Reducing energy loss from compressed air leaks

The hissing sound of compressed air leaks on a shop floor can be all too familiar. Not surprising, considering manufacturers are thought to waste around 30% of the compressed air they generate, even though it can account for up to a third of their energy use. According to The Carbon Trust, UK industry is using over 10TWh of electricity a year to compress air. With an estimated 30% loss, that’s a huge potential power and carbon-savings opportunity waiting to be claimed.

The British Compressed Air Society (BCAS) suggests aiming for a target of around 5-10% of air generated lost to leakage but warns leak rates on an unmanaged plant could be as much as 40-50%.

Small leaks multiply

A single 3mm hole could cost more than £4,000 a year in electricity (fig 1). Multiple small leaks – a hole in a hose, a failed seal, a faulty valve, poor coupling or joint - are all ‘low hanging fruit’, fixed in no time at all. But, if the pressure drops, it’s all too tempting to crank up the power – increasing the load on the compressor, and probably just pushing more waste out from the weakest points.

Fluctuations in pressure compromise production efficiency. There will be more unplanned maintenance interventions, more unexpected machine downtime and the compressor’s service life will be shorter.

Product quality and reject rates will suffer if air is not delivered at a constant, optimum pressure. Starved of air, a torque wrench will not tighten correctly, a cylinder will lose force so that parts are not correctly positioned, delicate products could be dropped by vacuum suckers.

To be sufficiently robust, permanent instrumentation is clearly desirable, despite requiring a modest capital investment. A range of measuring devices have been necessary to determine flow, pressure and temperature and gain the required insights. Tracking power demand has often been a matter of manual calculation using these values.

Tracking power demand

Real-time, instant shop-floor readings of the actual compressed air energy being expended has not really been possible, up until now. At SICK, we spotted an opportunity to design a new kind of thermal flow meter that measures flow, pressure and temperature simultaneously as gas passes through the flow channel, then uses an on-board algorithm to calculate the energy consumption of the process in kWh.

By comparing this value to the electrical power demand of the compressor, the SICK FTMg thermal flow meter enables accurate detection of changes in the efficiency of a pneumatic system, thereby detecting leaks and monitoring energy consumption in real time.

Not only are these calculations clearly displayed on the instrument itself, production and maintenance teams gain the transparency to monitor, trend and record operating efficiency and energy consumption.  Interventions can therefore be planned to identify and eliminate leaks by strategically placing FTMg sensors on a machine cell compressed air system, or on a sub-ring of the delivery system, for example. All this information is available in real time via dashboard read-outs, accessed via a mobile phone, PC or through the PLC control system, as well as via IT or cloud-based systems.

The SICK FTMg’s dynamic calorimetric measurement principle is extremely accurate, capable of reliably detecting even the smallest changes. The straight measurement channel design ensures accurate measurement with almost zero pressure loss as gases flow through the sensor during measurement.

Cost of ownership

Manufacturing industry is facing an unprecedented dual challenge of economic recovery and carbon reduction; even becoming a ‘netzero’ organisation is a serious aspiration for many organisations. Especially in challenging economic times, compressed air waste offers a ‘’quick win” opportunity for major savings that more than rewards investment in instrumentation, easily demonstrated as part of a total cost of ownership justification.

Darren Pratt is Industrial Instrumentation Product Manager for SICK UK