Stove Gaskets VS Furnace Cement

[titan]

Is it just me or are more stove-makers turning to gaskets in place of furnace cement?If so,why?Are gaskets more reliable(they can't really crack),do they seal gaps better?Are the stove manufacturers building sections with closer tolerances that lend themselves to the use of gaskets instead of spooning the furnace cement into those seams?I assume both methods of construction work fine when done properly but maybe one trumps the other overall?I'm not advocating one over the other but gaskets could potentially alleviate some of issues I've seen\read about where excess cement plugged-up primary air inlets or gummed-up damper plates.I'm currently burning two welded steel boxes, so I'm curious about other's experiences with sectional stoves(CAST-IRON,SOAPSTONE).

 

[Corie]

Gaskets are nice for a number of reasons. Some that come to mind for me is that they make disassembly and reassembly MUCH easier and less messy and they allow more expansion at the joints (although this probably isn't an issue anyway).

 

[Gooserider]

Basically gaskets are much faster and easier to assemble quickly and consistently. Stove cement works, but is generally a pain to deal with, it's messy, fussy to deal with, makes dissassembly difficult, it's hard to be consistent with it, etc... Gaskets are much superior, cut them to length, stick them in the groove and put your parts together...

This is NOT to say one should avoid stoves built with stove cement that are otherwise desirable, just that gaskets are a bit easier to work with, and arguably are better technology.

Gooserider

 

[jtp10181]

I had to replace a cast piece on a cast stove that I think had been used for one season. Surprisingly the bolts came out fairly easy. All I had to do was use a pneumatic pump jack to lift up one side of the stove since the piece being replaced had the legs on it.

 

[Gooserider]

Gaskets cost more than cement, the whole system cost more. Instead of molds that hold the cemented parts together,

the stove has to be re-engineered to include bolt sockets. From the manufacturer's standpoint service just became a lot easier.
One does not have to rebuild the entire stove to replaced a damaged piece. There is a trade off, gaskets do wear out and heat will loosen bolts.
Naturally every manufacturer will expound new models: Like the new, better, improved ..

I believe you will also find bolts in cemented stoves, so you really aren't adding any additional for gasketed stoves. What we were told on the tour was that the main re-engineering that was done to switch from cement to gaskets was changing the design of the grooves where the parts went together. I asked if there was any reason that a cemented stove couldn't be re-assembled with an appropriately sized gasket, and got a rather evasive answer boiling down to "no comment" - obviously they can't reccomend it, and probably can't even say it is possible, but I thought it interesting that he didn't have a reason why it *couldn't* be done... Note though that according to Elk, it would not be code compliant to put a cement stove together with gaskets since it hadn't been tested in that configuration and the UL / EPA certs wouldn't be valid.

Gaskets do cost more than cement, but reduce the need for as much jig fixturing and saves assembly time and work. Once the re-engineering to use gaskets is done, the parts cost no more to make. So if you look at the total cost of going from "pile of parts" to "assembled stove" I think a strong case can be made for gaskets being less expensive. We were also told that if they had to replace a part for any reason (say chipped enamel) it was a 5 minute job at the factory, and quite reasonable to do at the customers home for a dealer, whereas the same job with a cement stove would require complete dismantling, which takes longer at the factory, and would require hauling the stove back to the shop for a dealer, thus you have big savings on repair work.

I guess a valid question would be, do gaskets hold up longer than refractory cement joints?. I think time will tell I don't know the answer.

Agreed time will tell, but I would suggest that indications are that gaskets would last as long or longer than cement. We know that cement stoves require periodic rebuilding to fix leaks, and that it's major a major task to do so. However there are LOTS of gasketed things (like car engines) where if the gaskets aren't disturbed, the joint will last the life of the unit.

Given that gaskets are going to be easier to change than cement, I would even go so far as to say they'd still be an improvement even if they did need to be replaced at intervals about the same or even a bit shorter than needed to rebuild cement stoves.

How often do bolts have to be re-tightened? What happens if the are over tightened? I mean, you will be dealing with bolts that have been exposed to extreme heat

Looking in the gasketed VC manuals that I have, there is no mention of needing to re-torque the gaskets, or discussion of torque specs, so I would assume you would use the "industry standard" values for that size bolt, and no real need for re-torqueing - the gaskets aren't getting disturbed, there isn't significant parts movement, and they aren't under pressure, so I don't know why they'd need much in the way of maintainance.

how easy will it to be to snap one off will the rust and become frozen in their sockets. Ever deal with auto exhaust manifolds? Then you know what heat does to bolts,
Many times one snaps them off or strips them because they become frozen in the sockets? Will manufactures use stainless Steel bolts and high temp Neversieze?

Can't speak for other brands, but VC is using Stainless bolts on their stoves, and is putting high temp Never-seize on them, so I would not expect to see a major problem with bolts getting stuck. (It is also worth noting that a stove bolt doesn't see the same road chemicals and moisture that a car engine sees, and probably less extreme temperature cycling)

Point being; it is hard to answer the original question, till gaskets are time tested ,but as one can see another set of issues has to be factored

Agreed, but I think the bottom line will be that the gasket stoves are easier to maintain long term, and that there is no significant difference in day to day use.

Gooserider

 

[titan]

A couple of weeks ago,I was scrutinizing two Hearthstone Heritage units on a local dealers' floor when i was unimpressed with the cement covering at the firebox seams.I'm sure all seams were well sealed because there was so much excess cement in places-it looked like it was applied by a drunk with Parkinson's disease.I was told that Hearthstone can't make them fast enough to meet demand.True or not, that doesn't cut it in my mind.Yes it's important to be sure that everything is sealed up tight but too much can be more than enough.I'm not trying to condemn or single out Hearthstone(I like the look of their products);maybe I'm too fussy,maybe this is common practice when assembling sectional soapstone units?

 

[Corie]

I agree with you 100% on that. When I was looking at VC stoves at the show in Reno, I noticed oozing cement all over the place, significantly more messy than when I rebuild a cast stove myself.


WHen I mentioned it to MSG he said that's the way it always is, no matter what company. Looks like amatuer work to me. Guess some of us have a higher attention (and annoyance factor) to detail.

 

[titan]

The first thing I noticed was the lever that opens the grate;it wouldn't budge because it was plugged up with pieces of cement that had broken free from the hanging "stalactites" above.I haven't seen any Woodstock stoves up close;I'm curious as to whether or not they're a little more tidy due to the HANDMADE claim.

 

[Todd]

My old Hearthstone had excess cement all over and my Woodstock is all nice and smooth like someone took pride in their work.

 

[Corie]

The difference between a craftsman and an assembly line minion.

 

[alfio]

The difference between a craftsman and an assembly line minion.

you got that right corie, the problem is production . Companies are pushing production over quality , I know first hand having been in production most of my working life .

 

[Bill]

I would think a gasket would last longer because it can flex, fill in uneven areas, and isn't brittle.

 

[begreen]

Hey Corie, do all stove manufacturer's use essentially the same cement or are there significant differences? Whatever is used in the Jotul seems tough as nails.

 

[Corie]

That's a good question BeG.

I've seen several different brands on the market, some of which look of MUCH higher quality than others. Not sure which brand each company is using. I've used Rutland up until this point, but I was recently turned on to a much better brand that I'll be experimenting with the next time I do a stove rebuild. The name escapes me, I'd have to check when home.

 

[elkimmeg]

I think many are speculating here Many refractory Joint stoves lasted over 20 myears or more. Since this recently new (gasket construction) should we wait 20 years or so to Make the comparison? I can remebmbner changing glas gaskets flue collar gaskets and gaskets that were not part of moving parts and I know these gaskets were less than 5 years old?
Does one also realize that there is more to cement joints than just put in on the two surfaces One many parts are groved and filled with cement and overlaping occures on both sides.
HJaving r taken a few apart the joint are quite strong Also there are bolts and threaded rods that are used in unison for stove construction No stove relies on cement alone.

I think a lot here are speculating ..never torn down and rebuilt a cement stove. I have and I ccan tell you removing old cement is a chore. It was made to last.

You know gaskets can get pinched over tightened installed wrong Streched Alter the same refractory cement hold the gasket in the grove

O just wanted to point some factors out to me I'm not convinced which is better maybe in 20 years from now I can make a value judgement .

One other consideration, would one re-use a gasket if they took out the gasketed part or would all disturbed gasket joint require new gaskets?

 

[Corie]

That's the thing about rebuilding a cast iron stove though Elk. From what I've seen, often times the cement is still hardened in place, but it may not have ever made contact with the piece it was supposed to bond to. I noticed this A LOT inside the aspen, not so much in the older dutchwest stoves. I think going to gaskets means there is less potential for sloppy cement work to result in unsealed seams. Although that could just be me being hopeful.

Also I like the gasket idea because it means if you need to tear the stove down to replace a component or clean out some hidden chamber, its easy to put it back together. I know you know, as do I and anyone else who has rebuilt a couple cast iron stoves, that tearing it down and prepping it for new cement is a royal pain in the butt. You spend hours chipping hardened cement and then after sticking it back together, would have to do the exact same thing when you tear it down again.

The top of the aspen is gasketed and that makes it very convenient to remove the top for periodic cleaning or to replace the baffle firebricks.

 

[elkimmeg]

What about the ability to recaulk the seams without a rebuild. I have done that with great sucess. Especially when there is a limited problematic seam that needs to be addressed simple easy fix done without and dissesembly

 

[Corie]

Yeah, that's a good point Elk. Hadn't thought of that, because I've also recaulked a leaky seam that was easily accessible.


Hypothetically though, if the gasket fit was correct, leaky seams wouldn't be possible, because a little chunk of the gasket wouldn't crack off and fall out. In a perfect world of course.

 

[Gooserider]

What about the ability to recaulk the seams without a rebuild. I have done that with great sucess. Especially when there is a limited problematic seam that needs to be addressed simple easy fix done without and dissesembly

I don't know that it's necessarily an "either / or" thing to choose between gaskets and cement - I know when I'm putting an engine together, I often put glue on the gaskets, especially ones that I'm not planning to pull apart any time soon. It isn't done, normally, but why wouldn't it be possible to run a thin layer of cement under and on top of the gasket to ensure that all the gaps are sealed? It would be a real bear to get apart, but might give the best of both worlds?

I also don't see why if one had a leaky seam on a gasketed stove why one couldn't attempt to seal it with cement the same way one would a cement stove? Either way my understanding is that the recaulk approach is considered a less than optimal repair, but sometimes is worth a try to keep a stove going (possibly just long enough to get through the season to when it's convenient to do a total rebuild)

Gooserider

 

[Corie]

I agree Goose. But why would a leak even open up on a gasketed seam if two components were properly assembled and pressed together. Its not like the gasket will crack and fall out in chunks like cement.

 

[begreen]

That's a good question BeG.

I've seen several different brands on the market, some of which look of MUCH higher quality than others. Not sure which brand each company is using. I've used Rutland up until this point, but I was recently turned on to a much better brand that I'll be experimenting with the next time I do a stove rebuild. The name escapes me, I'd have to check when home.

The stuff used by Jotul is like porcelain. It's is much tougher than the Rutland and has good, strong bonding. When I rebuilt the 602 I used Rutland and the rebuild worked well, but I wonder about the quality of the cement.

 

[Gooserider]

I agree Goose. But why would a leak even open up on a gasketed seam if two components were properly assembled and pressed together. Its not like the gasket will crack and fall out in chunks like cement.

Purely speculative here, but I might suspect a joint that maybe hadn't been put together 100% right in the first place, or possibly if there was an overheating problem that burned out the gasket material - maybe one of those glowing VC's? I don't know what the temp rating is on the gasket material, but I wouldn't be surprised if it was lower than for cement.

Gooserider

 

[Corie]

True true. I suppose there is a legimate argument to made for both joint types.