Abstract: A pulse tube refrigerator comprises a fixed pressure casing (3) containing cold parts and a removable pressure casing (2) containing serviceable parts. The fixed pressure casing (3) and the removable pressure casing (2) are coupled together via a joining member (1). During cooling operation the joining member (1) is arranged such that refrigerant fluid flows between the fixed and the removable casings. During servicing the joining member is arranged to cut off flow of refrigerant fluid between the fixed and removable casings, such that refrigerant in the fixed casing is trapped and parts in the removable casing are accessible for servicing. After servicing, substantially pure refrigerant fluid is pumped into the removable casing (2), the fixed and removable casings are re-joined and the joining member (1) is arranged such that refrigerant fluid flows between the casings again.

Abstract: A multiple port rotary valve for flow switching comprises a rotor (2), a stator (7), a compressor supply (8) and a compressor return (6). Gas is supplied via the compressor supply throughout a switching cycle such that the rotor is lifted away from the stator (7). The valve further comprises a balance ram to counteract the effect of the differential pressure produced by the compressor supply, such that a gas seal is formed at the rotor/stator interface.

Abstract: A pulse tube refrigerator comprises a fixed pressure casing (3) containing cold parts and a removable pressure casing (2) containing serviceable parts. The fixed pressure casing (3) and the removable pressure casing (2) are coupled together via a joining member (1). During cooling operation the joining member (1) is arranged such that refrigerant fluid flows between the fixed and the removable casings. During servicing the joining member is arranged to cut off flow of refrigerant fluid between the fixed and removable casings, such that refrigerant in the fixed casing is trapped and parts in the removable casing are accessible for servicing. After servicing, substantially pure refrigerant fluid is pumped into the removable casing (2), the fixed and removable casings are re-joined and the joining member (1) is arranged such that refrigerant fluid flows between the casings again.

Abstract: A multiple port rotary valve for flow switching comprises a rotor (2), a stator (7), a compressor supply (8) and a compressor return (6). Gas is supplied via the compressor supply throughout a switching cycle such that the rotor is lifted away from the stator (7). The valve further comprises a balance ram to counteract the effect of the differential pressure produced by the compressor supply, such that a gas seal is formed at the rotor/stator interface.