Non-expendable K type test sensors for TUS as per AMS 2750E 2

[hastelloyC]

Any expert in familar with AMS 2750E could help to answer the specific question for me?
That is for the usage of non-expenable K type test sensors for TUS sensors.

In Figure 1, it is mentioned that non-expandable E&K type sensors are not permitted for re-calibration if used above 500F.

In my understanding those could still be reused with restrictions of 3.1.3.4 and 3.1.3.5. However, this was only mentioned for using exclusively under 1200 F (650 C). So what about those above 650 C? How many times or how long could it be used (for non-expendable E & K type sensors above 650 C)?

 

[EdStainless]

Not permitted.
The drift in type K is huge, and at first it drifts one way, and then the other.
Just by Type N and be done with it.

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P.E. Metallurgy, Plymouth Tube

 

[hastelloyC]

EdStainless,

Thanks for your reply.
Non-expendable type K is not premitted for TUS testing at all? Is there any clear statement on this?

I am not quite understanding the idea behind this. As you can see, for recalibration, the expendable base metal sensor is not permitted while it is conditionally permitted for non-expenable base metal sensor. It looks like non-expendable sensor is 'superior to' expendable sensor. When it comes to reuse, as listed in the table, the expendable base metal could be used subject to restriction of U formula (> 650 C), why non-expendable (supposed to be superior) could not be reused?

 

[EdStainless]

It is a combination of temperature and time that limits use.
The upper limit for K is much lower than most people are accustomed to using them at.
It clearly says that you are not allowed to re-calibrate K if used above 500F.
You have to read the rest of the details, but you can only use a K in protected environment up to 1200F once.
K's are simply a poor choice if you are going above 500F, and there are better options below that also.

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P.E. Metallurgy, Plymouth Tube

 

[hastelloyC]

EdStainess,

Thanks again for your reply.

Yes, it says type K is not allowed to be re-calibrated if used above 500F, but that's for re-calibrate rather than re-use. I am checking about the re-use of K type as test sensors. It should be different from re-calibration (As you can see, for using of non-expendable base metal senors as load sensors, recalibration is not permitted, but re-use is limited by number of uses, temperature of use, and
calendar days since first use).

I am also agree that there are better choices for selecting other types. But if some suppliers already used K type sensors for TUS, should we say Yes or No? What's the justification from the requirement of AMS 2750 itself?

 

[AidanMc]

I was taught that type K can only be re-used if you remove the portion that was exposed to temperatures above 500F (see 3.1.3.1 and attached image). This is a confusing interpretation to me because the paragraph in reference is referring to damaged thermocouples. It is however what I learned in an eQualearn class hosted by PRI and taught by an experienced auditor. I cannot recommend those classes enough when it comes to learning AMS 2750 requirements.

Aidan McAllister
Metallurgical Engineer

 

[EdStainless]

If this subject is truly of interest to you then I suggest that you loin SAE and the AMS committee that handles this spec. You don't have to attend meetings, just vote online and you vote 'waive' on things that you aren't involved in. This way you will see what is being discussed and have some background. You will also know what is coming in the next revision.

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P.E. Metallurgy, Plymouth Tube

 

[ZANX]

Expendable thermocouples (thermocouple wire covered with fabric or plastic). Base metal expendable thermocouples - you are allowed to use these thermocouples for TUS -Type K included. The number of uses is limited to 30 if used below 650 degrees celcius. between 650 and 980 degrees celcius you can use these max 32 times. if used above 850 degrees celcius you can only use these once. For interpretation of the AMS2750 please consult the HT Pyrometry guide, I find it very helpful.

 

[Dalinus]

Hello All,

can I ask you, from your personal experience, what type of thermocouple is the best choice (price, durability) for TUS on furnaces(up to 80 m3) with temperature range 250-1100°C?

And second one, where can you buy or get acces to that HT Pyrometry Guide?

Dalin

 

[AidanMc]

You can access the Pyrometry Reference Guide free from PRI through their eAuditnet system. If you're going to be doing Nadcap work, you'll have to get familiar with eAuditnet pretty quick.

Once you access eAuditnet, you can get to the Reference Guide through Resources > Documents > Public Documents > Heat Treating > Handbooks & Guides. It does have quite a lot of information in it regarding interpretations of AMS 2750 as well as a number of FAQs for common questions.

Aidan McAllister
Metallurgical Engineer

 

[Dalinus]

Thank you. I tried throught our company username and password, but I cant see any handbooks in Heat Treating section. I can only see handbooks and guidelines in Welding section. Is it possible, that there is some restricted acces?

 

[ZANX]

No, if you've got access to eAuditnet.com you should be able to access all handbooks and guides on eAuditnet. Please check with eauditnet why you can't access these.

 

[hastelloyC]

Expendable thermocouples (thermocouple wire covered with fabric or plastic). Base metal expendable thermocouples - you are allowed to use these thermocouples for TUS -Type K included. The number of uses is limited to 30 if used below 650 degrees celcius. between 650 and 980 degrees celcius you can use these max 32 times. if used above 850 degrees celcius you can only use these once.

This is clearly stated in section 3.1.3.3 for use of expendable TC. My question is what's about use of nonexpendable base metal TCs for TUS?

In section 3.1.5.3, it was mentioned for the life of nonexpandable base metal load TCs. But nowhere mentioning the test TCs.


It's quite confusing.

 

[ZANX]

Hi Hastelloy,

Figure 1 of AMS2750 gives you the requirements for reuse and recalibration of TESTS and LOAD sensors. According to Figure 1
the reuse of non expendable TUS test sensors is 3.1.3.4 to 3.1.3.5
3.1.3.4 Any base metal TUS thermocouples used below 650 is limited to 90 uses or three years. From this I take that you cannot reuse any base metal thermocouple for TUS above 650 degrees celcius.
3.1.3.5 Non expendable base metal TUS thermocouples used under 650 degrees celcius shall be limited to no more than 90 uses or three years. Para 3.1.3.5 is applicable to TUS Test thermocouples and Para 3.1.5.3 is applicable to load thermocouples. From this it looks like you cannot reuse of base metal thermocouples used above 650 degrees Celsius.

 

[hastelloyC]

ZANX,

You might be right. But why is it not clearly stated as "Not permitted if used above 500F" as that for recalibration?

 

[Dalinus]

No, if you've got access to eAuditnet.com you should be able to access all handbooks and guides on eAuditnet. Please check with eauditnet why you can't access these.

Problem solved. We are in transportation and power generation industry so we had access to TPG only, not NADCAP(aerospace). After request PRI granted us the access to aerospace industry so now we are able to see HT Handbook and Guide. I am looking forward to useful informations.