This invention relates generally to a multi-stage barrel type centrifugal pump and more particularly to a preassembled unit or cartridge forming an inner assembly for a multi-stage barrel type centrifugal pump having all working pump parts including bearings, seals, and thrust balancing device, as well as the impeller and diffuser adaptable for insertion in and removal from the fixed outer casing for the pump.
It is well known that in the replacement of the working parts of prior art multi-stage barrel type pumps that it is first necessary to dismantle and remove the bearing seals, balancing device and inner elements, then replace the required working parts, and then reassemble all the elements and associated parts for the pump.
The replacement and reassembly process requires adjustments in axial and radial rotor position to obtain satisfactory running clearances between the moving and stationary parts of the pump, and the overall process of element replacement requires many hours of labor in the field where labor rates tend to be high and during which time the pump is not available for service. One effort to meet and overcome this problem is shown in U.S. Pat. No. 3,927,763.
The present invention overcomes this problem of barrel type centrifugal pumps by providing a preassembled, adjusted and aligned unit or cartridge having all the working parts of the pump; i.e., bearings, seals, and balancing device as well as the impellers and diffusers; which can be installed or removed easily from the barrel or outer casing for the pump, and renewal of the pump merely requires the removal and installation of a preassembled replacement unit or cartridge.
The unit or cartridge concept is made possible by means of a special rig or frame which duplicates the pump casing in supporting the unit or cartridge. This permits all adjustments to be made and checking of the rotor for free rotation to be done before installation in the pump.
The fixture can also be moved to the assembly point near the pump and in this context acts as a carrier for transporting the cartridge.
Thus, precise assembly and adjustment can be made at the machine or service shop where more highly trained personnel are located and where labor charges are less costly.