Top tips for correctly specifying a compressed air system
Generating compressed air accounts for a significant portion of total energy costs in industry, so ensuring wastage is kept to an absolute minimum should be a key concern for businesses.
For this reason, whether you’re investing in a new compressed air system or upgrading an existing one, it’s important to make sure to specify all elements correctly. This will help reduce costs, improve operational efficiencies, and reduce the risk of downtime throughout the system’s lifetime. Here are some aspects that deserve special consideration during the specification process.
Sizing correctly
It’s critical to make sure a compressor and dryer is sized correctly for the job it’s required to perform. Over-specifying is unnecessary and can be costly, both in the initial outlay and any on-going maintenance requirements. Instead, the equipment should be appropriately sized for the demands placed upon it.
The first step is to calculate the maximum and minimum air pressures required, as well as the compressed air flow needed, by installing a data logging device. This will allow you to specify a system that provides enough air for your requirements at maximum efficiency.
It is also important to ensure the air receiver is sized and located correctly, as this has a direct impact on reliability and energy efficiency. The air receiver should be sized (in litres) to be at least 6-10 times the compressor’s free air output (in litres/s). An undersized receiver can cause the compressor to cycle frequently in response to small changes in pressure
One way to save the energy and cost incurred by cleaning and drying compressed air is to treat all the compressed air to the minimum acceptable level, and then improve the quality at the points of use to the required level.
Consider variable speed technology
Compressors are at their most efficient when operating at full load. Even when off-load, the power consumed can be 20-70% of the on-load power, so variable speed control can save a large amount of energy, but only if the air demand fluctuates. A compressor that runs at full load will consume more energy if a variable speed drive is fitted, so it’s important to understand your usage before fitting a variable speed drive and, if retrofitting to existing machines, be sure to consult the manufacturer first.
Optimising pipework
Because not all parts of a network operate the same hours or to the same pressure, you can save energy by ‘zoning’ your compressed air system. This way, only the pressure that is required for each zone is supplied. You can do this by removing or isolating redundant piping so that it doesn’t leak out of hours.
You can also minimise pressure drop and allow for possible expansion by selecting large radius bends instead of elbows while ensuring piping is properly supported will minimise movement and sagging, further reducing leaks and the build-up of fluids.
For larger systems with numerous take-off points, a ring main distribution system is recommended. When selecting pipe material, consider alternatives to traditional galvanised steel, which will eventually corrode and has a much rougher internal surface.
Specification tips
Compressors should be located in a dry, clean, cool and well-ventilated area. It takes more energy to compress warm air than cool air, so a compressor room should be kept as near to ambient temperature as possible. The air inlet to the compressor house should also be sited on a north-facing wall if possible, or at least in a shaded area, with a grill to prevent debris entering.
Be sure to fit drain traps and valves to components where water will condense, such as aftercoolers, air receivers, dryers and filters. Inefficient condensate drains are a major cause of leaks and wasted energy; electronic level sensing drains offer a particularly energy efficient solution.
Lastly, selection of air treatment equipment is vital to achieving the required air quality standard and avoiding unnecessary pressure drops.
Improve efficiency with HPC KAESER and BCAS
HPC and its Authorised Distributors are experienced and qualified to design, install, and tailor the compressed air system to meet specific and individual requirements. Peace of mind is also provided that all work will be in accordance with HPC guidelines and current legislation.
HPC is a member of the British Compressed Air Society (BCAS), which is spearheading a campaign to cut compressed air energy wastage. The goal is to take the equivalent of 317,000 cars off the road, saving UK business over £147.5 million. Visit the BCAS 10% Taskforce website to find out more.