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The compresed air marketplace offers a wide variety of options from the very simple to the high-spec. Within that broad sweep, some 75 per cent of applications are for compressors with unit power less than 30 kW (40hp). This presents repair shops, service garages, small metalworking companies and other SMEs with the challenging task of matching a specific range of application requirements to the most appropriate type of smaller compressor with the right performance characteristics, and at an affordable price.
Now major advances in design and technology make it possible for compressed air users to take advantage of the guaranteed reliability, efficiency and economic benefits of the latest generation of smaller workplace rotary screw compressors.
Rotary screw compressors provide many distinct advantages over their reciprocating and vane counterparts in terms of size, air delivery, duty cycle and longevity. In addition to overall energy efficiency, rotary screw air compressors offer multiple benefits compared to other compressor technologies. These features include low noise output, light weight and small footprint for point-of-use plug-and-play installation. They also offer continuous operation at temperatures of up to 46 °C, extremely low oil-carryover into the delivered air, simplified maintenance procedures and zero loss of capacity over time.
Furthermore, smaller screw compressors can be tank mounted to enable additional air storage capacity, while full-feature variants with an integrated dryer and oil-water separator protect the compressed air network and end-user output.
The piston or reciprocating air compressor has traditionally been regarded as the most economical and least expensive type of air compressor. In its simplest form, it is still the most common type found in the automotive service industry. In more demanding roles, technically advanced versions can incorporate multiple compression stages to make them particularly suitable for high-pressure applications, such as PET bottle blowing.
The main drawback is that the average piston compressor can only work for about 50 to 60 per cent of its duty cycle i.e. the amount of time a compressor can continuously operate without stopping to prevent overheating in a given period. These units require adequate cooling time between cycles, otherwise they can overheat and possibly fail. The rotary screw air compressors, on the other hand, run cooler and are designed to operate continuously at 100 per cent duty cycle. Component wear is the other issue with piston or reciprocating compressors. Just like a car engine, reciprocating compressors feature piston rings and other components that are in direct contact with each other and suffer wear over time. With that wear comes a decrease in performance, oil carryover and excessive heat generation. They tend to run hotter as efficiency decreases and operating time increases.
A lubricated rotary screw compressor is designed so that the compressor oil seals the internal rotors, preventing parts from wearing out. Unlike a reciprocating compressor that loses performance with age, the rotary screw compressor can maintain the same level of performance throughout its long service life. They also offer multiple benefits compared to other compressor technologies. These features include low noise output, light weight and small footprint for point-of-use plug-and-play installation. They also offer continuous operation at temperatures of up to 46 °C, extremely low oil-carryover into the delivered air, simplified maintenance procedures and zero loss of capacity over time.
In addition, smaller screw compressors can be tank mounted to enable additional air storage capacity, while full-feature variants with an integrated dryer and oil-water separator protect the compressed air network and end-user output.
It is a similar story with rotary vane compressors. The simple vane principle has the longest track record since its introduction almost 100 years ago. However, such design longevity and simplicity does not necessarily equate to energy efficiency. Neither does it allow for a full range of capabilities in comparison to those offered by rotary screw compressors in terms of turndown rates, speed range limitations and energy demand.
In much the same way as the piston compressor is affected by component wear, the vane operating principle involves continuous sliding in and out of the rotor vane slot within the stator casing. As a result, both the vane and slot are subject to excessive wear, eventually leading to failure of the vane and all that entails.
There are also significant disadvantages in terms of vane compressor’s maximum speed, which affects output. For instance, as vane compressors rely on centrifugal force to operate, their maximum speed is limited to 1000 to 1100 rpm, which is a third of that for a screw compressor air element.
It is clear to see that the innovative developments embodied in advanced rotary screw compressor technology provide a clear advantage in performance and compatibility with SMEs needs. That is why Atlas Copco has introduced the all-new GL15-22kW low-investment compressor range, alongside its upgraded G7-15 and GX2-7 EP series, to offer robust performance, simple installation and maintenance, plus easy control and monitoring to air users in the 2-22kW (4.0 to 22.8 l/s) segment.
The all-new GL15-22 belt-driven, fixed-speed compressor family has been designed to provide quiet, efficient, powerful and reliable performance combined with minimum total cost of ownership. The 15, 18 and 22 kW compressors within the range increase free air delivery by a competitive 7.2 per cent margin, while also reducing the specific energy requirement by a significant 5.6 per cent compared to previous models.