Since appearing on the market, master controllers have helped to significantly enhance the efficiency of compressed air stations. The latest generation of these intelligent technical systems pushes the boundaries of compressed air efficiency even further and delivers added value that pays off in all sorts of ways. Providing precision monitoring and control, these multi-taskers not only keep an eye on the compressed air system as a whole, but also supply data for a range of applications. In short, they provide greater convenience, further enhance reliability, minimise costs and can be applied to an even wider range of uses.
The drive toward efficiency, reliability and most importantly, sustainable resource usage and energy savings, is increasingly compelling developers and users to optimise existing solutions even further. Modern installations are comprehensive systems, including compressors, cooling systems, dryers and filters. Even the individual components have auxiliary systems, such as ventilation or cooling water systems. Moreover, modern compressed air stations are often beneficially incorporated into heat recovery processes in order to achieve best possible use of the available energy. The range and number of individual components comprising a complete compressed air system can therefore be considerable.
Complex systems such as these require an organising principle of sorts, which is where master control systems come into play. By monitoring the individual components and optimally co-ordinating the interaction between them, these controllers transform the individual ‘players’ into a truly cohesive team that operates reliably and efficiently.
Up until now, use of such systems had yielded a certain degree of optimisation. For instance, master controller systems such as the SAM with 3D control have, for some time been capable of coordinating multiple compressors with different internal control systems, ensuring that they supply the required and set working pressure with maximum energy efficiency.
Better communication amongst components
Yet there were still certain aspects that harboured significant potential for improvement. For example, communications between the components and controllers still presented considerable potential for development and refinement. Some compressors are equipped only with floating contacts that merely signal the basic status of the compressor (running/not running) and do not feature integrated controllers capable of detecting and communicating more detailed status information about the compressor.
Furthermore, within the wide range of different bus systems available on the market, many are not compatible with one another at all or can only be made compatible with difficulty. This makes it difficult to communicate all the necessary information regarding a system’s status.
Contemporary Ethernet-based bus systems enable more straightforward integration and communication of large data volumes. Systems equipped with modern internal controllers therefore already rely on Ethernet technology in order to communicate with other networked systems.
Latest generation of management systems
The latest master controllers are true management systems which act like master controllers, yet are capable of much more. Compressed air management systems, such as the SAM 2, are designed to provide energy-optimised management of the compressed air station as a whole. Easy to operate, they also supply data for various output and evaluation forms, and ensure optimal, predictive maintenance and efficiency of the entire compressed air system.
Innovative communications infrastructure
The new management systems gather information regarding the connected components and measurement points via the network and are able to transfer this data rapidly without limitation to a centralised control system for evaluation. A closed, secure network ensures that the data is secure and cannot be accessed from outside the system without access permission.
Graphical interfaces ensure straightforward operation
Once in the system, the data is visually displayed for maximum intelligibility and is also easy to access. The components of the compressed air station are represented graphically and can be individually called up with just a few clicks. Once configured, the information can be displayed on the controller itself or on a PC or centralised control system via web transfer. Users can select specific data they wish to transfer; for security reasons the functions can only be accessed from the controller itself.
The collected data then opens up a range of monitoring, evaluation and application options.
Optimal energy management of components
The primary uses of a management system are to provide compressed air production monitoring and to automatically optimise compressed air system performance. For example, whilst also ensuring maximum operational reliability and efficiency, the compressors and treatment components are switched on and off as needed, or operate at partial load, so that compressed air quantity and quality always remain in step with actual demand.
The new compressed air management systems are available for compressor stations of varying sizes. Currently, up to 16 compressors can be integrated for monitoring and control, thanks to special network technology.
An eye on system parameters
The management systems additionally monitor all other relevant system parameters, such as the temperature and pressures in the compressor and compressed air treatment system, as well as ambient environmental conditions. This means the control system can also check whether compressor cooling functionality is performing as required and whether environmental conditions (temperature, pressure) are consistent with the relevant requirements.
Where heat recovery systems are used, all associated parameters are also integrated in the management system.
Using an integrated, freely programmable control logic module, peripheral devices necessary for compressor station operation can be flexibly programmed, to open inlet or circulating air louvres, for example.
However, progress isn’t restricted to system operation alone. Maintenance represents a key area to consider when it comes to maximising cost-effective compressed air production. It goes without saying that poorly maintained systems with contaminated coolers or filters, for example, also operate with impaired specific output values.
New management systems therefore, also take maintenance parameters into account and include them in overall optimisation strategies. Over the long-term, preventative maintenance not only reduces both energy consumption and costs, but also helps boost value-retention of the system as a whole. Moreover, the complex monitoring enables the creation of predictive maintenance schedules.
Documentation and management
In addition to control of the compressor package itself, the latest generation of management systems also enables the gathering, forwarding and evaluation of important data to produce documentation in accordance with ISO 50001.
The new management systems collect data regarding air consumption and, where applicable, heat recovery. Based on this data, costs are automatically calculated and can be assigned once again to the various individual components within the system.
These functions, including visualisation, are accessed via the web using standard browsers without the need for any additional software.
Compressed air management systems can therefore determine and collate a range of key metrics, including evaluation and analysis of compressor status, time period comparisons, threshold value evaluations, energy tables, cost tables and capacity.
Integration of older systems
Of course, the benefits of monitoring and maintenance are most effective when the compressed air station components (e.g. compressors, filters, dryers, etc.) feature the latest technology. But what if the existing system doesn’t correspond to the latest standards? Well, there’s no need for worry, as compressed air management systems also allow integration of older, less advanced systems. Although monitoring is more difficult if the available compressor system is not appropriately technically equipped, it is still possible. Depending on how modern the technology is, integration is accomplished via different types of controllers or bus converters.
Retrofitting only where necessary
Anyone considering retrofitting an existing compressed air installation with a new compressed air management system should be aware that this strategy doesn’t necessarily make sense for every system. The age of the existing machines determines whether a retrofit will actually deliver advantages. If they already feature temperature and pressure sensors and the filters are monitored, retrofitting is relatively straightforward. The signals already being transmitted are usually conditioned locally by signal conditioning devices and can then be retrofitted for use with Sigma Net Bus Converters or Sigma Bus Converters.
If the existing system has no monitoring points at all and the compressors are relatively old, then it likely doesn’t make sense to equip the systems with additional sensors. This is because technical development over the years has resulted in significant efficiency gains, which of course also applies to the world of compressors. In such cases, it is advisable to consider a completely new system ready equipped with modern monitoring and sensor capabilities. The overall potential efficiency gains and energy cost savings can quickly offset the associated investment cost.
Potential savings depend on the current situation
The extent to which installation of a new compressed air management system yields energy savings depends on the current situation of each individual operator. In the past, compressed air stations were rarely conceived with a comprehensive energy efficiency concept in mind, and even today this approach is not universal. This being the case, it is older stations in particular that present the greatest potential for improvement. When such stations are updated to the latest technology, the potential savings are considerably higher than for systems that are already optimised.
Controllers have been on the market in various forms for several years. The leap from the once common, traditional cascade control to controllers with average target pressure, such as the SAM1 (Sigma Air Manager) delivered energy cost savings of up to twenty percent. The next leap to SAM1 with 3D control and demand pressure control yielded around a further six percent in energy savings. The new control system is still being tested, but it is already clear that the savings potential will be even greater.
New compressed air management systems minimise interface problems and require no additional software to provide valuable cost monitoring information. Compressor station master controllers are increasingly evolving into management systems that not only control the compressors in accordance with compressed air demand requirements, but which also monitor the compressed air system as a whole, as well as associated auxiliary systems. This is performed with optimum efficiency and maximum evaluation potential in mind, which in turn, delivers improved reliability with more detailed information regarding the system and significantly reduces operating costs.
Authored by Dipl.-Ing. (FH) Erwin Ruppelt, Head Project Engineer, and Dipl. Betriebswirtin Daniela Koehler, Press Officer from Kaeser Kompressoren SE (Kaeser Compressors ).