High voltage machine mainwall insulation material behavior when exposed to raw natural gas

Natural gas recovery from subsea fields is increased by use of artificial lift, utilizing subsea compression technology to boost the gas flow. Such machines consist of a high-speed, high voltage electrical motor integrated into the same casing as the compressor and where the motor is cooled by the process gas injected from the compressor itself. Since the insulation system is in direct contact with the process gas it has to possess excellent chemical resistance and mechanical strength to withstand rapid decompression. Various types of mica-based mainwall insulations were exposed to an environment consisting of hydrocarbon gas, condensate and a mixture of water and monoethylene glycol (MEG) at 150 bar and 130°C. Physical and mechanical parameters of the samples were evaluated. The process gas ageing tests revealed that the mechanical strength of the mainwall insulation is mainly dependent on the selected resin and the degree of resin saturation inside the insulation.