Cause analysis of wear and scorching accidents in turbine thrust bearings

There are many reasons why a steam turbine’s thrust bearing can burn out: 1. Substandard lubricating oil, with water present in it or the oil being too dirty; 2. Insufficient amount of oil; 3. Inappropriate thrust clearance; 4. Blockage in the balance pipes, resulting in excessive axial force; 5. The steam turbine running out of control; 6. Problems with the thrust bearings themselves, such as inflexible rotation of the bearing elements, a weak babbitt layer, or abnormal thickness of the bearing elements; 7. Issues with the thrust plate, such as excessive end-face runout or insufficient surface finish of the thrust plate; 8. Problems that occur during installation

What was said on the 2nd floor covers it all pretty well. As a supplementary point, turbine surge as well as excessively high or low oil temperatures can both cause the thrust bearings to burn out.

There are issues with the rotor design, such as poor axial force balance, which causes the thrust bearings to become overloaded

It can be considered from three aspects: 1. There are defects in the manufacturing of the rotating parts, such as the rotor, thrust disc, bearings, etc. 2. It is related to installation issues such as inappropriate clearance of bearings, inadequate sealing clearance, and damage caused by improper installation. 3 is the increase in axial force caused by the operating process. There are many reasons for each specific aspect.

As a supplementary note: 1. Large fluctuations in the steam pressure of the nearby turbines cause the axial force to vary greatly. 2. The oil temperature remains excessively high. 3. Uneven heights of the thrust bearings can all lead to damage to the bearings

The last edit to this post was made by lucy751b on 2012-1-2 at 21:16. Reply to 2# 565026033: Another issue is related to the design – the diameter of the balance disk is too small, which results in low axial forces on both sides of the balance disk. As a consequence, the axial forces that can counteract each other are also low, leading to high axial forces on the rotor and excessive temperatures in the bearing shells

Thank you to all the moderators for their active participation! The discussion on the topic of \"Cause Analysis of Wear and Scorching Incidents in Turbine Thrust Bearings\" has been largely concluded. Based on the posts from various users, the main points can be summarized as follows: Analysis of the causes of wear and burnout in turbine thrust bearings. Causes of wear and burnout in thrust bearings: 1. Water impact: If there is water present in the steam, the speed of water is lower than that of the steam; this causes water droplets to block the blade passages and strike the back of the blades, generating a large thrust force that pushes the rotor backward. As a result, the tungsten alloy in the thrust bearing melts, leading to an accident ； 2. Salt deposition on the blades: Salt deposition on the blades reduces the flow area, increases the pressure in various sections of the flow path, raises the pressure difference across the blades, and increases the enthalpy drop. This leads to an increase in reactance, thereby resulting in an increased axial thrust and ultimately causing accidents ； 3. The steam seal gap of the partition is too large, or the gap at the joint of the partition is too large, resulting in severe steam leakage. This increases the pressure difference across the blades, leading to an increase in thrust and thus causing an accident ； 4. The oil is not clean; it has deteriorated, contains impurities, or has water in it ； 5. Low oil level: A low oil level in the tank, or poor oil quality that causes clogging of the filters, can lead to reduced oil delivery by the pump. When bubbles in the oil enter the thrust bearing, these air bubbles cannot withstand the thrust and burst, thereby destroying the oil film; this leads to friction between the thrust disc and the working pads, resulting in damage to the thrust bearing ； 6. Poor quality in the casting and installation of the thrust bearings; for example, impurities present in the tungsten alloy, uneven distribution of forces on the various thrust pads, and sticking of the thrust pads ； 7. The thrust disc is uneven or rough, or the tightening force on it is insufficient, causing it to become loose during rotation ； 8. Spherical jamming or excessive tension in the integrated thrust support bearing ； 9. A fault occurs in the oil supply to the bearings (such as the breakage of the positioning pin of the main bearing, which causes obstruction of the oil inlet holes), resulting in the destruction of the oil film ； 10. The balancing force that counteracts the axial thrust disappears or decreases ； 11. Restricted unit expansion: Uneven expansion leads to uneven loads on the various bearing pads of the thrust bearings, resulting in localized overloading and thus bearing pad burnout ； 12. When the unit suddenly loses load, an axial thrust in the opposite direction to the steam flow may occur, which can also lead to wear of the non-operating bearing pads of the turbine thrust bearing.

I have learned about it, but based on my own experience, I have encountered situations where improper selection of the lubrication method prevented heat from being removed in time, resulting in the bearing burning out!

In addition, it is necessary to check whether the steam seal of the rotor balance disk is worn; if wear leads to poor balancing, it can easily cause scratches on the thrust bearings； Additionally, dirty lubricating oil is also one of the common causes

Reply to 10# HarvestFarmer: “It is necessary to check whether the steam seal of the rotor balance disk is worn; if it is worn, the balance effect will be poor, which can easily lead to scratches on the thrust bearing.” This is a sentence from the original poster’s post. May I ask the original poster: Where is the steam seal of the balance disk? How can its wear affect the balancing effect, and how can it cause scratches on the thrust bearings?