DECISION RULES RELATED TO TESTING AND UNCERTAINTY OF MEASUREMENT IN TESTING in the IECEx System
General policy
1. In accordance with the requirements of Clauses 7.1.3 and 7.8.6.1 of ISO/IEC 17025:2017 the testing laboratory TL CCVE has published its “ Decision Rule” related to the results of each test carried out in the laboratory at the web-site http://ccve.ru
2. Due to the safety factors incorporated in the types of protection, the uncertainty of measurement of good quality, regularly verified/calibrated measurement equipment is considered to have no significant detrimental effect and need not be taken into account when making the measurements necessary to verify compliance of the equipment with the equipment requirements of the relevant part of IEC 60079*.
DECISION RULES
Unless otherwise specified, TL CCVE makes a decision based on the “shared risk” principle
Where an indicated value is close to a limit value, such that the uncertainty of measurement is greater than the difference between the two, it is not possible to state definitively that either compliance or non-compliance has been demonstrated.
In such circumstances, the reading of the measuring instrument is taken as the true value, and declaring compliance or noncompliance on that basis gives an equal probability that either:
• compliance has been confirmed when it could not be absolutely demonstrated; or,
• non-compliance has been confirmed when it could not be absolutely demonstrated
(within the limits of uncertainty of the measurement).
Thus, the manufacturer and the end user of the equipment have an equal shared risk as to whether the equipment exactly meets the technical criteria of the specifications.
When approving the test reports CB CCVE is of the opinion that, as a certifying authority, it has an equal obligation to the manufacturer and the end user of the equipment, and that with respect to test measurements, subject to special conditions in accordance with IEC 60079-0, this shared risk is acceptable, since measurement uncertainties are quite low due to the use of standardized test methods, regularly verified/calibrated measuring equipment, and appropriately trained qualified personnel.
For qualitative, as opposed to quantitative, test results based on controlled and measured conditions, a conclusion is made (for example, compliance or non-compliance) and the uncertainty of measurement is not evaluated.
* In accordance with Note to 26.1 of IEC 60079-0:2018.
REPORTING
1. As a rule, TL CCVE does not state the value of uncertainty of measurement in the test reports relative to assessment of conformity to the requirements of standards series IEC 60079.
2. If there is a specific requirement of the customer or the normative documents to state the uncertainty of measurement, TL CCVE specifies the uncertainty of measurement in the test reports.
If the values of uncertainty measurements are required to be specified in the report, either the uncertainty values given in the calibration certificates of the measuring instruments or the uncertainty calculation, as appropriate, are provided.