Congratulations!

You are the second in as many weeks to pose the same enquiry!

So summarising the basic advice given on that:

1) First things first… Never try to operate a dry regulator, except perhaps once very carefully to see if it does move. If it doesn’t, don’t force it. This is because if it stuck on scale, moving it could score the valve face.

2) The bush and its seal in the backhead could be seized, especially from long storage. So investigate that simply by removing the gland nut. The gland might be an O-ring, graphited yarn or something a bit more “sophisticated”. It is worth renewing anyway.

3) Remove the inner dome and examine the regulator itself, which I think on this locomotive is a disc rotating on a circular face to bring drilled ports in line. If it is scaled up, use ordinary domestic scale-remover – the sort applied with a cloth of brush. Wash it off with soft water – living in a hard-water area I have just used rain-water similarly in overhauling the fittings on a 7-1/4″ gauge version of the same engine.

Yours looks as if it has operated with similarly hard water, which is why I suspect scale as well as probably solidified gland packing.

That should cure it!

While the inner dome is off see if the boiler could do with descaling. Even if not, it is well worth giving it a good washing out.

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Now for that main bush in the backhead.

It should be held by studs and nuts, not screws – especially slotted ones!. Same with the inner dome) If you remove the flange there may be enough of the broken ones protruding to grip them with pliers and very gently ease them out.

I would help them by supporting the boiler standing on its nose, and leaving it overnight with ‘Plus-Gas’ or similar penetrating fluid on them. Not WD-40 unless you really have nothing better. It will work but not so effectively.

If not, I would suggest making a dummy version of the flange in mild-steel with the holes for the broken screws drilled tapping-size or smaller only, to be screwed on to guide drilling the broken bits out. Be very careful not to break through into the boiler… though that have already been done. Clean the threads with the appropriate bottoming tap.

Only three or four complete turns of a fastenings actually do anything but more would be better if the thread is not in best condition.

Make a set of studs from stainless-steel, but do not use stainless-steel of the same grade for the nuts as they might gall. I would use both stainless studs and bronze nuts (or brass nuts, as these are outside the boiler). You could use plated mild-steel nuts, but smear some copper-based anti-seize grease on the threads.

Little I can add to Nigels answer ! I would take the dome off so you can see whats going on. The last time this was asked it was a tight packing gland on the regulator rod. As for the use of hex heads/nuts this is OK IF there is room round the hole to get a ring spanner in ? Stainless 316 for  studs and bronze or brass nuts. Good luck. Noel

A careful study of Nicks drawing will give you an idea as to how to dismantle, it doesn’t look easy, the more so with the passage of time, build up of scale Etc. The dome should come off with gentle persuasion, but the regulator will I fancy need the steam pipe removing so that the regulator can be unscrewed from the various 40 tpi threads. The steam pipe to the wet header and may be even the wet header it’s self will have to unscrewed. Not an easy job. Good luck. Noel.

Oh Dear- poor Juliet seems to have had a rather hard life before you rescued her!

Whoever made that boiler seems to have struggled to do so, too, as there is nearly as much silver-solder lost over the surface as there should be in the joints. Some shows signs of over-long heating, too. However, all that wasted solder is not a structural or functional fault – just an expensive mess. More worrying to me is the battered state of the regulator-rod gland and the valve near it; and I hope it’s only an optical illusion that makes the end of the rod look bent. Errr, why is the metal around the fire-hole and the stay-head grey?

Anyway, back to the immediate question……

It does seem built-up scale is the fault so I’ll assume so……

Thank you Nick for posting the drawing.

My caution would be, dismantle only as necessary but since we’ve now established the backhead gland is no longer a problem apart from the broken screws, the dome will need removing as you’ve started.

Use descaler first to remove as much external crud as you can, including around those dome studs. Some of more greenish stuff on the whole thing might actually be residual silver-soldering flux, or copper salts from it having remained on there.

You don’t want oil inside the boiler if you can help it, but the dome flange might need some help with penetrating-oil. Before trying that though, try more descaler. Citric acid solution or proprietary kettle descaler is effective without risking it lunching on the metal too much.

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If really necessary, and this is not something I would try lightly for the obvious reason we’ve already seen, you could try removing the dome studs, aiming for just alternate ones first. Mark the dome and bush flanges for re-assembly orientation, if not already marked, as we can’t guarantee it has sufficient angular accuracy for easy fitting.

To remove and refit these studs, use a proper stud-box or the locked-nuts method, and again, let them slumber in penetrating-oil first.

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Now, once the regulator is exposed, and probably seen as coated in scale, use the descaler again to clean it as well as possible before trying to move or dismantle anything.

Examining Nick’s drawing, the steam circuit looks very frail as designed. It’s unlikely anyone now would screw that header mounting straight into the tube-plate, or the backhead flange into the backhead, as the drawing specifies, although your example looks as if it does have a separate mounting silver-soldered in place.

So I’d be wary of trying to dismantle that wet header. We don’t want any washing-out water in the cylinders, but the boiler is off the locomotive anyway, so push some hose onto the superheater outlet to drain into a suitable receptacle.

Now refit the backhead gland, at least for the time being, enough to support gently trying to operate the regulator as the valve frees off.

This done, feed some descaler solution down that vertical inlet, and let it work. Tip it out – it won’t hurt ending up inside the boiler – give it another dose. Using hot water will speed the reaction somewhat, but give it plenty of time.

Empty that, rinse with distilled / fridge-defrosting / filtered rain – water. Carefully try operating the valve. Of course, if that was already open, the descaler solution will be in the superheater or drain – but if this locomotive suffered much priming, the superheater will likely be partly scaled-up too. Raise the end of the tube to keep the descaler in place.

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So the whole approach then is to try to cure the problem without taking too much apart, and especially if at all possible, without disturbing those very fragile pipework threads. Let’s hope we don’t need get that far!

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While at it, remove and descale the external fittings, and when replacing them, use copper shim washers for orientation and sealing. The latter may be helped by a thin smear of non-hardening jointing compound on the thread, but don’t use PTFE tape. That can shed slivers capable of blocking gauge-frame water-ways, or preventing clack-valves closing properly.

Interesting….

I half expected the boiler’s innards to be scaled up but from what little is visible, perhaps it is not as bad as I’d feared. (I do live in a hard-water area and have seen what that can do to a miniature boiler.)

There seems a trace of scale around the inlet, and it would not take much to jam the regulator

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Yes – It looks as the outer disc on the backhead is a separate item from the brazed-in bush, so should come off. There is a vague hint someone has removed it at some time in the past – it looks like a little scar adjacent to the hole at about “one o’clock” as if from a screwdriver used as a makeshift wedge or crowbar.

I wonder what those peculiar bruises are from.

May we have a photo or two of the front end so we know what we might encounter if further dismantling is necessary?

The blower-valve outlet seems to have suffered a bit of a knock. I noticed that on the first photo. It might not matter too much as long as the union nut still screws on, and the coned area is not distorted.

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Clive – How might the two broken studs stop the regulator from rotating? They hold two static parts together, and the metal still in the holes was there all along.

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BTW does the locomotive look in fair fettle generally? It will be good to see her back in service!

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I gave my own “Big Sister” of Juliet a preliminary hydraulic test (not the certification test – I can’t certificate my own engine!) today, aiming for working-pressure only. I have no worries about its boiler structurally – built in 2000 by Reg Chambers to replace the worn-out, original steel one, it is not even very old in operating-hours. The engine has not run since 2011, but has slumbered in proper storage conditions.

A lot of small but annoying leaks on fittings, including one or two that will be very hard to correct, and together ensuring it would not hold pressure especially above 40psi.  I suspect the major loss is back through either of the two pumps… and an axle-driven pump on a hefty 7-1/4″ g. loco with inside valve-gear, is not designed for easy servicing!  I think this ‘un is going to have two injectors, but keeping its hand-pump.

So that’s three new clack-valves on the shopping-list for “The Fosse”….

As the drawing shows and as suggested I think by others including Clive the reason the regulator gland and flange will not separate from the bush in the boiler is the flange is screwed onto the tube that contains the regulator rod which in turn is screwed into the regulator body and then the steam tube that takes the output from the regulator is screwed into the regulator body and in turn screwed into the header – follow on the drawing.  If there were no broken studs preventing the gland flange rotating then there is a chance if you screwed out the steam collector pipe (the slot in the top is to enable it to be screwed in / out) and all the other threads are securely locked then the complete regulator could be unscrewed from the header at the smokebox tube plate and withdrawn through the back head – but the broken studs prevent that.  So…..the only really viable alternative is to unscrew the header from the tube plate and steam pipe – which will then allow the complete regulator to be withdrawn from the back head bush without needing to rotate it. Reassembly will however be something of a nightmare to pick up both the thread in the tube plate and the thread on the steam pipe and have everything else in the correct positions.  I am sure it can be done but it will be a real pain to do it.

I have had stuck regulators on a couple of engines and I just lit a fire and steamed them up, the heat was sufficient to get them moving.  I would add this was on known and previously tested boilers before anyone throws their hands up in horror and was not done in a public place!

Paul.

On 13 October 2024 at 23:05 Nigel Graham 2 Said:

Clive – How might the two broken studs stop the regulator from rotating? They hold two static parts together, and the metal still in the holes was there all along.

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More fully explained by Paul Kemp above. According to the drawing the studs were screwed in place after the regulator was assembled, (screwed ),into the boiler.

As shown in the drawing, LBSC screwed the studs directly into the copper of the backhead. My take is that, as built, the boiler has a bronze bush to take these studs, which is better practice. Unless there are other differences though, the problem remains the same. Difficult to be sure from just the pictures.

Hi, at least one busted screw, which will stop the regulator being unscrewed, is shown by the red arrow below.

Regards Nick.