Rich

Thanks for your comments - even though you put words in my mouth.

1) I fully support as much training as any company will support its people in participating in and I in no way even compare this forum to any kind of training
2) I do not support this forum as a replacement for training
3) As for inspection company "having it down pat" I do make the assumption that their advertising is not false and that the free market would wash false claims away in a short order - perhaps you can shed additional light if you know something different about these commercial claims

To the point of my posts on this thread: It is rather frustrating when responses are "email off list" or "here is training course" without any further addition of usable application information. It happens in other areas of the board also. If you are prepared to tell one person off list - why not ten? Then why not 100? Then why not simply post it.

As for trainers and camera sellers - no one on the forum seeks charity in the form of a FREE training course however this is a "discussion" board - not a directory.

Once again - recommending training is perfectly appropriate on this board and links/phone numbers are also great. It would simply be nice to see some content with it.

You are right in one major sense about me not getting it - I am still very mystified by the difficulty of this application - hence my desire to see an actual discussion.

I hope that clears up where I am with this thread - and again - thank Rich - your perspective and advice is a big addition to this forum.

Terry O

This message has been edited. Last edited by: Terrence O'Hanlon,

I found a previous discussion on a vendor discussion board with some interesting comments from Geezer

quote:

Looking over the the procedure given by Ron Lucier on heater tube evaluation, I find that it doesn't provide near enough information and is not accurate in all assumptions. I offer the following for your consideration...

1. "Scale" on the tubeskin surfaces will not tend to look cooler than the tube. These areas will, in fact, look hotter...significantly hotter! In fact, they will be hotter because of differences in heat transfer efficiency between the tube skin (cooled by the process material) and the scale which is not cooled as effectively by internal process cooling.

2. The emmisivity value of .85 is not consistent to produce accurate temp measurements. For instance, 347 SS will have a much lower "e" value than low chrome at the same temp. Also the "scale effect" talked about in item one will require systematic "e" value adjustments to better account for the "true" skin temp in significantly scaled regions. In addition, the "e" value will vary with temperature, sometimes considerably!

3. The angle of the shot will greatly affect the accuracy of the IR. "e" values would have to be reduced to arrive at a more accurate temp if shooting, say, at the far side tube in a long firebox.

These are just a few ideas, there is much more to consider, I would love to see a forum, where training is offered specifically for heater/boiler inspections. Let me know if you ever organize one. I'll be there!

and Gaston

quote:

I fully agree with Geezer (very pleased to meet you) as regards the scale, the emissitivity, and that there are plenty of things to be yet considered.

Furthermore, after so many years of using different equipments to measure tubes, I have reached the conclusion that it is not possible to establish a General Procedure for this type of inspection, as the one it is being presented. This may lead to an inexperienced operator to committing significant errors.

Each furnace should be considered in particular, where the surface status of the tubes is not the only factor to the taken into account, but there are also many other decisive factors, among them, the fuel for burners (Fuel Gas, Fuel Oil, or combinations of them).

It requires a considerable amount of basic notional knowledge of materials, heat transfer, etc. A determinant would be the experience and number of inspections performed in the different types of furnaces and in their varying operating conditions.

Due to the complexity of this issue, I believe the most advisable thing to do is to interchange experiences and know-how on a personal basis at some kind of meeting of experienced operators, from which to draw the fundamental guidelines to be taken into account.

These comments seem to underline the difficulty with this application.

Terry O

www.itimaging.com is the updated website for the link posted previously.

Caveat --- I have not done this sort of work in YEARS, but......in work dating back to the 70's, I have yet to see anything that would give me confidence in temp accuracy in applications such as this. Most of my experience dealt with radiant wall furnaces in ammonia, methanol, and H2 production. The real issue here (or at least in my day.....) was how good is good enough. The root problem is what do we take as an accurate (reference) temp source? Thermocouples ? Dual band radiometry?

There are two independent reasons to measure furnace tube temperatures - process, and tube life projection. At least in my admittedly ancient days, the process reasons were that furnaces were being run so close to the process limits (coking, etc.) that small changes in temp could dramatically affect process performance. Likewise, if the issue is maximum metal temperature due to creep failure modes, then again small temp differences can make dramatic differences in predicted creep rupture tube life. In some processes (steam reform syngas for example) the bulk tube temp may actually slightly HEAT up going across the tube wall.....the process is after all exothermic.....so if the goal is to measure the maximum metal temperature experienced by the tubes, how do we accurately do that with IR pyrometry if the maximum metal temp is indeed NOT at the observed surface......?? Anybody remember the Kellog Millisecond ethylene furnace technology.....?? Now THERE is a temp measurement challenge.....

The ammonia industry spent a LOT of money with Battelle Institute (an outfit not known for being slackers...) in 70s and 80s investigating creep failure and remaining life estimates on furnace tubes, and of course, accurate temp measurement was key. To my recollection, Battelle never really was able to answer the question of what was the "best" way......

Don said it nicely. I have quite a bit of experience inspecting Reformer Tubes and I also train plant inspectors on the proper techniques for temperature survey.

I presented a paper at this year's IRINFO on this subject.
http://www.irinfo.org/Articles/2_1_2008_james.html

However, this paper does not go into Temp. Accuracy details but rather inspection technique. I feel you must master the technique before you can attempt temperature readings.
My next paper on this subject will address temperature measurments and equipment settings.

When it comes to accuracy, I always say that you are only as accurate as your reference and someone (you or the client) must make a decision as to which reference is accurate enough for their particular needs. We are in the real world and nothing is absolute (except death) or perfect. Especially when it comes to furnace tubes.

I look forward to you all reading my paper and please comment and give me your views and experiences as I am always learning new things every time I inspect a Reformer. Don't worry you wont hurt my feelings ;-)