Ultra low freezer thermometers, best practices?

[duff999]

Hi All

We recently had a supplier audit and we were challenged on our freezer temperature monitoring. Currently we have several negative 80 freezers, and we do spot temperature checks twice a day. Does any one have any best practice suggestions on how others are monitoring their freezers, using calibrated thermometers in several different locations inside the freezer.

We do plan on installing a temperature monitoring systems, but currently it is not active.

Do we have any recommendations on what type of traceable thermometers I should be using.

Any help is greatly appreciated.

 

[Tidge]

I have only limited experience with freezers, but if you are concerned with temperature excursions I can describe what did a million years ago when I was worried about something getting "too warm". "Too cold" was not a concern in my application.

I used an OMRON brand temperature controller that allowed me to set two different alarm conditions (monitoring a type K thermocouple). The lower alarm condition would trigger the cooling system, my intention was to keep the area below a certain temperature and I had studies that allowed me to set this alarm limit. The second alarm condition was set at my excursion point and I wired in a relay that would energize and lock an indicator lamp ON... there was a push button that could be used to de-energize the relay. This setup let me know at a glance if there had been a temperature excursion without having to go back and scrub the logged data. The same principle can be applied if you want to set up an indicator for excursions at the other end of the temperature scale.

 

[Zero_yield]

For our freezers (and ovens and refrigerators), we do charts (physical or electronic) that can be reviewed to confirm the equipment stayed at the proper temperature for the documented time. We also do audible alarms for if the temperature falls out of spec.

 

[BradM]

Hello there!

So first, a little more about what you currently have. You have freezers, and in each of them there are thermometers located throughout. Were the locations part of a mapping study (min/max/ average)? How did you determine how many went in the freezer?

You say you perform spot temperature checks twice a day. Does that involve opening the freezers, observing the thermometers, and writing those values down somewhere?

 

[duff999]

Hello there!

So first, a little more about what you currently have. You have freezers, and in each of them there are thermometers located throughout. Were the locations part of a mapping study (min/max/ average)? How did you determine how many went in the freezer?

You say you perform spot temperature checks twice a day. Does that involve opening the freezers, observing the thermometers, and writing those values down somewhere?

Thanks for the reply Brad.

We have not done an official mapping study, however this was brought up during the audit, and there concern were "hot spots".

For the spot check, we do have thermometers in the freezers that are read by the lab personal during their morning and evening walk throughs. My thought was to purchase additional traceable thermometers that can handle the negative 80 spec's. For the mapping, I will have to do additional research as to where the optimal placement would be for these.

 

[Tidge]

For our freezers (and ovens and refrigerators), we do charts (physical or electronic) that can be reviewed to confirm the equipment stayed at the proper temperature for the documented time. We also do audible alarms for if the temperature falls out of spec.

For the past case I described, I was concerned that there might be an excursion when no one was around to witness the alarm, and I didn't want to have to wait for people to review charts to know if there had been an excursion. I suppose if the alarm indicator doesn't deactivate if the excursion goes away, this is less of a concern.

 

[dwperron]

These days with the availability of inexpensive digital thermometer / dataloggers out there I cannot understand why they are not being used on every temperature chamber that needs "calibration". A constant log of chamber temperatures, the ability to set alarms, placement of probe(s) in critical areas, all justify the relatively small expense involved.
I have never understood the idea of taking a snapshot of the temperature twice a day as being adequate to demonstrate that the chamber maintained temperature for a product or process, never mind those places that expect an annual calibration to be adequate for that job!

 

[BradM]

These days with the availability of inexpensive digital thermometer / dataloggers out there I cannot understand why they are not being used on every temperature chamber that needs "calibration". A constant log of chamber temperatures, the ability to set alarms, placement of probe(s) in critical areas, all justify the relatively small expense involved.
I have never understood the idea of taking a snapshot of the temperature twice a day as being adequate to demonstrate that the chamber maintained temperature for a product or process, never mind those places that expect an annual calibration to be adequate for that job!

Good points.

Minimally, you can put some thermometers in there, run the wire out the door and connect to something. That way the door doesn't need to be opened to take readings.

 

[BradM]

Thanks for the reply Brad.

We have not done an official mapping study, however this was brought up during the audit, and there concern were "hot spots".

For the spot check, we do have thermometers in the freezers that are read by the lab personal during their morning and evening walk throughs. My thought was to purchase additional traceable thermometers that can handle the negative 80 spec's. For the mapping, I will have to do additional research as to where the optimal placement would be for these.

Yes!! I would be concerned with the lack of mapping of the chambers. Are you sure it wasn't done during the initial commission of the chambers?

I would have them mapped. Once they are mapped, I would consider placing a probe in the min/ max/ and average location for temperature mapping.