Oil seal is used to seal the rotating shaft in mechanical equipment, and the cavity is basically static, so the oil seal is also known as rotary shaft lip seal ring. The oil seal is mainly composed of sealing body, reinforced framework and self tightening spiral spring.

The function of each part is as follows:

1. Lip end

The lip end is a wedge shape, which acts as a sealing fluid by pressing the surface of the pressure shaft at the end.

2. Sealing lip

The sealing lip is a flexible elastic body, which can keep a stable sealing effect under the influence of mechanical vibration and pressure change of sealing fluid, and plays a role in maintaining the stable contact state between the lip and the shaft surface.

3. Dust lip

The dust lip is a secondary lip which is not connected with the spring to prevent dust invasion.

4. Cooperation Department

The matching part is to prevent the leakage and invasion of fluid from the contact surface between the outer shaft surface of the oil seal and the inner surface of the cavity while the oil seal is fixed in the cavity hole.

In addition, the spring can increase the compression force of the sealing lip to the shaft and maintain the compression force.

When the oil seal is fixed in the cavity, the metal framework plays the role of maintaining the combining force.

Since we have identified the name of each part, how can we check whether the oil seal is qualified?

1. Check the appearance quality. The surface of the framework oil seal must be smooth and clean, without burr, crack, bubble, missing angle and impurity embedding; the edge of the oil guard lip is sharp angle, without notch, burr and uneven phenomenon. The contact width between the lip and the shaft is generally 0.13-0.5mm, and the best width is 0.25mm; the adhesion between rubber and reinforcement ring shall be tight without looseness, deviation of reinforcement ring is not allowed, and no iron is exposed on the inner and outer surfaces; the convex characters on the oil seal plane shall be marked with "shaft diameter × outer diameter × height", manufacturer name and trademark, and the handwriting shall be clear.

2. Measure the size of oil seal with vernier caliper, and it is better to use scale plug gauge to check whether the tightness of combined gasket is appropriate. If the inner diameter of oil seal is greater than 30-90mm, the tolerance is - 1.0 - + 0.7mm; if the oil seal height is greater than 4mm, the tolerance is - 0.3 - + 0.40mm. According to the need and premise, the oil resistance function test can be carried out. The weight change should be - 3% ～ + 5% after soaking in 25 transmission oil at (70 ± 5) ℃ for 24h, and the weight change should not exceed + 20% when immersed in the mixture of 120 gasoline (75%) and benzene (25%) at (20 ± 5) ℃. According to the requirements of the manufacturer, the oil seal edge should be suitable with the matching journal. If it is too small, the service life of the oil seal will be affected, and if it is too small, the sealing function will be poor.

3. When the machine is working, the radial force of the oil seal lip to the shaft causes an oil film with a thickness of about 2.5mm between the interfaces, which is the essence of the framework oil seal