Basic Knowledge of Sealing

The role of sealing:

1. Prevent internal leakage

2. Prevent external impurities from invading into the interior

3. Absorb impact energy

4. Noise reduction, heat insulation, (insulation)

Sealing is a measure taken to prevent fluid or solid particles from leaking between adjacent joint surfaces and prevent foreign impurities such as dust and moisture from intruding into the internal parts of the machine and equipment. At the same time, the mechanical equipment can maintain a good locking effect under long-term pulling and impact, and stop and reduce the external energy transmission. In short, auto wire seal is a measure taken to isolate the inside and outside.

Seal classification

According to the materials of the sealing pair, it is divided into hard seal: the two sides of the sealing pair are made of metal materials or other harder materials are called "hard seals"

Soft seal: The two sides of the sealing pair are made of metal materials on one side and elastic non-metallic materials on the other side, which is called "soft seal".

Seal classification

Static sealing:

There are three main categories: gasket seal, rubber seal, and direct contact seal. According to the working pressure, static sealing can be divided into medium and low-pressure static sealing and high-pressure static sealing (above 10MPa). Medium and low-pressure static seals are commonly used for gasket seals with softer materials and wider gaskets, while high-pressure static seals use metal gaskets with harder materials and narrow contact widths.

Auto Wire Seal

Dynamic seal:

It can be divided into two basic types: rotary seal and a reciprocating seal. According to whether the seal is in contact with its relative moving parts, it can be divided into contact seal and non-contact seal. The contact seal has good sealing performance, but is limited by friction, wear, and heat generation, and is only suitable for occasions where the linear velocity of the sealing surface is low. The non-contact seal has poor sealing performance and is suitable for higher speed occasions.

Non-contact seal: gas film, oil film, labyrinth, etc.

The performance of the sealing material is an important factor to ensure effective sealing. The selection of the sealing material is mainly based on the working environment of the sealing element: use temperature, working pressure, working medium used, and movement mode. The basic requirements for sealing materials are as follows:

1. Have certain mechanical properties, such as tensile strength, elongation, etc.;

2. Appropriate elasticity and hardness, small compression permanent deformation;

3. High temperature and low-temperature resistance, no decomposition and softening at high temperature, and no hardening at low temperature;

4. Compatible with the working medium, without swelling, decomposition, hardening, etc.;

5. Good oxygen resistance and aging resistance, durable;

6. Wear and corrosion resistance;

7. Easy to form and process, low price;

The sealing materials are usually rubber materials, and a few also use composite materials to make sealing elements.

Commonly used synthetic resin sealing materials:

Among the commonly used synthetic resins, the most used is polytetrafluoro Zene resin. Incorporating different filling materials into poly tetra fluoro Zene can improve and enhance its comprehensive physical and chemical properties, thereby expanding its scope of use. Therefore, the PTFE resin sealing material can be applied to the sealing of working media such as petroleum-based hydraulic oil, water-oil emulsion, water-ethanol-alcohol-based hydraulic fluid, and phosphate-based hydraulic fluid.

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