Cost savings in the air

Published:  10 September, 2015

Compressed air is a tertiary form of energy, created through the use of electricity which in turn is typically generated by the burning of a primary fuel source – coal, gas or oil. Of the original natural resource, only around 4% of the energy can be successfully converted into compressed air as the rest is lost as both waste heat and through transmission lines. PWE looks at how to cut the cost of compressed air.

Any leak or wastage of compressed air can be incredibly costly for manufacturers. The Carbon Trust estimates that a single 3mm leak can cost more than £700 per year in wasted energy, and when this is multiplied across the various pipes, hoses and valves in a large facility, the cost could run into many thousands of pounds. Conversely, effective maintenance of a compressed air system accounts for as little as 7% of the total cost of running a compressor over a ten year period, showing just how much a small investment could potentially save.

If leaks lead to fluctuating system pressure, production can be interrupted leading to the costs of unplanned downtime and emergency maintenance or replacement while in serious cases, reduced service life or even complete equipment failure can occur. In addition to wasting energy and money, leaking compressed air also presents a safety risk through blowing air and noise.

Leaks typically occur in hoses and couplings; pressure regulators; pipes, flanges and pipe joints; or in manual condensate valves. Leaving equipment running is also a source of compressed air loss – from leaving the compressor and air-using equipment itself running overnight or when not in use, or from leaving shut-off valves open. Compressors left idling uses around 40% of its full load, giving an immediate opportunity for energy and cost savings.

Detecting leaks is not usually a task which can be done manually – though leaks produce noise, it is often inaudible to the human ear especially over the general noise of a factory, and small leaks of just a few millimetres would not necessarily be perceptible by touch. The most common and convenient method of detection is through ultrasound equipment. Following detection, the second stage is to calculate the total cost of the leak. Here, technical experts will take into account the running conditions of the compressors (based on the weekly length of time in operation), the cost of electricity, the system pressure, and the efficiency of the compressor. The resulting calculations can fully quantify the cost of the leak by machine, department, area or even factory.

Ongoing monitoring

While regular surveys are vital in containing air leaks, ongoing monitoring is also possible through the installation of an air flow meter to the system before the air preparation equipment. This ensures a proactive approach and lasting solution for dealing with future leaks by immediately identifying any increases in air usage which can then be investigated further.

Even if an annual investigation reveals that no leaks are present, cost savings can still be made. As compressed air is usually generated at the compressor’s maximum pressure, even a 10% reduction in pressure can deliver energy savings of up to 5% (based on the compressor working at 7bar, 100psi). The Carbon Trust recommends making ‘small, incremental reductions’, all the while monitoring the system to ensure operations are not compromised. Similarly, the method of compressed air delivery could often be optimised to run more efficiently – replacing open-ended pipes with venturi-style nozzles can use 30% less compressed air as well as quietening the system.

Indeed, in some applications compressed air may not be the best option. Using compressed air for drying, for example, is highly costly compared with the alternative option of using blowers or even rejected heat from the plant compressor. Some hand tools are much more efficient when electrically-powered as opposed to using compressed air, and as a general rule compressed air should not be used to provide motion – these should be powered electrically unless used in an ATEX environment or explosion risk exists.

The cost of an individual air leak might seem modest, but when leaks occur at multiple points throughout a facility the costs can spiral. Investing a comparatively small amount into planned maintenance, comprehensive audits and ongoing monitoring – in partnership with an expert equipment and solutions provider – can deliver significant cost and energy savings.

Case study

Iain Hanson, product manager at Brammer said his company was called upon to conduct such an audit at the Banbury site of Mondelez, one of the UK’s best-known names in food and beverage production. This particular facility is the company’s largest coffee plant in the world, with the capacity to produce 100 million jars of instant coffee per year. Brammer provides an ‘Insite’ service to this and four other Mondelez facilities – effectively a Brammer branch on the premises, an Insite supplies and manages a wide range of maintenance, repair and overhaul (MRO) products including fluid power products, bearings and tools for a customer, and can also be called upon to support value-adding projects.

In one such instance at Mondelez in Banbury, the Brammer team was asked to investigate when an unplanned interruption to freeze-drying operations threatened to impact heavily on output. At the time, air compressors were running at full capacity meaning a considerable amount of air was being lost from the system, potentially at great expense.

Brammer’s immediate compressed air audit and analysis, using ultrasound, identified significant leaks which totalled more than £191,000 per year – to say nothing of the costs of downtime associated with equipment repair or failure. A programme of bespoke remedial action was prepared which at a cost of just £4000 for repair components and materials, delivered a huge saving for Mondelez. 

Following the successful repairs, a pneumatic equipment awareness day was organised with support from Brammer and one of its key partners Festo. Awareness of issues surrounding compressed air and engagement among the production team was vastly enhanced, and as a result the facility now conducts an annual survey aimed at identifying and rectifying leaks before they pose a major issue.

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