Chimney weight / identification

[1990Jotul]

I was wondering how consistent the weight of a given chimney model should be. I just purchased some 6" Duravent Duratech. I accurately weighed a 48 inch section of it as being 14.6 pounds. This would be 3.65 pounds per foot. The Duravent website states that this chimney is 5 pounds per foot. That's quite a difference. Do individual sections tend to vary that much? Does anyone think there could be something wrong with my new chimney?

On a related note, the old Chimney that I am replacing is 8" inner diameter, 10 inch outer diameter. It is stainless on both the outer skin and inner liner. It says "Made in Canada" on the top lip of each section. I have both 36 and 24 inch lengths. When I cut one open, it contained a pulpy/powdery fill. It was purchased in 1991 and I am guessing that it may be Security Chimney SecureTemp. I accurately weighed a 36 inch section and it was 27.0 pounds, or 9 lbs per foot. I just looked at the Security website and saw that this Chimney is listed as weighing 7.2 lbs per foot. Could it be that I have misidentified the Chimney model or did this model get lighter in more recent years?

Any information / opinions are appreciated.

 

[webby3650]

Perhaps your scale is inaccurate?

 

[EatenByLimestone]

Perhaps they weighed a 1 foot piece. (4) 1 foot long pieces with connecting hardware between them probably weigh more than a single 4 foot long piece without any.

 

[1990Jotul]

Perhaps your scale is inaccurate?

As I stated, the weights were measured "accurately", meaning that they were done using a calibrated scale (three point calibration, at weights both above and below the measured weight, with a midpoint close to the measured weight). The weighing was conducted in triplicate (with no differences in reading, thus the average = separate readings). Additionally, one of the chimney specimens (the Duravent) weighs significantly less than expected, while the older unknown Chimney (suspected to be Security Secure Temp) weighs significantly more than expected- this would also suggest that the unexpected readings are not due to the scale being out of calibration.

 

[1990Jotul]

Perhaps they weighed a 1 foot piece. (4) 1 foot long pieces with connecting hardware between them probably weigh more than a single 4 foot long piece without any.

I have no idea how the Chimney manufacturers establish their linear Chimney weights, but they publish them on a per foot basis. The three foot and and four foot sections that I weighed were single piece assemblies, with no connecting hardware on them, so I would expect that they should weigh pretty close to a 1 foot weight, multiplied by number of feet in length.

 

[webby3650]

As I stated, the weights were measured "accurately", meaning that they were done using a calibrated scale (three point calibration, at weights both above and below the measured weight, with a midpoint close to the measured weight). The weighing was conducted in triplicate (with no differences in reading, thus the average = separate readings). Additionally, one of the chimney specimens (the Duravent) weighs significantly less than expected, while the older unknown Chimney (suspected to be Security Secure Temp) weighs significantly more than expected- this would also suggest that the unexpected readings are not due to the scale being out of calibration.

Geez dude! I’m almost certain your are the first person to ever weigh a section of chimney. Weights and measures your career or a hobby?

 

[1990Jotul]

Actually neither. This whole exercise started as a very inprecise gut feeling about the weight not being right just from holding it. I had previously noted Duravent's specification of 5 lbs/per foot, only because I wanted to know what the approximate load was going to be on my my ceiling supports. It was then simple math leading me to expect a four foot section I was about to carry up the ladder to weigh 20 lbs. It just didn't feel like it. In fact, it felt substantially lighter. Since I really do care about the safety performance of something as critical as a chimney, I believed it was worth the diligence to get actual weight measurements on the piece. When I took the weight, it was so far off from expected that I then felt I need to insure the accuracy of those measurements. If you think about it, what good is a measurement if you don't know it's accuracy? After all, as you try to resolve the problem, someone can simply say "Perhaps your scale is inaccurate?"

 

[webby3650]

Was it not a legitimate suggestion considering you’ve weighed 2 different brand that were off? Seemed like it to me.
Contact dura-vent if our are concerned.

 

[1990Jotul]

A completely legitimate question. That's why I went to the trouble of ensuring the weighing was accurate and then explicitly stating it twice in my original post. I will be contacting Duravent. Thanks.

 

[webby3650]

Sorry, I overlooked the explicit accuracy mentioned twice in your post. Most people here are just trying to help, after all, that’s why you came here right? Looking for help? Eliminating a few of the obvious possibilities is a place to start. Many people overlook the obvious.

 

[begreen]

It's kind of unusual to list the pipe weight as that will vary with the diameter. I'm wondering if this is possibly shipping weight? Jotul1990 can you provide a link to the page with the weight?

EDIT: Nevermind, I found it under the benefits. Maybe DuraTech switched insulation to a lighter material?

Light weight Thermo Tech insulation makes pipe sections lighter (5lbs per ft for 6” diameter) to allow the manufacture of 5’ lengths, thus the installer has fewer trips up the ladder for a quick and easy installation

 

[EatenByLimestone]

To be fair, they may have rounded on their literature.

 

[1990Jotul]

It's kind of unusual to list the pipe weight as that will vary with the diameter. I'm wondering if this is possibly shipping weight? Jotul1990 can you provide a link to the page with the weight?

EDIT: Nevermind, I found it under the benefits. Maybe DuraTech switched insulation to a lighter material?

Light weight Thermo Tech insulation makes pipe sections lighter (5lbs per ft for 6” diameter) to allow the manufacture of 5’ lengths, thus the installer has fewer trips up the ladder for a quick and easy installation

I think what you quoted is what I saw. Duravent gives pretty limited information on the weight of their products (as compared to some other manufacturers). As you saw, they actually only provide the weight for 6" Chimney (which is what I happen to be using). Security Chimney provides it for all of their diameters (see the attached image). That was how I knew what it should be for their 8 inch. They also added the foot note that the actual product may vary by up to 10%. That would still not explain the 9 lbs/ft I weighed (7.2 +10% would be 7.9 lbs). Of course I am guessing that it is Security SecureTemp and it is 26 years old, so I am sure the product could have changed in that time. I am not really concerned about that as much as I am the DuraTech I am putting in to replace it. As webby3650 suggested, I really need to contact Duravent about that. I am waiting until I get a chance to weigh a second piece I already put in place (for completely different reasons, I need to take it down and will use this opportunity to weigh it) It will be interesting to see if the Chimney is consistently underweight, before contacting them. As it stands, the one piece is about 25% below what they state.

 

[1990Jotul]

To be fair, they may have rounded on their literature.

You are certainly correct. They did not provide any tolerance on that specification, so one can't really know whether the weight I measured is considered normal or not. They did state that weight to the whole number (5 lbs) using no decimal. Technically 4.5 lbs would be a more precise value still consistent with their claim. In that case, my measurement of 3.65 lbs would only be 19% underweight. But that is still quite a bit. Also, it would be surprising Duravent wasn't publishing that lower number because, as you can see in begreen's post above, they were using that weight for the purpose of making a point that they are lighter than most of the competition. They even have a table where they show the weight of the competitor's products. Most are heavier than the 5 lbs they claim their product is, but one is shown to be 4.2 lbs ft. (ICC Excell). You would think that if my chimney was normal, they would have published that weight (3.65 lbs). It would have given them even better bragging rights. In any case, I would be thrilled to have an ultra light chimney, as long as it is representative of the material used during certification testing. My concern is having something substantially lighter than it is supposed to be.

 

[begreen]

It appears that the DuraTech info was written to be competitive. If so it's probably by the marketing dept. which might explain the error. I note that the Secure Temp weights have a 10% allowable variance.

Checking some other lengths of chimney would be interesting. Also checking with DuraTech to see what changes they may have made since the literature was written would also be interesting. They have undergone ownership change since our pipe was installed.

FYI, M&G their parent company also owns Security chimney.