介绍离心泵的英语作文

The magnetic pump consists of a pump， magnetic actuators， motors of three parts. Key components of magnetic actuator by the external magnetic rotor sleeve， inner magnetic rotor and non magnetic components. When the motor drives the outer magnetic rotor， the magnetic field can penetrate the air gap and non-magnetic material， driven by the magnetic rotor and impeller connected for synchronous rotation， to achieve non-contact power transmission， the dynamic seal into static seal. As the shaft， the rotor is within a magnetic pump， isolated sets of completely closed to completely solve the problem of "run， run， drip， leak， remove the oil refining chemical industry flammable， explosive， toxic and harmful media through the pump seal leakage security risks， effectively ensure the workers health and safety of.
First， the working principle of magnetic pump
N of the magnet (n is even) arranged according to the laws in the magnetic clutch assembly inside and outside the magnetic rotor， the magnet part consisting of magnetic coupling system. When the inside and outside the two poles in different relative displacements， two poles between the angle phi = 0， the lowest energy magnetic system; when rotates to the relative displacement of two poles， pole angle between phi = 2 pi /n， the maximum magnetic energy of magnetic system. Remove the external force， due to the magnetic system of magnetic poles repel each other， magnetic magnet will return to the lowest energy state. So the magnet generates motion and drives the magnetic rotor to rotate.
Two， structural characteristics
1 permanent magnets
Permanent magnet operating temperature range is made of rare earth permanent magnet wide (-45 - 400 DEG C)， high coercivity， magnetic anisotropy direction is very good， also won't happen in the same demagnetization phenomenon when is close， is a good source of magnetic field.
2 isolation sleeve
In the metal isolation， isolation sets in a sinusoidal alternating magnetic field， in a cross section perpendicular to the direction of magnetic field lines induced eddy currents and transformed into heat. The expression of eddy current is:. Among them Pe eddy current; K constant; rated speed of N pump; T magnetic drive torque; pressure within F spacer sleeve; inner diameter of D spacer sleeve; resistivity of material; tensile strength of material. When the pump design is good， T， n is a given condition， to reduce the eddy current only from F， D， etc.. Selection of high resistivity， high strength of the non-metallic materials to produce isolation sets， the effect is very obvious in reducing the eddy current.
3 control of coolant flow rate
When the pump works， a small amount of liquid must be used to flush the gap between the inner magnetic rotor and the isolation sleeve and the friction pair of the sliding bearing. The flow rate of the coolant is usually 2%-3% of the pump design flow， and the annular gap between the inner magnetic rotor and the isolation sleeve produces high heat due to eddy currents. When the coolant is not enough or poor flushing holes to plug， will result in permanent magnet medium temperature is higher than the operating temperature of the inner magnetic rotor gradually loses magnetism， the magnetic actuator failure. When the medium is water or water base liquid， the temperature rise of the annular gap region can be maintained at 3-5， when the medium is a hydrocarbon or oil， the temperature rise of the annular gap region can be maintained at 5-8.
4 sliding bearing
Magnetic pump sliding bearing material impregnated graphite， filled PTFE， engineering ceramics， etc.. Because the engineering ceramics have good heat resistance， corrosion resistance and friction resistance， the sliding bearing of magnetic pump is made of engineering ceramics. Because the engineering ceramics are very crisp and the expansion coefficient is small， so the bearing clearance must not be too small， so as to avoid the occurrence of axle bearing accident.
Due to the magnetic pump sliding bearing to transport the media for lubrication， it should be based on different media and the use of working conditions， the use of different materials production of bearings.
5 Protection Measures
When the magnetic actuator driven components running in case of overload or rotor stuck， magnetic clutch master and slave unit will automatically slip to protect the pump. The magnetic drive permanent magnet on the rotor in the active role of the alternating magnetic field， will produce eddy loss， magnetic loss， resulting in permanent magnet temperature， magnetic clutch slip failure.
Three， the advantages of magnetic pump
Compared with the centrifugal pump with mechanical seal or packing seal， magnetic pump has the following advantages.
1 pump shaft from the dynamic seal into a closed static seal， completely avoid the media leakage.
2 no independent lubrication and cooling water， reduce the energy consumption.
3 by the coupling drive into a synchronous drag， there is no contact and friction. Low power consumption， high efficiency， and with damping vibration damping effect， reducing the impact of the motor vibration on the pump and pump cavitation of the impact of the motor.
4 overload， the internal and external magnetic rotor relative slip， the motor， the pump has a protective effect.
Four， running notes
1 prevent particles from entering
(1) there are ferromagnetic impurities and particles into the magnetic actuator and bearing friction is not allowed. (2) the transfer of the easy crystallization or precipitation of the media to be promptly washed (after the pump to the pump cavity filling the water， running 1min after discharge clean)， in order to protect the life of the sliding bearing. (3) the delivery of media containing solid particles should be filtered at the inlet of the pump flow tube.
2 prevent demagnetization
(1) magnetic moment can not be designed too small. (2) should be in the specified temperature conditions， the medium temperature is strictly prohibited. The temperature sensor of the outer surface of the magnetic pump isolation sleeve is provided with a platinum resistance temperature sensor to detect the temperature rise of the ring gap region， so that the temperature exceeds the limit alarm or stop.
3 prevent dry friction
(1) no idling. (2) the medium is prohibited to take time off. (3) the outlet valve is closed under the condition of the pump running time should not exceed 2min， to prevent overheating and failure of magnetic driver.
磁力泵由泵、磁力传动器、电动机三部分组成。关键部件磁力传动器由外磁转子、内磁转子及不导磁的隔离套组成。当电动机带动外磁转子旋转时，磁场能穿透空气隙和非磁性物质，带动与叶轮相连的内磁转子作同步旋转，实现动力的无接触传递，将动密封转化为静密封。由于泵轴、内磁转子被泵体、隔离套完全封闭，从而彻底解决了“跑、冒、滴、漏”问题，消除了炼油化工行业易燃、易爆、有毒、有害介质通过泵密封泄漏的安全隐患，有力地保证了职工的身心健康和安全生产。
一、磁力泵工作原理
将n对磁体（n为偶数）按规律排列组装在磁力传动器的内、外磁转子上，使磁体部分相互组成完整藕合的磁力系统。当内、外两磁极处于异极相对，即两个磁极间的位移角Φ＝0，此时磁系统的磁能Z低；当磁极转动到同极相对，即两个磁极间的位移角Φ＝2π/n，此时磁系统的磁能Z大。去掉外力后，由于磁系统的磁极相互排斥，磁力将使磁体恢复到磁能Z低的状态。于是磁体产生运动，带动磁转子旋转。
二、结构特点
1．永磁体
由稀土永磁材料制成的永磁体工作温度范围广(-45－400℃)，矫顽力高，磁场方向具有很好的各向异性，在同极相接近时也不会发生退磁现象，是一种很好的磁场源。
2.隔离套
在采用金属隔离套时，隔离套处于一个正弦交变的磁场中，在垂直于磁力线方向的截面上感应出涡电流并转化成热量。涡流的表达式为： 。其中Pe－涡流；K—常数；n—泵的额定转速；T－磁传动力矩；F－隔套内的压力；D－隔套内径； 一材料的电阻率； —材料的抗拉强度。当泵设计好后，n、T是工况给定的，要降低涡流只能从F、D、 、 等方面考虑。选用高电阻率、高强度的非金属材料制作隔离套，在降低涡流方面效果十分明显。
3．冷却润滑液流量的控制
泵运转时，必须用少量的液体对内磁转子与隔离套之间的环隙区域和滑动轴承的摩擦副进行冲洗冷却。冷却液的流量通常为泵设计流量的2%-3%，内磁转子与隔离套之间的环隙区域由于涡流而产生高热量。当冷却润滑液不够或冲洗孔不畅、堵塞时，将导致介质温度高于永磁体的工作温度，使内磁转子逐步失去磁性，使磁力传动器失效。当介质为水或水基液时，可使环隙区域的温升维持在3-5℃；当介质为烃或油时，可使环隙区域的温升维持在5-8℃。
4．滑动轴承
磁力泵滑动轴承的材料有浸渍石墨、填充聚四氟乙烯、工程陶瓷等。由于工程陶瓷具有很好的耐热、耐腐蚀、耐摩擦性能，所以磁力泵的滑动轴承多采用工程陶瓷制作。由于工程陶瓷很脆且膨胀系数小，所以轴承间隙不得过小，以免发生抱轴事故。
由于磁力泵的滑动轴承以所输送的介质进行润滑，所以应根据不同的介质及使用工况，选用不同的材质制作轴承。
5．保护措施
当磁力传动器的从动部件在过载情况下运行或转子卡死时，磁力传动器的主、从动部件会自动滑脱，保护机泵。此时磁力传动器上的永磁体在主动转子交变磁场的作用下，将产生涡损、磁损，造成永磁体温度升高，磁力传动器滑脱失效。
三、磁力泵的优点
同使用机械密封或填料密封的离心泵相比较，磁力泵具有以下优点。
1．泵轴由动密封变成封闭式静密封，彻底避免了介质泄漏。
2．无需独立润滑和冷却水，降低了能耗。
3．由联轴器传动变成同步拖动，不存在接触和摩擦。功耗小、效率高，且具有阻尼减振作用，减少了电动机振动对泵的影响和泵发生气蚀振动时对电动机的影响。
4．过载时，内、外磁转子相对滑脱，对电机、泵有保护作用。
四、运行注意事项
1．防止颗粒进入
(1)不允许有铁磁杂质、颗粒进入磁力传动器和轴承摩擦副。(2)输送易结晶或沉淀的介质后要及时冲洗（停泵后向泵腔内灌注清水，运转1min后排放干净），以保障滑动轴承的使用寿命。 (3)输送含有固体颗粒的介质时，应在泵流管入口处过滤。
2．防止退磁
(1)磁力矩不可设计得过小。(2)应在规定温度条件下运行，严禁介质温度超标。可在磁力泵隔离套外表面装设铂电阻温度传感器检测环隙区域的温升，以便温度超限时报警或停机。
3．防止干摩擦
(1）严禁空转。(2）严禁介质抽空。(3)在出口阀关闭的情况下，泵连续运转时间不得超过2min，以防磁力传动器过热而失效。