Editor's Note: This post was originally published in 2017 and has been updated for accuracy, comprehensiveness, and new information.
When you have a compressed air system that uses more than one compressor or dryer, it can be difficult to determine which machine to run when. This is especially true if your demand for compressed air fluctuates daily! Compressed air consumption is seldom constant, which means that many compressor installations are designed flexibly and use a combination of compressors with different capacities and speed-controlled motors.
Why Use Central Controllers in Compressor Installations?
In compressor installations, the use of a central controller lets the system maintain a predetermined pressure within tight limits to provide economic operation of the installation. To achieve this, the system must be capable of predicting demand, while at the same time sensing both the load on the compressor and how quickly the pressure changes. Using these values, the system performs calculations that make it possible to predict the air demand and will either load/off-load or start/stop the connected compressors. In a correctly dimensioned installation, the pressure fluctuation will be kept within ± 0.2 bar.
Modern intelligent controllers focus on operational efficiency and will select the most economical compressor or compressor combination, if compressors of different capacities make up the system (i.e. if a system is comprised of a VSD and fixed-speed compressors). The central controller will ensure the compressors run continuously loaded, thereby minimizing idling periods and providing optimal economy. In many cases, it’s also possible to connect older machines to these systems, thereby modernizing the entire compressor installation in a relatively easy manner.
Benefits of Central Controllers for Compressor Systems
Keep in mind that if the system isn’t properly managed or controlled, there is a risk of producing too much air, which translates into higher operating costs. The solution is simple: a central controller! Below we cover six specific reasons your compressed air system will benefit from central controllers:
Flexible Machine Sequencing. Controllers ensure that machines work in groups and adjust to meet demand. In a fixed system, there might be a certain order in which machines are used to meet air demand. In a flexible system with a controller, the best combination of machines is used.
Workload Equalization. By spreading the workload over multiple machines, a central controller avoids unnecessarily overloading individual machines. A controller can also prioritize the use of the most economic machines over older, less effective versions.
Continuous Use of VSD Machines. VSD compressors are the most energy efficient machines for variable load. A central controller can ensure that these machines are prioritized over base-load or single speed compressors.
Regulation of System Pressure. With a central controller, machines can operate within a predefined and narrow pressure band. This allows the system to meet demand while still optimizing energy efficiency.
Shutdown Scheduling. Central controllers can help operators schedule maintenance and avoid incurring extra costs during non-working hours. Scheduled shutdowns should be part of any predictive maintenance plan.
Fewer Service Visits. By utilizing flexible machine sequencing, workload equalization and shutdown scheduling, central controllers help machines reduce premature wear. This leads to fewer service visits, and subsequently lower service and maintenance costs.
Using a modern central control system can help the compressors run optimally for different operating situations while enhancing safety and availability. Selecting the right regulation method encourages energy savings through lower system pressure and a better degree of utilization, which is optimized for each machine in the installation. The control system also balances the work load between different machines, which ensures increased availability and reducing risk of unplanned downtime. Using central controllers also allows programming for automatic pressure reduction in the entire system during operation at night and on weekends.