Mechanical seals and hydraulic seals differ significantly in several aspects. The main differences between them are as follows:

1. Working Principles

• Mechanical seals: They mainly rely on the fluid pressure perpendicular to the end face of the rotating axis, the elastic force (or magnetic force) of the compensation mechanism, and the cooperation of auxiliary seals to keep the end faces attached and slide relatively, thereby preventing fluid leakage.

• Hydraulic seals: They achieve a sealing effect through local deformation of the sealing element. For example, a rotary shaft lip seal utilizes the combination of an elastic diaphragm with a lip shape and a metal skeleton. The sealing lip is usually energized by a spring to make it fit tightly against the shaft surface and prevent fluid leakage.

2. Application Scenarios

• Mechanical seals: They are typically used in rotating fluid machinery such as pumps, compressors, and reaction agitators, as well as in seals for gearboxes and ship propeller shafts. They are suitable for various complex working conditions, including high speed, high pressure, high temperature, low temperature, strong corrosion, and presence of solid particles.

• Hydraulic seals: They are mainly applied in hydraulic transmission systems, such as oil cylinders, pumps, and motors. Their primary function is to prevent oil leakage from the sealing gap and block external dust, impurities, and other contaminants from entering the hydraulic transmission system.

3. Structure and Materials

• Mechanical seals: They have a relatively complex structure, consisting of components such as a stationary ring, a rotating ring, and auxiliary sealing rings. The materials used must possess excellent wear resistance, corrosion resistance, and high-temperature resistance, such as silicon carbide, tungsten carbide, and stainless steel.

• Hydraulic seals: They have a relatively simple structure, mainly composed of sealing elements and sealing grooves. Their materials are mostly elastic materials like rubber and polyurethane, which can adapt to changes in pressure and temperature in the hydraulic system.

4. Sealing Performance

• Mechanical seals: They offer advantages such as minimal leakage, stable sealing performance, and long service life. They can maintain good sealing effects under various complex working conditions, ensuring the normal operation of equipment.

• Hydraulic seals: Their sealing performance is relatively inferior and easily affected by factors such as temperature, pressure, and medium. Therefore, when selecting hydraulic seals, appropriate types must be chosen based on specific application scenarios and requirements.

In summary, mechanical seals and hydraulic seals differ significantly in terms of working principles, application scenarios, structure and materials, and sealing performance. When choosing a sealing method, a comprehensive consideration of specific application scenarios and requirements is necessary.