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94. Improvements in and relating to vacuum vessels
279
Abstracts 88--94
Vacuum Apparatus and Auxiliaries 21.
P u m p s and P u m p Fluids
21 88. Improvements in or Relating to Vapour Operated Vacuum Pumps. United States. One of the disadvantages of vapour operated ~Jumps is that the liquid or pump fluid is usually an organic material which is readily oxidized or otherwise deteriorated when exposed to the atmosphere at the temperature required for operation. F o r this reason precautions must be taken against exposing hot pump fluid to air at pressures substantially higher than the operating pressure of the pump if damage to the pumping fluid is to be avoided. Where rapid pump down cycles are required some operators prefer to use valveless systems and take the precaution of cooling the p u m p fluid from its operating temperature to a safe temperature before exposure to atmosphere. This reduction in pump fluid temperature has been achieved by turning off the boiler heating element and waiting for the pump fluid to cool or by providing cooling coils around the exterior of the pump casing in the vicinity of the boiler. Pump fluid is then cooled by circulating a cooling fluid such as water to the external coil. The advantage of these methods is the time required for re-heating the p u m p fluid to its operating temperature. This patent describes a vapour operated pump in which the fluid is cooled rapidly by internal cooling coils which are arranged to cool only the upper portion of the pool of pump fluid which is the only part exposed to the atmosphere. The advantage of this method is that only a portion of the fluid is cooled so that it may be quickly re-heated for cycling operations. This provides a vapour operated pump with an extremely short heating cycle time. A full description of the apparatus is given. A quench coil is situated internally at the top of the boiler and when water is circulated is capable of cooling the surface of the fluid very rapidly. The normal operating temperature of a typical pump fluid is 200°C and by circulating tap water through a quench coil of the type described the temperature of the pump fluid was lowered from 200°C to 180°C in 20 sec, this temperature be-:ng considered the maximum safe value for the type of fluid. Thus atmospheric pressure may be admitted to the pump within 20 sec after cooling has started but in practice a safety factor is provided by passing cooling water through the quench coil for approximately 80 sec thus cooling the pump fluid to about 155°C. A curve of pressure against time shows how quickly the pump can be restored to operation after the fluid is cooled with the quench coil. Starting with a pressure of about 0.5 T o r t the cooling water is blown out of the quench coil with air and the heating elements are turned on. Within 3½ rain the p u m p is operating and has reduced the pressure to between 1.5 and 1 x 10 -4 Torr. A similar curve shows the length of time required by the same pump without the internal cooling coil and it is shown that this pump requires nearly 9 rain to achieve the same pressure as is possible when the quench coil is used. Thus the invention provides means for achieving a substantial reduction in the cycle time of a vapour operated pump. The position of the quench coil is not critical and rapid quenching of the fluid at the surface has been obtained with the quench coil located from a b o u t ¼ inch above to about ¼ in. below the normal operating level of the pool. Patent Specification by G. T. Gerow and R. J. Weeks, Brit. Pat. Spec. No. 809, 379, Feb. 25th, ]959. 21 89. Improvements in or Relating to Vapour Vacuum Pumps. United Kingdom. In any kind of batch vacuum process it is desirable that the system should be capable of being rapidly brought up to atmospheric pressure and rapidly revacuated. If the vacuum system is being pumped by a vapour vacuum pump it is undesirable that the pump boiler should be exposed
to air at atmospheric pressure whilst the fluid is hot. When the vapour pump is connected directly to the system being pumped it is necessary before bringing the system up to atmospheric pressure to interrupt the heating of the boiler of the pump and allow the boiler to cool before emitting air to the system. The disadvantage of this technique is that the boiler cooling and heating times make rapid vacuum cycles impossible. Thus many vacuum pumping systems have an isolation valve between the vapour pump and the system being pumped, together with a valve controlled by-pass duct from the system to the roughing pump. Such isolation valves may severely restrict the speed of the vapour pump. This patent describes a vacuum vapour pump which can be connected directly to the system to be evacuated and can be operated to produce rapid exhausting cycles from atmospheric pressure without dangerous exposure of the pump fluid to air. This pump is provided with a valve for isolating the boiler of the pump from the main duct supplying vapour to the jets. During the time that the boiler is isolated from the main duct, that is, during the idle period of the pump, a means of condensing the vapour is provided. Thus, the temperature gradients associated with the heat flow into the boiler and the pressure in the boiler respectively are maintained at predetermined controlled values so that upon reconnecting the boiler with the jet system the pump enters immediately into effective operation. The boiler pressure and the temperature gradient from the heater to the boiler shell are the same as the normal operating conditions of the boiler so that at the end of an idle period the pump attains its full pumping capacity instantaneously. It is also possible to permit the boiler pressure and temperature to rise by a predetermined controlled amount during the idle period so that upon restoring communication of the boiler with the main vapour duct the maximum mass throughput and the maximum backing pressure against which the pump will operate are temporarily increased and gradually return to normal as pump down proceeds. Patent Specification by B. D. Power, Brit. Pat. Spec. No. 806788, Dec. 31st, 1958. 21 90. Annular Jet Pump. Werner H. Haak and Frederick Vratny, Rev. Sci. Instrum., 30, 296. 21 91. Rough Pumping with Activated Charcoal R. L. Jepsen, S. L. Mercer and M. J. Callaghan, Rev. Sci. Instrum., 30, 377. 21:11
Molecular Pumping.
See Abstract No. 1.
22.
Gauges 22
92. Small, Lightweight Ionization Gauge Control Circuit. H. B. Benton, Rev. Sci. Instrum., 30, 887. 22 93. Principle of a Semiconductor Manometer in the Pressure Range of 1 mm to 10 -e ram Hg. M. Varieak and B. Saftie, Rev. Sci. Instrum., 30, 891.
23.
Plumbing
23 94. Improvements in and Relating to Vacuum Vessels. United Kingdom. A method of sealing together two parts of a vacuum vessel is described. The parts are metallized in the
280
Abstracts 95--101
vicinity of the sealing surfaces, and when held together a low melting point solder is applied to the seal. A smooth junction is obtained over the sealing surfaces. Brit. Pat., 799,277, 6 Aug. 1958. 23 95. Inflatable Gasket for the 72 in. Bubble Chamber. Luther R. Lucas and H. Paul Hernandez, Rev. Sci. Instrum., 30, 941.
24.
Valves 24
96. Metal Bakeout Valve for Ultrahigh Vacuum. Carsten M. Haaland, Rev. S.ci. lnstrum., 30, 947. 24
97. New Techniques with Attainment of High Vacua. Robert A. Rapp, Rev. ScL Instrum., 30, 839. 24
98. Ultrahigh Vacuum Valve. N o r m a n H. Axelrod, Rev. Sci. Instrum., 30, 944.
99. Large Ultrahigh Vacuum Valve. W. J. Lange, Rev. Sci. Instrum., 30, 602.
27.
24
L e a k Detectors and L e a k Detection
100. This Simple Method Finds Vacuum Leaks. Note by R. W, Naylor, Chem. Eng., 66, 1959, Sept. 1959.
27
27 101. A New Mass Spectrometer Leak Detector for General Use. A small portable mass spectrometer for table mounting adjustable for use with searcher gases of different masses such as H2, He, Ar, CO, 02, C2, H~, Butane, Freon, Town gas etc., may be used for vacuum as well as pressurized systems. The details of construction is described. One part of He in 106 parts of air may be detected. The resolution of the standard equipment is about 15 (defined as A M / M ) where M = mass of a singly charged ion. Hans-Weber Drawien and Kurt Kronenberger, Z. Instrkde, 67, 157-161, 1959.
Abstracts 88--94
Vacuum Apparatus and Auxiliaries 21.
P u m p s and P u m p Fluids
21 88. Improvements in or Relating to Vapour Operated Vacuum Pumps. United States. One of the disadvantages of vapour operated ~Jumps is that the liquid or pump fluid is usually an organic material which is readily oxidized or otherwise deteriorated when exposed to the atmosphere at the temperature required for operation. F o r this reason precautions must be taken against exposing hot pump fluid to air at pressures substantially higher than the operating pressure of the pump if damage to the pumping fluid is to be avoided. Where rapid pump down cycles are required some operators prefer to use valveless systems and take the precaution of cooling the p u m p fluid from its operating temperature to a safe temperature before exposure to atmosphere. This reduction in pump fluid temperature has been achieved by turning off the boiler heating element and waiting for the pump fluid to cool or by providing cooling coils around the exterior of the pump casing in the vicinity of the boiler. Pump fluid is then cooled by circulating a cooling fluid such as water to the external coil. The advantage of these methods is the time required for re-heating the p u m p fluid to its operating temperature. This patent describes a vapour operated pump in which the fluid is cooled rapidly by internal cooling coils which are arranged to cool only the upper portion of the pool of pump fluid which is the only part exposed to the atmosphere. The advantage of this method is that only a portion of the fluid is cooled so that it may be quickly re-heated for cycling operations. This provides a vapour operated pump with an extremely short heating cycle time. A full description of the apparatus is given. A quench coil is situated internally at the top of the boiler and when water is circulated is capable of cooling the surface of the fluid very rapidly. The normal operating temperature of a typical pump fluid is 200°C and by circulating tap water through a quench coil of the type described the temperature of the pump fluid was lowered from 200°C to 180°C in 20 sec, this temperature be-:ng considered the maximum safe value for the type of fluid. Thus atmospheric pressure may be admitted to the pump within 20 sec after cooling has started but in practice a safety factor is provided by passing cooling water through the quench coil for approximately 80 sec thus cooling the pump fluid to about 155°C. A curve of pressure against time shows how quickly the pump can be restored to operation after the fluid is cooled with the quench coil. Starting with a pressure of about 0.5 T o r t the cooling water is blown out of the quench coil with air and the heating elements are turned on. Within 3½ rain the p u m p is operating and has reduced the pressure to between 1.5 and 1 x 10 -4 Torr. A similar curve shows the length of time required by the same pump without the internal cooling coil and it is shown that this pump requires nearly 9 rain to achieve the same pressure as is possible when the quench coil is used. Thus the invention provides means for achieving a substantial reduction in the cycle time of a vapour operated pump. The position of the quench coil is not critical and rapid quenching of the fluid at the surface has been obtained with the quench coil located from a b o u t ¼ inch above to about ¼ in. below the normal operating level of the pool. Patent Specification by G. T. Gerow and R. J. Weeks, Brit. Pat. Spec. No. 809, 379, Feb. 25th, ]959. 21 89. Improvements in or Relating to Vapour Vacuum Pumps. United Kingdom. In any kind of batch vacuum process it is desirable that the system should be capable of being rapidly brought up to atmospheric pressure and rapidly revacuated. If the vacuum system is being pumped by a vapour vacuum pump it is undesirable that the pump boiler should be exposed
to air at atmospheric pressure whilst the fluid is hot. When the vapour pump is connected directly to the system being pumped it is necessary before bringing the system up to atmospheric pressure to interrupt the heating of the boiler of the pump and allow the boiler to cool before emitting air to the system. The disadvantage of this technique is that the boiler cooling and heating times make rapid vacuum cycles impossible. Thus many vacuum pumping systems have an isolation valve between the vapour pump and the system being pumped, together with a valve controlled by-pass duct from the system to the roughing pump. Such isolation valves may severely restrict the speed of the vapour pump. This patent describes a vacuum vapour pump which can be connected directly to the system to be evacuated and can be operated to produce rapid exhausting cycles from atmospheric pressure without dangerous exposure of the pump fluid to air. This pump is provided with a valve for isolating the boiler of the pump from the main duct supplying vapour to the jets. During the time that the boiler is isolated from the main duct, that is, during the idle period of the pump, a means of condensing the vapour is provided. Thus, the temperature gradients associated with the heat flow into the boiler and the pressure in the boiler respectively are maintained at predetermined controlled values so that upon reconnecting the boiler with the jet system the pump enters immediately into effective operation. The boiler pressure and the temperature gradient from the heater to the boiler shell are the same as the normal operating conditions of the boiler so that at the end of an idle period the pump attains its full pumping capacity instantaneously. It is also possible to permit the boiler pressure and temperature to rise by a predetermined controlled amount during the idle period so that upon restoring communication of the boiler with the main vapour duct the maximum mass throughput and the maximum backing pressure against which the pump will operate are temporarily increased and gradually return to normal as pump down proceeds. Patent Specification by B. D. Power, Brit. Pat. Spec. No. 806788, Dec. 31st, 1958. 21 90. Annular Jet Pump. Werner H. Haak and Frederick Vratny, Rev. Sci. Instrum., 30, 296. 21 91. Rough Pumping with Activated Charcoal R. L. Jepsen, S. L. Mercer and M. J. Callaghan, Rev. Sci. Instrum., 30, 377. 21:11
Molecular Pumping.
See Abstract No. 1.
22.
Gauges 22
92. Small, Lightweight Ionization Gauge Control Circuit. H. B. Benton, Rev. Sci. Instrum., 30, 887. 22 93. Principle of a Semiconductor Manometer in the Pressure Range of 1 mm to 10 -e ram Hg. M. Varieak and B. Saftie, Rev. Sci. Instrum., 30, 891.
23.
Plumbing
23 94. Improvements in and Relating to Vacuum Vessels. United Kingdom. A method of sealing together two parts of a vacuum vessel is described. The parts are metallized in the
280
Abstracts 95--101
vicinity of the sealing surfaces, and when held together a low melting point solder is applied to the seal. A smooth junction is obtained over the sealing surfaces. Brit. Pat., 799,277, 6 Aug. 1958. 23 95. Inflatable Gasket for the 72 in. Bubble Chamber. Luther R. Lucas and H. Paul Hernandez, Rev. Sci. Instrum., 30, 941.
24.
Valves 24
96. Metal Bakeout Valve for Ultrahigh Vacuum. Carsten M. Haaland, Rev. S.ci. lnstrum., 30, 947. 24
97. New Techniques with Attainment of High Vacua. Robert A. Rapp, Rev. ScL Instrum., 30, 839. 24
98. Ultrahigh Vacuum Valve. N o r m a n H. Axelrod, Rev. Sci. Instrum., 30, 944.
99. Large Ultrahigh Vacuum Valve. W. J. Lange, Rev. Sci. Instrum., 30, 602.
27.
24
L e a k Detectors and L e a k Detection
100. This Simple Method Finds Vacuum Leaks. Note by R. W, Naylor, Chem. Eng., 66, 1959, Sept. 1959.
27
27 101. A New Mass Spectrometer Leak Detector for General Use. A small portable mass spectrometer for table mounting adjustable for use with searcher gases of different masses such as H2, He, Ar, CO, 02, C2, H~, Butane, Freon, Town gas etc., may be used for vacuum as well as pressurized systems. The details of construction is described. One part of He in 106 parts of air may be detected. The resolution of the standard equipment is about 15 (defined as A M / M ) where M = mass of a singly charged ion. Hans-Weber Drawien and Kurt Kronenberger, Z. Instrkde, 67, 157-161, 1959.