COMPRESSORS u


Four decades of HallScrew compressors revealed


The HallScrew Compressor has been making its mark on the world stage for more than 40 years. The multi award-winning HallScrew Compressor is playing a vital role in systems in at least 85 countries worldwide. Many thousands are employed for deep freezing, process cooling and refrigeration – covering a wide range of industries.


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ecognised in the Queen’s Awards for Industry in 1984, the HallScrew Compressor has constantly evolved over the years, addressing


technological, market and commercial needs, and helping the UK to enhance its formidable reputation as the cradle of refrigeration innovation. Terry Young, the J&E Hall director responsible for screw compressor development, gave a talk to the Institute of Refrigeration about this iconic machine. He spoke about the many challenges encountered and overcome in the 48-year development of the HallScrew compressor, from open drive prototype to the modern models encompassing the latest innovations and design features to meet the exacting demands of industry. The talk has been nominated as one of the candidates for the IOR Kenneth Lightfoot Medal – the award for the best talk or webinar presented to IOR members. J&E Hall began the design and development of their own screw compressor in 1972, using a concept of single main rotor plus two gate rotors. It was a mechanism that had started life in 1960 compressing air but its potential as a refrigeration compressor had become evident.


HallScrew compressor 2 Reciprocating machines had dominated systems for many decades but the first Monobloc compressors, which ran at 50-60rpm were large, slow and heavy. “As knowledge of valve behaviour, bearings and weight improved, speeds increased to 250- 500rpm making it possible to achieve substantial savings in size and weight,” reflected Mr Young. “However, to be called high speed is only relative to the older slower machines. They were still massive and cumbersome with large footprints. It seems incredible that compressors as large as these were cast in the J&E Hall foundry in the middle of Dartford.”


Veebloc compressors arrived around 1960, 26 November 2020


with cylinders and pistons arranged in a V and W formation. They were highly compact and over a 20- year period speeds increased up to 1750rpm on some of the smaller V54 models. There were 30 Veebloc machines in the range before Halls decided to stop manufacturing reciprocating compressors in 1985. Twin screw Lysholm design compressors had been


introduced into the industrial refrigeration market as early as 1958, exploiting a gap between large reciprocating and centrifugal machines and by the mid-60s engineers were recognising the advantages of rotary instead of reciprocating action. Employing a screw instead of a piston eliminated valves – the most sensitive components of a reciprocating compressor. In 1966 Halls entered into a sales agreement with Howden, the UK licensee of SRM, and began the search for its own screw compressor. By 1972, a valuation team including IOR past president Dr Guy Hundy had chosen the Zimmern Single Rotor Mechanism, devised and patented by a French inventor, as a compressor with potential for future development.


HallScrew compressor 3 Using a rotor with a 260mm diameter design, engineers began work on a prototype codenamed HS26. Problems with the three-part casing, leakage and gate rotor material were encountered but valuable lessons were learned and in 1977 a much- improved compressor with a single-piece body and other benefits was produced. By 1978 J&E Hall had launched the HallScrew Compressor with capacities from 800-2500m3


/hr.


As research and development continued, liquid refrigerant injection was explored but due to uncertainties associated with non-oil lubricated element bearings and gland seals it was deemed necessary to provide an oil supply. By the end of the 1980s development work with simplified oil management systems had reduced the cost of oil injection below the more complex oil reduced compressors. The machines where phased out in 1990.


McQuay, predominantly air conditioning product


manufacturers, acquired J&E Hall in 1995. McQuay chief executive Joe Hunter – a J&E Hall apprentice in 1953 – instructed engineers to design a new ‘bullet proof’ range of compressors in a project code-named Frame 4. Nicknamed ‘the Mule’ due to its tough, reliable reputation, production began in late 1998 in the Italian and Chinese factories. Establishing


a dedicated research and development centre in 2000 was another milestone move in HallScrew development. The company urgently needed to satisfy industry


demand for a small low-cost compressor and in 2002 work began which paved the way for a single- gate rotor model incorporating a cyclone separator. It had efficiency levels similar to larger compressors but with considerable cost savings. In 2006 Daikin purchased J&E Hall, allowing both companies to pool their vast talent, experience and knowledge. It was decided that all future compressor developments would have dual application targets – air conditioning and refrigeration.


HallsScrew compressor 4 In the past it had been sufficient to produce compressors for the air conditioning market measured by full load efficiency. But it was known that the average chiller functioned at between 50 and 75% capacity. In 2006, compelled by increasing demands for higher part-load efficiency, the team were able to develop an Asymmetric Capacity Control system with slides controlled by independent hydraulic cylinders. Since the beginning of HallScrew development, compression geometries have been constrained by machine tools only capable of producing six- flute main rotors and 11-tooth gate rotors. But recently design engineers using five-axis milling machines have been able to open up a whole new world of exciting possibilities. As the Hallscrew compressor heads for a distinguished half-century of development even more efficient and faster models are in the pipeline. Prototypes have been produced with displacements from 535-1280m3


/hr. They are


capable of running at 120hz, driven by integrated speed drives. High efficiency separators, together with variable volume ratio, mean these machines can operate in an unprecedented range of speeds and conditions. It is a tantalising prospect for Terry Young, and his fellow HallScrew pioneers, as well as all those who have played their part in such an outstanding ongoing success story over the years. “Machines like this could only be dreamed about by those forward-thinking engineers all those years ago. The HallScrew story fits very well with the industry’s heritage of innovation. We are once again at the beginning of an exciting journey with the HallScrew,” he enthused.


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