Is calibration really required?

Dan M

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We manufacture fluids used in automotive, so the production process involves blending chemicals according to a recipe. The raw materials are either weighed in or pass through a mass flow meter. A question came up, do we need to calibrate the mass flow meters? We perform 100% final inspection of the finished product.

The flowmeters are not called out on the control plan. We do not call out measurement devices used in the production process on the control plan as we are aware that we will have to perform statistical studies on these if they are in the control plan.

Isn't up to us as an organization to decide if and how we verify / calibrate flow meters used in the production process? And this would be based on our risk assessment of what can happen if the flow meters are given erroneous readings. says: The organization shall determine and provide the resources needed to ensure valid and reliable results when monitoring or measuring is used to verify the conformity of products and services to requirements.

My interpretation of the above: Our flowmeters are used for process control, and not to verify the conformity of the product to the requirements. 100% final inspection of the finished product is how we verify the conformity of the product to the requirements. Measurement Traceability says: When measurement traceability is a requirement, or is considered by the organization to be an essential part of providing confidence in the validity of measurement results (then we must calibrate...)

My interpretation of the above: We decided if measurement traceability is required and essential (as long as our customers have not mandated it) for the equipment used in the production process.

Am I missing something or mis-interpreting?


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You are standing on solid ground in how you are interpreting 7.1.5
If you are fearing an audit finding I would suggest formally documenting your conclusion that the flowmeters do not require calibration, so you can present this to an auditor as proof that your organization did determine that equipment does not require calibration.

Ron Rompen

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Although I can forsee arguements with your auditor, I have to agree with your interpretation. YOU determine the calibration requirements/frequency/method, not the auditor. Two things that you could do to help support your position:

1) Do you have ANY history of customer complaints/nonconformances (including internal) which could be traced back to uncalibrated/improperly functioning instruments (such as the flow meter)?
2) Is your customer aware of your decision, and if so, have they agreed with it? This could also be supported by customer audits of your facility/process.


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Ok, my initial comment was pure provocation.
The raw materials are either weighed in or pass through a mass flow meter
Here is one.
The flowmeters are not called out on the control plan
Here is two, but unfortunately in your case one and two does not equal three.

There is a reason why flowmeters are there.
You use them and ignoring their indications will result in nonconforming product, am I right?
If so, it deserves mentioning in PFMEA.
Items mentioned in PFMEA, usually move into control plan.
Control methods in control plan go under calibration control to preserve its reliability.

You have to design manufacturing process, which meets IATF 16949 goal, by using defect prevention and reducing of variation.
Post-process inspection does not meet this goal.

There are cases when machine is equipped with gauges, which are not monitoring process variables.
E.g. machine manufacturer says, that minimum working pressure of it's pneumatic system is 0,35 MPa.
There is manometer installed to show current pressure.
You need it to check only when machine doesn't start at all, but indications - 0,35; 0,4; 0,45 are not affecting product characteristic variation.
Then you can put sticker "Beyond calibration system" or something similar.
But only when there is no relation between this process parameter and certain product characteristic.


Quite Involved in Discussions
If there is something that verifies after the flow meter and its not on the CP you do jot need to calibrate. Worked in automotive 22 years. 3.5 with flow meters, this never was issue. Very good question though.
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