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Introduction

Control & regulating systems Frequently you require a constant pressure in the compressed air system, which makes demands on the ability to be able to control the compressed air flow from the compressor centre.

There are a number of methods for this depending on, e.g. the type of compressor, permitted pressure variations, consumption variations and acceptable losses. Energy consumption represents approx. 80% of the total cost for compressed air, which means that you should carefully consider the choice of regulation system. Primarily this is because the differences in performance broadly overshadow the differences between compressor types and manufacturers.

It is ideal when the compressor's full capacity can be exactly adapted to an equal consumption, for example, through carefully choosing the gearbox's transmission ratio, something that is frequently used in process applications. A number of consumers are self-regulating, i.e. increased pressure gives an increased flow rate, which is why they form stable systems. Examples can be pneumatic conveyors, ice prevention, chilling, etc. However, normally the flow rate must be controlled, which often takes place using equipment integrated in the compressor. There are two main groups of such regulation systems:

1. Continuous capacity regulation involves the continuous control of the drive motor or valve according to variations in pres-sure. The result is normally small pressure variations (0.1 to 0.5 bar), depending on the regulation system's amplification and its speed.

2. Load/unload regulation is the most common regulation system and involves the acceptance of variations in pressure between two values. This takes place by completely stopping the flow at the higher pressure (off-loading) and resume the flow rate (loading) when the pressure has dropped to the lowest value. Pressure variations depend on the permitted number of load/unload cycles per time unit, but normally lie within the range 0.1 to 1 bar