Oven Qualification - Thermal profile during the OQ of a vacuum oven

S

sledesma

#1
Dear all,
I am writing to ask for some help in analysing the results obtained in a thermal profile during the OQ of a vacuum oven. It was carried out without appling vacuum, only thermal profile, with the set point at 105 centigrades (analog controler). The oven is 16 litres of capacity, and the test was carried out using 12 calibrated thermocouples during 2 hs (stability). The specification of the termal range is 103-107 C because the oven is used for API's loss on drying determination. 3 of the thermocouples have a medium temperature of 120 centigrades, they were near the top, 2 of them that where near the glass door have a medium temperature of 100 C and the other 7 have a medium temperature of 110 C. I want to know if the equipment have a problem or may be the test was not properly designed. What do you think? Is it common to have these differences in temperature profile in this kind of equipment? Thank you very much. Regards from Argentina!
 
Last edited by a moderator:
Elsmar Forum Sponsor
K

Kevin H

#2
Re: Oven Qualification

Sledesma, I'm not surprised at the temperature variation in the thermocouples at that low temperature. I'm guessing that the oven is heated electrically - and that you're relying primarily on radiation for heat transfer. (Actually with air in the furnace you'll get some heat transfer via convection as well). Radiation only becomes effective at high temperatures - say 1800 degrees F or 980 degrees C. I used to heat treat precipitation hardening stainless steel tensile specimens at 900 F to verify capability. I had to be at +/- 15 F through out the furnace - a furnace without atmosphere, just air, that was heated via electrical resistance. After doing a temperature uniformity study we had to restrict the acceotable working volume to about 1/3 of the actural furnace working volume to meet those requirements.
At the solutioning temperatures, about 1750 F if I remember correctly temperature uniformity was fine. Our final solution to the temperature issue was to purchase a furnace with a builtin fan to circulate the air iresulting in transfer via forced convection n the furnace so that were more uniform and had better heat transfer, not relying just on radiation and natural convection.

You'll probably see even worse uniformity if you test under vacuum, which I believe you should do, as conformity tests should reflect working conditions. And yes, doors, even when insulated are usually cooler. I'm not a furnace designer, just a user, so I can't help with your thermal uniformity problems. - One possibility would be to do what we did, i.e., restrict the usable volume of your oven to that which meets the temperature variation requirements of your test.

The uniformity that you're looking for at the low temperatures you're measuring will be extremely challenging to obtain in a vacuum oven. Best of luck on getting them.
 
M

MIREGMGR

#3
Re: Oven Qualification

With only radiation as a heat transfer mechanism, what is the meaning of a reading from a thermocouple located away from the part? What is it measuring?

If the thermocouple is conductively coupled to an oven enclosure element, it's measuring the temperature of that element...which may have practically nothing to do with the spatial evenness of the radiation pattern, if in fact that would result in the desired part temperature profile.

If your heating mechanism is solely radiation and you're using thermocouples to measure temperature, they should be conductively attached to either a test part or a specially engineered object that's located where the production parts will go, and has appropriate characteristics to heat in the same pattern as the known actual heating pattern of the production parts. The thermocouples also should be locally radiatively shielded, so they measure the test part temperature via only conduction, without consideration of their own radiative heating characteristics.
 
S

sledesma

#4
Re: Oven Qualification

Yes Kevin H, this oven works with electrical resistences, and the test was carried out without applying vacuum, but the chamber is hermetically closed. So you said that in that condition the primary heat transfer is because of radiation. And so that the homogeneity will be poor at that temperature. Thank you very much for your contribution! I think the problem is being clarified!
 
S

sledesma

#5
Re: Oven Qualification

Thank you very much Miregmgr! Now I will only concentrate in the results of the TC that are near the working surface!
 

BradM

Staff member
Admin
#6
Hello there!

First, it sounds to me that your temperature specification is way too tight. Even with high quality Type T thermocouples you have +/-.75 C tolerance on each wire. So, you can have a total of 1.5 C deviation.;) That is not including any error within the recording device and other uncertainties along the way.

BTW... what kind of specifications were provided with the oven? If the oven was not designed for your particular uniformity, it may not ever be able to achieve it. Ovens have to have very high air exchanges per minute to achieve that type of uniformity.

What kind of oven is this? Is it a recirculating-air type oven, or is it constant temperature? If it is recirculating, there is a discharge and a return air. Generally the discharge side will be the hottest. Also, heat rises, so the top of an oven will be hotter than the bottom.

If this is a constant temperature vacuum oven and your process will involve vacuum, you really should consider running the profile with the vacuum on.

I hope something here helps.
 
Thread starter Similar threads Forum Replies Date
J CQI-9 - Can OEM do Oven Studies? Reliability Analysis - Predictions, Testing and Standards 1
W Equipment for Oven Calibration, Uniformity and System Accuracy Tests AS9100, IAQG 9100, Nadcap and related Aerospace Standards and Requirements 6
S Performing PQ on a Small (tabletop) Air Heat Treating Oven ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 4
T Auditor states my Oven Thermocouples must be Calibrated General Measurement Device and Calibration Topics 18
I Is it common practice for a bake oven to require a CQI-9? AS9100, IAQG 9100, Nadcap and related Aerospace Standards and Requirements 1
M Traceable Calibration Of An Oven Thermometer General Measurement Device and Calibration Topics 4
D How to Calibrate and Verify a Heating Oven General Measurement Device and Calibration Topics 3
J Moisture Detection and Measurement in Vacuum Oven (Plastic Dryness) General Measurement Device and Calibration Topics 2
WEAVER Thermocouple Extension Wire for Temperature Measurement in an Oven General Measurement Device and Calibration Topics 9
N Is Air Burst test for oven treated condoms still required under ISO 4074? Other Medical Device Related Standards 1
P NADCAP Certified - Heat Treat Continuous Belt Driven Oven question AS9100, IAQG 9100, Nadcap and related Aerospace Standards and Requirements 3
M TS 16949 and Form, Fit or Function? What about Calibration of Oven Controllers? IATF 16949 - Automotive Quality Systems Standard 5
K Pyrometry Question - Furnace and Oven Instrument Calibration IAW AMS 2750 AS9100, IAQG 9100, Nadcap and related Aerospace Standards and Requirements 9
N Can a Calibrated Digital Thermometer be used to monitor my oven? General Measurement Device and Calibration Topics 12
B Calculating Measurement Uncertainty in Oven Calibration (using thermocouples) Measurement Uncertainty (MU) 4
W Oven Leak Test Method - Integrity of the chamber to hold gas Qualification and Validation (including 21 CFR Part 11) 3
W Is an Oven I/O/Q Validation Required or is Calibration Sufficient? Qualification and Validation (including 21 CFR Part 11) 7
B Temperature Gage on an Oven was Out of Calibration Period General Measurement Device and Calibration Topics 15
N Bench Top Oven Calibration Standards General Measurement Device and Calibration Topics 8
M Validation of Processes - Is Cl 7.5.2 applicable to bricktile firing in an oven? ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 12
P VMP template for a Dry Heat Depyrogenation Oven FAT thru PQ Document Control Systems, Procedures, Forms and Templates 1
T Oven Validation Protocol (procedure) needed General Measurement Device and Calibration Topics 19
R Paperless Chart Recorder to Monitor Oven Cycle Temperatures Manufacturing and Related Processes 5
R Setting Calibration Tolerance on Gauges - Oven Calibration and Stepped Plug Gage General Measurement Device and Calibration Topics 10
Adriane Need Help to Verify an Infrared Cure Oven General Measurement Device and Calibration Topics 9
Marc Convection Oven Cooking - If you have one, do you like it? Cooked a turkey yet? Coffee Break and Water Cooler Discussions 17
C Oven Calibration Range: How many points? General Measurement Device and Calibration Topics 10
W Leak Detection - Oven Seals General Measurement Device and Calibration Topics 1
G MSA Studies on heat shock tests - Should we just be calibrating the oven? Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 1
V Process, component or full product re-qualification: leaded to unleaded solder Qualification and Validation (including 21 CFR Part 11) 7
DuncanGibbons Understanding the applicability of Design of Experiments to the IQ OQ PQ qualification approach Reliability Analysis - Predictions, Testing and Standards 0
Y Examples of TRB Reports for MIL-PRF-31032 Qualification AS9100, IAQG 9100, Nadcap and related Aerospace Standards and Requirements 0
Jane's Like-for-like critical raw material change qualification - type of testing/ number of lots required ISO 13485:2016 - Medical Device Quality Management Systems 3
K PQ validation qualification - Asked to write a PQ protocol ISO 13485:2016 - Medical Device Quality Management Systems 6
dinaroxentool Question about qualification as a medical device or accessory in Europe EU Medical Device Regulations 2
T Qualification testing of Lead acid batteries Reliability Analysis - Predictions, Testing and Standards 0
Z Qualification of AzureDevOps in Gxp Qualification and Validation (including 21 CFR Part 11) 12
E Equipment Qualification - IQ/OQ per ISO 13485:2016 section 7.5.6 Process validation ISO 13485:2016 - Medical Device Quality Management Systems 7
D Determining of sample size for 'Operational Qualification' AQL - Acceptable Quality Level 3
B VDA 6.3 Qualification as Process Auditor training course and exam VDA Standards - Germany's Automotive Standards 0
D Performance Qualification per GHTF Guidance Other Medical Device Related Standards 12
M Informational EU – Guidance on Qualification and Classification of Software in Regulation (EU) 2017/745 – MDR and Regulation (EU) 2017/746 – IVDR Medical Device and FDA Regulations and Standards News 2
dgrainger Informational MDCG 2019-11: Guidance on Qualification and Classification of Software in Regulation (EU) 2017/745 – MDR and Regulation (EU) 2017/746 – IVDR Medical Device and FDA Regulations and Standards News 0
H How to prepare Performance Qualification (PQ) for autoclave General Measurement Device and Calibration Topics 2
D ISO 13485 - Equipment validation , qualification Qualification and Validation (including 21 CFR Part 11) 6
DuncanGibbons Qualification vs Certification in an Aerospace context AS9100, IAQG 9100, Nadcap and related Aerospace Standards and Requirements 5
Z Operational Qualification for Injection Molding Supplier Quality Assurance and other Supplier Issues 6
S AIAG CQI Auditor Qualification and 3rd Party Certification Requirements General Auditing Discussions 2
D FDA Biomarker Qualification Program - Has anyone prepared an application? Medical Device and FDA Regulations and Standards News 0
R Qualification of Distributors such as McMaster-Carr and Digikey to Medical Device Companies ISO 13485:2016 - Medical Device Quality Management Systems 3
Similar threads


















































Top Bottom