Canned pumps are mainly used to transport toxic, flammable, explosive, highly corrosive, radioactive and precious liquids. Therefore, a large number of canned pumps are used in the chemical industry.
The cost of canned pumps is relatively high, and maintenance of canned pumps is an important task.
1, structure and principle of canned pump
The working principle of the canned pump is the same as that of the ordinary centrifugal pump, the difference lies in the drive motor. The motor of the canned pump is completely enclosed in the second layer of isolation sleeve or shielding sleeve, and leakage prevention mainly relies on the internal anti-corrosion shielding sleeve. The shielding sleeve is sealed and welded to ensure that the stator winding and rotor core are not immersed in the working liquid. The canned pump does not need to be lubricated. Its bearings are lubricated by its own working fluid circulation. This determines that the central shaft is a hollow shaft to facilitate the return flow of the lubricating working fluid.
2, inspection and maintenance of canned pump
2.1 daily inspection
① Check whether the outlet pressure gauge pointer is abnormal;
② Whether the current value is overloaded or abnormal;
③ Are there any abnormal sounds and vibrations?
④ Pay attention to whether the bearing monitoring pointer is within the red indicator band;
⑤ Temperature of various parts of the pump;
⑥ Check for liquid leakage.
2.2 Bearing Monitor
The bearing monitor is mainly used to monitor corrosion of the containment shell and bearing wear. A pointer in the red zone indicates that the monitor probe has ruptured and the high-pressure argon inside has leaked. This is caused by excessive bearing wear and requires replacement of the monitor, shaft sleeve, thrust plate, bearings and eccentric nut, at an approximate cost of 2600–2850 yuan. If operation continues for a long time after the pointer enters the red zone, impeller wear or motor burnout caused by wear of the stator and rotor containment shells is inevitable. Repair costs then generally rise to 20,000–30,000 yuan.
2.3 bearing
After the bearing exceeds the wear limit, it will cause the rotor shielding sleeve and the stator shielding sleeve to come into contact, causing damage to the stator shielding sleeve, so pay close attention to the inspection of the bearings during operation. If the pump vibrates or makes abnormal sounds during operation, the pump should be disassembled and the bearings should be inspected. If the wear amount of the bearings and sleeves exceeds 0.3 to 0.5 mm, they should be replaced based on the actual wear.
Judging from actual operating conditions, generally the wear of bearings is mainly radial, but axial wear cannot be ignored. Checking axial wear mainly involves the bearings and thrust plates. Even if the pump is running smoothly, regular inspections must be performed. Regular inspections require dismantling the pump and mainly checking the wear of the bearings. The regular inspection cycle for canned pumps using domestic bearings is 3 months, and the inspection cycle for canned pumps using imported bearings is 6 months.
3, key points of canned pump maintenance
① The pump should be comprehensively inspected regularly, paying special attention to the monitor, and if any abnormalities are found, stop the pump immediately.
② The canned pump relies on its own circulation for lubrication. It must not be operated with a flow cutoff or reversed for more than 1min.
③ The orifice plate is installed between the pump body outlet and the pipe flange. It is a stainless steel plate with a through hole smaller than the outlet pipe. Because the canned pump relies on its own circulation for lubrication, without the throttling effect of the throttling orifice plate, the pressure of the return liquid will be very low. The bearing cannot be fully lubricated, causing bearing damage. In addition, the orifice plate can further increase the pressure.
④ The inside of the jacket is filled with cooling water to reduce the temperature of the equipment. When the temperature of the transported liquid is high, a jacket must be installed.
⑤ Please pay attention to the following points when assembling:
Before installing the bearing into the bearing seat, place the lining into the cutout on the periphery of the bearing, insert the bearing into the bearing seat, and screw the stop screw into the lining. Do not overtighten the bearing, otherwise it will easily cause early wear of the bearing;
When installing the bearing seat, the circulation holes in the front bearing seat have the functions of exhaust and liquid drainage. The circulation holes should be aligned up and down and cannot be installed upside down.
Source: Internet