Frightening incident with a woodburner

[val douest]

I'm posting this partly to ask for advice and also in case it helps anyone else avoid a similar potentially very dangerous incident.

About four years ago we had a 10 Kw Godin woodburning stove professionally installed (by the local Godin specialist) in our small guest cottage.  It has worked very well, looks attractive and heats the cottage from cold in no time at all though as we have few visitors in the colder months it it not used very often.

Last night my daughter and son in law were getting ready for bed when the horizontal pipe connecting the stove to the interior vertical pipe suddenly became detached and fell towards the floor.  My son in law managed to push it away from the carpet with his shoe and my daughter ran to fetch my husband.  On examination (difficult because everything was very hot) it transpired that the two bolts which hold the cast iron exit flange to the main body of the stove had corroded and sheared off inside; this left this flange and the flue pipe to which it was attached free to fall on the floor.The bolts were standard, not stainless, but as everything came boxed from Godin ready to install they were presumably the ones intended for the job.

The bolts have been replaced and the stove is in use again - but if the pipe had come apart in the night, the gases escaping from the stove could have been lethal.  Both my son in law and my daughter are partially deaf (my son in law has hearing aids which are removed at night) so it is quite possible that the noise of the pipe falling would not have woken them.  

So - two things: first I guess it pays to check regularly that the exit pipe assembly on any woodburner is firmly bolted and secure.  And secondly, a question: would a standard CO detector detect the escape of gases from a woodburner?  If so, if it had a loud enough alarm it would probably wake even those with poor hearing - and the sound would also carry to us in the house next door. Any advice on monitoring/detection very welcome.

Thanks,

Val

[AnOther]

Sorry to hear of your incident and I'm sure we appreciate the warning but a couple of points come to mind.

I have what could possibly be the same woodburner, (Godin 3271 ?),

or at least the same manifold arrangement, so I know the screws you refer to and mine is assembled with

them, along with fire cement of course. Godin have been making this

model and style, and other stoves, for a very long time and I am

reluctant to accept your conclusion that the bolts simply corroded

through. From the fact that the whole flue fell to the floor when it

became detached I suspect that it may not have been installed with

proper or adequate support further up, usually there would be some sort

of bracket clamped around it and fixed in the roof space. A lack of

this support could have placed significant stress on the screws as

effectively they would now be supporting the weight of the entire

flue, something which they are clearly not designed to do and it is this which resulted in their failure..

If you wanted to fit a smoke detector then a CO (Carbon Monoxide) is what you want but it must be said that if you are burning properly seasoned dry logs then the potential emissions should be minimal and unlikely to be a serious health hazard. Frankly I think a far better and safer strategy is to not allow the fire to be burning overnight.

[powerdesal]

I must admit that I read the post as meaning that only the horizontal section fell away. ie the vertical pipe remained in place having separated at the male/female spigot joint on the bend.

I cant get my head round the thought of a carpet at the back of the stove as the inference is that the stove has a horizontal rear flue exit which then bends through 90 deg to a vertical stove pipe after a horizontal run.

I would have thought that the bend should have been immediately after the stove exit, rather than with a horizontal transition piece. Possibly the stove was designed as my thoughts and the horizontal section has imposed a bending moment on the flange bolts that they were not designed for.

[AnOther]

Mine has a 'T' at the back, a bit like this but black stove enamelled and with a removable bottom for cleaning, and it is just pushed onto the cast iron tapered outlet from the burner which is the bit which fell off val's. The fact that she said "this flange and the flue pipe to which it was attached free to fall on the floor" sounded to me like the whole shebang fell down in which case a meter or 2 of flue could easily have fallen on a nearby carpet. If it was just the 'T' piece it itself could have not been properly cemented into the vertical flue sections because just the weight of the flange and 'T' piece would not be sufficient to separate them.

[img]http://www.bricodepot.fr/charleville/files/files_maps/v1_pm/v1_pm_visuel/main/49408.jpg[/img]

[powerdesal]

Thats the sort of fitting I envisaged, but she mentioned a horizontal section which made me think that a straight section of flue pipe was between the outlet flange and the tee piece (or 90 bend ). Its very unusual for a bolted cast iron flange connection to fail on the bolts due to corrosion unless there are unusual stresses or extreme old age, by which time the whole issue would be looking very sad anyway, and probably totally corroded together.

4 years old is not a long time for cast iron

[val douest]

Many thanks for your helpful comments; here are some more details:

Our tee-piece is very similar to the one described by ErnieY, in our case blue and stove enamelled like his with a similar detachable plate at the bottom, and pushed onto the circular cast iron flange; the stove is a Godin 3721, and the manifold at the back is secured to the stove with four countersunk screws and some sealing cement. That part of the assembly is fine; it is the circular cast iron flange bolted to the manifold that fell off. There is no horizontal section between the cast iron flange and the tee-piece. In our case the vertical, stove enamelled pipe, connected directly to the tee-piece, did not have any further support, relying on the tee-piece remaining in position. So, in our case, if the two bolts securing the circular cast iron flange failed, then the flange, tee-piece, and about 1.6 metres of stove enamelled pipe, could (and did) fall down. Above the 1.6 metres, the flue changes to insulated pipe, and this is supported separately. There was no carpet at the back of the stove; that was to the side of the plinth.

I removed what remained of the bolts, which had clearly fractured; there were two, about 4mm diameter, and accessible only when the tee-piece has been removed. Normally they would have been adequate to support the whole assembly. Perhaps, as a result of this stove being used only occasionally during the winter, condensation caused these bolts to rust away when the stove was not in use; it is nevertheless correct, as powerdesal points out, that these bolts should not be expected to support the weight of a vertical pipe, as they do in our case.

There seem to be two things to do:

(1) support the vertical flue pipe properly, and

(2) replace the two bolts which failed with stainless steel ones

Even so, those of you who have a similar system, might like to check that the bolts concerned are sound, since they are exposed to the flue gases; if they do fail, gases could leak past the flange.

John (husband of Val)

[Théière]

A good point well made John.

Just wondered if you can tell from the condition of the bolts, do they look like they have been eaten away by corrosion or over tightened at installation, if they are only 4mm and a over enthusiastic person with a spanner they could easily part shear the bolts and corrosion finished them off.

Try to get A4 grade stainless if you can, they are the most resistant to chemical attack, be careful when tightening though as they are generally softer than the equivalent steel.

[AnOther]

Thanks for the further description John, it was as I read it then. Mine is a 3721 not 3271 as I wrote.

There can be no harm in fitting stronger SS bolts but at the same time I repeat my earlier comment about Godin being pretty experienced at making these stoves and that proper support for the flue has to be the correct solution.

[val douest]

Thanks again for your helpful comments/suggestions. In response to teapot's question, the bolts sheared off at the head end, indicating to me that they had indeed been overtightened, and corrosion did the rest. I found that the holes would actually take 6mm bolts, which made me wonder whether the correct ones were fitted originally. Anyway, I shall now look for stainless steel replacements of the grade suggested. Also, as ErnieY has pointed out, proper support for the flue is required.

John

[AnOther]

From memory mine are about 4mm and are as supplied. Going up from that to 6mm, even non SS, will be more than adequate if you do add a flue support.

[Chancer]

4mm did seem a bit small and I think you are probably right that they should have been 6mm.

Even 4mm bolts paired would take the static load of many many flues, I concur with your overtightening hypothesis and suggest that it was actually thermal expansion that did the rest, this would have broken even 10mm bolts if they had been taken beyond the elastic limit.

I remember at tech college one demonstration with a Hounsfield tensometer rig, A 1" diameter steel bar restarined at one end by a hardened 6mm shear pin was heated with a gas torch for a few minutes, as the bar expanded the slack was taken up on the machine tensioning leadscrew finally the whole thing was left to cool, within a few minutes one of the pins sheared with an impressive bang that I have never forgotten.

[AnOther]

Sorry if the needle seems stuck on the record but I've just looked at mine again and although the 2 bolts in question are no longer visible having put it together myself I can say with certainty that they are the same size as 4x visible 4mm bolts which hold the entire manifold together. Addtionally there is a blanking plate on a second outlet lower on the manifold and that too is secured with 4mm bolts so I think we can say that it is definitely NOT a case of the wrong ones being supplied.

I'll shut up now, got a bag to pack and a plane to catch, that 4 letter word WORK beckons [:(]

[TefkaC]

Be very careful about using stainless steel fixings, they are not the cure all that people believe them to be as they fatigue and crack leading to fracture. Also be very careful about going off Godins design as you can be introducing other factors i.e. larger bolt can lead to overstressing in other areas.

I would suggest you get professional help.

Sorry to hear about the narrow escape and hope it all comes good in the end..

 

Charlie.......

[bixy]

I think it is true that the fumes from a woodburner are nothing like as dangerous as those from a coalburner. Nevertheless why take a chance for the sake of the outlay of a few euros. We have a CO alarm permanently on when the stove is in use.

Patrick

[Théière]

[quote user="TefkaC"]

Be very careful about using stainless steel fixings, they are not the cure all that people believe them to be as they fatigue and crack leading to fracture. Also be very careful about going off Godins design as you can be introducing other factors i.e. larger bolt can lead to overstressing in other areas.

I would suggest you get professional help.

Sorry to hear about the narrow escape and hope it all comes good in the end..

 

Charlie.......

[/quote]

Ooh scary, best we just sit on the floor together and tell sad stories. [:D]

Be careful about using stainless steel fixings, they are not the cure all that people believe them to be as they fatigue and crack leading to fracture. Just like the ordinary steel ones as supplied by Godin, except stainless is more resistant to harsh environments and does not rust. More expensive though which is why Godin would not supply them.

Be careful about going off Godins design as you can be introducing other factors i.e. larger bolt can lead to overstressing in other areas. We are not talking about moving parts here, its a static chimney flue.

I would suggest you get professional help, The Titanic was built by professionals, The Ark was built by a amateur.

 

[Val_2]

Every week at the moment in the local press here there are stories of people being found either dead or unconscious from woodburning stoves emitting carbon monoxide fumes especially when the owners have gone to bed or fallen asleep in the evening in front of them.One of the signs of poisoning is bad headaches and then vomitting before unconsciousness and finally death follows.

[TefkaC]

[quote user="teapot"][quote user="TefkaC"]

Be very careful about using stainless steel fixings, they are not the cure all that people believe them to be as they fatigue and crack leading to fracture. Also be very careful about going off Godins design as you can be introducing other factors i.e. larger bolt can lead to overstressing in other areas.

I would suggest you get professional help.

Sorry to hear about the narrow escape and hope it all comes good in the end..

 

Charlie.......

[/quote]

Ooh scary, best we just sit on the floor together and tell sad stories. [:D]

Be careful about using stainless steel fixings, they are not the cure all that people believe them to be as they fatigue and crack leading to fracture. Just like the ordinary steel ones as supplied by Godin, except stainless is more resistant to harsh environments and does not rust. More expensive though which is why Godin would not supply them.

Be careful about going off Godins design as you can be introducing other factors i.e. larger bolt can lead to overstressing in other areas. We are not talking about moving parts here, its a static chimney flue.

I would suggest you get professional help, The Titanic was built by professionals, The Ark was built by a amateur.

 

[/quote]

 

I obviously don't know your background Tea Pot but I worked in engineering for 40 years+ and no before you come back that doesn't make me an expert if fire installations but I do have expertise in fixings.

Just a couple of points, from the original post I thought it had moved i.e. sheared. The Titanic didn't sink because of bad design but peoples incompetance in the use of it

I take it from your last line of the posting you must be a very happy person 

I do think there are too many people with little or no experience ready to hand out advise on these forums,  

 

Regards.

Charlie..........

 

[AnOther]

Sorry teapot but I have to stand behind TefcaK here. He makes a good point and I think the sarcasm was uncalled for.

Do you honestly believe that Godin would

compromise both safety and their reputation for the sake of a couple of

bolts which would likely increase the cost of manufacture of a stove retailing at over $1000 by no more than a couple of cent's !

Accept it, the bolts supplied were perfectly adequate for purpose had the flue been installed with the correct independent support.

Although it could be argued that SS would have been better

simply because of that material's more robust nature extending that logic would see hundreds if not thousands of other items

fitted with SS screws or bolts, potentially increasing their cost significantly, for absolutely no tangible benefit.

[Théière]

If an appology is called for.

Tefcak sorry for the sarcasm.

It is squarely based on years in the engineering industry, lots of people standing around muttering and scratching of heads, focus groups, endless meetings, eventually someone has to make the decision. I doubt Brunell could have existed in this day and age.

Do I believe that Godin's bean counters would try and cut costs, defintely. Many a serious accident has been caused by just that, remember Nasa and the shuttle, people died for the want of an "O"ring Engineers and Technicians overuled.

To quote Tefcak The Titanic didn't sink because of bad design but peoples incompetance in the use of it. Twas it not supposed to manufactured "unsinkable" and had they manufatured it according to the drawings of Thomas Andrews and not cut corners to save money, wrong kind of rivets and shortened bulkheads, bloody bean counters again.

Yes I believe the bolts supplied, if tightened correctly were perfectly adequate with the correct additional support.

If the bolts need replacing and new ones have to be purchased why not upgrade? If that ever needs to come apart which bolt would you favour undoing?

ErnieY [:D]