Alstom Power at Rugby operates an environmental chamber used for scale testing of low-pressure turbine designs. It utilised sulphur hexafluoride as the working fluid, an extremely potent global warming gas with usage now restricted under the F-Gas Regulations.
STS was commissioned to investigate a suitable "heavy gas" substitute, redesign the gas management system accordingly and provide budget costs for the conversion.
Our research indicated that, of a range of potential options, R134a provided the best technical solution with the required level of safety.
As part of the exercise we approached the revalidation of existing components with a view to minimising the project costs and reducing the chamber fill and extraction times to maximise testing productivity. There was a further requirement to modify the gas management system to accommodate higher pressure ratios for high pressure turbine testing, and this was achieved simply by rearranging the compressor staging.
Relative changes in the working fluid density meant the specification of new receivers for increased storage volume, as well as finding the best solution for gas generation, which was achieved using waste heat, providing a significantly reduced lifecycle cost for the plant. There was also previously a problem with desiccant drying of the extracted gas, and STS recommended a minor hardware modification to the existing filter that significantly reduced bypass flow, thereby increasing the drier effectiveness. Finally, to deliver user-friendly control of the complete system, STS supplied a revised control philosophy that provided "one-touch" operation.
The project was subsequently completed at a cost within the STS budget estimates, and in operation the plant met all of our design intents and the customer's expectations.