GB956731A - Improvements in or relating to multiple stage centrifugal pumps, compressors or the like - Google Patents

Abstract

956,731. Centrifugal pumps and compressors. DE LAVAL STEAM TURBINE CO. April 17, 1962 [Aug. 11, 1961], No. 14918/62. Heading F1C. In a multistage centrifugal pump, compressor, or the like comprising a housing containing a casing formed by a number of annular sections assembled in stacked relationship, successive stage impeller means rotating within the casing and means for bleeding fluid from an intermediate stage of the pump, compressor, or the like, the bleed means comprises at least one axially directed passage in the casing formed by intercommunicating passages in adjoining sections thereof, one of the annular sections having a radially directed passage therein connecting the first-mentioned passage with the interior of the casing, and a passage in the housing communicating with the first-mentioned passage and leading to the outside of the housing. In the centrifugal pump shown, an outer steel casing 2 contains an inner casing formed by joining concentric annular interstage portions, such as 12 and 14, and an end portion 10 by tie rods 15 (see Specification 956,732) which are anchored at their ends by shoulders engaging a flange 17 and are installed in a heated condition. The liquid is supplied through inlet 16, volute 18 and guide vanes 19 to the first stage impeller 6, from where it flows through diffuser 20 to the remaining stages. Some of the liquid leaves the second stage through a group of six by-pass ports 32, arranged approximately opposite the cross-over passage of the second-stage diffuser 24, and thence passes through six passages 30 in portion 12, six aligned passages 36 in portion 10 and three passages 46 in the outer casing 2. Circumferential channels 34, 38, 40, 44 interconnect the passages. The passages 46 discharge into a chamber 48 which is connected through welded connection 50 to auxiliary equipment or the like. The channel 44 and holes 47, aligned with the passages 46, are provided in an annular stainless steel insert 42 welded to the casing 2. Portion 10 is pulled against the insert 42 by bolts (not shown) anchored in the casing 2. Two connections 50 spaced approximately 180 degrees apart, each associated with a separate cross-over passage in the same diffuser, may be provided to feed separate units, or they may be connected 'externally to combine their output. A number of separate connections may be provided which are circumferentially spaced and each associated with a different stage of the pump, thereby providing a selection of pressures. The interstage portions 12, 14 are machined from duplicated stock parts, and the diffusers 20, 24 may be similarly constructed.