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渣漿泵采用雙吸葉輪與單吸的優(yōu)勢
用兩個相互對稱的單吸葉輪背旅背的放在一起構(gòu)成的雙吸葉輪，使兩個大小相等、方向相反的軸向力相互抵消了。但由于兩邊密封間隙不完全相同，葉輪不對中等原因，還會產(chǎn)生不大的剩余軸向力，需要由軸承承受。
(2)在兩級泵和多級泵中可以采用葉輪對稱排列的方式來平衡軸向力
如圖2-54所示，即將兩個葉輪或一組葉輪背靠背或面對面的對稱安裝在一根軸上串聯(lián)工作。盡管在單個葉輪上仍有軸向力作用，但對整個轉(zhuǎn)子來說，軸向力得到基本平衡，不過由于間隙的影響，還存在有一定的剩余軸向力，需要有推力軸承配合使用。這種方法在單吸兩級懸臂泵和蝸殼形多級泵中使用較多。這種方法容積損失很小，但會帶來泵的結(jié)構(gòu)較復(fù)雜。
(3)平衡孔或平衡管。
如圖2 -55所示，在葉輪后蓋板上裝一個直徑與前蓋板密封環(huán)直徑相等的密封環(huán)，同時在葉輪后蓋板密封環(huán)直徑以下處開平衡孔，或加平衡管，使后蓋板密封環(huán)以下處壓力與葉輪
進口處壓力相等，這就能平衡大部分的軸向力，剩余的軸向力很小。
平衡孔、平衡管平衡軸向力的方法結(jié)構(gòu)很簡單，它的缺點是有一部分液體回流到葉輪入口增加了泵的容積損失，密封環(huán)磨損后泄漏量更大，所以密封環(huán)磨損后應(yīng)及時修理更換。同時，從平衡孔回流的液體沖擊了葉輪進口的液體，又造成了水力損失，所以泵的效率會略有下降。
(4)平衡盤裝置平衡軸向力
①平衡盤裝置平衡軸向力的工作原理
平衡盤裝置平衡軸向力一般用于節(jié)段式多級泵， 如圖2-56所示。葉輪輪轂(或軸套)與泵體(或平衡套)之間有一個徑向間腺b之外， 在平衡盤與泵體平衡板之間還有一個軸向間隙b。，平衡盤的后面通過平衡管與泵吸入口相通。
這樣，徑向間隙前的壓力就是未級葉輪背面的壓力p，為泵的出口壓力。而平衡盤后的壓力po為接近泵的入口壓力。由于p-Po的壓差，液體從葉輪背面流經(jīng)徑向間隙b到平衡盤前，壓力下降到p"，然后再流過軸向間院bo到平衡盤的后面，壓力下降到Po，最后通過平衡管回流到泵的進口。
在平衡盤上的兩側(cè)，存在著壓力差p’-Po;就產(chǎn)生了一個向后的作用力，其方向與葉輪上的軸向力正好相反，這個力就是平衡力。
當葉輪上的軸向力大于平衡盤上的平衡力時，將泵的轉(zhuǎn)子推向前移動，此時使軸向間隙bg減小，增加了液體流經(jīng)平衡盤的阻力，因而就減小了泄漏量q。由于泄漏減少，液體流經(jīng)徑向間隙的阻力減小，壓力降也就減小，平衡盤前的壓力p'就升高了。由于p'的上升，壓差p'-po增加，就增加了平衡力。轉(zhuǎn)子不斷向前移動，平衡力不斷增加，到某一位置時，平衡力和軸向力相等，達到了平衡。同樣，當軸向力小于平衡力時，轉(zhuǎn)子將向后移動，移動一定距離后，軸向力和平衡力達到了平衡，
由于泵在工作中，運行點是經(jīng)常變化的，軸向力也就經(jīng)常變化，加上慣性力的作用，轉(zhuǎn)子會經(jīng)常發(fā)生軸向移動，以達到新的平衡，所以平衡盤平衡軸向力是動態(tài)的、自動的、完全的平衡軸向力。
由于用平衡盤平衡軸向力時，轉(zhuǎn)子經(jīng)常發(fā)生軸向移動，所以泵的軸承不能用推力軸承，而是能夠軸向移動的軸承。如用滑動軸承，滾動軸承用圓柱滾子軸承、滾針軸承等。如果采用其它滾動軸承不能軸向移動時，需裝在一個能軸向滑動的套中，套可軸向移動。由于轉(zhuǎn)子需要自由移動，就不能用在立式多級泵中。
平衡盤裝置平衡軸向力的優(yōu)點是自動的完全的平衡軸向力，無殘余軸向力，但它的缺點是有一定的泄漏量回到泵的進口，增加了泵的容積損失。同時由于平衡盤平衡軸向力時，需要有一個短暫的過程，所以在開泵停泵時會發(fā)生平衡盤與平衡板的摩擦，造成平衡盤和平衡板的磨損。尤其是在輸送有顆粒的臟的液體時，平衡盤和平衡板磨損更快。當平衡盤和平衡板的平面磨損后，bo間隙關(guān)不嚴，平衡盤不能及時打開，更加速了磨損，形成惡性循環(huán)，所以，當平衡盤、平衡板磨損后，應(yīng)及時給子修理或更換。渣漿泵廠家
Advantages of double suction impeller and single suction in slurry pump
The double suction impeller is composed of two symmetrical single suction impellers which are placed together, so that the two axial forces of the same size and opposite direction cancel each other. However, due to the different sealing clearance between the two sides and the improper impeller, there will be a small residual axial force, which needs to be borne by the bearing.
(2) in two-stage pump and multi-stage pump, the impeller can be arranged symmetrically to balance the axial force
As shown in figure 2-54, two impellers or a group of impellers are symmetrically installed back-to-back or face-to-face on a shaft to work in series. Although there is still axial force on a single impeller, for the whole rotor, the axial force is basically balanced, but due to the influence of clearance, there is still a certain amount of residual axial force, which requires the use of thrust bearing. This method is widely used in single suction two-stage Cantilever Pump and volute multi-stage pump. The volume loss of this method is very small, but the structure of the pump will be more complex.
(3) balance hole or balance pipe.
As shown in figure 2-55, a sealing ring with the diameter equal to that of the front cover plate sealing ring is installed on the rear cover plate of the impeller, and a balance hole is opened below the diameter of the rear cover plate sealing ring of the impeller, or a balance pipe is added to make the pressure below the rear cover plate sealing ring equal to that of the impeller
The pressure at the inlet is equal, which can balance most of the axial force, and the remaining axial force is very small.
The method of balancing the axial force of the balance hole and the balance pipe is very simple. Its disadvantage is that a part of the liquid flows back to the impeller inlet to increase the volume loss of the pump, and the leakage is larger after the seal ring is worn, so the seal ring should be repaired and replaced in time after it is worn. At the same time, the liquid flowing back from the balance hole impacts the liquid at the impeller inlet and causes hydraulic loss, so the efficiency of the pump will be slightly reduced.
(4) balance axial force of balance disk device
① working principle of balancing axial force of balancing disc device
The balance axial force of balance disc device is generally used for segmental multistage pump, as shown in Fig. 2-56. There is an inter radial gland B between the impeller hub (or shaft sleeve) and the pump body (or balance sleeve), and there is an axial clearance B between the balance plate and the pump body balance plate. The back of the balance plate is connected with the pump suction through the balance pipe.
In this way, the pressure before the radial clearance is the pressure P at the back of the impeller, which is the outlet pressure of the pump. The pressure Po behind the balance plate is the inlet pressure close to the pump. Due to the pressure difference of p-po, the liquid flows through the radial clearance B from the back of impeller to the front of balance plate, the pressure drops to P ", then flows through the axial chamber Bo to the back of balance plate, the pressure drops to Po, and finally returns to the inlet of pump through balance pipe.
On both sides of the balance plate, there is a pressure difference p '- Po, which produces a backward force, whose direction is exactly opposite to the axial force on the impeller, which is the balance force.
When the axial force on the impeller is greater than the balance force on the balance plate, the rotor of the pump is pushed forward, which reduces the axial clearance BG, increases the resistance of liquid flowing through the balance plate, and thus reduces the leakage Q. Due to the decrease of leakage, the resistance of liquid flowing through the radial clearance is reduced, the pressure drop is also reduced, and the pressure P 'in front of the balance plate is increased. As p 'rises, the pressure difference p' - Po increases, which increases the equilibrium force. The rotor moves forward continuously, and the balance force increases continuously. When it reaches a certain position, the balance force and the axial force are equal, and the balance is achieved. Similarly, when the axial force is less than the balance force, the rotor will move backward. After moving a certain distance, the axial force and balance force are balanced,
Since the operation point of the pump often changes, and the axial force often changes. In addition to the inertia force, the rotor will often move axially to achieve a new balance, so the balance axial force of the balance disk is dynamic, automatic and complete.
When balancing the axial force with the balance disk, the rotor often moves axially, so the pump bearing can not use the thrust bearing, but can move axially. Such as the use of sliding bearings, rolling bearings with cylindrical roller bearings, needle bearings, etc. If other rolling bearings cannot move axially, they shall be installed in a sleeve that can slide axially, and the sleeve can move axially. Because the rotor needs to move freely, it can not be used in vertical multistage pump.
The advantage of balancing axial force of balancing disc device is that it can balance axial force automatically and completely without residual axial force, but its disadvantage is that there is a certain amount of leakage back to the inlet of the pump, which increases the volume loss of the pump. At the same time, the balance plate needs a short process to balance the axial force, so the friction between the balance plate and the balance plate will occur when the pump is started and stopped, resulting in the wear of the balance plate and the balance plate. Especially when transporting dirty liquid with particles, the balance plate and balance plate wear faster. When the plane of balance plate and balance plate is worn, Bo gap is not closed tightly, balance plate cannot be opened in time, which accelerates wear and forms a vicious cycle. Therefore, when balance plate and balance plate are worn, repair or replace them in time. Slurry pump manufacturer
