Shielding pump maintenance technology

The canned pump is driven by a shield motor that places the stator winding and the rotor winding in sealed metal cylinders, respectively. The pump casing is sealed with the flange of the drive motor casing, and the pump of the pump shaft dynamic sealing structure is eliminated. Suitable for transporting precious liquids or radioactive liquids.

1 Regular inspection of shielded pumps In order to avoid and reduce the sudden damage of shielded pumps, canned pumps require regular maintenance. In the event of bearing alarm "alarm", it must be repaired immediately. The chemical plant is generally operated continuously, and the regular inspection of the canned pump is only performed when the unit is scheduled to stop. Most shielded pumps can be overhauled once a year. The maintenance method of the canned pump is: Disassembling the canned pump: clean the parts first, and then perform an apparent inspection on them. Then measure the size of the critical part and perform electrical inspection of the motor windings.

(1) Electrical inspection DC resistance check: The unbalance of the three-phase resistance must not exceed 2%. Insulation resistance check: The insulation resistance of the shielded pump motor winding can generally reach more than 100MΩ. If less than 5MΩ need to analyze the reasons, whether the insulation is damp, or whether the shielding sleeve has leakage points, etc. If there is no problem in the leakage detection of the stator shielding sleeve, the insulation is purely damp and needs to be dried, such as the stator shielding sleeve has problems, You need to replace the shield. The restorative repair of the canned pump is overhauled. In the case of a canned pump with damaged windings or shields, a major overhaul is required. The damage can be roughly divided into two types: one is that the stator shield is good, and the stator windings are earth-to-ground and phase-to-phase breakdown, and the coils are short-circuited and the windings are burned due to overload. The other is that damage to the stator winding is caused by the damage of the stator shield sleeve and the intrusion of the medium into the stator winding. In either case, the stator coil and shield must be replaced. Due to the special structure of the canned pump, replacing the stator windings becomes more complicated. The stator shield sleeve and the both end seal plates must be removed to remove the stator windings. After repairing the windings, new shielding and closing plates must be re-created. The material requirements are special, and the production accuracy is also required to be high.

(2) Mechanical inspection. Measure the bore diameter of the graphite bearing and the shaft diameter of the shaft sleeve, and observe the smoothness of their mating surfaces. Such as the graphite bearing and shaft sleeve fit clearance exceeds the maintenance standard (0.55-11kw with clearance, diameter difference is 0.4mm, 15-45kw with clearance, diameter difference is 0.5mm) or the mating surface is bad, need to be replaced according to the situation Bearings, bushings or thrust plates. Measure and check the upper and lower outer diameter of the impeller and the size of the inner diameter of the retaining ring and the pump seat that are matched with them. Whether the two matching clearances are within the range specified by the inspection standard, when the excess is bad, parts need to be replaced or other measures must be taken ( Such as: surfacing, inserts) to meet the requirements of the gap. Otherwise it will affect the pump performance, flow, head, axial balance and so on. Observe the inspection and inspection, the appearance of the rotor shield sleeve, in particular, pay attention to whether or not there is an abnormal situation at the weld, if necessary, testing and leak detection. After a long period of operation, the balance of the rotating parts may change. Therefore, it is necessary to assemble rotors together with rotating parts such as impellers for dynamic balancing tests.

(1) Stator winding replacement Stator winding replacement is similar to ordinary motors, except that the insulation level is higher, and most of the insulation is Class H. QY polyimide enameled wire, slot insulation, slot wedges, insulation bushings, lead wires and impregnating paints, etc. shall all be class H insulation materials. The principle of replacing the windings is as follows: repairing as it is, especially the number of turns of the coil can not be arbitrarily changed, the number of turns will significantly affect the main performance of the motor, and the wire diameter can be as long as it is close to the original total area, and the winding form and coil span should not change. .

(2) Replacement of the shielding sleeve Replacement of the shielding sleeve is the difficulty and special point of repairing the shielding pump, and it is the key to ensure the quality of the repaired shielding pump. To achieve the original machine level, we must pay attention to the following aspects.

(a) Material selection of shielding sleeve In the loss of the canned motor, the stator shielding sleeve has a large loss, sometimes reaching 2 to 3 times of the iron loss. The repaired shielding sleeve loss should be maintained at the original level. The stator shield losses PB are proportional to the thickness of the shield and inversely proportional to the resistivity ρ of the shield material. The shielding material must be a non-magnetic material with good mechanical properties and corrosion resistance. In order to reduce the eddy current loss, a material with a large resistivity must be used. Thickness should not be too thin, it is necessary to affect the mechanical strength, not too thick, too thick will increase the loss of the shield. The shielding sleeve of the imported canned pump is mostly made of a special stainless steel material called Hastelloy-c containing more than 50% nickel. The performance of this material can fully meet the above requirements. The resistance coefficient can be double that of the ordinary stainless steel 1Cri8Nig9Ti, that is, the loss of the shielding sleeve is 1/2 that of ordinary stainless steel.

(b) Manufacture of the shielding sleeve The production process of the shielding sleeve should be the difficulty and key point of the overhaul repair of the canned pump. Shielding sleeves require high dimensional accuracy and shape tolerances, and welding seams require very strict welding quality. Calculating, cutting, straight seam welding, rounding, press-fitting, girth welding, leak detection, etc. all have certain technical difficulties. The effective clearance between the stator and the rotor of the shielded motor is generally only 0.5~1.0mm. Therefore, it is required that the shield sleeve not only can press the stator and rotor core smoothly, but also must make the shield sleeve close to the iron core. Only in this way can the enough between the stator and the rotor be guaranteed. Effective clearance.

(c) Overall stator leak detection; after completion of welding of the stator cover plate and casing, press-fitting of the shield sleeve, and completion of the circumferential seam welding of the two ends of the shield sleeve, the entire stator should be subjected to leak detection. The method is: the inner cavity between the base and the stator shielding sleeve is filled with 0.5kg/cm2 pressure, and the entire stator is submerged in clean water. If there is a leak, bubbles will appear in the water. This is a simple method. And an effective leak detection method.

(3) Final assembly and inspection test After completing the repair of the stator and rotor, the qualified graphite bearing, bushing, thrust plate, seal ring, etc. can be assembled. After the assembly is completed, the rotor should be turned by hand. The rotation should be uniform and flexible. The rotor should have a certain amount of axial turbulence. The amount of turbulence should be within the range specified by the inspection standard: Shielding pump power kw0.55~3.75.5~1115~45 Axial motion mm0.9~1.51.4~2.01.8~2.5. After completing the assembly, check the DC resistance and insulation resistance. After the electrical performance is normal, the shield pump is immersed in the water tank as a whole (the junction box is on the water, and the water cannot enter the junction box). The nozzle can be covered. Observe the abnormality of the current, running sound and vibration. It is better if the test conditions can do the performance test of the pump.