The temperature of the boiler feed water pump is 160--170 ° C, and the outlet pressure is above 15 MPa. Considering the influence of temperature changes, most of the rotating parts of the pump use alloy materials with the same expansion coefficient. The impeller is mounted on the pump shaft, and finally has an axial clearance of about 0.50 mm to prevent the impeller from being thermally expanded at the initial stage of driving, and the impeller and the impeller are mutually squeezed, causing tensile failure of the pump shaft. The support of the pump shaft adopts a central support type, so that the thermal expansion of the pump body after the driving is radiated around the pump axis, the alignment of the unit is not damaged, and the rotor is finally centered in the pump casing.
In order to eliminate the influence of thermal expansion and contraction on the concentricity of the unit, the lower part of the high-pressure boiler feed pump housing is provided with a longitudinal sliding pin and a vertical sliding pin, which respectively match the pin groove and the pin hole on the pump base. The bearing housings of the pump are respectively installed on the front and rear sections of the two ends, and each of the bearing seats is provided with three adjusting screws for adjusting the concentricity of the bearing and the pump casing.
The impeller generates axial thrust during operation. There are two measures to balance the axial thrust of the multi-stage pump: for the horizontal split multi-stage pump, the impeller is symmetrically arranged, and the impeller is installed in the forward and reverse directions, so that the axial thrust of the impeller cancels each other, and the two are balanced; The centrifugal pump of the stage, because the time wheel is installed in the same direction, and the axial force direction is the same, the thrust balance device is installed at the rear end of the final stage impeller to balance the axial thrust generated by the impellers at each stage.
In general, the rotor of the segmented multistage centrifugal pump has a tilting force of 0.10-0.15 mm in the axial direction and 10 to 20 times per minute. Therefore, if the medium contains sediment or other solid matter during operation, the balance disc and the balance ring are easily worn. In order to resist wear and prolong the service life of the parts, the balance disc and the balance ring are usually made of wear-resistant metal, such as bronze and gray cast iron.
