Flow Meter Calibration - Outside Calibration Service vs. In-House Calibration

C

CDISO

Guest
#1
Recently, it was suggested that we start calibrating our own Flow-meters. We have 22 of them. The suggest-er felt that it isn't difficult, would save money, etc. The suggest-ee was not comfortable with the idea and said so.

I tend to agree with the suggest-ee because 1) At our ISO audit last May, the auditor wanted to see Calibration records for a piece of equipment. I had the work order showing that a Calibration was completed by an outside service instantly available, but he stated that he needed to see something with Traceability information on it. (We had that in the paper files). 2) If we need to provide Traceability information, we would need more than a calibrated bucket and a stopwatch.

I would like some guidance as to whether in-house calibration of flow-meters is compliant with the ISO 9001 standard, without purchasing calibration lab-quality equipment.

Thanks!
 

htquality

Inactive Registered Visitor
#2
I believe that if you approach the calibration properly, it can be done in-house with appropriate traceability available. You would need to use calibation equipment (another flow meter) that was calibrated with full traceability as well as appropriate tolerance that is higher (4:1 I believe) than the flow meters that you want to calibrate. So you might have to purchase a "better" flow meter, with traceable calibration, and use it to calibeate your other 22 meters in-house.
 

BradM

Administrator
Staff member
Administrator
#3
Recently, it was suggested that we start calibrating our own Flow-meters. We have 22 of them. The suggest-er felt that it isn't difficult, would save money, etc. The suggest-ee was not comfortable with the idea and said so.

I tend to agree with the suggest-ee because 1) At our ISO audit last May, the auditor wanted to see Calibration records for a piece of equipment. I had the work order showing that a Calibration was completed by an outside service instantly available, but he stated that he needed to see something with Traceability information on it. (We had that in the paper files). 2) If we need to provide Traceability information, we would need more than a calibrated bucket and a stopwatch.

I would like some guidance as to whether in-house calibration of flow-meters is compliant with the ISO 9001 standard, without purchasing calibration lab-quality equipment.

Thanks!
Good question! :agree1:

First, understand there are a lot of variables when it comes to flow, to name a few:

  • Flow Rate
  • Temperature
  • Pressure
  • Restrictions (if any)
  • Allowing adequate distance before and after flow rate
  • Achieving steady state
So I'm thinking of three approaches. One, if it is liquid, you might could use a method of placing a bucket on a scale, use a timer, and verify (by weight dispensed per time) if the flow is accurate.

The second, is to build a "dummy" system. You can have a dummy flow system with a flow standard, and have a spot for the U.U.T. in the flow system. Finally, you can add a spot for the U.U.T. in the current process system to verify the flow meters.

You can add up the uncertainties to the bucket/stopwatch system and see if it is sufficient. Other than that, I don't see how you could get around not purchasing a standard flowmeter. other than.... creating a dummy flow system and having a spot for three or four meters at a time. Then you could develop a comparison method with min/max deviation. However, there is no N.I.S.T. traceability here. :)
 

Hershal

Metrologist-Auditor
Staff member
Super Moderator
#4
BradM has a good answer. One thing you will notice if you peruse cal lab scopes, is there are not that many that do flow. It is a smaller and somewhat more specialized discipline within metrology and most cal labs have trouble with it.

Maybe for calipers inside cal can be done with assurance. But for some disciplines like flow, get an outside accredited lab.
 
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