Study on Anti-corrosion Methods Using Mechanical Seals for Slurry Pumps

Currently, mechanical seals are the most widely used sealing form in the chemical pump industry. Due to their advantages of low leakage and long lifespan, mechanical seals have become the main shaft sealing method in these equipment around the world.

Principles of mechanical seals for pumps:

Also known as end-face seals, mechanical seals are a type of sealing device used for rotating machinery shafts. They prevent fluid leakage by ensuring at least one pair of end faces perpendicular to the axis of rotation maintains contact and relative sliding under the pressure of the liquid and the elasticity of the compensation mechanism, as well as the assistance of the sealing element. The main function of mechanical seals is to convert vulnerable axial seals into relative end-face seals that are more difficult to leak. They are widely used in the sealing of rotating shafts in pumps, kettles, compressors, and similar equipment.

There are many types of mechanical seals for pumps, such as petrochemical pump seal and ceramic seals for pumps. Pump mechanical seals are generally composed of dynamic rings, static rings, compression elements, and sealing elements. The dynamic ring rotates with the pump shaft and tightly fits with the static ring to form a sealing surface, preventing media from leaking. The dynamic ring is pressed against the static ring face under the pressure of liquid in the seal chamber, generating appropriate pressure on the two-ring faces and maintaining a very thin layer of liquid film to achieve the sealing purpose. The compression element produces pressure and keeps the end faces tight when the pump is not running, ensuring that the sealing medium does not leak and preventing debris from entering the sealing end face.

The gap between the sealing dynamic ring and the shaft and the gap between the sealing static ring and the gland play a role in the sealing element while the elastic element buffers the vibration and impact of the pump. Mechanical seals are operated in combination with other parts of the pump, and their normal operation depends largely on their own performance, external conditions, and technical requirements for auxiliary sealing devices and the installation. Therefore, it is necessary to ensure the performance of their own parts, auxiliary sealing devices, and technical requirements for installation to achieve their intended effect.

Problems with the use of mechanical seals for pumps:

The parts of pump mechanical seals may experience failures during operation, such as wear, thermal cracking, deformation, breakage, spring relaxation, fracture, and corrosion. The auxiliary sealing ring may also crack, deform, break, or twist. It is vital to use high-quality components when constructing pump mechanical seals to ensure they operate smoothly and efficiently. Consider reaching out to reputable water pump mechanical seal suppliers to guarantee the quality of the parts used and to maximize the overall lifespan of the seals.

Common failures and reasons of mechanical seals:

Vibration and heat production of pump mechanical seals. During the rotation of the equipment, the roughness of the dynamic and static faces of the end-face seals may cause the clearance between the dynamic and static rings and the seal chamber to be too small, leading to oscillation and vibration as a result of collision. Sometimes poor resistance to corrosion and temperature, insufficient cooling, or the presence of particle impurities during installation may also cause vibration and heat in mechanical seals.

Leakage of mechanical seals. Leakage may occur during the static pressure test. Poor handling during installation may cause defects, deformation, damage, poor cleaning, or particle impurities on the sealing end face, or the loosening of positioning screws, inadequate compression of the gland or inadequate precision of the machinery, causing the sealing surface not to be fully mated, resulting in media leakage. If there is axial sleeve leakage, it may be caused by poor assembly, compression or damage of the axial sleeve seal ring.

Periodic or intermittent leakage. The periodic vibration of the rotor assembly or excessive axial movement may lead to leakage.

Frequent leakage of mechanical seals. Mechanical seal leakage is often caused by various factors: defects in the sealing end face, defects in the auxiliary sealing ring, or defects in the spring. Additionally, leakage may be caused by rotor vibration, poor quality or looseness of transmission, locking, and thrust parts.

Excessive vibration of pump mechanical seals may ultimately lead to a breakdown of the sealing effect. However, the cause of excessive vibration in mechanical seals is often not only related to the seals themselves, but also to other components of the pump.

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