渣浆泵机械密封的种类
(1)按液体压力平衡情况分
    ①部分平衡型:如图5-7所示，能平衡一部分液体压力对端面的作用，端面比压随液体压力增高减慢增加，可改善端面磨损情况，一般液体压力大于0. 7MPa或密度小于700kg/m3润滑性较差的液体需采用部分平衡型机械密封。
    ②非平衡型:不能平衡液体压力对端面的作用，在液体压力较高时，容易引起摩擦副的快速磨损，所以一般用于压力小于0.7MPa润滑性较好液体中。
(2)按摩擦副对数分
    ①单端面密封:用一对摩擦副，结构简单、制造、拆装容易，用于一般液体中。

②双端面密封:如图5 -8所示，有两对背靠背摩擦副，密封腔内通入比介质压力高0.05~0. 15MPa的外供封液，起堵封和润滑密封端面的作用。其结构复杂，需要有一套外供封液系统。所以，常用于腐蚀、高温、液化气、带固体颗粒和纤维、润滑性能差、高结晶、易挥发、易燃、易爆、有毒和贵重等的特殊介质中。

(3)按弹簧置于介质内外分

①内装式:弹簧置于工作介质之内，介质压力能作用于密封端面上，密封效果好，弹簧力较小，但弹簧在介质中易腐蚀，在介质无腐蚀性情况下，一般都用内装式。
    ②外装式:如图5-9所示，弹簧置于工作介质之外，介质压力不作用在密封端面上，端面比压受介质压力影响较大，当介质压力波动时，影响密封可靠性，不易形成液膜，摩擦端面易磨损。适用于强腐蚀液体或易结晶的液体或黏稠的液体。
(4)按弹簧旋转或固定分
    ①旋转式:弹簧随轴旋转，易受离心力作用而变形，影响弹簀性能，但其结构简单，径向尺寸小。对轴径不很大，转速不高的场合(线速度<25m/s)一般都采用旋转式机械密封。
    ②静止式:如图5-10所示，弹簧在静环处，不随轴转动。弹簧性能稳定，对介质没有搅动，但结构复杂，所以常用于轴径较大，转速较高(线速>25m/s)的情况下。

5)按弹簧数量分

①单弹簧：即单个大弹簧，其缺点是端面比压不均匀，转速高时受离心力影响较大，轴颈不同需不同弹簧，所以规格多。轴向尺寸大，径向尺寸小，但安装维修简单，弹簧压缩量允差大。适用于泵转子窜动比较大的场合，要特别注意的是弹簧的旋向，应与转动方向越转越紧的方向。
    ②多弹簧：用多个小弹簧，端面比压均勾。弹簧规格少，与旋转方向无关，轴向尺寸小，径向尺寸大，安装繁琐，适用于轴径较大转速较高的泵中。
(6)按结构分
    ①流体静压密封:在两个密封环之一的密封端面上开有环形沟槽和小孔，从外部引入比介质压力稍大的液体，保证端面润滑，减少磨损，增加寿命，它需设置一套外供液体系统，泄漏量较大，只用于高压介质和高速情况下，往往与流体动压密封组合使用。
    ②流体动压密封:在两个密封环之一的密封端面开有各种沟槽，如图5-11所示，由于旋转而产生流体动力压力场，引入密封介质做为润滑剂，适用于高压介质和高速运转的场合，常与流体静压密封组合使用。
(7)按弹性元件分:
    ①弹簧压紧式:用弹簧压紧密封端面，制造简单，但由于受辅助密封圈面温的限制，使用在温度不高的场合。
    ②波纹管式:图5-12为金属波纹管的机械密封，它是用波纹管压紧密封端面。密封环( 动环或静环)和波纹管制成一个整体，中间没有辅助密封圈，使用温度不受辅助密封圈材料限制，所以金属波纹管机封可使用于高温情况下，对于四氟波纹管、橡胶波纹管机械密封可用于腐蚀性介质中。渣浆泵厂家

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