Abstract: Constant flow width through the last stage diffuser of a centrifugal compressor is maintained against widening by the forces of differential pressure via a diffuser defined between oppositely positioned radial faces of a diaphragm and an annular diffuser plate secured spaced from the diaphragm at the desired width. Although slight movement occurs in the compressor components, the width of the diffuser flow passageway is not affected since its width is fixed and the diffuser plate is free to move because of the pressure balance provided by the annular cavity and vent holes extending through the plate.

Abstract: In a method of machining an upper conical surface in an annular impeller cover, a rotatable milling cutter has its cutting surface ground to an angle approximately equal to that of the desired conical surface configuration of the cover. The milling cutter is then caused to rotate and by the use of a three dimensional milling machine, the cutter is moved across the annular cover blank used for making the cover, cutting the conical surface and forming a plurality of integral vanes that project from the conical surface in circumferentially-spaced relationship.