Calibration Part 1: Supporting accuracy supports the bottom line

ABB’s Trevor Dunger explains the growing importance of calibration in promoting good practice and profitability.

At a time when companies across all industries are under financial pressure, everyone is looking to squeeze the maximum value they can out of their assets. We all know that you can’t manage what you can’t measure, so maintaining an accurate monitoring and control regime is essential. That’s just one reason why it’s the right time to think about how well your calibration regime is supporting your business.

Properly scheduled and effective calibration ensures that the readings emerging from instrumentation are accurate. Without it, measurements are essentially meaningless. The trouble is that maintaining an effective monitoring regime is not a “fit it and forget it” job. Periodic calibration is essential to maintain accuracy over the lifetime of almost every type of instrument.

This may be self-evident in some types of instrument, such as pH meters that rely on the sort of wet chemistry that can easily be disturbed. But even seemingly robust, solid state sensor elements such as thermocouples rely on electronics to relay their readings to plant control systems and electronic components are subject to aging from any number of factors, such as mechanical stresses or temperature fluctuations. It’s also worth noting that the same applies to the electronics of input cards, which provide the signals to controllers, so these should also be calibrated regularly.

The bottom line

Of course, some process measurements are more critical than others. So while flow meters carrying out fiscal measurements on petroleum products may need to be accurate to ±0.025%, a meter controlling the level in a water tank used for washing down machinery may only need to achieve ±5%.

Essentially it’s about optimising the process to generate the most income from the available assets, whatever the business. The ultimate goal might be increased production yields, reduced product give-away and over-charges, more consistent product quality and/or reduced product liability.

When should you calibrate?

The right time to calibrate a specific piece of equipment will depend on the type of instrument and the criticality of the job it’s doing. There are some common situations that typically call for calibration, such as:

• With a new instrument
• At time intervals specified by the manufacturer or regulator
• After a specified number of operating hours or usage cycles
• When an instrument has had a physical shock or vibration that might potentially put it out of calibration
• Following sudden changes in the weather
• Whenever the output appears doubtful

Who can help?

Suppliers and laboratories offering calibration services in Britain are accredited by The United Kingdom Accreditation Service (UKAS).

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