulking with Comsol

The owner was thinking of re-silver soldering, however , a few of us think this could cause more problems than it sorts.

The traction engine will have to be dismantled and the tubeplate cleaned. At the least, the smokebox may have to be removed, but for any hot process, the strip-down would need to be to a clear boiler.

Does anyone have any other suggestions or experience of any of the suggested methods above ?

[Deleted]

Hi Andy,

We had a similar problem with the tubes in my brother's 5" gauge Forney. That's a steel boiler with copper tubes. Unfortunately, the original builder had brazed or silver soldered the tubes in and some of the joints on the front tubeplate had cracked. We did the Loctite trick which held for about three years but the tubes have started to leak again. We didn't use any vacuum though so the Loctite (270) probably didn't seep into the cracks very far. My brother did try expanding the offending tubes without success - in fact it made it worse!

Not sure how we will tackle the problem this time. If we could get the tubeplate clean enough I'd be tempted to use Comsol this time. If all else fails it will be the Loctite again.

John

[jma1009]

i think that the 'correct' way would first be to show your club boiler inspector the leaks so that he can ascertain if they are 'pin hole leaks'. the boiler ought to be dismantled from the smokebox for this job and cleaned up.

if the leaks are pinhole leaks and if your boiler inspector approves the proposed method of curing same then i would be inclined to add clean diluted but still strong sulphuric acid to inside of the boiler (after cleaning same as thoroughly as possible) with smokebox downwards, then add some air under pressure after say 30 mins so that the strong dilute acid squirts out through the pinholes cleaning same. then repeat with hot soapy water.

if the tubes are in the middle i would heat up and run silver solder easyflo 2 on same so long as no other part of the tubeplate or boiler has had high melting point soft solder applied previously. otherwise caulk with 'comsol' generously. if comsol or equivalent has already been used on the smokebox tubeplate ive heard of loctite and ordinary araldite being used - though whether in this day and age your boiler inspector would agree with such methods is another matter. a bit of judicious scraping around all the joints wont go amiss.

as im sure you are well aware a silver soldered joint if well done will last indefinitely assuming phosphorous containing cheap silver solder hasnt been used. such problems your friend has however arent unknown. ive known leaking smokebox tubes repaired and caulked with ordinary araldite last for a further 40 years on a 90 psi copper loco boiler. in fact i remember a fullsize traction engine having soft solder of the cored resin type applied around the cylinder/boiler joint!

cheers,
julian

[ettingtonliam]

Dare I even suggest Radweld? It might work, and has the advantage over the other methods of not requiring the engine to be stripped down.

Richard

[pondok]

I've used sodium silicate on a previous boiler, but as it's so effective in sealing holes, all fittings have to be removed. It's also called water glass, easily found off ebay. In neat form, it's quite viscous and will block larger leaks, but suitably diluted is perfect for capillary weeps. Can be used either as mentioned above for loktite, with some vacuum in the boiler drawing it into the leak, or just pour it in to cover the area, pressurise the boiler to push it through the pinhole, then empty the boiler, play a flame over the area to help dry it, wash the boiler out thoroughly and leave overnight. 6 years later it was still completely sealed under 125psi hydraulic.

[ejparrott]

Sodium Silicate comes in a CO2 hardening form for making foundry cores too. I don't know how much difference there is between that and liquid glass, or whether it might be better suited.

[waggy]

Afternoon houstonceng,

Radweld has been mentioned and would work BUT, the solution is designed to remain in the system. I've no idea how it would react in a boiler, the constant evaporation / replenishment of the water would no doubt thicken the solution which may cause damage to cylinders, injectors and the like? Best not used methinks?

A very useful expander can be easily made up using small taper pins positioned around a larger taper and held in place with an elastic band or O ring. All the thin ends point in the same direction, the thin end of the whole thing sitting in the tube concerned, the fat end needs to be a larger diameter than the tube internal. Some form of drive to turn the centre taper and firm pressure applied to push the nest of pins into the tube whilst turning it and you'll expand the tube. Removal dead easy, just turn and pull. Use as many small diameter pins as possible, the more pins the less chance of distorting the tube and making things worse. Not a sure fire fix but they do work.

Good luck,

Waggy.

[robmort]

Radweld is mainly sodium silicate (water glass) with some additive (e.g. clay, ground walnut shells, copper dust...) and does not have to be left in the system (for car radiators it is just easier to do so), so it can be removed from the boiler after it's done its job.
But sodium silicate solution is just as easy to use and obtain.

Rob

[Midland]

May 20, 2014 9:55:22 GMT John Baguley said:

Hi Andy,

We had a similar problem with the tubes in my brother's 5" gauge Forney. That's a steel boiler with copper tubes. Unfortunately, the original builder had brazed or silver soldered the tubes in and some of the joints on the front tubeplate had cracked. We did the Loctite trick which held for about three years but the tubes have started to leak again. We didn't use any vacuum though so the Loctite (270) probably didn't seep into the cracks very far. My brother did try expanding the offending tubes without success - in fact it made it worse!

Not sure how we will tackle the problem this time. If we could get the tubeplate clean enough I'd be tempted to use Comsol this time. If all else fails it will be the Loctite again.

John

Hi All

This is an old thread but it has taught me a little. I have a leaky tube in the firebox and went to loctite for their opinion and they thought 648 might be enough to seal it and resist the heat. So I have cleaned the tube end back to bare metal, wire brushed in a dremel and then cleaned it with the Loctite cleaner, attached the vacuum and applied the 648. It seemed to disappear so either I am a hero or a bloody fool! Will fess up tomorrow. The Comsol route just seems to messy and risky so I run this weekend or buy a new boiler. Thanks John, your post imspired me to try.

Cheers David

PS Ed, in case you are there, the Aspinal gets put back again although I nowr have a holder to do the last operation. Determined to do it this year.

[ejparrott]

I'm here....poor old Aspinal !

[Deleted]

Hi David,

We finished up using Loctite again on the leaking tubes and it's fine again at the moment. Dry as a bone. It's very difficult to do anything else really as the smokebox is part of the boiler barrel so the tubeplate is deeply recessed and very hard to get at. Strangely, the firebox ends of the tubes have never given any trouble.

John

[Midland]

Hi All

UPDATE

Holding at 90 psi on the tender hand pump. the job was easy. The longest task was to make a fitting to connect my safety valve bush to the vacuum cleaner. Then wire brushed the area with my dremel, turn on the sucker and apply the 648. Full report Sunday but if it works I have 45 ml of the stuff to share with those leaking tubes!!!

Cheers David

[nonort]

if a tube leaks it must have a hole from the inside of the boiler (pressure side) to the atomosphere side (oustside). Personally I would need reasurance that the joint had enough penetration of the silver soldered joint to be sound before attempting any repair. The integrety of the boiler must be of the utmost concern. Hence the requirement in the green book to inspect the boiler during construction. Most places in a boiler can be seen via wet header and dome holes using an endoscope or fibre optic camera.

[Midland]

Hi All

Tested my Loctite repaired boiler this morning. It held 200 psi as it did 20 years ago!! Just saved a couple of £thous.

Happy bunny now

David