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Dave K. Banerjea

Quality Insider

Gauge Calibration: It Starts (and Ends) With the Label

How to set up a practical labeling system

Published: Thursday, January 16, 2014 - 19:13

When we think about gauge calibration management, we usually think of the actual calibration process: sending the gauge to the calibration lab, comparing it to a traceable measurement standard, making changes to the gauge to bring it into the calibration range, entering the calibration results into a software database, attaching the calibration label, and then putting it back into circulation.

What was that last item? Oh yeah, the calibration label. That innocuous little thing we add at the end of the process. We hardly think about it. And yet, it would be safe to argue that our calibration efforts mean nothing if the calibration label is wrong, illegible, or missing.

A successful gauge calibration system will be effective only if users can readily and easily identify gauges and when they are due for calibration. Therefore, the key to proper gauge identification is a reliable labeling system. Properly filled out calibration labels communicate important calibration information and due dates to gauge operators. In addition, gauge labeling is critical for compliance with many standards. For instance, in ISO 9001:2008, subclause 7.6.a, states that measuring equipment shall “be calibrated or verified, or both, at specified intervals, or prior to use....” Further, 7.6.c states that measuring equipment shall “have identification in order to determine its calibration status.” The label is that identification.

Using a legible and appropriately durable label, any gauge and its calibration status can be quickly determined at a glance, eliminating guesswork and improving productivity, thus reducing costs and liability risk.

Handwritten vs. printed labels

With handwritten labels, if you don’t take special care to write legibly with an appropriate writing utensil, cover the label with a protective sleeve, and appropriately position the label to avoid excess wear, the label becomes stained, smeared, and illegible. Handwritten labels result in wasted time in the field, duplication of effort, and a risk of not being ISO 9001-compliant.

Another issue with handwritten labels is human error in transcribing information from your gauge calibration software to your labels.

As inconvenient as the problems just mentioned, a worse situation can arise if a hard-to-read label leads operators to use an out-of-calibration tool to measure critical components. All of those components may need to be recalled to be remeasured, resulting in huge costs and, possibly, litigation. Think of fasteners on an aircraft that must be attached with a specific amount of torque. An out-of-cal torque driver could lead to overtightening or undertightening a fastener, which could lead to catastrophic failure. In most cases, it is the user’s responsibility to verify that a tool is within its calibration date prior to using. The label provides that verification.

With high-resolution, custom-printed, laminated labels, these types of issues are less likely to arise. Printing labels directly from your calibration software ensures legibility, accurate information, and consistency with your gauge calibration software. If the labels are a high-quality material and laminated, they are far more durable as well. Custom labels can be printed as needed, so neither time nor material are wasted. And if you perform calibrations in the field, portable calibration label printers are available that offer all the same advantages.

Although printed labels are key to good labeling practices, a good system goes beyond simply including the correct information on the label. It’s important to consider other factors that can affect your labeling system and how well the labels integrate with your calibration tracking system. Here are some points to consider when setting up a labeling system:

Should the labels be permanently affixed or removable?

Depending on their use, a label might be permanent or removable. For example, a barcoded gauge ID label is intended to be permanent because gauge IDs rarely, if ever, change. Other permanent types of labels might include “No Calibration” gauge labels, which are intended to stay with the gauge forever. Keep in mind that even “permanent” labels can be removed with some effort.

“This is particularly important with ID labels,” says Craig Howell, president of CPM Labs, a calibration lab in Rancho Cordova, California. “Many small gauges don’t have serial numbers on them, so the ID label is the only way we have of tracking the gauge throughout its lifetime. If that label falls off, there is no way of knowing anything about the calibration history of that gauge. We basically have to start from scratch.”

Calibration labels, on the other hand, must be removable. They need to be removed and replaced at the time of calibration. Depending on the instrument’s environment, this type of label needs an adhesive strong enough to hold up under typical usage but still be somewhat easy to remove. You should test the label to be sure that the temporary adhesive is strong enough to prevent the label from repeatedly falling off and having to be reattached, but not so strong as to make removing the label a chore. Labels that don't attach properly will eventually end up on the floor or the sole of someone's shoe.

“We get gauges where the calibration label is completely missing; all you can see is a sticky outline of where it used to be,” says Howell. “Or we will get a box of gauges to be calibrated, and when we open the box, half the labels are just sitting in the bottom of the box. We have no way of knowing which labels go with which gauges.”

Another use for temporary labels is when the calibration label is changed after each use based on the number of usage cycles (sometimes called a “calibration issue” label). A gauge like this would be something that’s easily thrown out of alignment when it’s used more than the recommended number of times. For instance, that gauge’s schedule could say that it goes through an average of two cycles per day and has to be calibrated every 10 cycles (about five days). So, if the gauge has already gone through two cycles in the past and then is issued out, the calibration issue label would show that the estimated calibration due date is four days away (i.e., the remaining eight cycles would elapse by then).

Let’s say that gauge is returned only one day after being issued. It has gone through another two cycles but isn’t issued again for another two weeks. Even though the gauge has passed the initial estimated due date, it’s still not due for calibration because not all cycles have been used.

These types of labels keep the user aware of how long they can use the instrument before it’s due for calibration. So, every time such a gauge is issued, the estimated calibration due date changes, requiring a new label. Because these labels are changed quite often, a weaker adhesive is usually needed.

Regardless of the types of labels you choose, be sure that the surface for the label is clean, dry, and, if possible, slightly roughened to allow for ideal adhesion.

What information must be included on each label?

If the same information is required for all gauges in all departments, one standard label type may work; if the amount of information differs, several different types of labels may be required. A robust labeling system should allow you to easily change from one labeling template to another.

Will label color play a role in the labeling system?

In keeping with establishing a visual workplace, the easier it is to identify a gauge’s use or status, the better. Labels can be color-coded so that at a glance, the user can distinguish instruments by department, building, month of calibration, or other criteria.

Evaluate the environment in which your gauges are used to help determine label material or adhesive

Should the label material be paper, laminate, or polyester? A high-quality laminated label will stand up to water, oil, temperature extremes, abrasion, and chemicals. Some label printers automatically apply the laminate material over thermal ink printing, resulting in a highly durable product that will stand up to the harshest environments.

Howell has seen many instances of gauges coming into his lab with ink-jet printed paper labels. “Oil from machining processes get on the user’s hands, and then onto the label, and can make the label practically unreadable,” says Howell.

Various label types may be required depending on application: standard adhesive, extra-strength adhesive, tamper-proof, or even flexible tape for labeling over edges or around curved surfaces. As described above, adhesive is an important but often overlooked factor. Try out various adhesive types or strengths on your tools to see which one works best for your application. It wouldn’t be unusual to need different adhesive types for various classes of tools.

How does labeling integrate with your calibration system?

Many of today’s calibration software programs feature the ability to print labels directly from the software database. The main advantages of a direct connection between the calibration database and a label printer are minimizing data-entry errors, excellent readability, durability of labels, and time savings.

Properly labeling your instruments and using a comprehensive calibration management software solution will allow you to effectively track all of your instruments. Your calibration software should include issue/return tracking functionality. This is made easier if you have a barcode reader and use barcoded labels. You simply scan the gauge’s barcode, automatically populating the software with the gauge’s information, saving even more time and ensuring data accuracy.

This type of functionality allows you to track each instance of a gauge being loaned out or sent out for calibration or repair, as well as its return to the crib. You will be able to locate any gauge at any time, and run detailed reports to identify which gauges are used most often and by whom.

Though a gauge label seems like such a simple thing, it’s the cornerstone of a successful calibration system. Spend some time analyzing your needs and developing a labeling system that will serve your needs now and in the future.

Dave K. Banerjea is president and CEO of CyberMetrics Corp., a Quality Digest Daily content partner.

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About The Author

Dave K. Banerjea’s picture

Dave K. Banerjea

Dave K. Banerjea is president and CEO of CyberMetrics Corp., developer and worldwide distributor of GAGEtrak calibration management, FaciliWorks CMMS maintenance management, and SUPPLIERtrak supplier quality assurance software.

Comments

Calibration Stickers ....are Passe

Calibration labels are 1950s military type process thinking.   I have observed those who simply place stickers on all assumed equipment just prior to an audit, with auditors assuming everything is calibrated.   its nonsense.    Calibration stickers are messy, sticky goo on ones most expensive insturmentation.   Further they usually will not survive continual shop floor use and handling, becoming illdgable or falling off all together. 

Looking at the current ISO MSS there are two requirements in clause 7.1.5 

1- General clause - Determine and provide resources to ensure valid and reliable results when M&M is used to verify conformity to requirements .... This is not a requirement for traceable calibration, this requirement is explained in (a) and (b),  the requirement (a) being suitable (the correct discrmination) and (b) maintained to ensure fitness for purpose (legal wrangling for tool maintenance)  Finally maintaining documented information as to fitness for purpose.   This does not mean a calibration sticker. it simply means proving documented evidence of continued fitness for purpose. aka did someone at some point (a point which the organization decides) check the gage to assure its still functioning or capable of functioning?   That its in plain english terms the M&M instrument is not beatup or bunged up to the point its no longer functional (aka ensure fitness for purpose), and was that check documented?   

This requirement would apply to all M&M gages which verify the product meets requirements (aka the gage is relied upon to relase product to the customer).  The determination how and when to check an instument for its "continued fitness for use" is left to the organization.   That decision is based upon reasonable expectations of damage which might occur based upon the environment the gage is sublect to.   One extreme would be an envrionment where the gage is banged about on an assembly line, as it swings from an air line being banged about on items in close proximity (tables, feed rollers etc) and the opposite being an instrument which is fixed (stationary) which is not in an environment where it might become damaged (ie a pressure gage attached to a pipe that is not subject to impact or other damage),  The first gage would require a check far more frequent than the latter.   One might be a weekly check and the ogher an annual or by annual check.   Remember if the gage is used to record the result of inspection, then be smart enought to include with that inspection at some interval, a record to gage was checked.    No stickers required ....

2- starts out with the term When traceablility is a requirement.  or determined to be essential, this is the requirement for calibration of an M&M instrument and it has two initial tests (its either required or determed by the organization to be essential)  Requirements come from customers or legal entiies and determined to be essential is related to the risk of neglegence (aka  the organizations duty of care). 7.1.5.2 (b) only states "Identified in order to determine their status"  It does not state by whom or how.   Therefore calibraion stickers are not a requirement.   The gage simply needs to be identified so its status of calibration can be determined.   The standard further does not indicate that an operator be the one to determine the status of calibration, that decision is left up to the organization, who determines calibration status. 

Since all M&M tools are required to be checked #1 at come point in time and since some M&M tools are required or determined necessary to be calibrated at some point in time, then what is the harm for incorporating these two events together?    If the M&M gage is identified and it can be determined that it was checked and calibrated? are stickers really necessary?    The reasonable answer to that question is of course not