Improve Hermetic magnetic pump operation reliability method
一.features
1． Structure: the Hermetic magnetic pump is suction radial and axial discharged horizontal completely no leakage centrifugal pumps, pump shaft through magnetic coupler drive, no rotaing shaft seal device, hermetic magnetic pump realizes "zero leakage".
2． Bearing: the Hermetic magnetic pump drive shaft through the rolling bearing to support, rolling bearing is lubricated by its own lubricating grease, Pump shaft through hydraulic sliding bearing to support.
3． Magnetic couplings: the Hermetic magnetic pump magnets are high quality of rare earth permanent magnetic material, its highest irreversible retreat temperature can reach 350-400 ℃, fully guarantee magnetic couplings with reliable performance. When at normal work, magnetic coupling and three-phase asynchronous motor synchronicity, stable performance. And permanent magnets has high stability, which can prevent when assemble and disassemble rotor or pump in the maximum transmission torque produced adverse effects.
4． Sliding bearing lubrication and magnetic couplings cooling: by pump conveying media lubrication and cooling, without plus lubricant and cooling water system.
5． Axial force balance: at work, the Hemetic magnetic pump axial is automatic balanced by hydraulic, promote disc only start and stop withstand momentary axial thrust effect.
二、 common faults and analysis
1． Pump operation condition fluctuations caused problem: the Hemetic magnetic pump axial is through hydraulic balanced way automatic balance. In the actual cases if operation parameters (the inlet pressure, outlet pressure) shaky and easy to destroy Hemetic magnetic pump hydraulic balance, make sliding bearing big radial and axial force and cause bearing damage.
2． Pumps due to the cavitation erosion caused problem: the pump produced cavitation is mainly caused by the pump inlet pipe resistance, conveyance medium, volumetric gas compared with more than inadequate, pump suction pump can head is inadequate. The pump cavitation erosion hardest happen when pump cavitation violent vibration, hydraulic balance will cause serious damage, pump bearing, rotor or impeller damage. This is the common cause of Hemetic magnetic pump faults.
3． No medium or conveyance medium low flow: make bearing dry, burn broken bearings. The Hemetic magnetic pump is by conveyance medium to sliding bearing provide lubrication and cooling, under not open inlet valve or the outlet valve circumstance, sliding bearings because there was no transport medium lubrication and cooling and cause damage.
4． Segregation damage: Hemetic magnetic pump couplings are because pump transport medium cooling, if medium have hard particle, is very easy to create isolation scratches or sweep, sometimes if maintenance methods is improper, may also caused isolation damage.
三、 methods and ways
1． equipment and pipeline installing requirements
（1） pump inlet pipe and outlet pipeline should be support, in order to prevent the transfer to pump extra load, pump can not be used as the pipeline structural point, to ensure that pipeline system that provides for thermal compensation measures.
（2） when inhaled pressed head is low, entrance line should as short as possible, to prevent cavitation. Entrance line should have proper size to ensure the flow speed is not more than 3m/s, in conveying easy vaporization of fluid or gas velocity, in conveying easy vaporization fluid or gas, ensure flow speed is no more than 1 m/s.
（3） Outlet pipeline should install a regulator to adjust pump flow and head. In using longer outlet pipeline or two pump parallel, suggest install additional unidirectional check valves.
（4） the entire pipeline system and auxiliary piping shall carefully rinsed, in order to prevent the scrap iron and welding slag, or other foreign material into the Hemetic magnetic
pump. For new piping systems, entry pipe shall be provided with a filter.
（5） Pipe design shall consider pump exhaust.
（6） to realize the continuous operation and suggest pump installing a backflow pipeline, install the minimum flow orifice plate, to ensure continuous operation, sliding bearings have enough lubrication and cooling.
As shown in figure 1, reflux pipe line from the outlet valve or one-way check inverse valve before derivation, through the minimum flow orifice plate to return liquid storing the tank. This type installation can realize the automatic vent pump.
（7） Hemetic magnetic pump must work within the designated work range. To control the maximum flow, suggest install a suitable maximum flow orifice plate in outlet pipe. (figure 1 shows)
2． Process monitoring:
Hemetic magnetic pump design features, generally don't need repairs, but so as to ensure the normal operation and safe work, should use process monitoring device, strict management.
（1） Inlet tank liquid level protection control is necessary, inlet tank should be fitted with level transmeter or level switches, the entrance tank liquid level reduces to a certain degree, automatic stop pump operations to protect the pump.
（2） pump body shall be provided with a temperature sensor, monitoring magnetic stator and pump bearing temperature, protect magnetic bearings and the magnetic stator.
（3） pump outlet shall be provided with liquid level regulator, according to the inlet tank liquid level adjustment to convey medium emissions.
（4） should install differential pressure sensors and switches, measuring pump export and entry pressure differential, when it is lower than setting value, stop the pump automatically, protecting the pump.
（5） the vibration of the pump is tiny, larger vibration and noise means failure.
（6） to guarantee the normal work, should guarantee the pump in figure 2 shows working within the flow and head scope, the minimum and maximum working capacity, head in performance curve all have instructions.
（7） to avoid producing cavitation, Hemetic magnetic pump in conveying easy vaporization fluid will require minimal inhaled pressure head (emin), calculated by next type: (emin) (m) = pump NPSH (m) + inlet friction loss (m) + safety allowance (m), it is usually 0.5 m.
3． operating key point
（1） perfusion and exhaust
In order to make the Hemetic magnetic pump can normal operation, we must fully perfusion and exhaust. Completely open pump suction pipe and reflux pipe, outlet pipe valve, can achieve Hemetic magnetic pump automatic vent. When conveying liquefied gas or liquid vaporization easily, repeated several times, until ensuring the pump full filled of fluid so far. If conveying cryogenic liquid, only can start untile pump flow components cooling to liquid temperature, so can ensure fluid has reached the pump ministries.
（2） set-up procedure
Magnetic coupling model is according to drive motor choice, so as to realize the normal functions, but start in the improper circumstance, (such as excessive motor power, outlet valve open excessive or high voltage, etc.), will exceed magnetic coupling maximum torque, making pump weren't working properly, so must note to start correctly.
A. completely open inlet pipeline valve,
B. close outlet pipeline valve,
C. start motor,
D. opened outlet pipeline valve slowly,
E. adjusting outlet valve until it reaches normal work pressure,
F. for making pump runs normally, should make pump within the allowed working scope.
四 .Operational and maintenance note:
1. The Hemetic magnetic pump never allowed to work in dry friction condition and outlet pipe valves closed, or will cause sliding bearing damage!
2. Must work with motor synchronously, if pump is failure (head is too small), indicates that has exceeded the magnetic coupling maximum torque, should be avoided long time work in discomfortable conditions.
3. Under normal working circumstances, occur vibration, larger the noise and power growth, explain bearing happens wear (lubrication insufficient) shall immediately check.
4. Hemetic magnetic pump rolling power bearing is deep groove ball bearing, rely on its own grease for permanent lubrication, but also regular inspection, and change regularly.
5. Magnetic couplings failure does not mean permanent magnets damage. But in failure condition to work long hours, because of its low rotating speed, bad sliding bearing lubrication, will cause the sliding bearing damage.
6. Rotor components and driving components have higher magnetic, when assemble and disassemble hemetic magnetic pump, we shall consider magetic power scope. It may have certain effect to electricity and electronics device, pay attention to keep a certain distance!
7. Long placed, if the conveyed liquid will produce crystallization or solidification, should use suitable fluid to wash pump.
