Right first time, every time

Published:  13 August, 2015

Mick Broughton, UKAS calibration manager at AMETEK Land Instruments, looks at how periodic calibration of infrared thermometers by a UKAS-accredited laboratory is essential for maintaining quality, efficiency and safety within the production process.

Temperature is one of the most frequently measured parameters. Accurate temperature measurement is needed to manage and monitor the process because it has a direct effect on quality, safety and efficiency. Ensuring accurate temperature measurement therefore requires regular, traceable, calibration.

Thermometers that are not periodically calibrated may provide false readings and the consequences of this are poor quality, safety issues, energy inefficiency or reduced Mean Time Before failure (MTBF). All of these have the potential to affect the reputation and financial performance of the entire company.

How often should you calibrate your thermometer?

There are a number of reasons why it is necessary to carry out periodic calibration. Conditions on site can have a significant influence on the accuracy and stability of the temperature measurement. Dirt, dust, vibration, EMC and physical impacts or shocks (from dropping portable instruments!) are all typical causes of drift in performance and accuracy whilst the instrument is in use. Whilst the Land infrared products are designed to be inherently stable and have protective housings designed for these harsh industrial environments the only way to ensure performance is verifying the instruments performance in a calibration laboratory.

We are frequently asked the question what is the manufacturer’s recommendation on how often an infrared thermometer should be calibrated. For industries operating outside a quality standard that defines the calibration period, ultimately the judgement must be made on a risk assessment basis. The key variables to include in this assessment are:

• What are the accuracy requirements of the process?

• What is the criticality of the temperature measurement?

• What industrial environment is the instrument operating in?

• What is the frequency of use?

Whatever frequency is chosen it gives you the option to track the instruments ‘calibration history’. By doing this, it is possible to see how quickly instruments track off stable. If the graphed data shows steady, stable measurements over an extended duration, then calibration may not need to be carried out as frequently, again depending on industry and customer needs. Conversely if the measurements track off trend relatively quickly it is a sign that further investigation and possible more frequent calibration is needed.

Frequency of calibration is therefore a balance between risk and cost of material being spoilt, plus other factors specific to each business. Often we have thermometers returned for calibration only after it has been noticed that there is a difference in the temperature reading between the infrared thermometer and a fixed thermocouple. Ideally the thermometer should have been calibrated well before this stage.

The general rule to follow is: just because any piece of electrical equipment is working doesn’t necessarily mean that it is accurate. Once a decision has been made to calibrate you need to decide whether to go down the Certificate of Conformity route (factory calibration), or full UKAS calibration. The difference between the two is that the former meets a minimum set of regulatory, technical and safety requirements whereas UKAS goes beyond this by ensuring calibration is carried out in accordance with the highest ISO/IEC 17025:2005 standards.

Why UKAS calibration?

There are a number of benefits to choosing a UKAS accredited laboratory:

High quality

When you use an external laboratory for calibrating an infrared thermometer, in effect, the quality of their calibration services will ultimately determine the quality of product leaving your factory gate. Therefore, if you are going to have your equipment calibrated it makes sense to use a UKAS approved laboratory because it operates to ISO/IEC 17025, the standard against which UKAS accredits laboratories.

Improve efficiency

Being 100% confident of the accuracy of UKAS calibrated temperature readings means that you know that your production process is operating within the correct range. An instrument that has drifted over time could be reading lower than the actual temperature resulting in a higher than optimum energy input to the process.

Improved MTBF

Temperature accuracy is key on processes such as hydrogen reformer tube measurement where a 15oC higher temperature can result in a 50% reduction in tube lifetime. Traceable calibration allows the user to run such processes for the maximum time between rebuilds.

Summary

Investing in high quality infrared temperature measuring equipment and then using a UKAS-accredited laboratory for calibration services means that readings are demonstrably traceable to a national standard. If you decide to use an external laboratory, choosing one that is accredited for calibration services by UKAS is a guarantee that your infrared thermometer will be returned to you meeting the highest international standards - ISO/IEC 17025.

There is an added benefit of using a manufacturer’s UKAS-accredited laboratory because it gives you the option of applying a correction factor to the manufacturer’s instrument, improving practical measurement uncertainty to better than specification. In high precision industries such as medical device processing, this can form part of a demonstratable quality ethos.

Ultimately, calibrating your infrared temperature measuring equipment at a UKAS accredited laboratory means this aspect of your production control system will be right first time, every time. The relatively small investment of calibration as part of a product quality system or maintenance plan is insignificant compared to the consequences of lost production or failing product. Ultimately using a UKAS calibration laboratory reduces your risk further because it is providing you with calibration services that meet the highest internationally recognised standards that ensure full traceability of the instruments performance over the lifetime of operation.”

AMETEK Land Instruments has been manufacturing a range of high precision industrial infrared thermometers and imagers for the steel, glass, petrochemical sectors for nearly 80 years. Alongside this it has operated UKAS accredited calibration laboratory No.0034 for the last 45 years. All its infrared thermometers and imaging equipment are supplied with a Certificate of Conformity as a minimum. Alternatively, the company can supply full UKAS calibration on new equipment or those returned for calibration. Its UKAS accredited calibration services meet national and international standards including ISO/IEC 17025:2005, ISO 9001, AMS 2750E, HTM2010 & HTM2030, plus other country specific requirements.

For further information please visit: www.landinst.com

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