API 6A-Annex M Qualification of Heat Treating- No.of thermocouples for Calibration

[Qual7Eng]

Hi, Please i need your supports, and get clarified the below ,

Refering Below extract from API 6A

A minimum of nine thermocouple test locations shall be used for all furnaces having a working zone greater than
0,3 m3 (10 ft3).
For each 3,5 m3 (125 ft3) of furnace working zone surveyed, at least one thermocouple test location shall be used,
up to a maximum of 40 thermocouples.

My intrepretation for TUS of furnace with volume 53 cubic meters working zone was 16 thermocouples(ie, 53/3.5=15.14 No.s) to be used during calibration, an auditor explained the same in another way that 16 + 9 a total of 25 No.s Thermocuples shalll be used.

Please i need your supports, and get clarified.

 

[valvit]

The number of thermocouples required is not additive. You are correct, 16 thermocouples are required.

Valvit

 

[danw2]

I don't know how closely API tracks AMS 2750, the pyrometry standard for aircraft heat treating.

Industrial Heating ran this table in 2010 for the D version of 2750 (current version is E) for number of thermocouples based on a volumetric calculation.

The table splits the auditor's quantity of 25 and your quantity of 16 at a middling 20 (@57m3)

The original article and table are still on-line at
Link

I'm told that in the aircraft sector the auditor wins these kinds of arguments.

 

[Qual7Eng]

thanks alot.. now can we use production furnace thermocouples for TUS ??

 

[redpicker]

Please tell me this wasn't an API auditor. I have seen some stupid stuff from auditors over the years, but this one is really over the edge.

I don't see how the auditor could win this one.

Consider a sign at a gas station:
Minimum charge for any amount over 1 gallon: $9.00
Charge for gasoline shall be $3.00 per gallon.

So, according to this auditor, if you bought 6 gallons, you'd have to pay $27 (instead of $18)?

now can we use production furnace thermocouples for TUS ??

Are you asking if you can use spare production T/C's for your survey?
I have never seen it done, but there is no reason it couldn't be done (provided proper documentation).

In general, however, the survey T/C's are Type K (Chromel/Alumel) and the production T/C's are Type S (Platinum/Pt-Rh). The cost of one Type S T/C could pay for a whole whole spool of Type K. It is common to run the survey with a few extra T/C's just in case one of two of them should fail during the survey.