Hello All,

 I have an image of a fire tube in a boiler that I would like to get input on. We are led to believe that the fire tube specifically the lime green outlined tube in the picture has a stress fracture and is leaking water into it, creating steam. The IR photo shows that the tube is very clean compared to the rest, in fact shiney, with no lime or scale build up. What my question is about the photo is that if the tube is clean, which it is, is it causing the IR camera to read it as a higher temperature?, comparing it to the rest of the tubes in the picture that have scale build up that are reading lower temperatures? Upon preliminary investigation we are believing that the tube does in fact have a water leak but we need input from you to tell us why it is showing a higher temperature and image on the camera?

 Thanks,

 Reliabily Team

General Mills Belvidere

There is a good bet the shiny tube is simply reflecting the heat of the surroundings while the others are not. The surroundings, at least those being reflected (possibly a portion of the thermographer?) are warmer than the tube bundle and so the reflective tube shows up as warmer.

 

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Thermally Yours,

John
ASNT NDT Level III #48166
The Snell Group
www.thesnellgroup.com
www.thermalsolutions.org
800-636-9820

John may be correct here. It may just be reflection. However, I feel that you are using the wrong NDT method to find out if you have a leak at your tubesheet section. What you need to do is either a Liquid Penetrant Test (Dye Penetrant) or a Magnetic Particle Test. Also you will need to perform a hydrostatic test. These test will find cracking and leaks at the tubesheet area of these fire tube boilers.

 You are performing IR on a boiler that is offline and not generating any type of heat. So IR will not be able to tell you anything. Unless you are somehow inducing heat via pulsed thermography, inductive heating or some other heating means. Even with this, there is still the issue of high reflection errors.

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Sonny James
Thermal Diagnostics Limited
www.tdlir.com
Medical Division
www.infraredclinic.com
NDE Institute of Trinidad Ltd.
www.learnndt.com

Just gonna add to John's words that you could try to sway your body and camera from side to side and look at all the tubes again. If you can, try to control what is behind you. If you look close at my signature image, you can see the effect of reflection on the name plate.

Have you tried to play with other Pallets? Great observation on the visual inspection.

Let us know what you get

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Cary Weaver
cary.weaver@owenscorning.com
DoUSeeGreen.com
Maintenance Specialist
Thermology L3

I agree with Sonny you need a different testing method. When it comes to Chillers or Boilers(Tubes) I would go with Eddy Current Testing. This group is really good and will come to you they are located in Charlotte NC. Hussein Sadek is my contact and he is a Level III guy with great staff, he was even President of ASNT at one time.

http://www.tciintl.com/services.php

Jeff

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Jeff Gadd
Vision Infrared Services
www.visioninfrared.com

Hi Jeff,

You are correct that performing eddy current testing on heat exchanger tubes are the norm. However, for carbon steel tubes, ET is not well suited due to the high permeability of carbon steel resulting in a decrease depth of penetration. Remote field testing is most commonly used for carbon steel tubes or also IRIS Ultrasonic Testing. But I know where you are coming from and you are correct.

I think however, the issue with this particular instance is not an actual tube leak but a leak at the expanded or rolled tube at the tubesheet. I cannot see the image that well and I do not know if the tubes have been seam welded onto the tubesheet. If the problem is simply on the tubesheet and weld, then PT or MT is used on all welds to look for cracking. If the problem is in the tube at the rolled joint or inside, then RFT or IRIS may be needed. However, IRIS cannot detect cracking so RFT may be the better bet for cracking under the tubesheet.

It is always good practice to make sure all is OK with a final hydro test. This way any missed leaking tube can be identified before the boiler is placed back into service.

In my many years as a boiler and pressure vessel inspector and NDT inspector, I have seen many conditions such as this.

 

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Sonny James
Thermal Diagnostics Limited
www.tdlir.com
Medical Division
www.infraredclinic.com
NDE Institute of Trinidad Ltd.
www.learnndt.com

I think we are moving off topic here. This is very common with us crazy inspectors and thermographers . I think the main question is not how to find the leak, but what is going on with the IR. So this comes back to John’s assumption that it may just be a reflection problem. But then it comes back to using IR in this instance is non-productive as the boiler is cool and offline and not being heated. Therefore nothing of value will be seen with IR in this instance. The elevated temperature may just be an emissivity issue and a source of reflection. The shinier the surface finish the worst IR results are.

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Sonny James
Thermal Diagnostics Limited
www.tdlir.com
Medical Division
www.infraredclinic.com
NDE Institute of Trinidad Ltd.
www.learnndt.com

I am sure you have other images of this boiler, can you post them I think we might get a better ideal if we had more images to view.

Lee,

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Idaho Thermal Imaging LLC
Votum Thermography LLC,
Meridian, Idaho
208-941-2545 Cell