Generally treated as a support function, compressed air is widely used in production facilities for the operation of process machinery and the actuation and control of pneumatic valves, cylinders and controllers. Ben Soderling reports.

The quality and availability of compressed air may have a significant effect on a plant's core production. CompAir, a manufacturer of compressed air and gas systems, uses the Vaisala DRYCAP Hand-Held Dewpoint Meter DM70 for measuring pressure dewpoints in its AirAudit, part of its AirWorx service.
The audit measures a number of parameters associated with the performance of compressed air systems, aiming at improving their energy efficiency.
CompAir is a leading global manufacturer of compressed air and gas systems, with production facilities in the UK, Germany, the US, Canada and China. CompAir's compressors, equipment and services are used worldwide, providing high-quality economic, clean and reliable compressed air and gas for numerous applications. AirWorx is a service where the customer can purchase the compressed air needed from CompAir with no need for capital investment.
Seen as a support activity, compressed air seldom warrants the attention it really deserves. Industry is currently using 8 - 10percent of its electricity consumption to compress air and in general some 30percent of the compressed air generated is wasted. In a recent study for the EU entitled 'Compressed air systems in the European Union - Energy, Emissions, Savings Potential and Policy Actions', the author's introduction states that 'savings in the range of 5 to 50percent are possible'. CompAir's idea is to take the capital cost out of this equation and simply realise the operational savings by outsourcing the production of compressed air through an AirWorx supply agreement.
For measuring pressure dewpoints as part of the AirAudit, CompAir are using the Vaisala DRYCAP Hand-Held Dewpoint Meter DM70. For this service, an instrument was needed that could handle both very dry air with dewpoints down to -70°C and systems with condensate. Generally the expected dewpoint for compressed air systems with compressed air drying is between 5 and -40 °C but as dryers do not always function properly the sensor needs to be able to handle wet conditions as well.
The sensors that we previously used needed re-calibrating once they got wet, but the DM70 has operated well despite condensation. For CompAir with a global presence it was also valuable to have a partner with a global presence so that support could be found locally if/when required. The DM70 is reliable and offers user-friendly features, such as several language options.
Producing dry, oil-free and dust-free compressed air at a low cost is the aim in a compressed air system. Filter systems are used to remove oil and dust, and dryers are needed to adjust humidity. Regardless of the drying or filter system, clean dry compressed air comes at a premium price and measurements are essential to ensure that you are getting what you pay for. In measuring actual compressed air system pressure dewpoints, CompAir has found that where desiccant dryers are used to provide sub-zero dewpoints, more than 50percent of systems do not work due to lack of maintenance. Because the sites did not have a measurement system installed, they had no idea of the problem.

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Ben Soderling is Development Manager, AirWorx CompAir, High Wycombe, UK. Vaisala Oy is based in Vantaa, Finland. www.vaisala.com