What is a sealed bearing, bearing seal type

 

The so-called sealed bearing is a dust-proof bearing, so that the bearing is sealed well to keep the bearing smooth conditions and normal working environment, give full play to the function of the bearing, prolong the service life of the bearing, and have a suitable seal for the rolling bearing to avoid the leakage of the smoothing agent and the invasion of dust, water vapor or other dirt. This is conducive to the protection of the bearing.

 

Bearing Seal Type:

The sealing device structure of rolling bearings is mainly divided into contact seals and non-contact seals.

 

Non-contact sealing of bearings

 

Bearing non-contact sealing is a sealing method that designs a small gap between the shaft and the end cover of the bearing housing. This type of sealing structure does not contact the shaft, so there is no friction and wear, and it is suitable for high-speed rotation. To enhance the sealing effect, the gap can be filled with grease. Bearing non-contact seals mainly include: gap seal, oil groove seal, labyrinth seal, oil slinger seal, etc.

 

1. Gap sealing

The gap seal is to leave a small annular gap between the shaft and the bearing cover through hole, the radius gap is 0.1-0.3mm, the longer the gap is smaller and smaller, the better the sealing effect.

 

2. Oil groove sealing

 

The oil groove seal is processed with an annular oil groove at the journal of the inner cavity of the bearing seal end cover, and the oil guide groove is radially distributed, and each annular oil communicates through the oil guide groove and communicates with the oil tank, and the number of annular oil groove and oil guide groove is determined by the size of the seal end cover.

 

3. Labyrinth sealing

The basic principle of this sealing is to create a flow channel at the seal with great flow resistance. Structurally, a small tortuous gap is formed between the stationary part and the rotating part to form a "labyrinth".

 

4. Oil slinger sealing

 

Contact seals for bearings

Contact sealing is the sealing method of the end or lip contact shaft of vulcanized synthetic rubber on the steel skeleton, and its sealing performance is better than that of non-contact sealing, but the friction is huge, and the temperature rise is relatively high. The contact zone of the shaft and seal needs to be lubricated, usually with the same lubricant as the bearing. Contact seals mainly include: felt ring sealing, leather bowl sealing, sealing ring sealing, skeleton sealing, sealing ring sealing, etc.

 

1. Felt ring sealing

A trapezoidal groove is opened on the bearing cover, and the fine felt of the rectangular part is placed in the trapezoidal groove to contact with the shaft, or the gland is pressed axially to make the felt ring compressed and generate radial pressure to hold it on the shaft, so as to achieve the purpose of sealing.

 

2.The leather bowl is sealed

 

A sealed leather bowl (made of materials such as oil-drawn rubber) is placed in the bearing cover and pressed directly against the shaft. In order to enhance the sealing effect, a ring coil spring is pressed on the inner ring of the leather bowl, so that the inner ring of the leather bowl has a tighter fit with the shaft.

 

3. The sealing ring is sealed

Seals are often made of leather, plastic or oil-resistant rubber and can be made in different profiles as required. The 0-shaped sealing ring has a circular profile, relying on its own elastic force to press on the shaft, with simple structure and easy assembly and disassembly. J-shaped and U-shaped seals are also commonly used, both of which have a lip-shaped structure.

 

4. Skeleton sealing

 

In order to improve the overall strength of the leather bowl seal, the metal lining with an L-shaped cross-section and an annular shape is installed in the oil-resistant rubber, so that the leather bowl seal is not easy to deform, and the service life is improvedIn the case of <7m/s, most of the centrifugal pump bearing boxes are currently sealed with skeleton.

 

5. Sealing ring sealing

This is a kind of annular seal with a notch, it is placed in the ring groove of the sleeve, the sleeve rotates together with the shaft, and the sealing ring is pressed against the inner hole wall of the stationary part by the elasticity that the notch is pressed, and it can play a sealing role, and this kind of sealing is more complicated.

 

Selection of bearing seal structure

 

When choosing a bearing seal structure, the main factors to consider are: lubricant, that is, whether it is oil or grease; Linear velocity of sealing parts; installation error of the shaft; The size and cost of the installation space, etc.