February 2020

optimising energy efficiency. In a multiple compressor installation, the controller regulates the system pressure by starting and stopping compressors and controlling VSD speed. Thanks to the controller’s built-in intelligence, compressor performance is optimised in all conditions. A tighter pressure band is achieved, resulting in lower energy costs and increased system stability. Multiple pressure bands can be set to avoid wasting energy during non-productive hours and stable pressure contributes to sustained production quality. System status and operating parameters of each connected compressor can be presented on a clear interface at all times. Shutdown scheduling – Central controllers can help operators schedule maintenance periods for non-working hours to avoid incurring extra costs. Scheduled shutdowns should be part of any predictive maintenance plan. Fewer service visits – By utilising flexible machine sequencing, workload equalisation and shutdown scheduling, central controllers help machines reduce premature wear. This leads to fewer service visits, and, subsequently, lower service and maintenance costs. Production security – System pressure not only depends upon the compressor output, but also on other components such as filters, dryers, and receivers Without the system pressure control offered by a central control unit, there is the risk that pressure anomaly alerts may be overlooked and application process output affected as a consequence. rated unit will be triggered to balance the required pressure level. Optimised central control Here is how a multiple compressor installation benefits from optimised central control: Flexible compressor sequencing – Controllers ensure that compressors work in groups and adjust to meet demand. In a fixed system, there might be a specific order in which units are employed to meet air demand. In a flexible system with a central controller, the optimum combination of machines is assured. Workload equalisation – By spreading the workload over multiple compressors, a central controller avoids unnecessary overloading of individual machines. A controller can also prioritise the selection of newer, more economic compressors over older, and less efficient versions. Continuous use of VSD machines – Without doubt, VSD compressors offer the most energy- efficient solution for variable load operations. A central controller ensures that in a mixed unit installation VSD compressors are prioritised over baseload or fixed-speed compressors. In multiple VSD compressor installations, equaliser controllers will maintain compressors in their optimum performance zone, but advanced optimising controllers are able to keep the VSD units to their precise optimum performance point. Regulation of system pressure – With a central controller, machines can operate within a pre-defined and narrow pressure band. This allows the system to meet demand while still 22 | Plant & Works Engineering www.pwemag.co.uk February 2020 Process, Controls & Plant Focus on: Compressed Air Advanced controllers In recent times there have been major advances in the concept and capabilities of centralised controllers. Depending on needs, users can benefit from conventional compressor room sequence control or take the opportunity to opt for the top-of-the-range energy optimisers. These provide advanced priority management, smart machine selection based on continuous monitoring of air demand, control of ancillary equipment, as well as logging and export of critical data. Atlas Copco says it Optimizer 4 controllers, the successor to its ES units, offer opportunities to select the most efficient combination of compressor units at defined working pressures while balancing unit running hours for all types of rotary stationary compressors ? VSD, fixed-speed, oil-lubricated, oil-free, turbo or low-pressure. Connectivity is not confined to same brand units or to a single location within a production site, enabling remote control via Wi-Fi, Ethernet, communication bridges and repeaters. In support of the of users’ ISO 50001 energy management system continuous improvement system targets, the latest optimiser controllers enable LAN and SCADA system connection to any device for data control and extraction, together with local visualisation and analysis of energy consumption and efficiency. What is more, advanced central control optimisers are designed from the outset to meet the smart factory’s future Industry 4.0 connectivity requirements.