In this article Rick Randall looks at what ISO 9001 & AS9100 mean by ‘fitness for purpose’. Rick is an experienced management systems consultant and author. To get in touch with Rick, go to his mentor profile here.
ISO 9001 & AS9100, sec. 184.108.40.206 require the organization to “retain appropriate documented information as evidence of fitness for purpose of the monitoring and measurement resources”.
What does “fitness for purpose” mean?
Both ISO 9001 & AS9100 are ambiguous on this point as the authors appear to have either not fully formulated a meaning for the requirement or lack the ability to sufficiently articulate their intent in text. Unfortunately, upon reading ISO/TS 9002:2016, “Quality management systems — Guidelines for the application of ISO 9001:2015”, we gain no further insight.
In my experience, while ISO 9001 auditors generally ignore this requirement, AS 9100 auditors have interpreted it to mean two things (in combination):
- The instrument must possess the accuracy, precision, range, and resolution required for the measurements and/or tests to be undertaken, and
- The instrument must be calibrated to its full capability – or otherwise identified as to its limitations (as per ISO 9001/AS 9100, sec. 220.127.116.11b).
While I rarely find issues with instrumentation lacking the required accuracy, precision, range, and resolution (other than torque wrenches), I regularly identify issues where instruments are not calibrated to their full capability. This usually appears when a company has decided to calibrate their measuring instruments “in-house” – using personnel with little or no training in calibration (i.e., metrological confirmation).
For example, typical calipers require verification of the O.D. (Outside Dimension) jaws (checking parallelism and linearity), I.D. (Inside Dimension) jaws, depth rod, and the “Step” feature (as detailed in US Air Force T.O. 33k6-4-552-1 “Calibration Procedure for Calipers-General”, dated 30 July 2013).
Yet, I’ve visited companies where calibration records indicated that only the O.D. jaws had been calibrated… without verifying parallelism or sufficiently verifying linearity. On the production floor I witnessed personnel using calipers for O.D. measurements, I.D. measurements and depth measurements. When asked why the company had not calibrated the calipers to their full capability, their answer was that they didn’t know how to configure their gage blocks to perform the other calibrations… so a lack of competence in metrology was likely their root cause. Because the company had performed only a partial calibration, they received a nonconformance for failing to ensure the “fitness for purpose” of their calipers.
Using another example, let us assume that a company has a 0-500 Lb. weighing scale that is only used to weigh items in the 100-150 Lb range. So they only calibrate it for the 0-200 Lb. range, rather than the full 0-500 Lb. range. IF the calibration record fails to reflect this AND this limitation is not described in the calibration status (ISO 9001/AS 9100, sec. 18.104.22.168b), then that would be a nonconformance BECAUSE users would assume that it is calibrated to its full capability.
However, if the calibration record reflected the limited calibration AND the “calibration status” labeling clearly indicated that it was a “LIMITED CALIBRATION” along with a description of the limitation (i.e., “0-200 Lbs ONLY”), then the weighing scale would be “fit for purpose” (and address the calibration status being identified per ISO 9001/AS 9100, sec. 22.214.171.124b). While the “Limited Calibration” concept is not specifically addressed in ISO 9001 or AS 9100, the concept is well established and is described in ANSI/NCSL Z540.3-2006 (R2013), sec. 5.2.1 & 126.96.36.199 (although not mentioned in ISO/IEC 17025:2017).
The “Limited Calibration” concept has been so widely adopted that pre-printed labels are readily available. HOWEVER, these labels MUST describe the limitation… or include a reference to a document fully describing the limitation.
The below label would be acceptable:
However, the label shown below may NOT be acceptable because it fails to describe the limitation.