St Marys Cray Turbo Expander – Southern Gas Networks (SGN)

Technica have been selected to provide Process, HV Electrical, LV Electrical, Control & Instrumentation and Software Configuration design services for the St Marys Cray Turbo Expander Project.

The natural gas pressure reduction station, owned and operated by Southern Gas Networks at St Marys Cray, near Orpington, Kent is to be modified to generate electrical power to supply the local electrical distribution network. The modified installation will take high pressure gas from the Southern Gas Network Transmission System and reduce the pressure through a turbo expander coupled to an 11 kV generator. Prior to expansion the gas will be pre-heated to 70oC using low pressure water as the process heating fluid. The heated process water will be provided by a natural gas fuelled combined heat and power (CHP) set supplemented, as the heating demand requires, by low pressure hot water boilers. The CHP sets will also generate electrical power to supply the local electrical distribution network and provide high temperature water and low temperature water for process gas heating. To provided separation and the avoidance of contamination of the CHP sets and process water systems, heat will be recovered from the CHP and Boilers via intermediate heat exchanges.

All the new equipment will be housed within a purpose built acoustic building. A new Control Room and LV and HV Switch rooms will be also built to house the new control equipment.