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渣漿泵機械密封的種類
(1)按液體壓力平衡情況分
①部分平衡型:如圖5-7所示，能平衡一部分液體壓力對端面的作用，端面比壓隨液體壓力增高減慢增加，可改善端面磨損情況，一般液體壓力大于0. 7MPa或密度小于700kg/m3潤滑性較差的液體需采用部分平衡型機械密封。
②非平衡型:不能平衡液體壓力對端面的作用，在液體壓力較高時，容易引起摩擦副的快速磨損，所以一般用于壓力小于0.7MPa潤滑性較好液體中。
(2)按摩擦副對數(shù)分
①單端面密封:用一對摩擦副，結構簡單、制造、拆裝容易，用于一般液體中。
②雙端面密封:如圖5 -8所示，有兩對背靠背摩擦副，密封腔內(nèi)通入比介質(zhì)壓力高0.05~0. 15MPa的外供封液，起堵封和潤滑密封端面的作用。其結構復雜，需要有一套外供封液系統(tǒng)。所以，常用于腐蝕、高溫、液化氣、帶固體顆粒和纖維、潤滑性能差、高結晶、易揮發(fā)、易燃、易爆、有毒和貴重等的特殊介質(zhì)中。
(3)按彈簧置于介質(zhì)內(nèi)外分
①內(nèi)裝式:彈簧置于工作介質(zhì)之內(nèi)，介質(zhì)壓力能作用于密封端面上，密封效果好，彈簧力較小，但彈簧在介質(zhì)中易腐蝕，在介質(zhì)無腐蝕性情況下，一般都用內(nèi)裝式。
②外裝式:如圖5-9所示，彈簧置于工作介質(zhì)之外，介質(zhì)壓力不作用在密封端面上，端面比壓受介質(zhì)壓力影響較大，當介質(zhì)壓力波動時，影響密封可靠性，不易形成液膜，摩擦端面易磨損。適用于強腐蝕液體或易結晶的液體或黏稠的液體。
(4)按彈簧旋轉或固定分
①旋轉式:彈簧隨軸旋轉，易受離心力作用而變形，影響彈簀性能，但其結構簡單，徑向尺寸小。對軸徑不很大，轉速不高的場合(線速度<25m/s)一般都采用旋轉式機械密封。
②靜止式:如圖5-10所示，彈簧在靜環(huán)處，不隨軸轉動。彈簧性能穩(wěn)定，對介質(zhì)沒有攪動，但結構復雜，所以常用于軸徑較大，轉速較高(線速>25m/s)的情況下。
5)按彈簧數(shù)量分
①單彈簧：即單個大彈簧，其缺點是端面比壓不均勻，轉速高時受離心力影響較大，軸頸不同需不同彈簧，所以規(guī)格多。軸向尺寸大，徑向尺寸小，但安裝維修簡單，彈簧壓縮量允差大。適用于泵轉子竄動比較大的場合，要特別注意的是彈簧的旋向，應與轉動方向越轉越緊的方向。
②多彈簧：用多個小彈簧，端面比壓均勾。彈簧規(guī)格少，與旋轉方向無關，軸向尺寸小，徑向尺寸大，安裝繁瑣，適用于軸徑較大轉速較高的泵中。
(6)按結構分
①流體靜壓密封:在兩個密封環(huán)之一的密封端面上開有環(huán)形溝槽和小孔，從外部引入比介質(zhì)壓力稍大的液體，保證端面潤滑，減少磨損，增加壽命，它需設置一套外供液體系統(tǒng)，泄漏量較大，只用于高壓介質(zhì)和高速情況下，往往與流體動壓密封組合使用。
②流體動壓密封:在兩個密封環(huán)之一的密封端面開有各種溝槽，如圖5-11所示，由于旋轉而產(chǎn)生流體動力壓力場，引入密封介質(zhì)做為潤滑劑，適用于高壓介質(zhì)和高速運轉的場合，常與流體靜壓密封組合使用。
(7)按彈性元件分:
①彈簧壓緊式:用彈簧壓緊密封端面，制造簡單，但由于受輔助密封圈面溫的限制，使用在溫度不高的場合。
②波紋管式:圖5-12為金屬波紋管的機械密封，它是用波紋管壓緊密封端面。密封環(huán)( 動環(huán)或靜環(huán))和波紋管制成一個整體，中間沒有輔助密封圈，使用溫度不受輔助密封圈材料限制，所以金屬波紋管機封可使用于高溫情況下，對于四氟波紋管、橡膠波紋管機械密封可用于腐蝕性介質(zhì)中。渣漿泵廠家
Type of mechanical seal
(1) according to the liquid pressure balance
① partially balanced type: as shown in Fig. 5-7, it can balance the effect of part of liquid pressure on the end face. The specific pressure of the end face increases slowly with the increase of liquid pressure, which can improve the wear condition of the end face. Generally, the liquid pressure is greater than 0.7MPa or the density is less than 700kg / m3, and the partially balanced mechanical seal is required.
② non balanced type: it can not balance the effect of liquid pressure on the end face. When the liquid pressure is high, it is easy to cause rapid wear of friction pairs, so it is generally used in the liquid with better lubricity and pressure less than 0.7MPa.
(2) logarithm of massage pairs
① single face seal: with a pair of friction pairs, it is simple in structure, easy to manufacture and disassemble, and used in general liquid.
② double end face seal: as shown in Figure 5-8, there are two pairs of back-to-back friction pairs. The sealing cavity is filled with external sealing fluid 0.05 ~ 0.15Mpa higher than the medium pressure, which plays the role of sealing and lubricating the sealing end face. Because of its complex structure, a set of external sealing liquid supply system is needed. Therefore, it is often used in special media such as corrosion, high temperature, liquefied gas, with solid particles and fibers, poor lubrication performance, high crystallization, volatile, flammable, explosive, toxic and precious.
(3) place the spring inside and outside the medium
① built in type: the spring is placed in the working medium, the medium pressure can act on the sealing end face, the sealing effect is good, the spring force is small, but the spring is easy to corrode in the medium, in the case of no corrosiveness of the medium, the built-in type is generally used.
② external mounting type: as shown in Figure 5-9, the spring is placed outside the working medium, and the medium pressure does not act on the sealing end face. The specific pressure of the end face is greatly affected by the medium pressure. When the medium pressure fluctuates, the sealing reliability is affected, and the liquid film is not easy to form, and the friction end face is easy to wear. It is suitable for strong corrosive liquid or easily crystallized liquid or viscous liquid.
(4) rotate or fix by spring
(1) rotary type: the spring rotates with the shaft and is easily deformed by centrifugal force, which affects the performance of elastic sheath, but its structure is simple and its radial dimension is small. Rotary mechanical seal is generally used in the case of small shaft diameter and low rotation speed (linear speed < 25m / s).
② static type: as shown in figure 5-10, the spring is at the static ring and does not rotate with the shaft. The spring has stable performance and no agitation to the medium, but its structure is complex, so it is often used in the case of large shaft diameter and high speed (line speed > 25m / s).
5) according to the number of springs
① single spring: that is, a single large spring. Its disadvantage is that the specific pressure of the end face is not uniform. When the rotating speed is high, it is greatly affected by centrifugal force. Different springs are required for different journal, so there are many specifications. The axial dimension is large, the radial dimension is small, but the installation and maintenance are simple, and the spring compression tolerance is large. It is suitable for the occasion of large displacement of pump rotor. Pay special attention to the rotation direction of spring, which should be more and more tight with the rotation direction.
② multiple springs: multiple small springs are used, and the end face is evenly connected with specific pressure. It is suitable for pumps with larger shaft diameter and higher speed.
(6) by structure
① hydrostatic seal: a ring groove and a small hole are opened on the sealing end face of one of the two sealing rings to introduce a liquid slightly higher than the medium pressure from the outside, so as to ensure the lubrication of the end face, reduce wear and increase service life. It needs to be equipped with a set of external liquid supply system, with a large amount of leakage, which is only used in high-pressure medium and high-speed situations, and is often combined with hydrodynamic seal.
② hydrodynamic seal: there are various grooves on the sealing end face of one of the two sealing rings, as shown in Figure 5-11. The hydrodynamic pressure field is generated due to rotation, and the sealing medium is introduced as lubricant, which is suitable for high-pressure medium and high-speed operation, and is often combined with hydrostatic seal.
(7) according to elastic elements:
① spring compression type: the seal face is compressed by spring, which is simple to manufacture. However, due to the limitation of the surface temperature of the auxiliary seal ring, it is used in the situation of low temperature.
② bellows type: figure 5-12 shows the mechanical seal of metal bellows, which uses bellows to compress the seal end face. The seal ring (moving ring or static ring) and the bellows are integrated. There is no auxiliary seal ring in the middle, and the service temperature is not limited by the auxiliary seal ring material. Therefore, the mechanical seal of metal bellows can be used in the case of high temperature, and the mechanical seal of Teflon bellows and rubber bellows can be used in the corrosive medium. Slurry pump manufacturer
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