Stainless pipe taking on copper color

[DianeB]

Seems to have appeared overnight. Happened to notice it this morning and husband who was home yesterday denied seeing the stove overheat - he said it was so warm he let the fire go out and did not relight until last night - just 3 small splits and did not get above 500. I could have missed the color change last weekend. In any event wondering if I had a small fire in the T area. The part of the flex pipe going thru the damper also looks discolored and I seems the label is gone from the duro vent. I called a sweep to come check it out for us and clean the chimney on Sat. What do you guys think? Did we have a fire in the T area?

 

[Dune]

http://www.bssa.org.uk/topics.php?article=140

 

[Beetle-Kill]

http://www.bssa.org.uk/topics.php?article=140

Nice link. Sums that up.

 

[Jags]

Dune - that is a cool link. Thanks.

For anyone looking at the chart on the link, remember, those number are in C not F.

 

[DianeB]

Dune - that is a cool link. Thanks.

For anyone looking at the chart on the link, remember, those number are in C not F.

Not sure I am getting this. But here I go. For my stainless to be dark yellow (closest to copper) the temp in myu pipe was 12,506 F (1 C = 33.8F)

Seems like a pretty darn hot pipe if it got that hot?

 

[Jags]

Not sure I am getting this. But here I go. For my stainless to be dark yellow (closest to copper) the temp in myu pipe was 12,506 F (1 C = 33.8F)

Seems like a pretty darn hot pipe if it got that hot?

No. the conversion would be 698F. Not out of line. The liner is designed for 1100-1200F.

The conversion is 5/9 or 0.5555555

 

[DianeB]

No. the conversion would be 698F. Not out of line. The liner is designed for 1100-1200F.

The conversion is 5/9 or 0.5555555

Jags, if my pipe was 698, would my stove have been higher? Is it common for the stainless to turn a coppery color. (my conversion factors were way off, thanks)

 

[BrotherBart]

My stainless elbow off the top of the stove and the liner going up from there have been a golden color since about the first month or so of burning. In December 2006. Flue temps get pretty darn hot on reloads.

 

[Dune]

Jags, if my pipe was 698, would my stove have been higher? Is it common for the stainless to turn a coppery color. (my conversion factors were way off, thanks)

Yes, your stove was most likely hotter, not that that is a problem.
As BB pointed out, his pipe is a golden yellow (what we call dark straw).

Also, please be aware that the colors of oxidation of S.S. are influenced by more factors than temperature alone, most importantly (and contrary to the link)
the state of polish of the surface. The higher the polish, the brighter and richer the colors.

 

[DianeB]

Tahnks everyone. Sweep is coming tomorrow AM to check it out. Probably a good idea as I am new to EPA burning and we had a long shoulder season and I may have created creosote that fell into the T behind the stove. Sweep said I could have had a quiet burn in there and he also mentioned the polished surfaces of the stainless (coatings left on after polish) could have caused the discoloration. But I just noticed the label on the pipe is now gone, I think burnt off. Arround the connections of the "T" I am noticing the color is more blue than copper which would indicate from the chart
Dune provided, could have been hotter in those areas than the rest

 

[bag of hammers]

Not sure I am getting this. But here I go. For my stainless to be dark yellow (closest to copper) the temp in myu pipe was 12,506 F (1 C = 33.8F)

Using DianeB conversion factor, that means the outside temp here right now is @ -720 . Better put another log on the fire....

(sorry Diane, could not resist...)

 

[slindo]

I've made a few SS motorcycle exhaust systems over the years, and they always turn straw-colored. They typically see 900 to 1000 F or so.

 

[DianeB]

I've made a few SS motorcycle exhaust systems over the years, and they always turn straw-colored. They typically see 900 to 1000 F or so.

More orangey than straw and a little blue at the seems of the T. Sweep coming tomorrow. I want to see how he disconnects the bottom of the T. I may need to do that in between sweeps myself to get out the creosote that may fall to the bottom of the T....does anyone else do this?

 

[Lumberjack]

Another variable in this is the type of stainless. The table presented was for 304. I believe some liners are 316, which is more heat resistant.

The other interesting factor is time.


Time
Laboratory tests done to establish the published heat tint colour charts have usually been based on heating for one hour. As exposure time is increased, the temper colours can be expected to deepen ie make it appear that a higher exposure temperature may have been used.

When you have 1000's of hours on your flue, I suspect a change in color can be expected.

If it is indeed only oxidation, you should be able to polish it off.


To add to the discussion, what is it that some liner mfgs claim to add to the stainless mix....titanium? Can't recall. I believe they claim it ups the max temp limit.

 

[tfdchief]

I once took my cap off the chimney and it had so much crud on it I set it on the concrete drive and put about a thimble full of gasoline on it and lit to get the creosote burning. It is now yellow, brown, purple, and blue

 

[Dune]

Another variable in this is the type of stainless. The table presented was for 304. I believe some liners are 316, which is more heat resistant.

The other interesting factor is time.


Time
Laboratory tests done to establish the published heat tint colour charts have usually been based on heating for one hour. As exposure time is increased, the temper colours can be expected to deepen ie make it appear that a higher exposure temperature may have been used.

When you have 1000's of hours on your flue, I suspect a change in color can be expected.

If it is indeed only oxidation, you should be able to polish it off.


To add to the discussion, what is it that some liner mfgs claim to add to the stainless mix....titanium? Can't recall. I believe they claim it ups the max temp limit.

321 is titanium stabilised but I can't see the extra expense for a chimney liner.

Even 316 is uncalled for, though someone could offer it.

Believe it or not, 304 and 316 are remarkably similar, both being 18-8 stainless steel, though with a relatively significant increase in cost for 316. 316 does resist surface oxidation better, but hardly noticeable visually, in terms of heat oxidation. With the addition of titanium, 321's cost mandates it use only when necassary.

http://www.metalshims.com/t-321-Stainless-Steel-technical-data-sheet.aspx

Type 321 is a stabilized stainless steel which offers as its main advantage an excellent resistance to intergranular corrosion following exposure to temperatures in the chromium carbide precipitation range from 800 to 1500° F (427 to 816° C). Type 321 is stabilized against chromium carbide formation by the addition of titanium.
While Type 321 continues to be employed for prolonged service in th4e 800 to 1500° F (427 to 816° C) temperature range, Type 304L has supplanted this stabilized grade for applications involving only welding or short time heating.

 

[firefighterjake]

I once took my cap off the chimney and it had so much crud on it I set it on the concrete drive and put about a thimble full of gasoline on it and lit to get the creosote burning. It is now yellow, brown, purple, and blue

Ah . . . the firefighter method of home repair . . . either douse it with water, beat it with an ax or set it on fire. It will either be fixed or be in so much disrepair that you will need to buy a new one of whatever you were attempting to fix, clean, etc.

 

[tfdchief]

Ah . . . the firefighter method of home repair . . . either douse it with water, beat it with an ax or set it on fire. It will either be fixed or be in so much disrepair that you will need to buy a new one of whatever you were attempting to fix, clean, etc.

Guilty!

 

[DianeB]

So the Sweep just left. He found I woulld say about a pint or so of creotose. Mostly powder and some flaking that he said came from the top, 2 inches was at the bottom of the T and he re-positioned the set screws east/west instead of north/south on the plate at the bottom of the T so that every couple of weeks I could open it up and remove stuff falling to the bottom of the T. He said it was a fair amount and not bad for the amount of wood I have burned. He said he would not have installed the stove the same way. He would have cut out the damper a bit so that the pipe not crimped through the damper but could be the full round 6 inches. He said in Mass, for stoves installed in fireplaces, the fireplace has to be left as a working fireplace so most installer do not cut out part of the damper to have the pipe round. Tokeep it round and keep things legal if damper cut and be legal, our installer would have to have installed a top sealing damper and that would have been another $250, The sweep would have recommended that it be done so the pipe would not have been crimped through the damper. He said everything I had though was 100% safe and again not too much creosote, but I could have had some burning in the T that caused the discoloration. I think I have seen the top sealing dampers adv. here on hearth.com