GB999900A - Improvements in or relating to the manufacture of pumps, compressors, turbines or the like - Google Patents

Abstract

999,900. Centrifugal pumps and compressors; turbines. DE LAVAL TURBINE Inc. Nov. 2, 1961 [Nov. 21, 1960], No. 39343/61. Headings F1C and FIT. In a method of manufacturing any one of a number of similar stator assemblies of identical length for a pump, compressor, turbine, etc. within a determined range of dimensions and machine capacities employing a single series of identical diaphragm blanks, each blank having a radial annular portion and a cylindrical portion which extends axially of the outer periphery of the annular portion, the annular portion is formed of a thickness which is not less than the maximum thickness and materially in excess of the normal machining allowance at the minimum thickness within the determined range of dimensions and the cylindrical portion is formed with an axial width in excess of the required finished width by an amount at least equal to the difference between the maximum and minimum thickness of the annular portion within the determined range of dimensions, either or both of the opposed radial faces of the blank being machined to reduce the axial thickness of the annular portion to the required dimension and to reduce the cylindrical portion to the required finished axial width such that a number of such finished machined diaphragms, when assembled in axially stacked relationship with end diaphragms, provide a stator assembly of the required dimensions for a particular machine capacity. In the multi-stage pump shown in Fig. 1, diaphragms 12, 14, 16, formed with interlocking rabbets, are assembled into an outer casing barrel 2 against a shoulder 7 and held together by tie members 24. During operation, the discharge pressure holds the assembly against the shoulder 7. Diffuser elements 18, Figs. 1 and 2, are nested within the diaphragms 12, 14 and secured to them by bolts 19. Diffuser vanes 23 spiral outwardly from their inlet edges 25, and return vanes 27 on the opposite side of each element 18 spiral inwardly from their inlet edges 26 to their outlet edges 28. Helical cross-over passages 30 lead 'the fluid from the diffuser passages to the return passages. Whirl-removing vanes 36 lead the fluid to the impeller eye of the next stage. Fig. 6 shows how a diaphragm casting 14A of stock size can be machined to suit pumps of different duties, i.e. having different sizes of impellers or numbers of stages, or both. For a low-capacity pump, the shaded portion 42 can be machined away to provide an axial dimension A 1 . For a highcapacity pump, the shaded portion 44 can be machined away instead to provide a larger axial dimension A 2 . For intermediate sizes, material is removed from both ends of the casting. Similarly, the diffuser elements 18 can be machined from stock castings of ample peripheral width to provide the required finished widths of the passages on both sides of the element. For pumps of different lengths, different barrels 2 are provided. In the case of compressors, the impellers are usually of different sizes in successive stages, necessitating correspondingly different amounts of machining of the diaphragms and diffuser elements. The invention is also applicable to turbines for gas or liquid.