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Up Topic Welding Industry / Inspection & Qualification / Measuring base metal temperatures
- - By clutch (*) Date 01-14-2009 03:01
Hey does anyone know if infrared (point and shoot) thermometers are an approved means to checking temp of base metals or is the temp crayons the only real way to go
Parent - - By 803056 (*****) Date 01-14-2009 03:39
The infrared thermometers have their place. The user must understand that they are "calibrated" for the heat radiating from a "black body", so, taking a reading from a reflective surface such as stainless steel, aluminum, nickel, etc. will yield large errors. However, iron that has a rough surface, mill scale, or some rust will yield pretty good results.

I've had errors on the order of 150 degrees F when using a infrared thermometer on nickel alloys. That's a problem in my book. Luckily I double checked my readings with the thermal-couple.

I use a thermal-couple for monitoring preheat and interpass when qualifying procedures or anything other than carbon or low alloy steels.

Best regards - Al
Parent - By BryonLewis (****) Date 01-14-2009 03:53
Fine answer.  Now I can stop wondering about it.
Parent - - By CHGuilford (****) Date 01-14-2009 17:27
I used galvanized steel roofing for a heat shield for my basement wood stove. 
If I point my infrared thermometer at it on the stove side I get readings all the way up to 400 degrees.  Yet at no time is the metal so hot that you can't keep you hand on it - it gets no higher that 90 degrees actual temp..  I surmise that the thermometer is reading the reflected infrared from the stove itself.

On the metalbestos pipe- pointing the gun at a  splotch of flat black paint will give readings about 100 degrees higher than when I point at a shiny section right beside that.

As Al said, infrared thermometers do have their place but the user needs to be aware that readings can vary by a lot.
Parent - - By ctacker (****) Date 01-14-2009 19:07
you can get a lot closer readings on shiny surfaces by laying a cloth or paper down and taking the reading from it.
Parent - By CHGuilford (****) Date 01-15-2009 17:18
Actually, flat black spray paint works nicely but it wreaks havoc with my PQR test plates :)
Parent - By BryonLewis (****) Date 01-14-2009 03:52
Fine question.  I have thought about that method too, but never really got around to asking about it.  Good show.
Parent - By 3.2 Inspector (***) Date 01-14-2009 07:15
It is an approved method!

As Al state it can have quite an error margin.

3.2
Parent - - By dlmann (**) Date 01-14-2009 10:19 Edited 01-14-2009 10:23
Look for an infared thermometer with an adjustable emissivity feature.  There are handheld models out there with this feature.  Having the ability to adjust emissivity overcomes the drawbacks mentioned by Al.  As far as being approved I would think if you included a thermometer that gave you consistent repeatable results in your QA program you would be OK.  I would have the sales/tech rep demonstrate to me that is would give the desired results on the different surfaces you work with.

regards, Donnie Mann
Parent - By HgTX (***) Date 01-20-2009 23:45
Ditto on the adjustable emissivity feature.

Also make sure you're not taking too much advantange of not having to have direct contact with the part; if you stand too far away it will affect the accuracy.  They're no good across the room, and even over the welder's shoulder is seriously iffy.

I'll try to ask around and get some better details.

Hg
Parent - - By jwright650 (*****) Date 01-14-2009 12:19
If this instrument can effect the quality or the final acceptance or rejection the product, you might want to consider maintaining the certification of conformance and set a schedule for how often the instrument is calibrated to assure repeatable results.

Just a thought, if you are looking to add this equipment to your list of inspection tools.
Parent - - By Lawrence (*****) Date 01-14-2009 12:40
JW,

How do I calibrate my crayons?
Parent - - By jwright650 (*****) Date 01-14-2009 12:54 Edited 01-14-2009 13:04
L,
<grin>I never had an auditor tell me that I had to. Tempil Sticks say on the box that they guaranteed accuracy within 1%. However after a search of thier site, I don't see any supporting documentaion should an auditor ask for it.
http://tempil.com/index.asp

firing off an email to them now.......

edit: their site has a problem with the Contact/Inquiry page....Bummer
Parent - - By js55 (*****) Date 01-14-2009 13:29
Contact pyrometers are a better tool. They are not subject to infrared error, and they are verifiable.
Parent - - By hogan (****) Date 01-14-2009 15:30
I use an IR thermometer, but we mainly deal with carbon steel. It is calibrated to ASTM E77 but i still verify readings with coupler and/or crayons randomly.
Parent - - By BryonLewis (****) Date 01-14-2009 16:20
Using the Farm Code mentioned in other threads, all you have to do is lick your finger and put it on the metal.  If it sizzles then its preheated enough. :-)
Parent - - By jwright650 (*****) Date 01-14-2009 16:28
Where do you affix the calibration sticker on the licked finger once it sizzles?
Parent - - By BryonLewis (****) Date 01-14-2009 17:15
You will have to get it tattooed on there after the skin graft!  Duh, everybody knows that!  :-)
Parent - - By js55 (*****) Date 01-14-2009 17:48
NO, no, no. Since the finger and all its attachments are a part of the same temperature monitoring system, and in fact are disfunctional without them, you can tattoo the calibration data anywhere. I usually have my temp monitoring systems tattoo the data on their butt. That way the auditors only care to verify it one time. Forever.
OK I'm done.
Parent - - By 803056 (*****) Date 01-14-2009 19:57
Back to the real subject matter. It isn't a case of calibrating the instrument.

Each surface affects the emissivity of the heat radiating from the mass/surface. A true "black body" is a body that absorbs all the energy directed to it and re-radiates all the energy. It has a emissivity of 1. The infrared thermometer is "calibrated" using a "black body". An example of a surface that would approach the same emissivity as a "black body" is an asphalt driveway.

Other surfaces that are polished or have different emissivity will result in erroneous readings unless the thermometer is adjusted for the type of material being tested. You could use a contact pyrometer, tempil stick, or thermal-couple to get a "true" reading of the temperature and adjust the infrared thermometer to register the same temperature. You would have to readjust the thermometer for each material you are working with to get "accurate" temperature readings. The point is that adjusting the thermometer to one surface type having a specific emissivity is not going to yield good results with all materials.

Best regards - Al
Parent - - By Stephan (***) Date 01-15-2009 17:53
Hmmmmm...

excellent information, Al!

And again I've learned something new!

If I understand this correctly, we are now back at Jeff's recommendation saying:

Quote: "Contact pyrometers are a better tool. They are not subject to infrared error, and they are verifiable." Unquote. ?

This under the recommendation that these "contact pyrometers" have no particular restrictions or drawbacks depending to material surface to be measured, or to the particular operator using the thermometer?

Or in other words: They are more "universal" and simpler in use?

If so, are they also "cheaper" compared to an infrared thermometer?

Thanks and best regards,
Stephan
Parent - - By kipman (***) Date 01-15-2009 23:00
Stephan,
Contact pyrometers are not useful in all situations.  One that comes to mind for me is flame straightening of steel weldments to correct distortion.  When flame straightening, the hotter you can get the workpiece directly under the flame the easier it is to achieve the distortion corrections.  However, it is also important to limit the maximum temperature in many cases so as to not negatively affect the metallurgical properties (such as on TMCP or Q&T steels).  Therefore the best approach is to shoot for a narrow temperature range.
It is simply not practical to use a pyrometer to measure this - you need to try to measure directly under the flame.  In my experience Tempil sticks are the best method for doing this.
Regards,
Mankenberg
Parent - By Stephan (***) Date 01-15-2009 23:36
I see...

So finally it's as always in our trade.

Each method, what ever it is, has its very specific benefits and particular drawbacks and thus its specific justification, and yet also in this field there's no "temperature measurement allrounder" found by now.

Thanks Kip!
Parent - - By jwright650 (*****) Date 01-15-2009 18:59
Hey Al...and others,

What's your take about proving to an auditor that the tempil sticks are as accurate as they guarantee on the box?(should this question ever arise, I would like to have a plausible answer...LOL)

My welders have 150, 225, and 1200 tempil sticks in their tool boxes....and I keep a 250 for verifying the rod ovens.
Parent - - By Milton Gravitt (***) Date 01-15-2009 19:26
John thats a good question because we have an audit coming up soon. If you where using a tempil stick while they where making there rounds it might come up. Do you think the company that make the tempil stick can give a certificate of  certification or some analysis of testing.
                                              MG
Parent - - By jwright650 (*****) Date 01-15-2009 19:35
I looked on their site and couldn't find any type of certificate of conformance, even tried emailing them  to ask for something and their contact page doesn't work.
Parent - - By Stephan (***) Date 01-15-2009 21:08
John,

happy new year first off, even though it's a few days old already.

I would like to agree with what Milton said: "Good question!"

Have tried to find some particular information to this. What I could read on some German websites was an accuracy of +/- 1% of the stick indicated temperature, measured.

The German text book "Lexikon der Physik" (encyclopedia of physics) edition of 1971, explains an accuracy of +/- 5°C (41°F), under "advantegous" conditions, what ever this means.

Nonetheless I personally would rather trust a contact pyrometer more than a tempil stick, alone as for the consistency of the measurements (influence of the operator). What, e.g. if the operator is colourblind in even the particular range of colour change?

Best to you,
Stephan
Parent - - By 803056 (*****) Date 01-16-2009 03:34 Edited 01-16-2009 03:42
A good mechanic has a box of tool at his disposal. The right tool for the job at hand. It would be difficult to rebuild an engine with just one general purpose adjustable wrench.

A good welder or inspector has to have a variety of tools at his disposal and know what tool is best suited for the task.

I like the infrared thermometers when I'm on a job site monitoring welders for preheat and interpass temperature. In my humble opinion, +/- 10 to 20 degrees F isn't going to mean the difference between success and failure for the temperature ranges I'm concerned with. On the other side of the coin, I don't use the IFT when qualifying procedures and an accurate reading is needed for proper documentation. In that case I prefer to use a contact pyrometer or thermal-couple.

As for JW's question, I would heat a piece of metal to the temperature necessary to cause the specific temperature indicating crayon to melt and check it with a thermal-couple that is calibrated. I see no reason why each crayon would need to be tested before issuing them to the welders. Again, the temperatures ranges we are concerned with usually fall within a narrow range and a few degrees one way or another isn't going to cause a sane person angst. After all, all the tables and equations used to calculate preheat and interpass temperatures are approximations based on empirical solutions to observations made in the laboratory. The numbers are not hard finite numbers, they simply give us a warm fuzzy feeling that we are taking the necessary precautions to prevent cracking, etc. A comparison of preheat requirements between several welding standards will result in different preheat requirements for each.

I'm not saying that preheat and interpass temperature monitoring isn't important. I am a believer when it comes to preheating carbon and low alloy carbon steels, but the idea that precision measurements are necessary on every job is a step beyond reality of the situation. The need to be within 1 or 2 degrees of the minimum preheat temperature simply isn't going to make any difference in the success or failure rates of welds.

Like everyone that participate in the forum, I have my own opinion on different subjects and it is no better or worst than another person's opinion. When a code is involved, I let the "code do the talking" as Ken Coryell would say. If the code doesn't address the need to calibrate, who am I as a third party inspector, to require something over and above what the code requires? Calibrated fillet gages: where does D1.1 say they have to be? Calibrated temperature indicating crayons: again where in the code does it say they have to be?

There is a time and a place for precision measurements. When precision measurements are required, the inspector has to know which tool is appropriate for the task and whether the tool or gage needs to be calibrated. Most welding jobs don't require the precision of calibrated temperature indicating crayons, fillet gages, or a need to know how many fairies can dance on the point of a needle.

Best regards - Al
Parent - - By jwright650 (*****) Date 01-16-2009 13:56
Al, It's hard to reason with common sense...

But calibrated fillet weld gages, as you commented on are one of those items, I feel is unecessary...really, if they are worn that badly, toss them out......however the AISC auditors view that tool as a tool that is used in the acceptance and rejection of product or a tool that effects the quality of the product....so they make an effort to check my fillet welds gages and see that they are indeed verified to a gage that is tracible back to a National Standard.

I'm hoping ziggy will chime in here at some point and give us his take on the tempil sticks.
Parent - - By 803056 (*****) Date 01-16-2009 21:00 Edited 01-16-2009 21:34
Hello JW;

"the AISC auditors view that tool as a tool that is used in the acceptance and rejection of product or a tool that effects the quality of the product ....."

How do they want you to calibrate the hammers, screwdrivers, 10 pound mauls, etc.? Does the round of the face of the hammer have to conform to a specific radius, does it have to weigh 10 pounds within a fraction of a "stone" (a measure of mass). Does the flat end of the screwdrive have to be ground concave so it doesn't slip from the screw slot during use?

If you were working with NASA where there are specific requirements for some of the "crazy" questions I just posed, they aren't crazy requirements. However, the same considerations are simply immaterial in a structural steel shop.

I sometimes believe we are too eager to please and too eager go with the flow.

I see some of the same BS in the AWS ATF program. I want no part of it if it isn't adding value to the program. Layers of management, layers of complexity add cost with very little benefit to the customer.

Best regards - Al
Parent - - By CHGuilford (****) Date 01-17-2009 03:53
Now, now.  Calibrated hammers?  Clearly not needed UNLESS impact energy is required to be calculated for an essential variable that could affect the acceptability of the final product.  (CVN test machines?)

Now calibrated slag hammers - that's a different story.  We all know how important it is to have just the right handle shape and pick point hardness.  If those are off you just can't get good welds (the guys hanging out at tool crib taught me that - they oughta know, they've been welding for 2 whole years)

And calibrated flint strikers are an absolute necessity.  If your spark isn't right, you'll only light half the flame and then you can't get a good cut.  I'm not sure but I think the guy who taught me that is also the one who controls his amperage by standing on the ground cable to choke off the electrons (like a pinched garden hose).

More seriously (addressed to everyone), I haven't had an AISC auditor question temp stick precision.  If I did, I would question why that was a problem.
Auditors could pick on a lot-  how you check ratios if you have a shielding gas mixer, light meter for your MT lighting, torque wrench for threaded studs.  How many shops with UT capabilities own or have access to DS and RC reference blocks?  (I'm now all set in these areas except one, and I'm not gonna tell which one.  If I get hit on these next time, then I'll know the auditor reads this forum).
But all I focus on are the calibrations and standards that are spelled out as being required.  Usually,the standards get changed only when something has become a problem.
Parent - - By 803056 (*****) Date 01-17-2009 05:34
Sanity is all I ask for.

There is a time and place for precision measurements. There is a time and place where precision isn't necessary and simply adds cost to the project with no added benefit.

As for calibrated hammers, my point was that in rocketry, the cost of send mass into space is an expensive proposition. Everything is measured and weighed with precision because there is a need to do so. A time and place for everything.

A quality control system must be in tune with the work that is performed. That is sometimes lost on auditors because they suffer no consequence when they make unreasonable demands that  add cost, but do not add value or benefit to the product the customer is purchasing.

I like your approach. It sounds like a sanity check that works.

Best regards - Al
Parent - - By CWI555 (*****) Date 01-21-2009 15:34
"As for calibrated hammers"
You mean the 'Precision inertial energy impact delivery device'.
Parent - By 803056 (*****) Date 01-22-2009 03:19
You got it.

Al
Parent - By hogan (****) Date 01-19-2009 15:27
CH,
The DS blocks are fairly easy to make. RS are a little more difficult.
Parent - - By ziggy (**) Date 02-26-2009 14:16
John

In my experience, I have never seen a contract requirement for calibrated tempil sticks. I do not ask for such papers as I do my work.

I did have an interesting experience once where a qc tech used a 125 F stick in a 250 F holder to demonstrate that their rod oven was at temp. Strange how that works. He actually spelled out " 2 5 0" on the inside of the oven but it just did not feel like 250 F...what I mean is when an oven is at 250 F or above, you can "feel" it...if it is running colder you can tell that too...so when the qc tech demonstrated for me it just didn't make sense...so I asked him for the tempil stik...wrong color for a 250 F!

If I might just add a thought, I believe it was Voltaire that said "the problem with common sense is that it's not that common" I believe that to be true even today...300 years since Voltaire said it...that is one reason I find this forum to be refreshing because there are many voices here that bring "common sense" back into perspective. You, Al, Chet and many others with years of hands on experience bring a fine balance to the industry.

ziggy
Parent - - By jwright650 (*****) Date 02-26-2009 14:27
Thanks ziggy for giving me your perspective on this.

Funny story, wonder why they just didn't keep the ovens at the temp that they should be at in the first place? Seems counter productive to have to work so hard to get around rules that are in place. 125°F would probably keep the biscuits warm enough for breaktime though.
Parent - By ziggy (**) Date 02-26-2009 14:39
Funny you say that about biscuits John because my rule is...and I tell the guys this when we get to the ovens...if there is any food in there it's mine! Some of those tortillas are soooo good!

ziggy
Parent - - By Stephan (***) Date 01-16-2009 19:59
Thanks Al,

I guess it was a bit naive from me to believe that with the temperature measurement in materials it might happen some day, to find a thermometer principle quite similar to a clinical thermometer - in other words: One for them all! ;-)

Best regards,
Stephan
Parent - - By 803056 (*****) Date 01-16-2009 21:38
A thermal-couple is the best I can do. Even they have specific temperature ranges, so a couple of them are required if measuring widely differing temperatures.

I guess that's what keeps industry humming. Well, maybe not humming, toss in a cough or two here and there to replicate the current economy. :)

Best regards - Al
Parent - - By 803056 (*****) Date 01-17-2009 19:13
I thought my tirade and long winded rant would generate some discussions on the cost benefits of high level qualify control systems with all the bells and whistles.

I'm disapointed.

Best regards - Al  :)

Parent - By stuzhotwire (*) Date 02-20-2009 20:33
Al
Appreciate your take on the qa systems.  Throwing in my two cents I couldn't agree with you more on the necesity to calibrate such things as Weld gauges or even tape measures for that matter.  I believe some of their reasoning is, such as AISC, certifications for one company and its product requirements differ from another.  there are no special certifications that narrow in scope so we all have to do the same stuff.
Now to stop defending their cause, I attempt to use a common sense approach and keep it simple.  such as tape measures.  how do you calibrate a $6 tool?  I have the operators verify their tapes against a standard and sign off on a sheet in their area once a week.  If it is off they throw it out and get another one.  Welding gages are verified once a year.  Tools we can't verify but cost more to certify than to buy  we throw out at designated times base on use and life expectancy.  Any way I can show we attempt to give operators dependable measuring devices has been a winner with auditors.  Which should be the only point to a good auditor.  But sometimes even I loose my sense of commonality!
Parent - - By MBSims (****) Date 01-17-2009 19:47
I have been able to get a C of C in the past from Tempil for tempsticks for nuclear applications.  Call them on the phone (I know, it's the old fashioned way) and they should be able to send you something.
Parent - By jwright650 (*****) Date 01-18-2009 18:33
Thanks Marty..I'll give that a try.
Up Topic Welding Industry / Inspection & Qualification / Measuring base metal temperatures

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