For the maintenance of multistage pump, if conditions permit, first look at the manufacturer's maintenance manual and general assembly drawing to see what special areas need attention. I During disassembly: 1. Before removing the thrust bearing, use a dial indicator to measure the clearance of the balance disc and make records; 2. When disassembling the multi-stage pump, all parts must be marked according to the original matching sequence to avoid confusion and wrong installation during reassembly; 3. Small parts (such as keys) that are not easy to mark can be placed together with impellers or guide vanes (middle section) at the same level. 4. During disassembly, you can intuitively feel whether there are abnormal parts, such as loose fitting, etc. II Parts maintenance: 1. Visually check whether the surface of all parts is normal, and all mating surfaces must be free of collision, scratch, corrosion, etc; 2. Measure whether the tolerance of key mating parts is qualified with measuring tools; 3. Measure whether the clearance of impeller seal ring, shell seal ring, guide vane seal ring, interstage shaft sleeve, etc. is within the tolerance range. If the wear is too large, it needs to be replaced; 4. Check whether the bearing is intact; 5. All sealing rings and gaskets shall be renewed; Submersible pump III Reassembly: 1. Install the rotor and conduct dynamic balance test again; 2. Reassemble all parts in the reverse order of removing the pump. During reassembly, pay attention to measure the clearance value at each sealing ring again to ensure that there is no error; 3. Before installing the balance disc, measure the total amount of rotor string; 4. After installing the balance disk, measure the half string of rotor; 5. Compared with the total string quantity and half string quantity required on the general assembly drawing of the manufacturer, it shall basically meet the requirements of the drawing. Generally, the half string quantity is about half of the total string quantity; 6. Tighten all main bolts evenly, and pay attention to diagonal; 7. Suck a dial indicator on the shaft and rotate the shaft to mark the balance disc. The tolerance shall meet the requirements of the drawing and generally shall not exceed 0.06; 8. When installing the thrust bearing, pay attention to adjusting the clearance of the balance disc, and use the adjusting ring in front of the bearing to adjust the clearance of the balance disc to the requirements of the drawing.
What is the reason why the oil-free screw vacuum pump cannot be started?