Weight Calibration Standards - External Calibration Frequency

smryan

Perspective.
#1
Hi there again :bigwave:

We are a small, ISO9001:2008 certified manufacturer of capacitors. We have a regular calibration process that meets the requirements but a question has recently come up. How often do we HAVE to send out weight standards for recertification/calibration from a 3rd party? Its pricey - which is why the question came up.

The scales being calibrated with the weight standards are not used for fine measurements - the smallest quantities being measured being around 1 kg with 1 g resolution. The question posed by the guy signing the PO is: can we be compliant if we make our process an annual visual examination of the standards to assess any damage, and baring any visible damage, limit the send-out to once every 5 or 10 years?

Thanks in advance!
 
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Kronos147

Trusted Information Resource
#2
Re: Calibration Standards - External Calibration Frequency

Hello,

We are asking the same question about a surface plate we have on site. Everything else we can take to the calibration house and avoid the house call fee.

"The organization shall determine...." it's up to us to "state what we do, then do what we state."

"a) be calibrated or verified, or both, at specific intervals... carried out in a manner that is consistent with... requirements."

I figure with the surface plate, I can show a history of many years of calibration on the surface plate. Was it ever adjusted? Was the result of any product/process performed with the surface plate ever come into question? No.

I figure with a justification statement I can declare the calibration frequency of the surface plate to every 5 years as opposed to every 6 months or every year, the old frequency we used to have the vendor perform in house calibration.

For the case of counting scales, I would think maybe come up with some kind of periodic "verification" where the same 'control' objects are weighed on the different scales looking for consistency or something similar.

Anyone else have any thoughts?
 

qusys

Trusted Information Resource
#3
Re: Calibration Standards - External Calibration Frequency

Hi there again :bigwave:

We are a small, ISO9001:2008 certified manufacturer of capacitors. We have a regular calibration process that meets the requirements but a question has recently come up. How often do we HAVE to send out weight standards for recertification/calibration from a 3rd party? Its pricey - which is why the question came up.

The scales being calibrated with the weight standards are not used for fine measurements - the smallest quantities being measured being around 1 kg with 1 g resolution. The question posed by the guy signing the PO is: can we be compliant if we make our process an annual visual examination of the standards to assess any damage, and baring any visible damage, limit the send-out to once every 5 or 10 years?

Thanks in advance!
Did you ever analyze the data of the external calibration? I mean : how many times did you have any alert from the service that the scale were found out of calibration? Clearly you shall agree this item with your service, other it will issue only the certificate with accuracy and tolerance data.
If you did not have problem in the last XX year, you could perform a risk assessment to enlarge the timeframe. You coiuld also contact the equipment manufacturer of the scale to know about this issue.
In the third hypothesis you can adopt the "for reference only" if you do not use the measurement for process/product releasing. This last shalle be understood only by your organization.
 

smryan

Perspective.
#4
Re: Calibration Standards - External Calibration Frequency

Did you ever analyze the data of the external calibration? I mean : how many times did you have any alert from the service that the scale were found out of calibration? ....
If you did not have problem in the last XX year, you could perform a risk assessment to enlarge the timeframe. ....
In the third hypothesis you can adopt the "for reference only" ....
Its a weight set, not a scale.

I have only 2 years of data collected. Changes are 1000 times smaller than our scale resolution.

'for ref only' not an option. They are used for in-house calibration of the scales.
 

dgriffith

Quite Involved in Discussions
#5
Hi there again :bigwave:

We are a small, ISO9001:2008 certified manufacturer of capacitors. We have a regular calibration process that meets the requirements but a question has recently come up. How often do we HAVE to send out weight standards for recertification/calibration from a 3rd party? Its pricey - which is why the question came up.

The scales being calibrated with the weight standards are not used for fine measurements - the smallest quantities being measured being around 1 kg with 1 g resolution. The question posed by the guy signing the PO is: can we be compliant if we make our process an annual visual examination of the standards to assess any damage, and baring any visible damage, limit the send-out to once every 5 or 10 years?

Thanks in advance!
Whatever you choose, eventually you are going to have to demonstrate, through interval analysis, the reasoning and support of that decision. If you can do that, you can also determine the length of time supported. I should think that would make you compliant.
:2cents:
 

Big Jim

Super Moderator
#6
There are three main things I would like to point out in considering any calibration interval.

1) I doesn't hurt to ask your calibration service for their suggestion. They can't tell you what it needs to be, that is for you to determine, but they can be a useful resource.

2) You don't want to do it so ofter that it is a burden. That seems to be your question at the moment.

3) It needs to be often enough that you avoid the paragraph from 7.6 below the letters:

". . . the organization shall assess and record the validity of the previous measuring results when the equipment is found not to conform to requirements. The organization shall take appropriate action on the equipment AND ANY PRODUCT affected."

That is not a fun or rewarding exercise, so you want to calibrate often enough to avoid it.

In rough terms, for something that isn't used very often (the calibration weights), such as once or twice a year, you could probably go two or three years. Five or ten seems outrageously high and would carry a very high risk.

How much risk do you wish to take?
 

Hershal

Metrologist-Auditor
Staff member
Super Moderator
#7
Hi there again :bigwave:

We are a small, ISO9001:2008 certified manufacturer of capacitors. We have a regular calibration process that meets the requirements but a question has recently come up. How often do we HAVE to send out weight standards for recertification/calibration from a 3rd party? Its pricey - which is why the question came up.

The scales being calibrated with the weight standards are not used for fine measurements - the smallest quantities being measured being around 1 kg with 1 g resolution. The question posed by the guy signing the PO is: can we be compliant if we make our process an annual visual examination of the standards to assess any damage, and baring any visible damage, limit the send-out to once every 5 or 10 years?

Thanks in advance!
The first question is how often the weights are used. The next question is how they are stored and how they are handled. These two things will generally drive that answer.

A weight used weekly or daily, I would say needs to go on an interval not more than one year, and less is preferred.

If gloves or tweezers are not used to handle them, then the weight changes the minute they are picked up, because of finger oils.

Weights used once or twice a year, stored in a locked cabinet in a controlled environment, and always handled wearing gloves or using tweezers, I would say can be pushed up to five years.
 

Hershal

Metrologist-Auditor
Staff member
Super Moderator
#8
Re: Calibration Standards - External Calibration Frequency

Hello,

We are asking the same question about a surface plate we have on site. Everything else we can take to the calibration house and avoid the house call fee.

"The organization shall determine...." it's up to us to "state what we do, then do what we state."

"a) be calibrated or verified, or both, at specific intervals... carried out in a manner that is consistent with... requirements."

I figure with the surface plate, I can show a history of many years of calibration on the surface plate. Was it ever adjusted? Was the result of any product/process performed with the surface plate ever come into question? No.

I figure with a justification statement I can declare the calibration frequency of the surface plate to every 5 years as opposed to every 6 months or every year, the old frequency we used to have the vendor perform in house calibration.

For the case of counting scales, I would think maybe come up with some kind of periodic "verification" where the same 'control' objects are weighed on the different scales looking for consistency or something similar.

Anyone else have any thoughts?
Depends on what you are doing. If a place to put papers, then no schedule required. If general machine shop, should be at B Grade and likely an annual. If doing fine work like in a lab should be at AA Grade and most certainly annual at least.

The real issue if it is not the grade you need, is getting it lapped. That is as much an art as a science, and most are not good at it.

Hope that helps.
 

Kronos147

Trusted Information Resource
#9
1) I doesn't hurt to ask your calibration service for their suggestion. They can't tell you what it needs to be, that is for you to determine, but they can be a useful resource.
I thought that same thing. One very astute auditor asked me, "isn't that a conflict of interest?"

The calibration house wants to calibrate more!

Food for thought.
 

Hershal

Metrologist-Auditor
Staff member
Super Moderator
#10
I thought that same thing. One very astute auditor asked me, "isn't that a conflict of interest?"

The calibration house wants to calibrate more!

Food for thought.
No, not a conflict of interest. It is basically the same as Jiffy Lube suggesting that you change oil every 3000 miles. In point of fact, unless a Metrology professional is at the customer organization, the cal lab is the best source of advice for calibration cycles, excepting here of course.
 
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