For some small and medium-sized hydropower stations, due to reasons of unit manufacturing, installation, and operation management, the guide bearings are prone to problems such as oil rejection, excessive temperature rise, unstable bearing temperature, and bush burning. So what should I do? The supplier of Hydraulic Turbine Generator China will tell you next.
The main reasons for the excessive temperature rise of the guide bearing, the instability of the tile temperature, or the burning of the tile are as follows.
1. The gap between the journal and bearing pad of the generator guide bearing is increased.
The increase in clearance may cause the oil film between the journal and the bearing pad to be damaged or produce dry friction in a short time, resulting in a sharp rise in bearing temperature. If the measures are not taken in time, the alloy on the surface of the bearing shell may melt, or the unit will accidentally stop due to the overheating protection of the guide bearing. Unit mechanical and electrical imbalances will increase unit support vibration. Therefore, once there is obvious vibration of the unit support, the cause of the unit support vibration should be checked in time and eliminated to prevent the gap between the journal and the bearing shell from increasing. In addition, check and adjust the bearing clearance regularly.
2. Defective bearing structure and poor oil circulation.
3. There is too much or too little lubricant between the journal and the bush.
Too much or too little lubricating oil flow between the journal and the bearing pad may also cause the bearing pad temperature to rise too high. The flow of lubricating oil is too small to take away the frictional heat between the journal and the bushes in time; while the flow of lubricating oil is too large, although the circulation speed of the oil is accelerated, the hot oil enters the oil return pipe and flows into the journal without sufficient cooling.
4. The generator stator and rotor gap are not uniform.
Due to installation defects, loose rotor poles, etc., the generator's stator and rotor gaps are uneven, which will also cause the generator guide bearing tile temperature to rise. The reason is that the generator stator and rotor gap will be uneven, which will produce asymmetric magnetic tension. The asymmetric magnetic pull force will aggravate the vibration of the unit on the one hand, and on the other hand, it will overload some bearing bushes of the guide bearing, causing the temperature of the bushes to rise sharply, especially Pelton Turbine.
5. Bearing current.
During the operation of a hydro-generator unit, sometimes there will be a current passing between the journal of the guide bearing and the bearing pad, and between the mirror plate and the thrust pad of the thrust bearing. This current is the bearing current (referred to as the shaft current). When the shaft current passes through the friction part, it is easy to produce arc sparks, which will increase the temperature of the tile, cause the friction surface to burn, and cause an accident.
Measures to prevent shaft current are:
(1) When designing, installing and overhauling the unit, avoid axial magnetic flux and magnetic flux asymmetry;
(2) Insulation shall be provided between the thrust bearing seat and the oil groove, the back of the bearing pad, and the supporting plate, and the screws or pins on these sections shall also be insulated;
(3) For the umbrella unit, the upper guide bearing must be insulated from the ground; for the suspension unit, the upper guide bearing and the thrust bearing must be insulated from the ground.
(4) The embedded thermometer of the bearing bush must be insulated from the ground.
The reasons for the overheating of the guide bearing, the high temperature rise, and even the burning of the bushes include: mismatched lubricants, deterioration of the lubricants, poor scraper quality, blockage of the cooler, and insufficient cooler capacity.
The above is the introduction from the Francis Turbine manufacturer, I hope to help everyone.