Cracked collar on top of the stove

[Keeping Up]

The ring on the top of my Little Wenlock stove, were the flue exits, has cracked and will have to be replaced. Luckily replacements are easily available. It sits there now with about a 0.5mm gap showing; my question is, why do they crack?

 

The flue is about 3/4 inch smaller than the collar and the gap between them is sealed with a packing of flexible fireproof rope, with a thing filler of fire cement on top (it was professionally fitted). Is there anything I should do differently, or watch out for, when refitting it so that it won't crack again?

[Yoda]

Differential expansion.

 

However the chances are that it was already cracked and has now opened up.

 

How is the engine?

[Keeping Up]

Differential expansion.

 

However the chances are that it was already cracked and has now opened up.

 

How is the engine?

I guessed differential expansion, but they all have this and they don't all crack, so what should I do to make sure the next one doesn't crack? It definitely wasn't cracked when it was fitted (18 months ago) and was still OK all through last winter; the previous one (on our old stove) lasted 15 years without cracking.

 

The engine runs beautifully but still leaks oil and is awaiting repair.

[casper ghost]

The collar on my Little Cottager has also cracked.. I've bought what looks like a large jubilee clip, which is a steel ring over an inch wide and 3 or 4mm thick. It has bolts which allow it to be tightened up. I've put it around the collar and that has stopped the collar from breaking. Been ok for about a year now. These clips only cost just over a pound..

[Yoda]

If when hot, some cold liquids were spilt on the collar, that would cause the situation. A cold pot might as well, or as I wrote before, a very small crack when fitted.

 

Did you check all of the breathers on the engine as I requested to see if it stopped leaking? Crankcase pressure is a critical element in this sort of problem.

[Keeping Up]

The collar on my Little Cottager has also cracked.. I've bought what looks like a large jubilee clip, which is a steel ring over an inch wide and 3 or 4mm thick. It has bolts which allow it to be tightened up. I've put it around the collar and that has stopped the collar from breaking. Been ok for about a year now. These clips only cost just over a pound..

That sounds like a great solution, where did you get the clip from?

 

If when hot, some cold liquids were spilt on the collar, that would cause the situation. A cold pot might as well, or as I wrote before, a very small crack when fitted.

 

Did you check all of the breathers on the engine as I requested to see if it stopped leaking? Crankcase pressure is a critical element in this sort of problem.

I suppose it's possible that the collar was cracked part-way through from the inside; there's no way of telling.

 

On the engine I took out the dipstick as suggested and put my finger over the hole while revving the engine, I couldn't detect any pressure

[DHutch]

In the past when the colar on our flu pipe join cracked i put it down to water in the rope freezing, but its not cold enough for that.

- Get a new one and get it all stuck down with some nice flexible high temp silicon! Seams to work very well for use certainly, five years in now i think and still flexable even at the stove-flu joint.

 

 

 

Daniel

[Yoda]

That sounds like a great solution, where did you get the clip from?

 

 

I suppose it's possible that the collar was cracked part-way through from the inside; there's no way of telling.

 

On the engine I took out the dipstick as suggested and put my finger over the hole while revving the engine, I couldn't detect any pressure

 

Your a clown Jones! Your finger will take 8 psi, the seal will blow at one or two. Do as I asked, all of the checks. You know, it might save you money!

[casper ghost]

That sounds like a great solution, where did you get the clip from?

 

There is a place in Whitchurch in Shropshire where they do them, also Telford Farm Machinery on their web site they are listed as hose clips. They are very strong. I'm sure most agricultural places will do them, like Countrywide etc.

[dor]

One thing that causes the tops of stoves to crack is if the flue pipe isn't floating. If it is sitting on the top of the stove and too tight or fixed rigidly in the roof collar it will put a huge force on the top of the stove when it expands. The top of the flue should be held in the collar with flexible HT silicone. The bottom of the flue shoud then have a few mm clearance all round and below it; i.e. it should be effectively swinging. Then fill the gap between the flue and collar with more HT silicone, e.g. Delta.

Edited September 16, 2009 by dor

[Keeping Up]

Your a clown Jones! Your finger will take 8 psi, the seal will blow at one or two. Do as I asked, all of the checks. You know, it might save you money!

Yes I could take several PSI on the finger, but could surely detect one or two. You said "First thing to do is check that all of the breathers are clear therefore not pressurising the crankcase. Take the engine dipstick out and if oil pours our when running then that is an indicator of pressurisation". I checked the breather, it's clear, then removed the dipstick and no oil comes out of it. I then put my finger over it and could detect no trace of pressure.

 

Thanks to the others for the replies about the collar. It could indeed be that the pipe isn't sufficiently clear of the collar when cold; it's fixed with rope and fireclay at the top too, maybe it's too rigid. If I change the collar rather than adding an external clip, the flue would need to be taken out and re-fixed so I'll look into that aspect when I do.

 

Edited for speeling misteaks

Edited September 16, 2009 by Keeping Up

[LEO]

Hi,

 

Perhaps a possible reason for the collar cracking could be that the fire (assuming it is cast iron) is not being warmed up slowly enough. The helpful guidelines issued by UBC suggest that 'warming up cast iron stoves slowly each time it is lit, with a small fire prolongs the stoves's life'.

 

Leo

[WotEver]

There is a place in Whitchurch in Shropshire where they do them, also Telford Farm Machinery on their web site they are listed as hose clips. They are very strong. I'm sure most agricultural places will do them, like Countrywide etc.

 

Link: http://www.tfmsuperstore.co.uk/product.las...-(162/174)+4252

 

T.