US3074348A

US3074348A - Centrifugal pumps

Info

Publication number: US3074348A
Application number: US7904A
Authority: US
Inventors: Duncombe Edward; Saughall Great; Pugh Harold
Original assignee: UK Atomic Energy Authority
Current assignee: UK Atomic Energy Authority
Priority date: 1959-02-17
Filing date: 1960-02-10
Publication date: 1963-01-22
Anticipated expiration: 1980-01-22
Also published as: FR1248341A; FR83295E

Description

1963 E. DUNCOMBE ET AL 3,074,343

CENTRIFUGAL PUMPS Filed Feb. 10, 1960 2 Sheets-Sheet 2 WAVAQ NW M IMNTORS EDWARD DU'NCOME HAROLD PUGH iinited dtates 3,074,348 CENTRKFUGAL PUMPS Edward Duncombe, Great Saughall, Chester, and Harold Pugh, Wirral, England, assignors to United Kingdom Atomic Energy Authority, London, England Filed Feb. 10, 1960, Ser. No. 7,904 Claims priority, application Great Britain Feb. 17, 1959 1 Ciaim. (Cl. 10387) This invention relates to apparatus using centrifugal pumps for the sampling of radio-active liquids.

In plants handling radio-active liquids it is generally desirable to provide access points from which samples of the liquids can be taken for routine analysis purposes. These access points may take the form of sampling troughs in the liquid flow stream, but in order that maintenance required at the troughs can be carried out there has to be provision for by-passing the troughs, which involves additional plant itself requiring maintenance. Alternatively, the access points may take the form of sampling troughs removed from the liquid flow stream. There is then the need to deliver the liquid to the sampling troughs from the liquid flow stream using apparatus requiring as little maintenance as possible. It is an object of the invention to provide such apparatus.

The invention, in its application to the sampling of radio-active liquors, resides in apparatus comprising biological shielding having inside the shielding a pipe for radioactive liquors and outside the shielding a pipe for radio-active liquors drawn off from said pipe inside the shielding, a centrifugal pump having its inlet communicating with the pipe inside the shielding and its outlet connected with an outlet pipe coupled to the pipe outside the shielding, the apparatus having the characterising features that, first, the pump is contained within a casing extending from outside said shielding to be integral with the pipe inside the shielding, second the pump is removable from said casing through an aperture accessible from outside said shielding, third, the pump is provided with air lubricated bearings and driven by an air turbine and fourth, the outlet pipe and pipes feeding the bearings and turbine are contained within said casing to pass through the shielding.

By way of example, embodiments of the invention will now be described with reference to the accompanying drawings wherein FIG. 1 is a sectional elevation and FIG. 2 is a partly diagrammatic sectional elevation.

Referring to FIG. 1, a centrifugal pump 40 generally of stainless steel construction comprises a shaft 50 carrying an impeller 51, and is arranged so that the shaft 50 can be supported on an air lubricated thrust bearing 54, centralized on spaced air lubricated journal bearings 52 and 53, and rotated by an air powered turbine rotor 55.

The pump has a casing 56 comprising a circular section tube 57 to which is welded a flanged ring plate 58. An impeller base plate 59 is secured to the plate 58 by screws 60, the

plates

58, 59 forming a housing for the impeller 51. The plate 59 has an impeller inlet port 61 and the plate 58 has an impeller outlet port 62 connected to an outlet pipe 63. The tube 57 has a ring of holes 64 and a ring of vent holes 65.

The casing 56 further comprises a circular section tube 66, the

tubes

57, 66 being connected by a welded connecting ring 67. A bearing sleeve 68 is close-fitting in the ring 67 and has a flanged end 69 secured by screws 70 to a flanged mounting ring 71 welded to the tube 66. The bearing 52 comprises a stepped portion of the sleeve 68, the shaft 50 having a complementary stepped portion 72. The bearing 52 has a ring of orifice jets 73 (one of which is shown) equi-spaced around the stepped portion 72 of the shaft 50. Similarly the bearing 53 comprises 3,074,348 Patented Jan. 22 1963 iee a stepped portion of the sleeve 68, the shaft 50 having a complementary stepped portion 74. The bearing 53 has a ring of orifice jets 75 (one of which is shown) equispaced around the stepped portion 74 of the shaft 50. The bearing 54 comprises a ring of orifice jets 76 (one of which is shown) equi-spaced around the flanged end 69 of the sleeve 68, and the shaft 50 has an integral annular thrust plate 77. The bearing surfaces of the bearings 52, 53, 54, of the

stepped portions

72, 74 and of the thrust plate 77 are of a size and surface finish such as to maintain air lubrication.

The turbine rotor 55 comprises a first rotor plate 78 having a ring of curved blades 79 and a second rotor plate 80 having a ring of similarly curved blades 81, the

plates

78, 80 being secured to the plate 77 by screws 82. A deflector unit 83 located in a sleeve 84 welded to the ring 71 has a ring of curved deflector blades 85, the blades 85 being curved in the opposite direction to the

blades

79, 81. The plate 77 has an annular stepped portion 86 and a curved peripheral face 87, and the sleeve 84 has vent holes 88. A sleeve 89 vertically movable in an axial bore 90 in the shaft 50 houses a spring 91. The lower end of the spring 91 is attached to a pin 92 located by the shaft 50 and the upper end of the spring-91 is attached to a pin 93 each end of which is located in a notch 94 in the sleeve 89. The plate 78 has three equi-spaced pockets 95 (one of which is shown) each housing a ball 96 and having an associated inclined track 97. The sleeve 89 has secured to it three equi-spaced arms 98 (one of which is shown) each held by the force of the spring 91 on one of the balls 96. The sleeve 89 also has secured to it a cap 99.

The upper end of the pump 40 is enclosed by av cover plate 100 secured by screws 101 to a flanged ring 102 welded to the sleeve 84. The

parts

57, 58, 59, 66, 67, 71, 84, 100 and 102 form the casing 56. The cover plate 100 has a recess 103 into which extends a striker 104 of a closure member 105. The member 105 is movable vertically in a bore in the cover plate 100, the bore having a step 106 to position the member 105, and the bore communicates with a similar bore of air inlet pipe 107 welded to the cover plate 100. The pipe 107 and cover plate 100 are arranged to provide an inlet 108 to passageways 109 communicating with an annular space 110 bounded by the cover plate 100. Passageways 111 extend through the cover plate 100 from the annular space 110 to the top of the blades 79 of the rotor plate 78.

The jets 73, 75, 76 have a common annular space 112 bounded by the casing 56 and the sleeve 68, and an inlet pipe 113 communicates with the space 112 via a stub pipe 114 welded to the tube 66. Passageways 115 (one of which is shown) in the sleeve 68 connect annular space 116 between the

stepped portions

72, 74 of the shaft 50 with annular space 117 between the sleeve 68 and the plate 77. Passageways 118 (one of which is shown) through the flanged end 69 of the sleeve 68 extend from the annular space 117 to the region of the vent holes 88 in the sleeve 84.

The pump 40 is supported from a pipe 119, a mounting ring 120 welded to the pipe 119 being secured to to the pipe 123 so as to be integral with it. The impeller inlet port 61 communicates with the pipe 123 and the level of the radioactive liquors in the casing 122 is indicated by line 124. The casing 122 hasa flushing water inlet pipe 125 connected to a ring pipe 126 having holes 127. The casing 122 also has a support base 128 mounted on a floor 129.

FIG. 2 in which like parts to those shown in FIG. 1

are indicated by the same reference numerals, shows apparatus comprising a concrete biological shield 139 with the pipe 123 inside the shield 130 and a pipe 131 outside the shield 130 for radioactive liquors drawn off from the pipe 123. r The pump outlet pipe 63 is coupled to the pipe 131 by a pipe coupling 132. The casing 122 for the pump '40 extends from the inside to the outside of the shielding 13%) through an aperture 133; The shielding 130 has shielding walls 134, 135 supporting a removable top shield plug 136 giving access to space 137 into which the casing 122 extends. The pipe 119 extends upwardly in the casing 122 from the pump 40 and has an upper end flange 13% mounted on an upper end flange 139 on the casing 122, the casing 122 being closed at its uper end by a cover plate 140 secured to the flanges .138, 1 39. The

pipes

63, 107, 113 extend upwardly in the pipe 119 from the pump 40 and are sealed to the cover plate 140 in passage therethrough. The

pipes

107, 113 are coupled to

pipes

141, 142 by

pipe couplings

143, 144 respectively. The

pipes

131, 141, 142 pass through an aperture 145 in the shielding wall 134, the pipe 131 connecting to a sampling trough in the form "of a tank 146. The tank 146 is housed in a shielded space 147 having a removable top shielding plug 148, and has a cover 149 and a support base 156 mounted on the shielding 130. The pipe 141 is connected to a turbine air'main 151 and the pipe 142 is connected to a bearing air main 152, the

mains

151, 152 passing outwardly through the shielding. The cover plate 140 has an exhaust pipe 153 connected to a silencer 154 having an outlet pipe 155 passing out through the shielding. The pipe 123 is connected to a'tank 156 having a cover 157 and support legs 158. mounted on a floor '159. The liquor level in the tank 156 is indicated by dotted line 16%. In one application, the tank 156 contains highly radioactive aqueous raffinate from mixer settler apparatus using tributyl phosphate and water for the separation of uranium and fission product mixtures .obtained from irradiated nuclear reactor fuel elements. The aqueous raflinate flows from the tank 156 through the pipe 123 to be stored, and periodic analysis is carried out of the aqueous ralfinate going to storage. To this end the pump '40 is used to periodically deliver samples of the aqueous raflinate from the casing 122 to the tank 146 from which further samples may be taken by access to the space 147 through the plug 148. The operation of the apparatus is now described with particular reference to the operation of the pump 40.

The pump 40 is operated when required by supplying compressed air first to the jets 73, 75, 76 and then to the rotor 55. The air is fed to the jets 73, 75, 76 via the main .152, the pipe 142, the inlet pipe 113, the pipe 114 and the space 112. The air fed to the jets 76 impinges on the thrust plate 77 to provide support for the shaft 50 and to provide an air lubricating film between the flanged end 69 of the sleeve 68 and the thrust'plate 77. The air fed to the jets 73, .75 impinges-on the stepped

portions

72, 74 respectively, thereby centering and stabilising the shaft 50 and providing an air lubrieating film between the bearings 52, 53 and the stepped

portions

72, 74 respectively.

"The air is fed to the rotor 55 via the main 151, the pipe 141, the inlet pipe 107, the inlet 198, the passage ways 109 and the annular space 110. From the space 110 the air passes through the passageways 111 to impinge on the blades 79 to rotate the shaft 50. The air then passes through the deflector blades 85 to impinge on the blades '81 to provide additional rotational power to the shaft 50. The speed of the pump '40 is determined bythe pressure of the compressed airfeed to the rotor 55, and it is important to supply air to the jets 4 73, 75, 76 before it is supplied to the rotor 55 thereby ensuring air lubrication between the shaft '50 and the bearings 52, 53, 54 during operation of the pump 40.

The air fed to the jets 73 flows both upwardy and downwardly over the stepped portion '72 of the shaft 59. The air flowing downwardly exhausts from the pump 40 via the vent holes 65. The air flowing upwardly enters the space 116. Similarly, the air fed to the jets 75 flows upwardly and downwardly over the stepped portion 74 of the shaft 59. The air flowing upwardly enters the space 117 and exhausts from the pump 40 via the passageways 118 and the vent holes 88. The air flowing downwardly enters the space 116 whence it exhausts from the pump 4%} (together with the upwardly flowing air from the jets 73) via the passageways 115, the space 117, the passageways 118 and the vent holes 88. The air fed to the jets 76 flows inwardly and outwardly over the flanged end 69 of the sleeve 68. The air flowing inwardly exhausts from the pump 41% via the space 117, the passageways 118 and the vent holes 88, and the air flowing outwardly exhausts from the pump 49 via the stepped portion 86 and the vent holes 88. The air fed to the rotor 55 exhausts from the pump 40 via the vent holes 38, the face 87 serving to direct the flowing air leaving the blades 31 towards the vent holes 88.

Should the pipe 123 become emptied during operation of the pump 4th, the speed of rotation of the shaft 50 will increase until the balls 96 are urged radially out wardly by centrifugal force thereby rising up the tracks 97 and lifting the sleeve 89 (by means of the arms 98 and against the force of the spring 91) until the cap 99 hits the striker 1&4 thereby raising the closure mem-- her and thus closing the inlet 1118 and stopping the flow of air to the turbine rotor 55 until the speed of rotation of the shaft 50 falls sufliciently for the force of the spring to return the balls 96 to the pockets 95, when the closure member 105 will fall and open the inlet 103.

The holes 64 ensure that the liquor being pumped covers the impeller 51.

When it is required to remove the pump -48 from the casing 122-, access to the space 137 is achieved by removal of the plug 136. The

pipe couplings

132, 143, 144 are disconnected, and the cover plate 145 is uncoupled. The pump 4% with the

pipes

63, 197, 113, 119 is then readily withdrawable through the aperture 133. The pump 4t) is spray washed before removal by supplying water to theholes 127 'viathe ring-pipe 126 and the inlet pipe 125, and is normally withdrawn into a shielded container.

The greater part of the air fed to the bearings 52, 53, 5dand to the rotor 55 exhausts from the pump 46* from the vent holes =88 above the mounting ring 71. This exhaust air is well removed from the liquor level in the casing 122 and is unimpeded in passage to the exhaust pipe 153.

The use of gas lubricated bearings and air turbine drive is advantageous in that the pump can be operated for long periods with little maintenance.

- The turbine drive arrangement is also advantageous in that it eliminates the problem of avoiding lubricating oil contamination of the liquid being pumped which arises when an electric motor drive is used.

The arrangement of pump and elevated sampling trough is advantageous in that the apparatus is selfdraining through the pump when the pump is stopped.

We claim:

Apparatus comprising biological shielding having a base, upstanding side walls and top covers defining first and second enclosed spaces, a first pipe disposed below said base, a casing extending from said first enclosed space throughsaid base and connected'with said first pipe to form a fluid flowpath through the pipe and easing, a centrifugal pump disposed withinsaid casing below said base, said pump comprising a housing having an inlet port and an outlet port and first and second air inlet ports, a shaft disposed within said housing, an impeller secured to one end of said shaft and a turbine rotor secured to the other end of said shaft, said shaft and housing having adjacently positioned bearing surfaces, a second pipe connected to said first air inlet port for feeding pressurized air between said bearing surfaces to form air lubricated centralizing and support films for said shaft, a third pipe connected to said second air inlet port for feeding pressurized air to rotate said turbine rotor, said second and third pipes being contained within said casing to pass through said base, a fourth pipe connected to said outlet port and contained within said casing to pass through said base into said first enclosed space, a sample tank disposed Within said second enclosed space, and an inlet pipe connected to said tank and connected to said fourth pipe in said first enclosed space.

References Cited in the file of this patent UNITED STATES PATENTS 10 2,149,600 Guinard Mar. 7, 1939 2,864,552 Anderson Dec. 16, 1958 2,915,016 Weaver et a1. Dec. 1, 1959