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Summary of knowledge on centrifugal pump maintenance; Classification of chemical equipment maintenance – Planned maintenance: Maintenance is carried out according to a plan that is developed based on the management experience related to production equipment and the condition of that equipment. Depending on the maintenance tasks, frequency, and requirements, it can be further divided into minor repairs, medium repairs, and major repairs. Unplanned maintenance refers to maintenance work that must be carried out either while the equipment is still running or after it has been shut down, due to sudden failures or accidents that occur during operation. Characteristics of unplanned maintenance: Maintenance is difficult to predict in advance, making it impossible to plan for it; moreover, it requires short maintenance times, high quality of work, complex maintenance environments and operating conditions, as well as significant difficulties in carrying out the repairs. The maintenance ratio is high. Centrifugal pump shaft 1: Clean and inspect the pump shaft; it should be free from defects such as cracks or severe wear. If there is wear, cracks, erosion, etc., it should be recorded in detail, and the causes analyzed. 2. Test the straightness of the pump shaft of the centrifugal oil pump; this value should not exceed 0.05 mm over its entire length. The journal surface must be free of defects such as pitting and grooves; the maximum allowable value for surface roughness is 0.8μm, and the errors in roundness and cylindricity of the journal should be less than 0.02mm. 3. The parallelism error between the center line of the centrifugal pump’s keyway and the axis center line should be less than 0.03 mm/100. Centrifugal pump impeller 1: Clean and inspect the surfaces of each stage of the impeller. The impeller surfaces should be free from defects such as cracks or wear; the flow channels on the impeller surface should be smooth, without any scaling or burrs. The blades should also be free from cracks or thinning due to erosion. 2. Check the sealing rings at the inlet and outlet of the impellers at all levels; they should not be loose, and their surfaces must be smooth without any burrs. The maximum allowable value for surface roughness Ra is 0.8 μm, while the assembly clearance between the impeller and these sealing rings should be between 0.05 and 0.10 mm. Using the inner bore of the impeller as a reference, the radial runout of the impeller should not exceed 0.05 mm. The end face runout shall not exceed 0.04 mm. 3. The impeller and shaft are fitted with an interference fit, typically H7/h6. The interference fit between the key and the keyway is 0.09–0.12 mm, resulting in a clearance at the top of the centrifugal pump key after assembly of 0.04–0.07 mm. 4. The impeller must be statically balanced. For the centrifugal pump’s impeller, casing, and guide vane 1: Clean and inspect each stage of the impellers; there should be no defects such as wear, cracks, or erosion. 2. The anti-rotation pin of the impeller in the centrifugal pump should be free from bending, breaking, and loosening. The surfaces of the pump head and the seal ring of the pump casing should be free of pitting, scratches, or grooves. The maximum allowable value for surface roughness Ra is 0.8μm. The fitting clearance between the seal ring, the pump head, and the pump casing of the centrifugal pump should be between 0.05 and 0.10 mm, and the seal ring must not be loose. 3. Using the impeller of the centrifugal pump and the flange of its casing as references, measure the radial runout of the inner diameter of the sealing ring; this value should not exceed 0.50 mm, while the end-face runout should not be more than 0.04 mm. 4. Measure the gap between the seal ring of the centrifugal pump’s impeller and casing and its assembly seal ring; this value should be between 0.50 and 0.60 mm. Centrifugal pump throttle shaft seal 1: Clean and inspect the surface of the throttle shaft seal; it should be free from defects such as cracks or uneven wear, with a maximum allowable surface roughness value of 0.8μm ； 2. The throttle shaft seal of the centrifugal pump and the pump body use an H7/p6 fit. Based on the outer circle, measure the radial runout of the inner bore; this value should not exceed 0.02 mm ； 3. Measure the clearance between the throttle shaft seal of the centrifugal pump and the pump shaft; this value should be between 0.25 and 0.30 mm. Standards for maintaining centrifugal pump bearings: 1. The ellipticity and shaft diameter taper must not exceed one thousandth of the shaft diameter. 2. Roughness Ra of the shaft diameter surface