PURPOSE: To dissipate the turbo-expander energy without contaminating a turbo- expander.

CONSTITUTION: A non-contaminating energy dissipator 10 has a closed loop conduit 11 that is connected to a compressor 12, a pressure reduction valve 13 and a heat exchanger 14. A brake gas circulates in the closed loop conduit 11 from the compressor 14 to the pressure reduction valve 13, then to the heat exchanger 14 and finally back to the compressor 12, where the process repeats. The use of an inert brake gas prevents interactions between the brake gas and a hazardous process fluid from forming an explosive mixture. The closed loop conduit 11 has an outlet 19 so that the brake gas can be used for purposes other than circulating through the closed loop. A make-up conduit 18 and another control valve 17 can be added to the non-contaminating energy dissipator 10 so that brake gas that is lost through seals or other parts of the system can be readily replaced.