Structure and Function of End Thrust Bearing

Structure and Function of End Thrust Bearing

1. Structural composition of end thrust bearing

The structure of end thrust bearing is different according to its type, but its main components are basically the same, generally composed of thrust head, mirror plate, thrust pad, bearing seat, oil tank and oil cooler.

The thrust head is the mechanical part of the generator that bears the axial load and transmits the torque. It is usually fixed on the rotating shaft with a flat key and rotates with the shaft. The thrust head of the suspended generator is generally fixed on the upper end of the generator shaft by transition fit, and in the umbrella unit, it is also directly fixed on the hub or integral with the hub. The mirror plate is a rotating part fixed under the thrust head, which transmits the thrust load to the thrust pad, and is one of the key components of the thrust bearing. There is often an insulating pad between the joint surface of the mirror plate and the thrust head, which can be used to adjust the axis of the unit during installation. In recent years, some generators have canceled the mirror plate, and directly processed the required finish of the mirror plate on the end face of the thrust head.

Thrust pad is the static part of the enclosed thrust bearing and one of the main components of the enclosed thrust bearing. There are thermometer holes on the thrust pads for installing thermometers, which is convenient for operators to monitor the temperature of the bearing pads and alarm and trip when the temperature rises. Now there is a new type of fluoroplastic pad bearing, which has also been widely used. The bearing seat is a mechanism for supporting the bearing bush, through which it can adjust the height of the thrust pad, so that the force of each bearing pad is basically uniform; the oil groove is mainly used to store the lubricating oil for cooling and lubrication, and the entire end thrust bearing is installed in a closed oil groove. It can be a separate oil tank or a structure that shares an oil tank with the guide bearing. When the unit is running, the heat generated by the friction of the end thrust bearing is very large. Therefore, the lubricating oil in the oil tank not only plays a role of lubricating, but also plays a role of heat dissipation. The cooler absorbs the heat in the oil; the oil cooler cools the lubricating oil and cools the thrust bearing.

2. The role of end thrust bearing

The thrust bearing of the hydro-generator set is a sliding bearing that bears the weight of the rotating part of the entire hydro-generator set and the axial water thrust of the hydro-generator set. According to the theory of liquid lubrication, an oil film with a thickness of about 0.1mm will be established between the mirror plate and the thrust pad due to the rotating motion of the mirror plate, forming a good lubrication condition. At the same time, these forces are transmitted to the hydroelectric turbine through the thrust bearing The load frame of the machine and the foundation concrete. It is one of the components of the hydro-generator set.

An end thrust bearing with good performance should meet the following requirements: during the start-up process of the unit, an oil film can be quickly established; under various load conditions, the thickness of the oil film of the bearing can be maintained to ensure good lubrication; each thrust pad is stressed Uniform; the maximum temperature rise and average temperature rise of each thrust tile should meet the design requirements, and the temperature difference between the tiles is small; the circulating oil circuit is smooth and the air bubbles are few; the cooling effect is uniform and efficient; the sealing device is reasonable and effective; The deformation of the thrust pad is within the allowable range. When the above technical conditions are met, the end thrust bearing loss is low.