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渣漿泵機(jī)械密封的工作原理  

機(jī)械密封是一種旋轉(zhuǎn)軸動(dòng)密封，其特點(diǎn)是動(dòng)密封面垂直于旋轉(zhuǎn)軸線.所以安裝時(shí)的對(duì)中非常重要。因設(shè)有由彈性元件、輔助密封圈等構(gòu)成的軸向磨損補(bǔ)償機(jī)構(gòu)，因此機(jī)械密封具有使用壽命長(zhǎng)久和密封性能良好的優(yōu)點(diǎn)。
    圖中A、B、C、D四個(gè)點(diǎn)是可能泄漏的點(diǎn)。其中B、C、D是靜密封點(diǎn),可以較容易地依靠密封圈的壓緊防止泄漏。較困難的，也是最主要的密封點(diǎn)是動(dòng)環(huán)與靜環(huán)之間A處的動(dòng)密封。由于介質(zhì)壓力和彈簧力的作用，使密封端面上有一定的壓緊力，在動(dòng)環(huán)與靜環(huán)的密封端面之間形成很小的間隙，并保持間隙內(nèi)有一層液膜，間隙很小，介質(zhì)通過(guò)時(shí)阻力很大,從而阻止了液體的泄漏;而液膜的存在又可潤(rùn)滑摩擦副，減輕磨損，保證了密封效果。動(dòng)、靜環(huán)是機(jī)械密封的核心部件，由于相對(duì)滑動(dòng)產(chǎn)生磨損并發(fā)熱，因此要求動(dòng)、靜環(huán)材料應(yīng)具有耐磨、高導(dǎo)熱性及其他必要的機(jī)械性能。最主要的是耐磨性，特別是在發(fā)生短期干摩擦情況下，必須具有良好工作的能力。通常材料選配時(shí)是動(dòng)、靜二環(huán)采用一硬一軟配對(duì)，只有在特殊情況下，例如渣漿泵介質(zhì)含固體顆粒時(shí)，才以硬對(duì)硬材料配對(duì)使用。國(guó)內(nèi)常用摩擦副材料有石墨、硬質(zhì)合金、陶瓷及青銅等。石墨較多用作靜環(huán)，為了克服氣孔率高、強(qiáng)度低的缺點(diǎn)，一般采用浸漬樹(shù)脂或金屬的石墨。 浸漬的樹(shù)脂有酚醛樹(shù)脂、吠喃樹(shù)脂、環(huán)氧樹(shù)脂等。浸漬的金屬有巴氏合金、青銅、鋁等。用作動(dòng)環(huán)的硬質(zhì)合金一般是碳化鎢,其特點(diǎn)是硬度和強(qiáng)度很高，具有良好的耐磨性與耐高溫性，線膨脹系數(shù)低，但是脆性大，容易碎裂，加工較困難。常用作動(dòng)環(huán)的陶瓷是氧化鋁陶瓷，其優(yōu)點(diǎn)是規(guī)度極高且耐磨,并特別耐腐蝕缺點(diǎn)是比較脆.容易產(chǎn)生熱裂。

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.