Abstract: The invention provides an apparatus comprising a storage tank, a liquid piston compressor and a gas-fed device. The storage tank is configured to store liquefied gas therein. The liquid piston compressor is disposed downstream of, and in fluid communication with, the storage tank and is configured to receive boil-off gas from the storage tank and to compress the gas. The gas-fed device is disposed downstream of, and in fluid communication with, the liquid piston compressor, and is configured to receive compressed gas from the liquid piston compressor.

Abstract: The invention provides an apparatus for compressing a first fluid. The apparatus comprises a compressor piston comprising a piston cylinder and a piston assembly slidably mounted therein. The piston assembly comprises first and second spaced apart piston members defining a space therebetween. The space is configured to contain a second fluid used to cause compression of the first fluid. The piston assembly further comprises means for feeding second fluid to the space between the first and second piston members.

Abstract: The invention provides an apparatus comprising a storage tank, a liquid piston compressor and a gas-fed device. The storage tank is configured to store liquefied gas therein. The liquid piston compressor is disposed downstream of, and in fluid communication with, the storage tank and is configured to receive boil-off gas from the storage tank and to compress the gas. The gas-fed device is disposed downstream of, and in fluid communication with, the liquid piston compressor, and is configured to receive compressed gas from the liquid piston compressor.

Abstract: A system for obtaining helium that avoids boil off losses from the system. A combination of heat exchangers and a compressor are used to deliver helium at a temperature of 30° K and a pressure between 300 bar and 700 bar without significant boil off losses.