CFR 21 Part 820.72--Have you heard of "Once Only Calibration??

Chitchat

Registered Visitor
CFR 21 Part 820.72--Have you heard of "Once Only Calibration”?

Has anyone every come across the concept of “Once Only Calibration”? My calibration department currently takes this approach with certain gages and custom fixtures that are deemed to be inherently stable. For example, steel rulers are calibration before they are commissioned into production, it is the equipment owners responsibility to ensure that the rule is fit for use thereafter. No periodic calibration or no exit calibration is performed if and when the steel rule is made inactive. Another example would be, a glass reticle for the eye piece of a microscope – the parameters on the reticle are calibrated, reticle is installed in the microscope and the magnification set-up for the microscope is calibrated periodically, however the reticle is never checked again.

I’m concerned that this practice would not stand up to the full rigors of an audit particularly when one reads CFR 820.72(a) “Each manufacturer shall establish and maintain procedures to ensure that equipment is routinely calibrated, inspected, checked and maintained. The procedures shall include provisions for handling, preservation, and storage of equipment, so that it accuracy and fitness for use are maintained."

Any comments / feedback would be much appreciated.
 

Ninja

Looking for Reality
Trusted Information Resource
Re: Has anyone every come across the concept of “Once Only Calibration”?

An interesting topic, thanks for raising it.

There is a gray area between "calibration" and "verification" when you are down on the sharp end of the stick.
If I measure against a known good standard, it is a verification (or if it is known good, how do I know it's good...if I know its good because of NIST trace, isn't it a calibration?)
When in an audit...the gray disappears...calibration is required...but YOU determine the calibration period and the method of calibrating (well...you and your customers together...)

Rulers are an area of particular fondness to me since we use many of them and they cost so darn much to recalibrate.
A technique I learned about after a long search online has come in particularly handy for me, and has stood up to multiple audits:

Contact the manufacturer of the ruler/scale, get their manufacturing tolerances and put them on file.
Require (in the procedure) that an operator inspect the ruler at each use for obvious signs of damage, and not use a damaged instrument. Worn off increment labels is defined as damage.
In the calibration procedure, document that (for these rulers) the manufacturers logo will be treated as a calibration mark.

BIG NOTE: if your rulers see harsh use (machine shop, loading dock type area, etc.) I woulnd't even dream of using this approach...but I'm in a delicate area and the worst that will happen to a ruler is that it drops on the floor.
Exceptions: I would not use this approach for hooked end device like a tape measure since the hook can loosen...I use it only for single piece metal scales.
Make sure that the gradations of the rulers are far in excess of your measuring needs...and the manufacturing tolerances are much more precise than the measurement needs (like 20:1). They usually are in my experience.

Routinely calibrated: rulers are calibrated at every purchase...defined by the manufacturing tolerance.
Inspected/checked/maintained: by the operator at every use, and once a year by visual inspection for damage and readability.

(Should be interesting to see what the auditors on the forum feedback on this one ! ) :argue:
 

BradM

Leader
Admin
Re: Has anyone every come across the concept of “Once Only Calibration”?

Yes, I have heard of the term. Another label is "Initial Calibration". This would be to verify that an instrument/ equipment when installed, operates according to specifications. These are typically your "reference only instruments", or those that have been identified as not requiring routine activities.

Approaching your equipment using a risk-based approach seems like the best fit. Whether you calibrate (or maintain) something every three months or every three years, will depend on your identified risk factors.

Assuming something is stable and demonstrating something is stable are two different things to me. I have heard the argument about the optics never requiring subsequent verification, and I have issues with it. They have no R&R studies, material stability data, or even anything from the mfg. of the device. My advice is to establish a periodic interval for verification. Then, when you have the data to establish stability, then you can extend the intervals based on the data.

I think there are devices that can receive an initial verification only. However, that should be based on an identified risk assessment/quality impact, and additional data to support that a routine verification is not required. Otherwise, I will always recommend establishing a routine interval for it.
 

Randy

Super Moderator
Re: Has anyone ever come across the concept of “Once Only Calibration”?

They tried that with the Hubble and that dog don't hunt
 

Jim Wynne

Leader
Admin
Re: CFR 21 Part 820.72--Have you heard of "Once Only Calibration”?

I've move this post into the FDA forum because the OP's question is specific to FDA requirements, and answers involving general calibration/verification requirements might not be appropriate.
 
N

NumberCruncher

Re: Has anyone ever come across the concept of “Once Only Calibration”?

Hi Jim

Reading briefly through the Allan Report (look up 'AllenReportHST.pdf', sorry but I can't get the link to work) I get the strong impression that everyone wanted to believe that each individual part of the optics was ground correctly at the time of manufacture, despite evidence to the contrary.

"The Board's investigation of the manufacture of the mirror proved that the mirror was made in the wrong shape, being too much flattened away from the mirror's center (a. 0.4-wave rms wavefront error at 632.8 nm). The error is ten times larger than the specified tolerance"

An example of Once Only Calibration?

Even if it's not, I still think Randy has a great one-liner!

NC
 
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