Fitting a flue pipe

[ANarrowEscape]

Hi all

I had to dismantle the flue and collar due to corrosion. Anyway, replaced all the bits I needed to, including a new plate and collar on the roof. The question is, when fitting the flue back into the back of the fire, do I use a rubber sealant (heat proof of course) with the fire-rope, or use a heat cement? I believe the flue will probably will contract and expand - so is the sealant the best option? 

Thanks

 

[dor]

I’ve used a ring of rope to centre the flue, then ht silicone.

 No problems,just don’t let it get red hot.

[ANarrowEscape]

3 minutes ago, dor said:

I’ve used a ring of rope to centre the flue, then ht silicone.

 No problems,just don’t let it get red hot.

Okay ta.

What are you classing as red hot? I think the sealant has a rating of like 1000 degrees or something. It's a purpose one I think. I found some heat cement on the boat, so I'm assuming that's what the previous owners used - as it was a bit of a f#cker to get out.

[Tracy D'arth]

2 minutes ago, dor said:

I’ve used a ring of rope to centre the flue, then ht silicone.

 No problems,just don’t let it get red hot.

But, But, fireproof rope not mooring rope!   Flue 'n' Fire Seal 1500 degrees lasts better than ordinary silicone.    https://www.ebay.co.uk/itm/Silicate-Cement-Flue-Seal-Silicone-1500-C-Fire-Proof-Sealant-Stoves-Natural/193221588616?hash=item2cfce77688:g:u5MAAOSwPAld1~OA

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6 minutes ago, Tracy D'arth said:

But, But, fireproof rope not mooring rope!   Flue 'n' Fire Seal 1500 degrees lasts better than ordinary silicone.    https://www.ebay.co.uk/itm/Silicate-Cement-Flue-Seal-Silicone-1500-C-Fire-Proof-Sealant-Stoves-Natural/193221588616?hash=item2cfce77688:g:u5MAAOSwPAld1~OA

Yes lol, I've got fire-rope. Also got some of this left from another job so hoping I can use this. Looks similar, think it's only 1000 degrees, but damn, that's hot.

 

[bizzard]

In case the fluepipe becomes jambed solid in the collar and stove top plate. Expansion and contraction of metals is powerful. So, if this should happen the effect of the fluepipe expanding lengthwise might shove a bulge in the roof or push the stove and hearth down into the bilge, and when cooling and contracting might even leave the stove dangling in mid air by the fluepipe. My answer for this is ''Springs'', four engine valve springs with the stoves four feet mounted upon them. Engine valve springs are pretty tough and shouldn't cause the stove to wobble about much. As an alternative a car scissor jack could be placed under the stove and worked with its twiddle handle, but great vigilence and constant twiddling up or down will be needed as the stove and pipe heat up or cool down.  The springs will do this automatically but if fiddling and twiddling is your thing, then ''the scissor jack'' is for you and is jolly good practice if you get a puncture on your car, You might even become an F1 pit wheel changer.

[pete.i]

This is the stuff I used..................https://www.ebay.co.uk/itm/High-Temperature-Silicone-Sealant-Heat-Resistant-to-1200-C-Flues-Stoves-Glass/141192031302?hash=item20dfb36c46:g:SRsAAOSw2xRYbn3I

 

and stove door rope of the required thickness. I found that cement didn't last long.

[matty40s]

Use a ring of fire rope and cement on the stove top. 

Fire rope and heat resistant silicone in the roof collar.

[ANarrowEscape]

7 hours ago, pete.i said:

This is the stuff I used..................https://www.ebay.co.uk/itm/High-Temperature-Silicone-Sealant-Heat-Resistant-to-1200-C-Flues-Stoves-Glass/141192031302?hash=item20dfb36c46:g:SRsAAOSw2xRYbn3I

 

and stove door rope of the required thickness. I found that cement didn't last long.

Cheers, think I've got the right stuff, as bought the wrong sealant initially

7 hours ago, matty40s said:

Use a ring of fire rope and cement on the stove top. 

Fire rope and heat resistant silicone in the roof collar.

So cement over Silicon in the stove. Does it not crack?

[matty40s]

I wouldnt use silicon on the stove top at all.

I install flues with a ring of fire rope for the flue to sit on, get some cement round the inside of the collar, insert flue then force cement in and down with a flat blade screwdriver of palette  knife.

The expansion zone using rope, packing and silicone is in the roof collar.

[ANarrowEscape]

15 hours ago, matty40s said:

I wouldnt use silicon on the stove top at all.

I install flues with a ring of fire rope for the flue to sit on, get some cement round the inside of the collar, insert flue then force cement in and down with a flat blade screwdriver of palette  knife.

The expansion zone using rope, packing and silicone is in the roof collar.

Would it matter if the flue is at the rear rather than the top, as someone else advised me to use sealant as they had used cement and it cracked. Although, when I took the flue out to have the hearth done, I remember it was cement in the back. 

[Tony Brooks]

Cement will eventually crack. Unless the stove gets red hot the silicon will last better in my view. Almost indefinitely if the stove does not overheat. Its personal preference as far as i am concerned.

[ditchcrawler]

Didn't  Biz try different silicones on a stove to see how they  

[matty40s]

20 minutes ago, ditchcrawler said:

Didn't  Biz try different silicones on a stove to see how they  

..taste 

[ditchcrawler]

10 minutes ago, matty40s said:

..taste 

probably

 

[blackrose]

On 28/12/2020 at 16:44, matty40s said:

I wouldnt use silicon on the stove top at all.

I install flues with a ring of fire rope for the flue to sit on, get some cement round the inside of the collar, insert flue then force cement in and down with a flat blade screwdriver of palette  knife.

The expansion zone using rope, packing and silicone is in the roof collar.

 

Depends which silicone we're talking about. I certainly wouldn't use plumba-flue type silicone as it only goes up to about 300C, but Envirograf goes up to 1200C and can be used on stove tops. Much better than fire cement. I stopped using that years ago. Any heat resistant silicone stating 1000C should be fine.

 

https://envirograf.com/product/silicone-sealant/

 

Edited December 29, 2020 by blackrose

[ditchcrawler]

3 minutes ago, blackrose said:

 

Depends which silicone we're talking about. I certainly wouldn't use plumba-flue type silicone as it only goes up to about 300C, but Envirograf goes up to 1200C and can be used on stove tops. Any heat resistant silicone stating 1000C should be fine.

 

[blackrose]

Well I'm not sure bizzards tests were conducted in accordance with any testing standards whatsoever? We don't even know which high temp silicone he was testing?

 

I've seen plumba-flue which was adversely affected by heat, but not Envirograf. 

 

From the Envirograf spec sheet:

 

PERFORMANCE
This product was used in a number of fire resistance tests employing the general procedures and criteria or BS476: Part 22: 1987. It was used for sealing around a number of penetrations and expansion joints. Integrity ratings of up to 240 minutes were achieved.

 

In the early days I made the mistake of using plumba-flue on top of fire cement on the stove to flue deal to try to stop it cracking. It worked for one winter but then the plumba-flue failed and the cement cracked even though the stove never got to 300C. By way of contrast I've had Envirograf on the same joint (no cement) for well over 10 years now and it's never failed. That test is good enough for me. 

 

I guess everyone is free to use whatever materials they want on their own boat, but I can't help thinking it's a bit silly to potentially risk your life by not using the correct materials just to save a few quid. I'd hate to think of someone following the advice on the thread posted above and using ordinary silicone on their stove! Would you use a potentially inferior fire resistant board that hadn't been properly tested behind your stove because it was a bit cheaper and someone on this forum said it was ok? I wouldn't, but carry on by all means.

Edited December 29, 2020 by blackrose

[system 4-50]

On 27/12/2020 at 20:59, bizzard said:

contracting might even leave the stove dangling in mid air by the fluepipe.

this happened to my stove.

[Tony Brooks]

10 hours ago, blackrose said:

In the early days I made the mistake of using plumba-flue on top of fire cement on the stove to flue deal to try to stop it cracking. It worked for one winter but then the plumba-flue failed and the cement cracked even though the stove never got to 300C. By way of contrast I've had Envirograf on the same joint (no cement) for well over 10 years now and it's never failed. That test is good enough for me. 

 

 

I don't understand why the Plumba-flue and cement are referred to together unless it was one at the top and the other at the bottom of the flue. If they were both used together in a joint how can one be sure the filed cement did not cause a very thin bead of silicon to fail?

[blackrose]

On 30/12/2020 at 07:49, Tony Brooks said:

I don't understand why the Plumba-flue and cement are referred to together unless it was one at the top and the other at the bottom of the flue. If they were both used together in a joint how can one be sure the filed cement did not cause a very thin bead of silicon to fail?

The reason they are referred to together is because it was plumba flue on top of the cement - an experiment to see if the silicone would prevent the cement from cracking. 

 

I'm not sure how the cement would cause the silicone to fail - it's meant to be flexible isn't it? Also what makes you assume it was a very thin bead? It was reasonably thick bead as I remember as it was stuck to the rim of the collar on one side and the bottom of the flue on the other. The silicone did prevent the cement cracking on the surface for a while but I can assure you it failed independently of the cement. It's not the right stuff to be anywhere near the stove top. There are better high temperature silicone products on the market, but if you want to save a couple of quid and use Plumba flue or even bathroom silicone on your own boat for that you're perfectly free of course.

Edited December 31, 2020 by blackrose

[Tony Brooks]

28 minutes ago, blackrose said:

The reason they are referred to together is because it was plumba flue on top of the cement - an experiment to see if the silicone would prevent the cement from cracking. 

 

I'm not sure how the cement would cause the silicone to fail - it's meant to be flexible isn't it? Also what makes you assume it was a very thin bead? It was reasonably thick bead as I remember as it was stuck to the rim of the collar on one side and the bottom of the flue on the other. The silicone did prevent the cement cracking on the surface for a while but I can assure you it failed independently of the cement. It's not the right stuff to be anywhere near the stove top. There are better high temperature silicone products on the market, but if you want to save a couple of quid and use Plumba flue or even bathroom silicone on your own boat for that you're perfectly free of course.

Perfectly valid experiment but I just gave a reason why the silicon might have failed (if it was a very thin bead). I can't understand why the Plumba flue I used on my stove lasted years and when the small internal fixing screws that secure the collar to the top of the stove rusted through I had a hell of a job to dig out all the silicon. Maybe I did not run ,my stove as hard as you do.

[Tracy D'arth]

On 27/12/2020 at 20:59, bizzard said:

In case the fluepipe becomes jambed solid in the collar and stove top plate. Expansion and contraction of metals is powerful. So, if this should happen the effect of the fluepipe expanding lengthwise might shove a bulge in the roof or push the stove and hearth down into the bilge, and when cooling and contracting might even leave the stove dangling in mid air by the fluepipe. My answer for this is ''Springs'', four engine valve springs with the stoves four feet mounted upon them. Engine valve springs are pretty tough and shouldn't cause the stove to wobble about much. As an alternative a car scissor jack could be placed under the stove and worked with its twiddle handle, but great vigilence and constant twiddling up or down will be needed as the stove and pipe heat up or cool down.  The springs will do this automatically but if fiddling and twiddling is your thing, then ''the scissor jack'' is for you and is jolly good practice if you get a puncture on your car, You might even become an F1 pit wheel changer.

But.....But......  the stove has to be secured against movement for BSC

[matty40s]

3 minutes ago, Tracy D'arth said:

But.....But......  the stove has to be secured against movement for BSC

That's what mooring pins and piling hooks are for, make sure the lines are tight when the examiner comes and the stove wont move anywhere.?

[Alan de Enfield]

As long as you use an Audi jack it should be OK (and you get the best of both options), after all it is four-sprung-pork-technic