GB960736A - Improvements in or relating to centrifugal pumps - Google Patents

Abstract

960,736. Centrifugal separators. ABRASIVE DEVELOPMENTS Ltd. Feb. 25, 1963 [March 8, 1962], No. 8923/62. Heading B2P. [Also in Divisions F1 and F2] In a centrifugal pump, for a mixture of solids and a liquid, having a vertical impeller shaft 9 extending through an upper housing 26, having an upper annular closing wall 22, and through sealing means in the upper part of the housing 26, the sealing means comprising a sleeve 23 concentric with and providing an annular space 25 about the shaft 9, and provision for liquid from the back of the impeller 12 to enter the annular space 25 and form a seal therein, the sleeve 23 extends downwardly from the upper annular closing wall 22, the entry to annular space 25 is provided by the lower end of the sleeve 23, there is provided means for setting up whirling motion about the axis of the sleeve 23 and shaft 9 at least in the region of the entry to the annular space 25, and there is further provided an outlet 31 from the upper housing above the level of the entry to the annular space 25. The pump handles a mixture of water and abrasive solids. Some of the mixture whirling at high angular velocity in volute casing 1 passes through an annular opening 14 into the housing 26 where the solids are thrown outwards to leave substantially clear water in the central region. The substantially clear water passes from this region through the space 25 to an open chamber 27 preferably containing an impeller 24 which assists the movement of the water up the sleeve 23 and its escape through an outlet 29, connected to a pipe 30. Some of the mixture in the housing 26 is discharged through the outlet 31 which may lead back to the supply and some is recirculated within the housing and passed back into the volute casing 1 through the opening 14. Whirling motion may be imparted to the mixture by subsidiary blades 16 provided on the impeller 12 or adjacent the impeller on the shaft 9, or by stationary deflectors (not shown) on the lower end of the sleeve 23. The housing 26 and the volute casing 1 are lined with rubber to prevent erosion of their walls. In order to maintain the liquid seal when the pump is stationary the level W of mixture in the supply is preferably above the lower end of, and is normally above the upper end of, sleeve 23. The water passing through the pipe 30 may discharge to an automatic device which may be a valve for maintaining the water level at the required height in a vessel in the pumping system. Since the swirling action is less violent at the top of the housing 26 the abrasive particles are less concentrated in the radially outer region and the larger particles tend to be concentrated in the radially outermost zone. Thus, to some extent, the finer particles may be removed by a separate outlet disposed in an intermediate radial position and then passed to waste or to a separating means from which clear water is led back to the pumping system. The outlet 31 may be adjustable radially to any position intermediate the wall of the housing 26 and the sleeve 23. The pump may be used in the process of blasting metal and other surfaces with glass or other abrasive particles in water. According to the Provisional Specification the abrasive mixture passing through the outlet 31 is delivered back to the supply conveniently through a “, inch nozzle to prevent congestion. Also, pumps may be connected in series or parallel. Specification 840,671 is referred to.