Determining Calibration Intervals for Infrequently Used Equipment

calibration interval

Any organization that produces small orders of custom pieces is used to storing, and calibrating, seldom used equipment. This is especially true for organizations that carry an ISO 9001 certification or have stringent quality management programs. It may seem like instruments get calibrated multiple times between uses, which can be seen as unnecessary expense. Quality managers or technicians may question whether or not these infrequently used items have to be calibrated regularly, especially if the interval is short. Below are points to consider when adjusting the calibration cycle of equipment.

ISO 9001 Requirement

The first concern of many organizations is meeting ISO guidelines. Clause 7.6 outlines the requirements for Control of Monitoring and Measuring Equipment. The outline states that test equipment should be calibrated at regular intervals, or before use, in accordance with the Quality Program. The interpretation of this clause specifically addresses this issue. Instrument calibration dates can change if they are not in frequent use. The important point is that the instrument must actually be taken out of rotation and tested before use if the calibration due date has passed.

Talk to Your Calibration Lab

Start by talking to your ISO/IEC 17025 accredited calibration laboratory about the infrequently used equipment. Communicate how often you use the equipment versus how often you calibrate. There is no general rule for the best course of action. The type of equipment, age, potential power source, and frequency of use are all taken into account when calibration may change. The two most common options are an interval extension or calibrate before use policy.

Extending Calibration Intervals

A calibration interval extension is only an option if the item meets three criteria. The accrediting body and Quality Program must allow for an extended calibration cycle. The calibration interval should not exceed the manufacturer recommendation. The equipment must have a demonstrated, three year history of passing testing. Only if equipment meets these criteria should it be considered for a longer calibration interval.

Calibrate Before Use

Companies that have infrequently used equipment may choose a “Calibrate Before Use” strategy. In this scenario, equipment may pass the specified calibration interval but is documented and labeled to indicate that calibration must take place before use. Calibrate before use labeling should include the signature or initials of the Quality Manager and the date that the label was applied. Communicate this with your calibration provider so that they can help with future calibration due dates and recommendations.