Are you struggling to balance risk management with cost? This is a common problem when selecting calibration intervals. You want to calibrate often enough to minimize risk and at the same time minimize cost. Is this possible?
ILAC-G24 Guidelines for the determination of calibration intervals of measurements addresses the issue of when to calibrate and how often.
The most important factors are:
• uncertainty of measurement required or declared by the laboratory;
• risk of a measuring instrument exceeding the limits of the maximum permissible error when in use;
• cost of necessary correction measures when it is found that the instrument was not appropriate over a long period of time;
• type of instrument;
• tendency to wear and drift;
• manufacturer’s recommendation;
• extent and severity of use;
• environmental conditions (climatic conditions, vibration, ionizing radiation, etc.);
• trend data obtained from previous calibration records;
• recorded history of maintenance and servicing;
• frequency of cross-checking against other reference standards or measuring devices;
• frequency and quality of intermediate checks in the meantime;
• transportation arrangements and risk; and
• degree to which the serving personnel are trained.
This documents outlines several methods for reviewing calibration intervals. That being said we have seen 3 big mistakes in changing calibration intervals.
3 Big Mistakes When Changing Calibration Intervals
You have an upcoming audit and you want everything to be in calibration. If you are extending a calibration cycle based on an audit, you have a failure in your Quality Management System. Instead of changing the calibration interval you need to find out why the measurement and test equipment was not calibrated. We would recommend you revisit your risk management process. Why did this occur?
Single Gage vs. Class Of Gages
What is the justification of extending the calibration interval of one caliper and not all calipers? Expect this question from an auditor. If you are seeing drift in all gages except one then you have a serious problem. You need to perform a gage R&R and determine if a particular manufacturer, technician or environmental condition is the problem. We recommend that you purchase RP-1: Establishment and Adjustment of Calibration Intervals from NCSLI to understand the design and implementation of calibration intervals.
Asking Your Calibration Company
"ISO/IEC 17025:2017 section 4.1.1 Laboratory activities shall be undertaken impartially and structured and managed so as to safeguard impartiality."
It is improper for you to ask your calibration provider for recommendations on calibration intervals. You also are causing a very uncomfortable situation when you ask your calibration provider to extend calibration intervals. Once a gage has left the calibration laboratory they do not know what has happened to it. It may have been dropped or adjusted. It is nor fair to ask them to do this.
You may want to read 3 Things You Need To Know About Risk.