Dual helium compressors

A method to conserve energy in maintaining an interior of a building at a temperature in a range of 15 to 30° C. and providing redundancy in a Gifford McMahon (GM) refrigerator system that is operating at cryogenic temperatures by using a compressor system supplying gas to an expander, said compressor system comprising:

• an air cooled compressor having a first supply side and a first return side, wherein the air cooled compressor contains oil and further includes a pressure equalization valve that equalizes pressures within the air cooled compressor to prevent migration of the oil to the expander, and the pressure equalization valve opens to avoid having high pressure gas in the air cooled compressor blow the oil in the air cooled compressor back through the first return side when the air cooled compressor turns off,
• a water cooled compressor having a second supply side and a second return side, wherein the water cooled compressor contains oil and further includes a pressure equalization valve that equalizes pressures within the water cooled compressor to prevent migration of the oil to the expander, and the pressure equalization valve opens to avoid having high pressure gas in the water cooled compressor blow the oil in the water cooled compressor back through the second return side when the water cooled compressor turns off, and wherein the oil contained in the water cooled compressor is kept separate from the oil contained in the air cooled compressor,
• a gas supply manifold connected to the respective supply side of each compressor and a high pressure side of the expander,
• a gas return manifold connected to the respective return side of each compressor and a low pressure side of the expander, wherein the gas return manifold is configured to prevent gas from flowing from the air cooled and water cooled compressors toward the gas return manifold,
• a plurality of check valves formed on the gas return manifold to prevent the gas from flowing from either compressor into the gas return manifold, and a plurality of sensors to detect critical operating parameters connected to a controller, the controller operating the expander at rated capacity with either one of the compressors on and the other off and during the period when one compressor is being turned on and other compressor is being turned off, the method comprising:
• locating both of the air cooled and water cooled compressors inside the building for operation of the GM refrigerator system;
• comparing temperature outside the building and temperature inside the building;
• and
• operating one of the air cooled and water cooled compressors, to operate the GM refrigerator system, based on the comparison between the temperature outside the building and the temperature inside the building, comprising:
• operating the water cooled compressor and operating the GM refrigerator system with the water cooled compressor, when the temperature outside the building is greater than the temperature inside the building;
• operating the air cooled compressor and operating the GM refrigerator system with the air cooled compressor, when the temperature outside the building is less than the temperature inside the building;
• and
• switching to the nonoperating compressor in response to a failure of the operating compressor.