Message Board Thread - "Glass furnace Insulation Inspection?"

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Glass furnace Insulation Inspection? kmanka 4/19/2005
Is it possible to get accurate thermagraphic reading from a glass furnace that’s outside wall is constructed of steel and painted with aluminum paint? What is the emmissivity of aluminum paint?

Re:Glass furnace Insulation Inspection? TDLIR 4/19/2005
If what your asking is if you can still get accurate External Shell Surface temperatures of a furnace that has a steel shell and painted with AL paint, then the answer is Yes!

Attached is an image of a Steam Reformer with commonly used industrial AL grey paint. I inspect these types of refractory vessels all the time with great success.

With regards to the Emissivity value, It is always better to measure your E than guessing. Also, keep in mind that at areas of extreme heat due to refractory failure, the AL paint will burn off leaving the bare metal surface. The E value will then change as the surface has changed.

Hope this helps,

Sonny James
Re:Glass furnace Insulation Inspection? Howzie 5/19/2005
what method do you use on this type of work for Emissivity, thermocouple, paint manufactures specification!
Re:Glass furnace Insulation Inspection? Howzie 5/26/2005
My question to TDLIR was this, do you have a set method for emissivity, not possible you climb all the way to stick some black tape on!

Regards Howzie
Re:Glass furnace Insulation Inspection? TDLIR 5/26/2005

Sorry for taking some time to reply to your post. Been kind of busy with outstanding reports :-(

Well to answer your question on how I would actually measure my E on a vessel such as this would be:

1. Before my inspection I would first measure the E of the paint by using Black Electrical Tape and also an Exergen Contact Thermometer with a paint marker. I use these 2 methods in order to get as accurate as possible and in order to double-check my results.

And YES I can still get to each level via the stairs and catwalk in order to stick the tape and do my contact temp. measurements. Note that almost all vessels have stairs, catwalks and ladders you can use to get to the shell for contact temps.

2. I will then go to a few areas where there is paint flaking or burnt paint or rusted areas and get contact temps. for E compensation.

I now Have Measured E values for the Paint and Bare Metal Areas. Now during my inspection, I will know what E to use on the different surface conditions.

3. To top off all of this, I will then take a couple random contact temp of Hot Spots that I find in order to compare with my IR camera to check for accuracy. **Once I do Step #1 and #2 my acquired temps always found to be accurate.

1. Black Tape can only be used on surfaces that do not melt the tape.

2. The exergen thermometer is also an IR thermometer but is accurate to NIST traceable standards on Surfaces with an E greater than 0.80. That is why I walk with a paint marker to up the E.

3. I do NOT use portable hand-held TC thermometers. They are inaccurate and practically impossible to properly use.

4. With any of my E modifications, I always leave sufficient time for thermal equilibrium.

I have submitted a Paper on Refractory Inspection and Inspection Techniques and Procedures to IRINFO for me to present at their 2006 symposium in Orlando FL. So if you are there I will be more than happy to exchange ideas and techniques.

Best Regards,

Sonny James
Re:Glass furnace Insulation Inspection? Manuel 6/10/2005
"Is it possible to get accurate thermagraphic reading from a glass furnace that’s outside wall is constructed of steel and painted with aluminum paint?"
"What is the emmissivity of aluminum paint?"

hi ..
i worked for a glass plant for 13 years, making over 4 millions bottles a day for Annheusser-Bush company.

regarding the 2 questions: the first one it is important and i would like to think that you want to measure the temperature of the wall to try to identify where the refractories have important wear or try to detect 'rat holes'

the metal wall is usually used where the refractories are to 'thin' and to prevent that hot glass coming out from damaged alumina bricks. i have seen that sometimes alumina bricks from bottom of furnace are cooled down with air or water.

but the point is if you want to measure 'the aluminun paint' remember that is just PAINT not Aluminum metal, and when is exposed to this high temperatures it looses lot of IR reflections allowing to have high Emisivities values.
so, please take care and dont confuse 'aluminun paint' with 'aluminum surface'

the other question about the emissivity of aluminun paint have to see with the temperature, when paint is recently applied and heat has not reached Furnace temperature operation ot will be nice and shinny (low E value); but after a few weeks of appling heat it wil turn little darker increasing the E value.

The interesting areas of inspection on a glass furnace is depending on design, with heat recuperators, regeneration, etc. but the most important is to have thermal profile of
a) bottom (the glass wear out the bottom refractories)
b) the bubblers
c) the throat, if glass furnace have one,
d) the crown, sometimes it insulated but the most important area is all Joints.
e) thermocoples Stones.
f) Soldier bricks
g) the Salmers.

have fun with refractories, please visit my previus post at:

roberto cruz

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