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Article by Chris Beck originally appeared in Works Managment
Heliex Power, which is based in East Kilbride near Glasgow, has revolutionised the way factories and industrial sites generate power with their screw expander technology. This technology enables the recovery of energy from waste heat and low-pressure steam found in numerous applications across a range of industries.
What sets Heliex technology apart from other steam-based power generators is that it can operate with standard industrial ‘wet steam’ – steam that contains water droplets that would destroy traditional machines and generators. Heliex Power can generate power, re-energise low pressure steam and drive machinery and air compressors by utilising a factory or building’s existing steam supply.
The Heliex System converts expansion energy from steam into clean electricity via a wet steam cycle – the thermodynamic cycle of a heat engine that converts heat into mechanical work. The system works at 4,500rpm, driving a 3,000rpm asynchronous generator via a toothed belt transmission. More than 50 machines have been built and have achieved over 120,000 operating hours.
Bearings play a critical role in the performance of the screw expander machines. The bearings must withstand harsh operating conditions including high temperatures up to 200°C.
“In our Heliex Systems, the function of the bearings is to ensure that the components inside do not clash,” said Nick Alexander, engineering manager at Heliex Power. “In particular, very accurate location is required of the two rotors relative to each other. No oil is present in our machines, although the bearings themselves are oil-lubricated; water vapour is the only lubricant, and so keeping the rotors accurately located is essential. The tolerance between the rotors and the housing is also extremely tight. Movement and back-pressure are critical and so the bearings supplied by Schaeffler are preloaded accordingly. The bearings are also heat stabilised [heat treated] to ensure they can withstand the large temperature ranges that our machines operate in.”
“Schaeffler UK has been working closely with Heliex Power since the company was spun out from City University in 2010,” added Mike Addington, regional sales engineer (Scotland) for Schaeffler UK. “Initially, we were heavily involved in the engineering design work relating to the optimisation of the bearing arrangements for the steam screw expander system. We are now supplying bearings on a regular basis to Heliex for its current range of machines, as well as looking at custom bearings for ongoing machine development programmes at Heliex.”