To Calibrate or Not to Calibrate various Weight Scales

[Stijloor]

Since the requirement of calibration falls under section 7, it's permissible to exclude calibration from the scope specifying valid justification.

Which means that no weighing scales may be present in the entire process.

Good luck with that one...

Stijloor.

 

[michaelkhart]

Re: To Calibrate or Not to Calibrate

Stijloor - sorry - I think that I replied using the overall reply button and not to your questions specifically. Here it is below.

The process operator currently has instructions to use the container weight as a verification before they add the mixture in and weigh. This activity has been going on for years and the weight is established.

Worst scenario is that "something inadvertently goes wrong" and the batch is rejected later down the process because it does not pass visual inspection of critical characteristics. The batch would be scrapped.

 

[Stijloor]

Re: To Calibrate or Not to Calibrate

Stijloor - sorry - I think that I replied using the overall reply button and not to your questions specifically. Here it is below.

The process operator currently has instructions to use the container weight as a verification before they add the mixture in and weigh. This activity has been going on for years and the weight is established.

Worst scenario is that "something inadvertently goes wrong" and the batch is rejected later down the process because it does not pass visual inspection of critical characteristics. The batch would be scrapped.

Thank you for your response. I would be very hesitant to exclude 7.6 from your quality management system as advised by a previous poster.

I am sure that others will respond.

Good luck.

 

[BradM]

A couple of random thoughts...

1. A calibration service on measurement equipment by a competent vendor is always worth the cost. It just is.

2. There might be some merit to just having a performance verification. However, I would submit the weights used should be calibrated (with an identified tolerance/accuracy ratio) and an acceptance criteria for the pass/ fail.

To me, calibration can provide value to the organization. In your example, it is true that you have secondary quality inspection of the products. However, there is a cost(s) associated with scrapping the product and starting over. If you have an accurate, calibrated balance, and you can measure the product accurately and cut down on scrapped product, that service will pay for itself.

Or think of it this way. If you removed the balances tomorrow, would it affect anything? If you would have more scrapped product, then, the returned value from the balances is relevant.

If you have two balances that need calibration, I would think a competent vendor could come in once a year and take care of them. If you have a good cal lab around you, the vendor should be able to come on-site and take care of several things at once.

The decision to calibrate is your customers to make. I'm just suggesting that I believe there is value in having it done on the balances.

 

[Jim Wynne]

Which means that no weighing scales may be present in the entire process.

Good luck with that one...

Stijloor.

Let's remember that the standard says that calibration against traceable standards is required "When necessary to ensure valid results..." The OP has described a situation in which the organization has assessed the risk and rationally determined that calibration (as described in 7.6) is not necessary to ensure valid results. This means that the burden of providing evidence that calibration is necessary rests with the party questioning the organization's decision.

 

[Graeme]

Ask yourself - "Does it matter if the measurement result is wrong?"

If the answer is "Yes" then the scales should be calibrated. Presumably the weight of the materials (or the relative weights of several materials) has some relationship to product characteristics and quality. Is the cost of scrapping a batch (including disposal, lost sales opportunity, etc.) REALLY something you can always afford? Also, the weight of purchased raw materials is part of the contract between you and your suppliers. How confident are you that every package is always labeled correctly? (That goes to contract review and receiving inspection.)

If the answer to the first question is "No" (it doesn't matter at all if the measurement result is wrong), then ask yourself this question: "Why am I spending the time, money and other resources to make a measurement that doesn't matter?" If it makes no difference if the if the batch is right or not, then get rid of the scales completely.

Note that in most industries is is almost always less expensive to measure (using calibrated tools) as early as possible in the process than to rely on post-production inspection, measurement, rework, scrap, and waste disposal. However, it is a business decision that each business has to make for themselves.

 

[Jim Wynne]

Ask yourself - "Does it matter if the measurement result is wrong?"

If the answer is "Yes" then the scales should be calibrated. Presumably the weight of the materials (or the relative weights of several materials) has some relationship to product characteristics and quality. Is the cost of scrapping a batch (including disposal, lost sales opportunity, etc.) REALLY something you can always afford? Also, the weight of purchased raw materials is part of the contract between you and your suppliers. How confident are you that every package is always labeled correctly? (That goes to contract review and receiving inspection.)

If the answer to the first question is "No" (it doesn't matter at all if the measurement result is wrong), then ask yourself this question: "Why am I spending the time, money and other resources to make a measurement that doesn't matter?" If it makes no difference if the if the batch is right or not, then get rid of the scales completely.

Note that in most industries is is almost always less expensive to measure (using calibrated tools) as early as possible in the process than to rely on post-production inspection, measurement, rework, scrap, and waste disposal. However, it is a business decision that each business has to make for themselves.

The essence of this is: if you need to calibrate, calibrate, so the corollary is if you don't need to calibrate, don't. It's the latter bit of wisdom that's too often disregarded in favor or some form of alarmism regarding everything falling apart if a measurement is wrong. The OP clearly states that a form of calibration is taking place, and that the risks have been assessed, and a decision to forgo formal, traceable calibration has been made. In terms of both the standard (which is what the OP seems to be concerned with) and rational decision making, I see no problem with not doing formal calibration.

 

[Hershal]

The essence of this is: if you need to calibrate, calibrate, so the corollary is if you don't need to calibrate, don't. It's the latter bit of wisdom that's too often disregarded in favor or some form of alarmism regarding everything falling apart if a measurement is wrong. The OP clearly states that a form of calibration is taking place, and that the risks have been assessed, and a decision to forgo formal, traceable calibration has been made. In terms of both the standard (which is what the OP seems to be concerned with) and rational decision making, I see no problem with not doing formal calibration.

Bluntly put, if the calibration of the item does not matter, then REMOVE the item from the process, but if the item actually matters to the process, then calibrate the item.

 

[somashekar]

Re: To Calibrate or Not to Calibrate

Thank you for your response. I would be very hesitant to exclude 7.6 from your quality management system as advised by a previous poster.

I am sure that others will respond.

Good luck.

So rightly said.
Please read this the 7.6 a)
be calibrated or verified, or both, at specified intervals, or prior to use, against measurement standards traceable to international or national measurement standards; where no such standards exist, the basis used for calibration or verification shall be recorded.
Perhaps you are doing a verification at specified intervals, with your own basis. Keep this basis and results (records) of this periodic verification within your control of documents and records.
So in simple terms 7.6 applies.

 

[samsung]

Re: To Calibrate or Not to Calibrate

So rightly said.
Please read this the 7.6 a)
be calibrated or verified, or both, at specified intervals, or prior to use, against measurement standards traceable to international or national measurement standards; where no such standards exist, the basis used for calibration or verification shall be recorded.
Perhaps you are doing a verification at specified intervals, with your own basis. Keep this basis and results (records) of this periodic verification within your control of documents and records.
So in simple terms 7.6 applies.

Applicability of 7.6 is different from calibrating (or not calibrating) an equipment. The opening para of 7.6 says 'determine' the requirements for measuring & monitoring, so the organization should not only determine what characteristics to measure (products, services or processes) but also relate those characteristics to the determined requirements (of customers/ regulators or any interested party).

It's not to convey that the organization should exclude the entire clause 7.6 but taking the individual requirements within the clause, the specific requirements relating to calibration, can be excluded where valid results are not intended and necessary. It's hard to believe that there are processes where M&M doesn't apply but there are processes where formal calibration may not apply.

Records of calibration or verification, as I interpret from the stated the requirement, are required to be maintained only when it's necessary to ensure valid results.