Water & Wastewater Treatment

www.wwtonline.co.uk | WWT | january 2015 | 33 The interior of a ZS11 rotary screw blower Rotary screw blowers have been shown to use 30% less energy It's possible to enjoy quieter operation and reduce installation costs by choos- ing a blower with intelligent internal baffle design and canopy configura- tion. Sound levels can be down to 72 dB(A) so there is no need to provide noise-insulated rooms and doors. Could pulsations in the air delivery be a problem? It's not generally understood that vibrations and compression element pulsations affect blower efficiency. So it is best if your unit can deliver high frequency, low pulsation air. This can be achieved when air is delivered via the flexible hoses that feature on screw technology blowers. The hoses help to provide a smooth discharge and vibration de-coupling between the compression element and the filter housing. Consider installation time There are benefits to be derived from opting for advanced screw blowers incorporating plug-and-play technol- ogy. This is because they can be easily installed and quickly become active, thus the time and resource normally spent on set-up is minimised. What is the cost? Lifecycle cost comparison can be divided into three main considera- tions: investment cost, power cost and maintenance cost. In terms of upfront investment, some suppliers apply extra charges to ancillary items, while others offer simpler plug-and-play concepts. Power costs should be considered in terms of free air delivery and main- tenance costs can depend heavily on the likely need for replacement parts and the availability of warranties. How do the different types of blowers compare in terms of energy efficiency? The independent TÜV organisation measured the energy efficiency of a rotary screw blower against the performance of a conventional tri-lobe blower. In these like-for-like tests it was proven that the rotary screw blower was 23.8 per cent more energy efficient at 0.5 bar(e)/7psig and 39.7 per cent at 0.9 bar(e)/13psig. Relative values In addition to these few considerations there will be many other factors for the specifier to take into account such as bearing life, drive motor specification, pipework requirements, panel building and control systems.

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