Calibrator calibration interval standard

[sparky1976]

We have been sending our calibrators for calibration to recognize calibration lab. This always done once a year for the last 6 years since our plant startup.

This year I've been ask by Cost control manager, Why I need to send out calibrators for calibration every 12 months, and my stupidity come up and answer "we've always do that for the last 6 years" and he refuse to sign the PO.

Now I'm trying to convince him by showing standards or recognize guideline to do calibration for calibrators Yearly or biyearly.

Could some one help me what standard or guidelines for this calibrators calibration interval ?

Just for information we have 4 typical steam plants, and PM's for transmitter (field calibration) some every 6 months, some yearly.

Thanks
Pitat

 

[IRstuff]

calibration interval depends on when you think that the unit might go out of spec.

What is your historical data regarding the amount of deviation prior to calibration?

If you can show that prior to calibration, the instrument was close enough to being out of calibration by the next interval, you've made your case.

TTFN

 

[jeyaselvan]

As per the ISO norms, the calibration lab / agency are not supposed to specify any calibration periodicity for the instrument. It totally lies with the end user to decide on the periodicity of the instrument. You shall decide on the same considering the criticality of the instrument.

 

[ilan7]

The main issue is to have the calibration instrument with valid calibration certificate at all time when using them. If the calibration laberatory can give you a certificate good for more then one year - you do not need to calibrate them until the certificate expire.
As I know, for most equipment we are getting calibration certificate for one year, but there are some that we got for two and four years, like the dead whight pressure tester.

 

[jsummerfield]

Some properties change faster than others. Process analysis instrument calibrators likely drift at a higher rate than digital multimeters. You could establish a calibration schedule criteria based upon experience with like devices. More often, contracts or client relationships maintain the regular calibration schedule. I worked on a construction project that required a six-month schedule. Not justifyable for the application but it was their requirement.

John

 

[khan101]

Yamin,
There are two different types of calibration standards: a Primary Standard and a Transfer Standard.

A primary standard measurement is made using fundamental components (mass, length, time, etc.). Primary standard calibration devices are typically used and maintained by the metrology or calibration laboratory within an organization (or you can contract it out). The laboratory can then either directly calibrate the production instruments or calibrate instruments that will be used as transfer standards for calibration of the production instruments. You have to define what should be the calibration frequency based on your history and quality of equipment. I used to work in a company whose main customers were Boeing and Airbus and our customers defined the calibration frequency of our production instruments and calibrators (3 months and 1 year respectively).

A transfer standard is a secondary device that is traceable to a national laboratory or other recognized standards body (e.g.NIST1). Transfer standards are used in both laboratory and production environments and mostly for flow measurement.

Following is a link to an interesting article about calibration and calibrators.

http://www.meriam.com/Newsroom/pdf/TradeMag/GetAGripOnProcessVariables.pdf

 

[IRstuff]

A calibration lab CANNOT guarantee instrument performance at ANY time after or before it calibrates.

In fact, a calibration certification has NO time period associated with it.

A calibration lab does NOTHING DIFFERENTLY for and instrument with 6-month calibration vs one with 1-yr calibration.

TTFN

 

[Murphy625]

Limited Knowledge here but experience from Air Force Metrology Lab.

When I was in the AF, we used a paper system that monitored the calibration dates and results from each piece of equipment. As we calibrated things, (multimeters, scopes, gauge blocks, micrometers, etc) we would check the calibration records to see the units history.
If the unit was calibrated every 3 months but only adjusted on average of every 2 years, we would update the calibration interval to something like every 6 months or once per year.
If an item was found to always need adjustments, we would shorten the time interval.

Point is, you have to treat each piece of equipment as an individual unrelated. Even multimeters of the same make and model would frequently require different calibration intervals.

Hope this helps.

Murphy

 

[CMfgE1]

yamin,
Depending on your local regulations and whether or not your company is held to specific regulations by a governing body (i.e FDA,EPA, etc.) you might be required to use calibrated standards for your preventitive maintenance.
If you use a standard for calibrating your instruments (this is typical in any calibrating enviroment)it must be 10X greater accuracy than what you are calibrating! So unless your company has the means to check this accuracy on your standards....You must send them out to be certified!!

Tell that to your purchasing manager. And also tell him/her that it costs thousands if not hundreds of thousands of dollars (US) for the equipment to perform this certification.

 

[IRstuff]

10x is simply a rule of thumb.

MIL-HDBK-52B "EVALUATION OF CONTRACTOR S CALIBRATION SYSTEM" allows for the possibility of TAR of 1:1 or less, if the technology cannot support a higher TAR. MIL-HDBK-52B considers 4:1 a "high" TAR.

Bottomline is that your TAR should be good enough to support meeting your requirements. Anything beyond that will simply cost you money with possibly little benefit.

TTFN

 

[CMfgE1]

Also goto isa.org.
They have written many standards for calibrations and control systems. MIL standards really dont apply here. They are geared more for the manufacturing of equipment for the government. Basically you dont have to have your standards checked by anyone unless your company will be held responsible for it. If nobody will check that your standards have been calibrated I guess it doesnt matter. It is certainly not recommended since you now have no basis for accuracy when calibrating. Many industries require that standards are checked once a year by a third party source. This ensures the product they are making can be tracked and verified. Unless your selling your steam to somebody else I wouldnt worry about it.

Hope this helps