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Infra Red Scan Aluminum Cladding over insulation
06-28-2012, 09:43 AM (This post was last modified: 06-28-2012 04:03 PM by Gary Orlove.)
Post: #1
Infra Red Scan Aluminum Cladding over insulation
A thermographer asks the question:
Quote:We are trying to determine hot spots. Ambient temperatures may range from 70 F to ~100 F. Camera setting is in degree C. The surface is expected to be no more than 20 C above ambient. So we are looking for insulated areas of the process above this range. We are not interested so much in actual temperature but to identify inadequate insulation or hot spots. The equipment is mostly covered with anodized aluminum sheets (fairly shinny). Some of the area is exposed to natural light while other areas are exposed to shade. All areas are exposed to indoor type building lighting.

The camera is a FLIR EX320 ThermaCam with a 15mm IR LENS. What would be the recommended settings for the various conditions to show only hot spots?
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06-28-2012, 09:46 AM
Post: #2
ITC RE: Infra Red Scan Aluminum over insulation
We all know there can be potential problems with insulation covering pipes. The insulation can become water
logged or contaminated with other substances, which lessens its ability to insulate. The insulation is, in the
majority of cases, covered with stainless or aluminium cladding with a low emissivity, great for energy saving
and as a hard-wearing outer material for protecting pipes, but inconvenient for thermography.

The question remains: Can we see potential problems in insulation using a thermal imaging camera without
any other equipment if the aluminium or stainless is dirty or covered in a process by-product, grease, or other
material? If we are looking at a new install, we will have problems due to the low emissivity of the cladding
causing hot and cold reflections, or both, depending on the environment it is in.

During a recent Level 2 training course held in the UK at a petrochemical plant, this exact problem was
discussed with onsite engineers and trainers, and a possible low-cost solution was tested. The low cost
solution is to wrap the cladded/ lagged pipe in a fire blanket. It’s cheap; it’s fire retardant, which is ideal in a
process environment; and it has a high emissivity. The downside is that sometimes two people are needed to
hold the blanket onto the pipe in testing positions...

Read the attachment for the entire technique including camera settings.


Attached File(s)
.pdf  2004-057-Willis_FINAL.pdf (Size: 342.79 KB / Downloads: 63)
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06-28-2012, 12:36 PM
Post: #3
RE: Infra Red Scan Aluminum over insulation
Why not paint the pipes with a silicone based coating like this one
http://www.dampney.com/Upload/Products/Products28.pdf
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06-28-2012, 02:00 PM
Post: #4
RE: Infra Red Scan Aluminum over insulation
(06-28-2012 12:36 PM)acardoso Wrote:  Why not paint the pipes with a silicone based coating like this one
http://www.dampney.com/Upload/Products/Products28.pdf

The problem with painting the cladding is that you will degrade the insulation performance, because you have raised the emissivity and have thus raised the radiation heat transfer from the pipe.
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06-29-2012, 05:22 PM (This post was last modified: 06-29-2012 05:24 PM by acardoso.)
Post: #5
RE: Infra Red Scan Aluminum over insulation
(06-28-2012 02:00 PM)Gary Orlove Wrote:  
(06-28-2012 12:36 PM)acardoso Wrote:  Why not paint the pipes with a silicone based coating like this one
http://www.dampney.com/Upload/Products/Products28.pdf


The problem with painting the cladding is that you will degrade the insulation performance, because you have raised the emissivity and have thus raised the radiation heat transfer from the pipe.


Yes. Those kind of coating, usually, have an emissivity greater than 90%.
My experience tell me this. When I arrive to any plant and touch a pipe, if the fluid running inside the pipe is colder than ambient temperature, we feel the pipe cold; on the other hand, if the fluid is hotter, we feel the pipe warmer. Unfortunally, this is the usual standard. For me, insulation is normally under-specified. Since we cannot get rid of convection, wouldn’t be a better tradeoff, increase insulation. In this way, the steady state temperature of the pipe on the outside would be closer to ambient temperature, getting heat transfers by convection or irradiation meaningless.
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