GB1016859A - Self-priming axial-flow pumps - Google Patents

Abstract

1,016,859. Axial-flow pumps. CASCADE CORPORATION. July 9, 1964, No. 28352/64. Heading F1C. A self-priming axial-flow pump comprises a casing housing the impeller and formed so that a body of the liquid to be pumped is at all times available to the impeller as a priming liquid, and a stationary diverter contained within the casing in a discharge passage and formed so as to interrupt impeller-induced centrifugal motion of a fluid composed of the priming liquid mixed with air drawn by the impeller from the suction side of the pump and to lead the fluid to a zone relatively free of impeller-induced turbulence occupying a level no lower than the discharge end of the impeller and from which the contained air is free to escape by ascension. In the pump shown in Fig. 1, liquid is drawn through a suction pipe 16 into a chamber 14 and thence through a non-return valve 15 and a filter 17 to the pump casing 11, where it is acted on by stationary guides 23 and impeller blades 20. During priming, air from the suction side of the pump becomes mixed with the liquid. Transverse baffle plates 30, 35 at the pump outlet suppress the whirl component of the velocity of the mixture and therefore prevent centrifugal separation of the air from the liquid whereby separation does not occur until the mixture reaches a relatively calm zone containing liquid which is relatively free from air. The air then separates out under gravity and escapes through the pump discharge. As shown for the baffle 35, the baffles 30 and 35 may be perforated or slotted in whole or in part. In a modification, Fig. 9, the liquid discharge pipe 32<SP>1</SP> extends from the bottom of the pump casing, with a U-bend to provide a trap in which air-free liquid collects during priming. The air separating out above the baffle plates 30<SP>1</SP>, 35<SP>1</SP> escapes through a check valve 51 a which may be arranged to close in response to the rise of discharge pressure which occurs as priming is completed. Alternatively, it may be closed by a float or by a control handle 52. Figs 10 and 11 show a pump having a volute casing 60 at the discharge side. The mixture is guided upwardly between baffle ribs 70 and 72 and, after reaching a chamber 67, a major part of it returns downwardly along a passage 74. The large crosssectional area of the passage 74 slows down the mixture to allow the entrained air to escape. Guide vanes 63 are held in place by a tapered spring-pressed ring 65 which bears upon tapered plates 64 which each carry a vane 63. The pump shift may be vertical instead of horizontal.