Overhauling technology of boiler feed pump:

Two keys are provided between the impeller and pump shaft of the boiler in order to prevent the impeller from rotating by heat impact. The axial thrust balancing mechanism of this pump is composed of balance drum, balance plate, butterfly-shaped spring, and thrust bearing. The balancing capacity of balance drum is about 97%. In normal operation, the working interval between the balance plates is 0.76mm, the differential pressure between the front and back of balance plates is very little, which is about 0.05 Mpa, so the balancing plates do not play their role of balancing under normal condition. At this moment, the remainder thrusts are assumed by the thrust bearing. Only when thrust pad has failure, can the balance plates play its role in balance. Meanwhile, the device for axial displacement is equipped, it will interact to stop the pump when the axial shifting is over the acting value. Rotors are supported by two pairs of three- wedge sliding bearings at front and back, and the bearings are split bearing alloy tiles in horizontal. From the direct above, at every other 120mm, there is  an oil chamber, with pressure oil for forced lubrication.

The thrust bearing consists of two-way fan-shaped tile and butterfly-shaped leaf spring, and its lubrication is also forced by pressure oil. The shaft seals at both front and back are fluid dynamic pressure type of imbalanced mechanical seal, with cooling facilities including magnetic filter and cooler, and closed circulation system. The screw thread in the excircle of rotating seat and the screwy sheath with inner screw thread constitute screw pump, which makes the heat generated by the mutual friction of the sealing surfaces of moving  and static rings absorbed by the circular cooling water in cooler by water circulation, so as to guarantee the reliable cooling of sealing surface. Mechanical seal consists of non-compensation moving ring and compensation static ring. At the sealing positions  of moving  and static rings and the matched components, “O”-shaped rubber rings are equipped for sealing .

The coupler is of the lengthened gear-shaped coupler and is lubricated by oil injection of steam turbine oil and is sealed with outer cover. Before pump disassembly, firstly dismantle all pipe sections and the related auxiliary parts , then dismantle all components of  thermotechnical measurement prevent impurities from entering into the pipe and auxiliary parts. All openings shall be well sealed. When the feed pump is disassembled, all components shall be cautiously protected. The disassembled components and parts shall be put in sequences and on the clean board or rubber. Meanwhile, they shall be covered with  paper or clean cloth for fear of colliding and scratching the sealing surface. The  sleeves and components shall be disassembled in accordance with the stipulations of this rule or the requirement of the manufacturer’s drawing. Before disassembly, Steel prefix shall be struck well at all corresponding positions. With regard to those places needing exact alignment positions, they can be marked with lines  As the above mentioned, if there are such marks  it is not necessary to mark the components and parts with similar structure. Meanwhile, the steel Prefix or mark used in disassembling shall be distinguished. It is forbidden to marking on the working face of parts. With regard to the feed pump, it cannot be reinstalled only after it has been cleaned carefully. O-shaped seal rings shall not touch oils or molybdenum disulfide. In principle, it shall be changed after it has been used for a period of time. Asbestos sealing gasket and spirotallic gasket must be changed after it has been used for some time. And the  sealing gasket shall be changed  in accordance with requirements in drawing. As for the spirotallic gasket, if the thickness is more than 4.2mm (4.5 mm originally) and 3 mm (3.2 mm originally) respectively, it can be continued to be used, and if it is less than this thickness, it shall be changed.