What are the Pitfalls of On-Site Calibration Services?

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corollax

Hi, we have an in-house Cal Lab providing calibration services for our Production divisions. Recently, our Management calls for Cal Lab to perform more on-site calibration at the production facilities so that production staff do not have to waste time dismantling those calibration-due gauges from the various test-stands and send them to Cal Lab.

I am concerned that this arrangement may affect the quality of the calibration work and also detrimental to the sensitive cal masters by moving them around. Appreciate if anyone can provide some guidance on how to convince them to think otherwise, or point me to any existing articles on this subject.

Thanks.
 
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mikoyan

Re: What are the pitfalls of on-site calibration work?

We've used on-site calibration for a while and it has worked pretty well for us. The main pitfalls are keeping track of everyone's equipment and making sure that it gets calibrated (we have lots of service techs and many are not in during the week we do calibrations).

If you are using an ISO-17025 facility, they are supposed to do validation work on their stuff that goes out to do field calibrations. They are also supposed to account for any variations that may occur because of that. If the facility you are looking at is like ours, there are still things that they can not do on-site and will still have to go back. Just keep that in mind. Typically they will take their more robust stuff (some of the things used to calibrate multimeters and what not).

If you have alot of equipment, make sure you set up ample space for them and also make sure that they have access to phone lines and what not.
 
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Gert Sorensen

Re: What are the pitfalls of on-site calibration work?

Well, first and foremost. If you want your calibration to have any real value you need to make sure that the calibration results don't vary between the calibration performed at Cal-Lab and the calibration performed on site. Most calibrations have established procedures requiring a certain temperature and humidity and acclimatization to make sure that the measuring equipment performs as expected. When calibrating on site these requirements are seldom met. So, calibrate the equipment at the lab, record the temperature and humidity and then bring the equipment to the production site. A couple of days later, when the equipment has acclimatized you can re-calibrate it, noting the temperatur and humidity. The differences between the calibration can then be established and you have your - sometimes new - calibration values.

If the measuring equipment are used in different surrounding - temp. and rH - you would be wise to establish the link for each surrounding......

On site calibration do have the advantage, that it can be more cost efficient, and more importantly, that it gives the users a clearer understanding of the use and precision of the measuring equipment.

How to convince the cal masters? You could try to calculate the time saved for production, and using these figures you can argue that it saves the company money. You could try to convince them that it would increase the visibility of the work that the perform, and the importance of that work. You could cave in to their social needs, they would meet a lot of people :nopity:

Hope that this is useful.
 

Hershal

Metrologist-Auditor
Trusted Information Resource
Re: What are the pitfalls of on-site calibration work?

There are many differences.....some potentially negative effects can be minimized.....but the main thing is to know and compensate.

First, your cal techs have greater visibility on the shop floor.....the techs need to remember that.....

Second, your uncertainties will increase. That is unavoidable, but needs to be taken into account. Not just temp/RH, but other influences also as appropriate. These are Type B influences.

You should create a set of working standards. Keep the main standards in the lab under tight control, use them to create working standards that go to the shop floor to effect the calibrations. Don't forget to do the uncertainty calcs for the working standards and from them to the UUT.

As for uncertainty.....it is a critical part of traceability.....traceability requires documentation of the unbroken chain of comparisons and the uncertainties at each step.....if one of the two is missing, there is no traceability.

The documentation of the unbroken chain means that when you document the standard(s) used to create working standards, the standard, due date, and certificate number from its last cal are the bits of information needed to establish the link.

Also, keeping track of what items are where and when due is also a challenge, but good software can help with that.

Also, to increase the visible value of your internal lab, consider obtaining accreditation to ANS/ISO/IEC 17025. If you consider that, remember that there are three internationally recognized accrediting bodies in the U.S. (making the assumption that SEA means Seattle).....they are: IAS, A2LA, and NVLAP.

Hope this helps.

Hershal
 
C

corollax

Re: What are the pitfalls of on-site calibration work?

Thanks for your replies - good stuff indeed!

Btw, is it harmful to move a dead-weight tester around? I've heard the mechanism can easily be damaged by moving it around too much.

Yes, we are 17025 accredited. But I believe we cannot issue 17025 endorsed certificates for calibration work done outside the cal lab.

Thanks.
 

gard2372

Quite Involved in Discussions
Re: What are the pitfalls of on-site calibration work?

corollax said:
Thanks for your replies - good stuff indeed!

Btw, is it harmful to move a dead-weight tester around? I've heard the mechanism can easily be damaged by moving it around too much.

Yes, we are 17025 accredited. But I believe we cannot issue 17025 endorsed certificates for calibration work done outside the cal lab.

Thanks.
I'm not so ure about your last statement "But I believe we cannot issue 17025 endorsed certificates for calibration work done outside the cal lab."

Many accredited A2LA ISO/IEC labs do on-site calibrations and issue certs. Hershal or Jerry Eldred may be able to provide specifics in that regard.

As far as the main subject of the thread "What are the pitfalls of on-site calibration work?" There are a few ranging from work stoppage in which you have to schedule in advance, to discovering another non-related maintenance issue when equipment is down. causing further production delays.

On the posisitve spin, many times equipment takes longer and adds more cost in labor and downtime to disassemble to get a a gauge than it would be to calibrate the gauge on the equipment. This does not apply in every case, just some examples. On-site calibration also saves time and money on shipping and turnaround times.
 

Hershal

Metrologist-Auditor
Trusted Information Resource
Re: What are the pitfalls of on-site calibration work?

corollax said:
Thanks for your replies - good stuff indeed!

Btw, is it harmful to move a dead-weight tester around? I've heard the mechanism can easily be damaged by moving it around too much.

Yes, we are 17025 accredited. But I believe we cannot issue 17025 endorsed certificates for calibration work done outside the cal lab.

Thanks.

Dead weight testers getting damaged by moving them does happen, but it really depends on how robust the unit is and how it is moved.....generally, keeping it stationary is best and create a working standard from it when possible.

As for your accreditation.....check the notes at the bottom of the scope.....many ABs include a statement along the lines of calibration done on-site will have higher uncertainties. If you have this and no restrictions on the on-site portion, then likely you can take care of your production lines directly.....if you still have a question, then ask your AB for their opinion, as they actually own the scope.

Hope this helps.

Hershal
 
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