Patent GB-776631-A (GB)
Title: Centrifugal pump
IPC: F04D29/22
Filed: 1955-06-21
Abstract: 776,631. Centrifugal pumps; stuffing-box substitutes. LA BOUR, H. E. June 21, 1955 [March 1, 1955], No. 17969/55. Classes 110 (1) and 122 (5). A centrifugal pump comprises a kinetic liquid seal between the impeller shaft and the casing, a gas pressure retaining chamber surrounding the shaft above the liquid seal and communicating with the latter, and a rubbing seal between the chamber and the shaft. In the pump shown, the impeller blades 23 are carried by a sealing drum 28 which also carries sealing blades 39, 40, between which are interposed a stationary disc 38 integral with a sleeve 37 surrounding the impeller shaft 8. The impeller receives liquid by way of a strainer 64 and an inlet chamber 20 and discharges it by way of a discharge chamber 24 to an outlet F. The sleeve 37 is secured to the upper wall of chamber 20 in a gas-tight manner by means of a nut 43 and packing 45. A sealing gland 48 surrounding the impeller shaft at the top of a gas pressure retaining chamber 26 comprises a carbon ring 49 backed by fibrous packing and a number of coil springs 50 and bearing against a stationary plate 52. The gland 48 is secured to the impeller shaft by a screw 59 and sealed to it by an elastic ring 77. Any fluid passing the gland 48 is vented to atmosphere through a passage 58. Liquid in the bottom of chamber 26 can drain through the sleeve 37 by way of openings 46. If the inlet E is connected to a downwardly extending suction pipe and the outlet F is connected to a standpipe discharge pipe, with an initial charge of liquid standing in the chambers 20, 24 and the sleeve 37, the impeller blades 23 withdraw liquid from the chamber 20 and discharge it through throats 35 and discharge passageways 36 to the chamber 24. When the liquid is exhausted, air flows into the blades 23, and the resultant fall in generated pressure allows liquid to return through one or more of the throats 35. The returning liquid entrains some of the air and is again discharged by the blades 35. This recirculation eventually removes the air from the suction pipe, and normal operation proceeds. The sealing blades 39 withdraw liquid from the sleeve 37 and substantially empty themselves through the blades 40, which are of lesser radial extent than the blades 39. Liquid remains in the blades 40 to oppose the entry of air or other gas from the chamber 26. When the pump is shut down, a non-return valve 66 closes, leaving open a restricted passage 67 through which occurs a retarded backflow from the discharge pipe to the pump. Since the liquid is free to drain from the pump to the suction pipe, it does not tend to rise in the sleeve 37 higher than the level of the bottom of inlet passageway 21. If, however, there is a positive head at inlet of up to 10 feet, the liquid will be forced upward through the sleeve 37 into the chamber 26 when the pump is not running, compressing the gas trapped in the chamber 26 and thus achieving a level which is below the sealing gland 48. Where the discharge pipe holds a static head greater than 10 feet, the discharge pipe is provided with an automatic valve which closes when the electric driving motor 1 is switched off. When the pump is running, the liquid in the sleeve 37 is withdrawn, as before, by the sealing blades 39, but the positive inlet head may hold some liquid on the outer ends of the blades 39. Where the inlet head is greater than 10 feet, gas may be supplied through a connection 63 to increase the pressure in chamber 26, and automatic shut-off valves may be provided at both the inlet and outlet pipes. The pump can be flushed out, preferably while running, by admitting steam or gas under pressure through the connection 63. The impeller shaft is supported at its upper end only, in bearings 6, 7, and has a reduced portion 33 which extends loosely into a recess in the bottom wall of the pump casing to steady the lower end of the shaft during transportation. Specifications 559,086 and 588,939 are referred to.