Controlling Temperature and Time - Do I need to calibrate the thermostat?

[mjoakin]

This is for a car, we glue together plastic and foam using an adhesive that activates at 70ºC during 2.5 mins. We bought a pizza oven like. It got a thermostat and a dial to control the running band goes to 2.5 mins.

Do I need to calibrate the thermostat by a third lab? we used a turkey thermometer, we put the oven at 70ºC, the liquid screen of the oven says 70ºC but the turkey thermometer marked 50-55 ºC, so we increased the dial to (don't remember) let's say 85ºc and then we put the turkey thermometer by 2.5 and we got the 70ºC we needed. So I guess I can have a thermometer to "calibrate" or "verify" the oven and I'll meet requirements? I think calibrating the oven's therm is more expensive. But anyway, do I NEED to have a thermometer calibrated by and approved lab? is a MUST according TS?

 

[BradM]

Hi there!

I'm not sure about the TS requirement aspect. However, if I understand what you are doing...

You are using a thermometer to verify the product is reaching the desired temperature. Is the thermometer calibrated?

If you are using the thermometer to monitor the process, then I would think the oven temperature indicator is not used for monitoring/etc.

However, you mentioned 2 1/2 minutes for the process. Is that a critical exposure time? If so, you might want to perform some verification of the timing device used.

 

[qusys]

This is for a car, we glue together plastic and foam using an adhesive that activates at 70ºC during 2.5 mins. We bought a pizza oven like. It got a thermostat and a dial to control the running band goes to 2.5 mins.

Do I need to calibrate the thermostat by a third lab? we used a turkey thermometer, we put the oven at 70ºC, the liquid screen of the oven says 70ºC but the turkey thermometer marked 50-55 ºC, so we increased the dial to (don't remember) let's say 85ºc and then we put the turkey thermometer by 2.5 and we got the 70ºC we needed. So I guess I can have a thermometer to "calibrate" or "verify" the oven and I'll meet requirements? I think calibrating the oven's therm is more expensive. But anyway, do I NEED to have a thermometer calibrated by and approved lab? is a MUST according TS?

Is this control done to measure a special characteristic parameter reported in
the control plan? If so, I think , it shall calibrate it.
ISO TS does not tell you what to calibrate of not. It is just question of 7.6 of ISO 9001 where there are reported the rquirements to be meet for Monitoring and measurement devices

 

[mjoakin]

Well, it does not appear in customer requirements as a special characteristic, but the adhesive specs (specially manufactured for this customer and this very process) states it needs to be activated at 70ºC per 2.5 mins, now TS says "control that process", ok I will take measurements of the oven 3 times @ day ... with ... a calibrated equipment to certify oven temperature is ok ... now it became an issue, some parts at our customer's started delaminating ... cause? adhesive not activated correctly (not proper cure time was the customer's veredict) ... so I guess the answer to my question was pretty obvious

All I want is to cover my back, in my next TS audit if auditor asks "how do you verify the oven is correct" then I'll show him my turkey thermometer, he will ask "how do you know this measures the temperature correctly?" ... then I can show the calibration made by a certified lab ...

 

[mjoakin]

Hi there!
If you are using the thermometer to monitor the process, then I would think the oven temperature indicator is not used for monitoring/etc.

don't wanna use the oven's temp indicator for one reason: I can put the thermometer inside a UPS envelope and send it to a lab for a calibration, that's cheaper than hiring a Lab to come to my facilities to calibrate my oven's temp control / indicator / thermostat ... etc and stick a "calibrated" tag to the equipment ...