Many calibration technicians follow long-established procedures at their facility that have not evolved with instrumentation technology. Years ago, maintaining a performance specification of ±1% of span was difficult, but today’s instrumentation can easily exceed that level on an annual basis. In some instances, technicians are using old test equipment that does not meet new technology specifications. This article focuses on establishing base line performance testing where analysis of calibration parameters (mainly tolerances, intervals and test point schemes) can be analyzed and adjusted to meet optimal performance. Risk considerations will also be discussed – regulatory, safety, quality, efficiency, downtime and other critical parameters. A good understanding of these variables will help in making the best decisions on how to calibrate plant process instrumentation and how to improve outdated practices.

Process instrument calibration is just one of the many maintenance related activities in a process plant. The last thing you want to do is to have your limited resources wasting time performing unnecessary calibrations or using time-consuming, ineffective calibration procedures.

Yet, you need to make sure that all critical calibrations are completed, ensuring the site stays running efficiently with minimal downtime, product quality is maintained, while the plant remains regulatory and safety compliant, and audit-ready.   

This article discusses some critical items to address for a calibration program based on sound metrology fundamentals without a complete overhaul of the calibration program. Having properly calibrated process control instrumentation provides a high quality of process control, a process that will operate to design specifications, and prevents the process from being stressed as it compensates for inaccurate measurement data feeding the DCS. Realization of these benefits may be challenging to quantify and attribute to implementing any of the suggested changes, but conversely, implementation of the changes should not be extraordinarily burdensome on resources.  

An investment into calibration equipment and systems must be financially justified, just like any other business investment. But does a cheaper cost of purchase always mean a higher return on investment? Not necessarily. When building a business case for calibration calibration system investment, what may seem at the outset to be cheaper may not necessarily be so, if the evaluation is made from total or life cycle cost perspective instead of evaluating cost of purchase only.