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Refrigeration system designed for remote cold trap
Vacuum news
Helium liquefier A recently developed Philips helium liquefier is now marketed and serviced in Britain by the MEL Equipment Co Ltd. This is the first commercially available helium liquefier which employs Stirling cycle cooling machines and consequently operates reliably without supervision. The high thermodynamic efficiency of Stirling cycle refrigerators combined with a novel expansion ejector stage, eliminate the need for liquid nitrogen or hydrogen precoolants. Also, since the cooling and expansion circuits are free from mechanically acting parts, routine maintenance is well within the capacity of a laboratory technician. The liquefaction cryostat is vacuum insulated and contains the heat exchangers, gas purification units and expansion ejector stage. Twin, independent liquid helium transfer lines allow simultaneous filling of two storage containers. By means of a non-contaminating compressor and heat exchangers, of novel design, high impurity levels may be tolerated. Integrated purification units ensure tr0uble-free running for the best part of a week, while regeneration of the main units may be carried out without interruption of operation. Continuous runs of 100 hours or more are possible with inlet helium contamination levels of up to 5 per cent. Automatic control is provided allowing the system to be left running overnight. The output of liquid helium is 8 to 9 litres/hour which is considered ample for most laboratory requirements. Floor area, excluding storage containers is typically 6½× 10 ft and headroom 6½ ft. Power consumption is 11 k W for each of the two cooling machines and 6 kW for the compressor. M E L Equipment Company Ltd, UK Circle number 54 on Reader Enquiry Service card Cryogenic and vacuum components Now available in the United Kingdom for the first time is the range of seal off valves and vacuum accessories manufactured by Cryolab, Los Osos, California. The seal off valve, available in a variety of sizes and types combines the function of a relief valve and a vacuum shutoff valve in one component. They are widely used in cryogenic tankage, vacuum insulated piping and laboratory cryogenic dewars. The design prevents tampering and accidental loss of vacuum, yet provides a full bore opening for re-evacuation and is compatible with 10 -9 torr. Other components offered include vacuum flanges, inspection windows and relief discs, and also three sizes of vacuum jacketed cryogenic valves. Illustrated literature is available from the United Kingdom distributor, Robert Cupitt Limited, Aylesbury. Robert Cupitt Limited, UK Circle number 55 on Reader Enquiry Service card Refrigeration system designed for remote cold trap Ultra low temperatures are provided by Model PP-180 refrigeration system engineered by Cincinnati Sub-Zero Pro-
Philips helium liquefier ducts. The requirement was to provide temperatures as low as --185°F to a remote cold trap. The chamber in the cold trap is about three litres in volume, and must be maintained at a low temperature continuously. Three refrigeration systems operating in a cascade relationship, utilizing Freon refrigerants are required to supply the low temperature to the cold trap, located in an adjoining room. Inlet and outlet connections are provided. Thermal capacity at --120°F is about 2000 Btu/hr. The remote evaporator situated about 12 feet away contains baffles to which 100 ft of three-eighths inch od copper coil is fitted. Cincinnati Sub-Zero Products, USA Circle number 56 on Reader Enquiry Service card
Full-spectrum electromagnetic shielding A new combination high permeability, high conductivity electromagnetic shielding which provides full-spectrum shielding from 1Hz to 10 Gigahertz has been developed by Magnetic Metals Company. Designated as Shieldmu 30CU, the new full-spectrum shielding material consists of a 0.0014-inch layer of high frequency shielding cemented firmly to a 0.004-inch layer of low frequency shielding. The low frequency layer is fully annealed to assure permeability as high as
150,090. Available in sheet or tape form, the new Shieldmu 30CU is easy to use. Magnetic shielding can be formed simply by placing a piece of Shieldmu 30CU over the component and pressing it in place. The new material can be cut easily with ordinary scissors and offers a fast, economical method for determining the proper shielding required for sensitive components. The material is recommended for full-spectrum prototype, experimental, or production shielding of transformers, transistors, filters, tubes, relays, meters, recording heads, tachometers, motors, magnetrons, magnetic tape reels, microphones, or any sensitive component which must be protected from stray magnetic fields. It is also suitable for shielding of current-carrying conductors to prevent their fields from affecting surrounding equipment. Standard tape widths available include 1 inch, 2 inch, 4 inch, and 12 inch. Other widths are available on special order. Overall thickness of the standard shielding material is approximately 0.0074-inch including the interlayer adhesive (0.002inch). Other material thicknesses and combinations of materials can be supplied. Typical specifications of the electrical grade, thermosetting adhesive are as follows: adhesive strength of 40 oz/inch at a 90 ° pulling angle; rated for continuous use up to 130°C; non-conductive with an 285
Helium liquefier A recently developed Philips helium liquefier is now marketed and serviced in Britain by the MEL Equipment Co Ltd. This is the first commercially available helium liquefier which employs Stirling cycle cooling machines and consequently operates reliably without supervision. The high thermodynamic efficiency of Stirling cycle refrigerators combined with a novel expansion ejector stage, eliminate the need for liquid nitrogen or hydrogen precoolants. Also, since the cooling and expansion circuits are free from mechanically acting parts, routine maintenance is well within the capacity of a laboratory technician. The liquefaction cryostat is vacuum insulated and contains the heat exchangers, gas purification units and expansion ejector stage. Twin, independent liquid helium transfer lines allow simultaneous filling of two storage containers. By means of a non-contaminating compressor and heat exchangers, of novel design, high impurity levels may be tolerated. Integrated purification units ensure tr0uble-free running for the best part of a week, while regeneration of the main units may be carried out without interruption of operation. Continuous runs of 100 hours or more are possible with inlet helium contamination levels of up to 5 per cent. Automatic control is provided allowing the system to be left running overnight. The output of liquid helium is 8 to 9 litres/hour which is considered ample for most laboratory requirements. Floor area, excluding storage containers is typically 6½× 10 ft and headroom 6½ ft. Power consumption is 11 k W for each of the two cooling machines and 6 kW for the compressor. M E L Equipment Company Ltd, UK Circle number 54 on Reader Enquiry Service card Cryogenic and vacuum components Now available in the United Kingdom for the first time is the range of seal off valves and vacuum accessories manufactured by Cryolab, Los Osos, California. The seal off valve, available in a variety of sizes and types combines the function of a relief valve and a vacuum shutoff valve in one component. They are widely used in cryogenic tankage, vacuum insulated piping and laboratory cryogenic dewars. The design prevents tampering and accidental loss of vacuum, yet provides a full bore opening for re-evacuation and is compatible with 10 -9 torr. Other components offered include vacuum flanges, inspection windows and relief discs, and also three sizes of vacuum jacketed cryogenic valves. Illustrated literature is available from the United Kingdom distributor, Robert Cupitt Limited, Aylesbury. Robert Cupitt Limited, UK Circle number 55 on Reader Enquiry Service card Refrigeration system designed for remote cold trap Ultra low temperatures are provided by Model PP-180 refrigeration system engineered by Cincinnati Sub-Zero Pro-
Philips helium liquefier ducts. The requirement was to provide temperatures as low as --185°F to a remote cold trap. The chamber in the cold trap is about three litres in volume, and must be maintained at a low temperature continuously. Three refrigeration systems operating in a cascade relationship, utilizing Freon refrigerants are required to supply the low temperature to the cold trap, located in an adjoining room. Inlet and outlet connections are provided. Thermal capacity at --120°F is about 2000 Btu/hr. The remote evaporator situated about 12 feet away contains baffles to which 100 ft of three-eighths inch od copper coil is fitted. Cincinnati Sub-Zero Products, USA Circle number 56 on Reader Enquiry Service card
Full-spectrum electromagnetic shielding A new combination high permeability, high conductivity electromagnetic shielding which provides full-spectrum shielding from 1Hz to 10 Gigahertz has been developed by Magnetic Metals Company. Designated as Shieldmu 30CU, the new full-spectrum shielding material consists of a 0.0014-inch layer of high frequency shielding cemented firmly to a 0.004-inch layer of low frequency shielding. The low frequency layer is fully annealed to assure permeability as high as
150,090. Available in sheet or tape form, the new Shieldmu 30CU is easy to use. Magnetic shielding can be formed simply by placing a piece of Shieldmu 30CU over the component and pressing it in place. The new material can be cut easily with ordinary scissors and offers a fast, economical method for determining the proper shielding required for sensitive components. The material is recommended for full-spectrum prototype, experimental, or production shielding of transformers, transistors, filters, tubes, relays, meters, recording heads, tachometers, motors, magnetrons, magnetic tape reels, microphones, or any sensitive component which must be protected from stray magnetic fields. It is also suitable for shielding of current-carrying conductors to prevent their fields from affecting surrounding equipment. Standard tape widths available include 1 inch, 2 inch, 4 inch, and 12 inch. Other widths are available on special order. Overall thickness of the standard shielding material is approximately 0.0074-inch including the interlayer adhesive (0.002inch). Other material thicknesses and combinations of materials can be supplied. Typical specifications of the electrical grade, thermosetting adhesive are as follows: adhesive strength of 40 oz/inch at a 90 ° pulling angle; rated for continuous use up to 130°C; non-conductive with an 285