Thermal Shock Failure -Who Wants To Discuss It?

vquestfilms.com · January 27, 2012

I'm up for a discussion. I will start with a question that was asked in an unrelated thread.

Is the AIMCAL limit of 54% a "hard" limit or are there exceptions, other factors, etc?

If someone can attach the actual document rather than quoting it, that would help. :beer

TomTint · January 27, 2012

Rob, I hope we have clear air here, Im not spotlighting any product or any Mfr whatsoever. We are in the northeast and encounter more than our fair share of thermal shock. It is most often in the late fall. For the obvious reasons. I have had breakage over the years with almost every MFR and several different films. Even silver 20 type films. More often than not on IG breakage has occured because of flaws on the edge of the glass that was not visible untill the unit was removed. This is always tough to explain to the customer. I do believe that when it co es down to it, the straw that breaks the camels back is at all end SA. In one way or another it comes down to heat, to much, un even, to quick.... Is it not all about heat in some form?

vquestfilms.com · January 27, 2012

Rob, I hope we have clear air here, Im not spotlighting any product or any Mfr whatsoever. We are in the northeast and encounter more than our fair share of thermal shock. It is most often in the late fall. For the obvious reasons. I have had breakage over the years with almost every MFR and several different films. Even silver 20 type films. More often than not on IG breakage has occured because of flaws on the edge of the glass that was not visible untill the unit was removed. This is always tough to explain to the customer. I do believe that when it co es down to it, the straw that breaks the camels back is at all end SA. In one way or another it comes down to heat, to much, un even, to quick.... Is it not all about heat in some form?

Yeah we're good Tom, thanks for the message I really appreciate it. :beer

I will get beat on for saying this but as far as thermal shock goes... the condition of the glass, the type of glass, size of glass, shape, and the evironmental factors such as altitude, shadowing, orientation have a much bigger influence on what happens than TSEa.

Take annealed single pane clear for instance. You need a 70F in temperature difference across the glass surface to exceed its tensile strength. You can mount 5% on that glass and not be able to cross that temperature differential. UNLESS... you have some of the above-mentioned factors playing against you.

Then consider the condition of the glass. A clamshell which is very common on the bottom edge of large commercial glass or on arched glass. If you mount even the lowest absorbing silver reflective film, a bronze reflective, or even a 70% vlt you can crack the glass just as easily as using 5% limo. Film finds bad glass no matter what the film brand is and no matter what the vlt.

TomTint · January 27, 2012

In my little area of the world I really do not see a ton of SP glass, some but not much. The lion share is IG and more recently DP low E of various configurations. I have always been advised to use a product with a SA of 50% or less. Over the past few years with the introduction of dual reflective films.... That ratio has been stretched a bit. This past summer we did 4 stores for a national retailer that had ceramic film as the spec. The windows " to the best of memory " were 48x120 ish. That made me real uncomfortable but it was not my spec it was their standard. I can understand a crack running from a clam on the edge, I can understand partial shading, I guess I do not understand the metric that does not involve SA of some sort

EWF · January 27, 2012

Rob,

Spare me the psychoanalytics.

The following manufacturers publish their TSEa:

Panorama

Express

Solar-Gard

Llumar

Vista

Madico Sunscape

Sun-Tek

Madico

Hanita

Johnson

The following do not:

Huper

3M

Madico MAC

The AIMCAL publication you refer to is older, but has never been supersceeded. I follow them. What set of guidelines do you follow?

I am glad to see that you are addressing specifics in your post to Tom, but that much I was aware of.

The specific question is:

All other factors being equal - under what circumstances can a film with a higher TSEa pose a lower risk than a film with a lower TSEa?

A little history:

For me, the last time this was addressed was during a distributor meeting I attended in the early 1990s when I was working exclusively with a USA manufacturer. We were experiencing a spike in thermal cracking with a Nichrome film that was a big volume product. We could not understand why this particular film was breaking so many more windows than another film which had a higher TSEa. It was during a presentation that he explained how TSEa was the primary, but not the only factor. Again - all other factors being equal.

I should have taken better notes during that meeting because that was the only time I heard this discussed. I just can not remember what he told the group. Somehow I seem to remember that the color of the film was a factor - but that could be wrong.

Here the topic came up again and I was hoping that you could explain it. Instead - I am getting your analysis of my motives.

If you know the answer great!!! If not, I don't hold it against you. I just wish I knew so I could explain it to others when they ask as well as factor it in to our thermal shock warranty coverage.

-Howard

Tintguy1980 · January 28, 2012

My understanding of glass temp difference is that for annealed it is 50 degrees from central surface to edge (rather than 70), 100 degrees for heat-strengthened and 200 degrees for tempered before thermal shock is a consideration.

EWF · January 28, 2012

If someone can attach the actual document rather than quoting it, that would help.

AIMCAL WINDOW FILM COMITTEE

Recommendations For Avoiding Glass Failure

Page 2

Last parragraph

You had challenged me on it in a previous thread. I remember emailing that to you. I don't have access to it at this moment - but I can get it Monday.

They claim that 50-60% TSEa is OK. We stop at 54%

How about everyone else? What do you consider safe?

-Howard