Abstract: A detachable work extraction system includes an expansion engine including a self-sealing coupling adapted to detachably connect the expansion engine to a cold box, and a hydraulic work extractor operatively connected to the expansion engine. A gas can travel from the cold box to the expansion engine through the self-sealing coupling. The gas is cooled by expansion of the gas in the expansion engine and work produced by the expansion of the gas is dissipated by the hydraulic work extractor. The expansion engine includes a cylinder housing a piston. The cylinder has a first self-sealing coupling defining an inlet and a second self-sealing coupling defining an outlet. The first and second self-sealing couplings each have a spring loaded seal. In the absence of an external force applied to the seal, the seal prevents flow of gas through the couplings.