MEASURE FOR MEASURE
How to select a test and calibration partner
by Dilip Shah
If an organization is registered to ISO 9001 or accredited to ISO 17025, it needs to ensure the inspection, measurement and test equipment (IMTE) it sends out for calibration has measurement (metrological) traceability.1 It also needs to evaluate its calibration supplier. The following requirements from the standards should receive special attention:
- ISO 9001:2008, clause 7.4.1: "The organization shall evaluate and select suppliers based on their ability to supply product in accordance with the organization’s requirements. Criteria for selection, evaluation and reevaluation shall be established. Records of the results of evaluations and any necessary actions arising from the evaluation shall be maintained."
- ISO 17025:2005, clause 4.6.4: "The laboratory shall evaluate suppliers of critical consumables, supplies and services which affect the quality of testing and calibration, and shall maintain records of these evaluations and list those approved."
- ISO 9001:2008, clause 7.6(a): "Where necessary to ensure valid results, measuring equipment shall be calibrated or verified, or both, at specified intervals, or prior to use, against measurement standards traceable to international or national measurement standards; where no such standards exist, the basis used for calibration or verification shall be recorded (see 4.2.4)."
17025:2005, clause 184.108.40.206.1: "For
calibration laboratories, the program for calibration of equipment shall be
designed and operated so as to ensure that calibrations and measurements made
by the laboratory are traceable to the International System of Units (SI).
- "Note 1: Calibration laboratories fulfilling the requirements of this international standard are considered to be competent. A calibration certificate bearing an accreditation body logo from a calibration laboratory accredited to this international standard, for the calibration concerned, is sufficient evidence of traceability of the calibration data reported."
Body of work
If the customer is using an ISO 17025-accredited laboratory, the requirement for measurement (metrological) traceability is satisfied if the parameter and range calibrated by the laboratory is under its scope of accreditation (SoA).
It is useful, however, if the laboratory has been accredited by an accrediting body that is recognized under the International Laboratory Accreditation Cooperation Mutual Recognition Arrangement (ILAC MRA), which is illustrated in Figure 1.
The diagram shows the six ILAC MRA accrediting bodies in the United States. They are:
- ACLASS Corp. (www.aclasscorp.com).
- American Association for Laboratory Accreditation (A2LA, www.a2la.org).
- International Accreditation Services (IAS, www.iasonline.org).
- Laboratory Accreditation Bureau (L-A-B, www.l-a-b.com).
- The National Voluntary Laboratory Accreditation Program (NVLAP, http://ts.nist.gov/standards/accreditation/index.cfm).
- Perry Johnson Laboratory Accreditation (PJLA, www.pjlabs.com).
Under the ILAC MRA, any of the accrediting bodies evaluated by one of the regional cooperations is recognized by the other accrediting bodies evaluated by another regional cooperation. The regional cooperations conduct periodic peer evaluation assessments of the accrediting bodies in accordance with ISO 17011 standard before they are granted ILAC MRA status.
The websites of the accrediting bodies list all the laboratories they accredit. This includes laboratories in good standing, suspended, voluntarily withdrawn and making false claims of accreditation. This makes the websites good places to start the laboratory evaluation process.
The websites also maintain the SoA for each laboratory’s capability (parameter, range, calibration and measurement capability) and note when the SoA expires. An example is shown in Table 1, with a few sample measurement parameters.
Recognized accrediting bodies from other countries can be accessed by visiting the regional laboratory cooperation websites shown in Figure 1.
Sending calibration and testing work to an accredited laboratory satisfies the requirement for measurement traceability in ISO 9001 and ISO 17025 (Nos. 3 and 4 in the previous list). Before committing to send calibration or test work to a laboratory, however, be sure to study the laboratory’s SoA to ensure its best measurement capability (uncertainty) is considerably less than the artifact that is being sent for calibration.
A typical ratio used in the industry is 4:1, known as the test uncertainty ratio. For example, you don’t want to send your laser micrometer (uncertainty measured in nanometers) to a laboratory whose best measurement capability is achieved by use of a steel meter ruler (uncertainty of less than a millimeter).
Nos. 1 and 2 in the previous list ask for evaluation and selection criteria. These can be satisfied by documenting the requirement that only accredited laboratories shall be used for calibration and testing work. In addition, the organization should download the individual supplier laboratory’s SoA from the accrediting body’s website and file it as a record for evaluation.
The SoA also has an expiration date, which should be used as a base target for periodic reevaluation (normally every two years). It should be noted that accredited laboratories revise their SoA between evaluations. It may be a good idea to review the SoA from the accrediting body’s website before sending any equipment for test or calibration. Many organizations maintain supplier selection, approval and review activity in a spreadsheet with active links to SoA (see Table 2).
Speak the language
When requesting traceable calibration service, equivalent language should always be in the calibration purchase orders to protect the interest of the customer:
- ISO 17025 accredited calibration with "actual as found," "as left" and "measurement uncertainty" is required on all calibration certificates. This satisfies measurement (metrological) traceability requirements and provides history and performance of the equipment.
- If a specific method or equipment for test and calibration is desired, it should be specified (for example, manufacturer’s recommended method, industry standard ASTM method XXXX, tensile tester XYZ, multifunctional calibrator model ABCD or using triple point of water cell).
- Blanket statements of compliance and statements of measurement uncertainty shall not be accepted because they do not provide any information except for pass/fail. But, pass/fail also needs to be compared with the criteria.
- Accredited laboratory shall be accredited by an accrediting body under an ILAC MRA. In a global economy, this provides for international recognition of test and calibration data, and confidence in the integrity of data.
- If required, the calibration interval for the equipment should also be included. ISO 17025-accredited laboratories should not recommend a calibration interval in a report unless specified by the customer or superseded by a legal or regulatory requirement. The customer knows the end use of the equipment best and should determine the calibration interval based on use and experience.
Any purchasing document (for example, a purchase order or requisition) for test and calibration service should be technically reviewed before releasing it to the calibration or test supplier. The record of this technical review should be maintained. This may be documented on the copy of the purchase document.
Upon receipt of the calibration and test item, another documented technical review should be performed to ensure the customer received what it specified on the purchase document and that all contractual requirements were met.
The measurement uncertainty data requirement and using the accredited laboratory satisfies the requirement for measurement traceability as defined in ISO guide 99:2007.2
The topic of evaluating and qualifying an unaccredited laboratory as a test and calibration supplier shall be discussed in a future column.
References and note
- For more on this topic, see Dilip Shah, "In No Uncertain Terms," Quality Progress, January 2009, pp. 52-53.
ISO/IEC Guide 99:2007, International vocabulary of metrology—Basic and general concepts and associated terms.
ISO/IEC 17025:2005, General requirements for the competence of testing and calibration laboratories.
ISO/IEC 9001:2008, Quality management systems—Requirements.
Dilip Shah is president of E = mc3 Solutions in Medina, OH. He has more than 30 years of experience in metrology and applications of quality and statistics in metrology. He is a past chair of ASQ’s Measurement Quality Division and Akron-Canton Section 0810, and is co-author of The Metrology Handbook (ASQ Quality Press, 2004). Shah is an ASQ-certified quality engineer and calibration technician, and a senior member of ASQ.