Tag: measurement equipment

ISO 9001:2008 Requirement for Control and Monitoring of Measurement Equipment

Chemistry, micro testing, chemical analysis, sampling

Inquiry

I am trying to clearly understand the  ISO 9001:2008 requirement for Control and Monitoring of Measurement Equipment.  My question:

If a measurement equipment like a Karl Fisher Titrator or pH meter which is calibrated by the user with a known standard traceable to an international standard, then does the unit itself require to be periodically sent to a third party for calibration?  It is not clear to me.  In the past I have received a finding for not doing so.  As I read the standard it is not clear.  Can you provide exactly the clause and reference statement that would indicate and clarify its meaning.

Response:

Your question leads me to believe there was a valid reason for the finding you received. Calibration of a Karl Fischer Electrometric Titration unit is more of a validation and adjustment. That is, in one common practice, you use sodium tartrate dehydrate in a very fine powder form, along with other substances and follow all the steps of calibration.  However, (this is why sending your unit to a third party becomes necessary), you cannot be certain your unit is reading accurately if it hasn’t had a certified calibration by a third party. Example: Is the water equivalent (WE) of the titrant (Karl Fischer reagent or titrating solution) based on accurate calculations?

If you have a known standard which is traceable to national standards which you can use as a comparator, you might be able to set your recalibration periods fairly far apart. This would of course save you money. Nonetheless, unless you can show traceability of your Karl Fischer system, you are not compliant with the standard.

That was a good question and I hope this will help.

Bud Salsbury, CQT, CQI

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Measurement System Analysis

ISO/IEC 17025:2017 General requirements for the competence of testing and calibration laboratories

Question:

Is there ever an exception to the rule about needing full Measurement System Analysis for any instrument placed in the Evaluation / Measurement Technique column on the Control Plan?  If an instrument is listed on the control plan, does it HAVE to have GRRs done, in addition to having to prove stability?  Please base off of ISO 9001 and TS 16949 requirements, and if there is a difference between them for this requirement.   

Answer:

Thank you for this interesting question. Clause 7.6 of ISO 9001: 2008 makes most of this fairly clear. Any monitoring and measuring equipment used to verify conformity of product must “be calibrated or verified, or both, at specified intervals, or prior to use. . .” Notice I made ‘at specified intervals’ bold. This is just to bring to light the importance of calibration cycles. You/your organization can determine what those cycles will be based on the stability of the measuring tool, frequency of use, working conditions, etc. For example, if you were using a micrometer to check close tolerance parts and, you found it a good process to measure the parts frequently, this would be a contributing factor to the decision process. Then, if the working conditions included a lot of cutting fluids or perhaps a good deal of metal dust, another factor is added to the decision process. What I am driving at is this; once you have determined that the product conformity which you are checking is good and/or consistent and that your sample frequency is satisfactory, you would have no definite requirement for GRR’s on the measuring equipment. The calibrations and or verifications you do must be with equipment which is traceable to international or national measurement standards. If you use working standards as gages to check measuring equipment throughout production and those standards are traceable, then you are doing fine. The processes you use to verify the tools and any in-process measuring practices should be documented in Work Instructions or even with the use of photographs or flow charts.

In the second part of your question, you ask if there is a difference between 9001 and TS 16949. I reference section 7.6.1 of TS 16949. Here it is put straight forward:

7.6.1  Measurement System Analysis 

Conduct statistical studies to analyze variation present in the results of each type of MMD that is referenced in the Control Plan.

Use analytical methods & acceptance criteria that: 

Conform to methods and criteria in customer reference (MSA) manuals Or use other methods, if approved by the customer 

This is an automotive sector specific QMS standard. Herein it is necessary to consider safety and liability in everything you do. So, Gage R&R’s are a common practice. Nonetheless, the necessity for these is dictated by individual processes. Some may need them, some may not.

So, if an instrument is listed on YOUR control plan, GRR’s will become a requirement based on all the criteria I’ve noted above. A gage which has proven stability is most often safe from that requirement under 9001 but TS16949 has more extensive requirements.

Bud Salsbury, CQT, CQI

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ISO 9001, Control of Monitoring and Measuring Equipment

Audit, audit by exception

Q: In ANSI/ISO/ASQ Q9001-2008 Quality management systems — Requirements, clause 7.6,  there is a requirement which states: “When used in the monitoring and measurement of specified measurements, the ability of computer software to satisfy the intended application shall be confirmed.”

Do you have any guidance on how this can be established in an analytical laboratory?

A: To answer your question, I would first refer you to the note at the end of 7.6.  It reads:

“NOTE:  Confirmation of the ability of computer software to satisfy the intended application would typically include its verification and configuration management to maintain its suitability for use.”

Now, that can sound confusing to some folks. So, let me offer you some direction.  To “confirm” (verify) your software’s abilities, you need a known standard.  I’m not referring to a standard that is traceable to national standards.  I’m referring to data you know should be revealed as a failure by your software.

For example: You have samples from 10 subgroups and, you know that one sample, when analyzed, will be found to be nonconforming.  You can use a separate source to determine what the Cpk is, or you can simply identify which sample is out of tolerance and by how much.  When you use this known standard to test your analytical software, the results will tell you if it is suitable for use.

Most software is designed with some sort of pass/fail testing option.  Nonetheless, using a proven standard to verify your software brings it down to earth and more applicable to your needs.

Bud Salsbury
ASQ Senior Member, CQT, CQI

For more on this topic, please visit ASQ’s website.

Gage R&R Study on a Torque Wrench

Gage R&R, Torque Wrence

Q: I need information on performing a Gage R&R on a torque wrench. We are using the wrench to check customer parts.

A: For reference on both variable and attribute Gage R & R techniques, a good source is the Automotive Industry Action Group (AIAG) Measurement Systems Analysis (MSA) publication.

The traditional torque wrench is a “generate” device in the sense that it generates a torque to tighten or loosen a fastener (a nut or a bolt, etc.). So, in a strict sense, it is not a “measurement” device. Therefore, both preset and settable torque wrenches are set to a torque value and then used to tighten a fastener or loosen a fastener. When loosening a fastener, it will determine how much torque is required to loosen the fastener. Usually, the clockwise motion is for tightening and counterclockwise motion is for loosening in a torque wrench.

To conduct a variable Gage R & R study on a torque wrench, we would need a “measurement” device which would be a torque checker with a capability to register peak (or breaking) torque. Many such devices are commercially available and if a facility is using torque wrenches, it is a good idea to have one of these to verify performance of torque wrenches. Such a device is usually calibrated (ensure traceable accredited calibration) and provides reference for proper working of torque wrenches.

Now,  one would conduct a Gage R&R study using the typical format:

  • Two  or more appraisers.
  • 5 to 10 repeat  measurements at a preset torque by each appraiser, replicated 2 to 3 or more times.

A word of caution on torque wrenches and setting up the Gage R&R:

  • The measurement is operator dependent, so operators need to be trained on proper toque wrench usage techniques.
  • Ensure that torque is set between every measurement in the settable torque wrench to simulate actual usage between repeated readings.
  • Ensure the number of repeated reading and replicated readings are the same for all appraisers.

The templates for data collection are available in spreadsheet format  from commercial providers. Alternatively, one can design the template from the MSA publication referenced. The data would be analyzed using the guidelines from the MSA publication.

Good luck with the Gage R&R! It is a very useful and worthwhile exercise in understanding your measurement process.

Dilip A Shah
ASQ CQE, CQA, CCT
President, E = mc3 Solutions
Chair, ASQ Measurement Quality Division (2012-2013)
Secretary and Member of the A2LA Board of Directors (2006-2014)
Medina, Ohio
http://www.emc3solutions.com/

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Accuracy of Measurement Equipment

Automotive inspection, TS 16949, IATF 16949

Q: I work for an incoming quality assurance department. In our recent audits, the auditor claimed that high precision machines such as the Coordinate Measuring Machines (CMM) and touchless measurement system should have higher Gage Repeatability and Reproducibility (GR&R) values compared to less precise equipment such as hand-held calipers and gages. If this is the case, does Measurement System Analysis (MSA) cater to this by providing a guidance on what are the recommended values for each measuring equipment by general? If not, should we still stick to the general MSA rules, regardless of the equipment’s precision value?

A: When you noted “higher GR&R values,” that in itself can be a bit confusing because the GR&R value is a percentage of errors caused by repeatability and reproducibility variation. The higher the number, the more variation present — and the worse the measurement method is.

As far as I know, MSA doesn’t give specific guidance for recommended values depending on the measuring equipment. Also, I’m not sure of the validity of saying that a CMM is consistently more accurate than other equipment, such as calipers. Although the equipment may theoretically be more accurate, how you stage the part to be measured will also affect the amount of variability, as will the feature being measured.  Consequently, even though the CMM is theoretically more accurate, there may be 20 percent GR&R, mainly due to the holding fixture or the feature being measured. I’m sure you get the point here.

As far as I know, MSA manuals do discuss what the major inputs should be when deciding the amount of acceptable variation. It strongly recommends to look at each application individually to verify what is required and how the measurement is going to be used.

Another thing to consider is whether you are looking at the GR&R based on total variation or on the specified tolerance. Tolerance-based is more commonly used than total variation, but that may depend on the type of industry.

One thing I would like to mention is that if you have three people take 10 measurements each, and then dump the information into one of the common software programs, it will not matter if they take the 10 measurements with a dial caliper or with a CMM. The instruments’ “accuracy” should not be the deciding factor, but the tolerance base should be.

Also, ISO standards do not dictate GR&R values. If you do what your quality management system says you do, most auditors will not push such an issue. While some auditors may offer “opinions” and suggestions, such items are rarely cause for nonconformance findings.

I hope this helps answer your question.

Bud Salsbury
ASQ Senior Member, CQT, CQI

For more on this topic, please visit ASQ’s website.