COMPRESSORS FANS
Bitzer developed its own rotor profi les, which were new for refrigeration screw compressors, signifi cantly improving effi ciency for the capacity range. Initial testing with open drive compressor prototypes was successful, but production still required lots of manual fi ne-tuning. “Very high precision was essential for manufacturing, which is why we had to adapt every housing to the paired rotors at the beginning,” recalls Michael Loichinger, who is now in charge of prototypes’ manufacturing. He was hired in 1983 and immediately tasked with assembling the fi rst screw compressors.
Rapid development of screw compressors – with customer input After exhaustive development work, the fi rst semi- hermetic HS screw compressors and the fi rst open OS screw compressors were proudly introduced to the global community in 1983 for the fi rst time at the IKK trade fair in Nuremberg. “They were a hit,” recalls Hermann Renz. “Industry experts smirked at fi rst. They didn’t believe it would be possible to achieve the necessary precision in series production for the relatively small compressors.” The acceptable tolerances were much smaller than those of reciprocating compressors – but newly developed production centres and tools for processing the housing as well as an effi cient 3D measuring machine for production control made it all possible. The method of fi nish milling common at that time was replaced early on with a special grinding process to ensure very high precision in the fi nal step of rotor processing.
Optimisation and further development After presenting these innovations at the trade fair, Hermann
Renz was responsible for acquiring customers for the fi rst fi eld tests. A Bitzer expert was there to commission each fi rst system, as the technology was new for everyone and required special measures for compressor start-up and system control. The engineers took their experiences from the fi eld back to the assembly facility and to R&D for the purpose of optimising products and processes. “At the beginning, two of us assembled a few screw
compressors each week and produced diff erent components ourselves,” recalls Loichinger. “There were already two shifts and line assembly for the reciprocating compressors at that time. But the screw compressors quickly caught up. The high demand increased production signifi cantly, and open drive and semi-hermetic models were built in diff erent sizes.” Soon after they were launched, the compressors came equipped with Economiser connection and integrated capacity control as standard. Initial testing with frequency inverter for speed control kicked already off in 1984, and a water chiller was equipped with this innovative technology two years later, ensuring a whole new level of effi ciency in the part load range.
Bitzer initially only supplied the DACH region, but soon
began receiving orders for the new screw compressors from international companies located further abroad.
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3D measuring machine.
CSW105 series.
Based on the experiences during commissioning and service Bitzer optimised the screw compressor protection and expanded the functions of the electronic compressor protection device. In response to the surging demand for liquid chillers with higher capacities for comfort air conditioning and in process applications, Bitzer developed a new series in 1989, the HSKC compact screw compressors with fl anged-on oil separator for simple system integration. In 1999, a brand-new series, the CSH compact screw
compressors, was launched for use in liquid chillers and heat pumps. In the years that followed, it was continuously expanded for higher capacity steps and, since the launch of the CSW105 series in 2021, off ers a displacement range of up to 2,000 m3
/h at 50 Hz (cooling capacity approx. 1300 kW). The fi rst generation of semi-hermetic CSV compact
screw compressors with integrated, refrigerant-cooled frequency inverter was launched in 2012. The model range has continued to expand ever since and now boasts a displacement range of 1,200 m3
"Refrigeration was new territory for smaller screw compressors with
displacements below 300 m3
/h, /h (cooling capacity approx.
800 kW). Developed in parallel on the same platform, semi-hermetic and open drive compressors were designed for traditional use with external oil separator – with special suitability for parallel operation. The Bitzer product portfolio now also includes complete Ammonia Compressor Packs (ACPs).
which until then were only common in air compressor technology," says Hermann Renz.
www.acr-news.com • January 2024 15
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