Process fluid recycle system for a compressor assembly

A process fluid recycle system for a compressor assembly having at least a compressor driven from a gear case to recycle process fluid vapor flowing through a shaft seal, from the compressor to the gear case, said process fluid recycle system including:

• at least one coalescing filter to separate oil mist made up of said gear oil from the process fluid vapor;
• a recycle conduit, at one end, connected to a low pressure inlet of said compressor assembly and, at the other end, in flow communication with said at least one coalescing filter to return said process fluid vapor to said compressor assembly;
• two alternate flow paths to conduct said oil mist and said process fluid vapor from said compressor assembly to said at least one coalescing filter, one of the two alternate flow paths formed by an anti-back flow compressor in flow communication with said gear case such that operation of said anti-back flow compressor reduces pressure within said gear case below said compressor and a conduit also in flow communication with said gear case and having a valve to prevent flow of said oil mist and said process fluid to said gear case during operation of said anti-back flow compressor;
• and
• a controller to activate said anti-back flow compressor to ensure pressure within the gear case is less than that of the compressor, thereby to prevent gear oil from being driven from the gear case into the compressor through the shaft seal.