COMPRESSED AIR
USING ULTRASOUND TO PREVENT LEAKS AND SAVE ENERGY Oliver Pogmore of AVT Reliability
capacity. The financial impact of these leaks can accrue significantly over time. As one example, based on 100psi, at a cost of £7/million per m³ for one year (8,760 hours), a leak as small as 0.16cm can cost £846.00 annually. By doubling this to 0.32cm, the cost jumps to £2,721 annually. That’s just for one leak – imagine if a plant had ten leaks, or 50 leaks? This really is not an uncommon situation. In addition to being a source of wasted energy, air leaks cause a drop in system pressure, which can make air tools function less efficiently, adversely affecting production. By forcing the equipment to run longer, leaks shorten the life of almost all system equipment, including the compressor package itself. Increased running time can also lead to additional maintenance requirements and more frequent unscheduled downtime.
STEAM LEAKS
Steam leaks are typically found at valve stems, pressure regulators, connection flanges and pipe joints. If ignored, they can contribute to a drop in system pressure, resulting in heat loss and lower operating efficiency. At a pressure of seven bar (100psi), a cavity measuring just 3mm can cause the loss of 25,000 kg of steam per annum. Multiplying this by a typical steam production cost of £5.30 per kilogram would incur a loss of £132 a year. Considering that leaks are often not limited to one point of emission gives some measure of the potential for significant annual costs across a plant.
LEAK DETECTION USING ULTRASONIC DETECTION TECHNIQUES
“ M
ost industries use compressed air or steam – from clean-in-place procedures hydraulic tools. Yet many are unaware that they may be wasting thousands of pounds a year on wasted energy as a result of air
or steam leaks.
Most leaks are small in nature, which makes them both difficult to detect and easy to overlook or, in some cases, simply to ignore. But when considered collectively over the course of a year they can cost companies tens, if not hundreds, of thousands of pounds. To ignore them is to ignore the potential for quick-win operational efficiencies, improved safety, extended equipment lifespan and long term cost savings.
Leaks can be caused by a range of problems typical to any plant, including pipework corrosion, vibration from unsupported pipework, or insufficiently tightened fixings. But the end result is the same. The compressor runs less efficiently, more pressure is placed on the motor running it, so more energy is needed to maintain continuous production.
COMPRESSED AIR LEAKS
In a typical plant that has not been well maintained, the air leak rate may equate to between 20 and 30 per cent of total compressed air production
10 APRIL/MAY 2020 | FACTORY&HANDLINGSOLUTIONS
Leaks can be caused by a range of problems typical to any plant
Detecting leaks by normal visual or audible methods can be ineffective, especially when the leaks are small and set in the context of a noisy plant environment. Ultrasound circumvents both these barriers to pinpoint emissions and prevent small leaks from turning into big financial losses. During a leak, liquid or air moves from a high pressure to a low pressure and as it passes through the leak site, a turbulent flow is generated. This turbulence has strong ultrasonic components and typically the larger the leak, the greater the ultrasound level.
”
Ultrasound is a high frequency, short wave signal and the intensity of the ultrasound produced by a leak drops off rapidly as the sound moves away from its source. The sound will therefore be loudest at the leak site. Both steam and air leaks can be located, via both the atmosphere and solid surfaces, using a simple handheld portable ultrasonic detector. This electronically translates ultrasound frequencies down into the audible range, where they are heard through headphones and observed as intensity and/or decibel (dB) levels on a display panel.
The more advanced digital instruments contain onboard sound recording to capture sound samples for spectral analysis, providing both visual and audible reporting. They are connected to data management software, so the logged data can be downloaded to a computer for analysis.
THE BENEFITS OF ULTRASOUND
Energy efficiency should be a key focus for any company keeping a close eye on both the bottom line and its commitment to International Standards Organisation (ISO) 50001 standard for energy management systems. Unidentified leaks can be their silent enemy, nudging up energy use imperceptibly by reducing the efficancy of equipment, while at the same time diminishing its reliability and adding to the risk of unscheduled downtime and generating avoidable maintenance costs. Ultrasound roots these bad actors out. Because the high frequency ultrasonic
ENERGY CONSERVATION –
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