渣浆泵机械密封的工作原理  

机械密封是一种旋转轴动密封，其特点是动密封面垂直于旋转轴线.所以安装时的对中非常重要。因设有由弹性元件、辅助密封圈等构成的轴向磨损补偿机构，因此机械密封具有使用寿命长久和密封性能良好的优点。
    图中A、B、C、D四个点是可能泄漏的点。其中B、C、D是静密封点,可以较容易地依靠密封圈的压紧防止泄漏。较困难的，也是最主要的密封点是动环与静环之间A处的动密封。由于介质压力和弹簧力的作用，使密封端面上有一定的压紧力，在动环与静环的密封端面之间形成很小的间隙，并保持间隙内有一层液膜，间隙很小，介质通过时阻力很大,从而阻止了液体的泄漏;而液膜的存在又可润滑摩擦副，减轻磨损，保证了密封效果。动、静环是机械密封的核心部件，由于相对滑动产生磨损并发热，因此要求动、静环材料应具有耐磨、高导热性及其他必要的机械性能。最主要的是耐磨性，特别是在发生短期干摩擦情况下，必须具有良好工作的能力。通常材料选配时是动、静二环采用一硬一软配对，只有在特殊情况下，例如渣浆泵介质含固体颗粒时，才以硬对硬材料配对使用。国内常用摩擦副材料有石墨、硬质合金、陶瓷及青铜等。石墨较多用作静环，为了克服气孔率高、强度低的缺点，一般采用浸渍树脂或金属的石墨。 浸渍的树脂有酚醛树脂、吠喃树脂、环氧树脂等。浸渍的金属有巴氏合金、青铜、铝等。用作动环的硬质合金一般是碳化钨,其特点是硬度和强度很高，具有良好的耐磨性与耐高温性，线膨胀系数低，但是脆性大，容易碎裂，加工较困难。常用作动环的陶瓷是氧化铝陶瓷，其优点是规度极高且耐磨,并特别耐腐蚀缺点是比较脆.容易产生热裂。

Working principle of mechanical seal for slurry pump

Mechanical seal is a kind of rotating shaft dynamic seal, which is characterized by that the dynamic seal face is perpendicular to the rotating axis, so the centering during installation is very important. The mechanical seal has the advantages of long service life and good sealing performance due to the axial wear compensation mechanism composed of elastic elements, auxiliary sealing rings, etc.

Four points a, B, C and D in the figure are possible leakage points. Among them, B, C and D are static sealing points, which can easily rely on the compression of sealing ring to prevent leakage. The most difficult and important sealing point is the dynamic seal between the dynamic ring and the static ring. Due to the effect of medium pressure and spring force, there is a certain compression force on the sealing end face, forming a small gap between the sealing end face of the moving ring and the static ring, and keeping a layer of liquid film in the gap, the gap is very small, the resistance of medium passing through is very large, thus preventing the leakage of liquid; the existence of liquid film can lubricate the friction pair, reduce wear, and ensure the sealing effect. The dynamic and static rings are the core parts of mechanical seals. Due to the wear and heat generated by relative sliding, the materials of dynamic and static rings are required to have wear resistance, high thermal conductivity and other necessary mechanical properties. The most important is wear resistance, especially in the case of short-term dry friction, it must have good working ability. Generally, when selecting materials, the dynamic and static rings are matched with one hard one soft pair. Only in special cases, such as when the medium contains solid particles, can the hard pair be used. The common friction pair materials in China are graphite, cemented carbide, ceramics and bronze, etc. Graphite is mostly used as static ring. In order to overcome the shortcomings of high porosity and low strength, graphite impregnated with resin or metal is generally used. The impregnated resins include phenolic resin, barking resin, epoxy resin, etc. The impregnated metals are Babbitt, bronze, aluminum, etc. The cemented carbide used as the moving ring is generally tungsten carbide, which is characterized by high hardness and strength, good wear resistance and high temperature resistance, low coefficient of linear expansion, but it is brittle, easy to break and difficult to process. Alumina ceramics are commonly used as actuation rings, which have the advantages of high regularity and wear resistance, and especially corrosion resistance. They are brittle and prone to hot cracking.