Exploration of Common Faults and Countermeasures of Rolling Bearing for Railway Vehicles

Abstract: This article analyzes the reasons for bearing running out of the inner ring during installation and operation of water pumps, and the methods for handling bearing running out of the inner ring.

Keywords: water pump; Running within the inner circle; repair

 

A water pump is a machine that lifts and transports liquids. It converts the mechanical energy of the prime mover into the potential energy of the transported liquid. The pump shaft is an important component of the water pump, supporting all the parts that are mounted on the shaft. The pump shaft is equipped with bearings at both ends, which support the components of the shaft and bear radial or axial loads. The running of the inner ring of the bearing refers to the relative movement between the inner ring of the bearing and the shaft. When the running of the inner ring of the bearing is severe, mechanical jamming may occur, causing damage to the water pump and even burning out the motor. Therefore, in the installation, adjustment, operation, and maintenance of water pumps, great attention is paid to the problem of running the inner ring of the water pump. From the perspective of use, this article analyzes the reasons and treatment methods for bearing running the inner ring.

 

1. Reasons for running the inner ring of the bearing

1.1 Bearings and shafts use the same interference tolerance under different loads. The interference fit of the bearing is insufficient. The small tolerance load results in the friction between the bearing and the pump shaft neck, causing the bearing to run out of the inner ring.

The secondary impeller on the back of the 1.2 impeller is damaged, causing axial force and turning into an inner ring.

The axial fixing method of the bearing is unreasonable, which results in the inner ring only increasing in the diameter direction during the operation of the bearing.

The material selection for the 1.4 axis is unreasonable, and the bearing manufacturer is not legitimate.

The inner ring of the 1.5 bearing is not tightened axially with the shaft shoulder (locking nut, shaft end retaining ring).

 

2. Treatment of the inner race of the bearing

In order to prevent and reduce the phenomenon of bearing running out of the inner ring, before assembling the bearing, first check whether the tolerance requirements of the shaft are met, and then check whether the tolerance of the inner ring of the bearing is within the range specified by the national standard. Otherwise, replace it with a new bearing. If the inner ring of the bearing is worn on the shaft shoulder (lock nut, shaft end retaining ring), according to the wear situation, a pad can be added between the contact surfaces to achieve axial fixation. When adding the pad, attention should be paid to the assembly size. If there is an error in assembly, it must be reassembled. The inner race of the bearing mainly deals with the journal, and the specific method is as follows:

The simple and quick method for 2.1Z is:

(1) Use a sharp chisel to evenly chisel small pits on the shaft. Or use strong adhesive to stick a thin layer of metal skin on the shaft. These two methods cannot guarantee the service life.

(2) Using bearing locking adhesive is convenient and practical. When disassembling, simply heat the bearing, but the wear clearance should not be too large. This method ensures a long service life. The above methods can be used when the requirements are not very high, and the shaft should be replaced when the requirements are high.

 

2.2 Nickel brushed repair method.

Use organic solvents such as acetone and a polishing machine to remove the oxide scale, oil stains, paint and other dirt on the surface of the shaft neck. Then, clamp the metal nickel strip or block on the welding tongs of the electric welding machine as an electrode, and slide it uniformly on the shaft neck. The metal nickel produces explosive bubbles, which firmly melt on the surface of the shaft neck, forming an irregular, rough and porous nickel solution coating. Finally, turn it on a lathe to the specified size. This repair process is more suitable for pump shafts using rolling bearings and not suitable for pump shafts using sliding bearings.

 

2.3 Weld a layer of metal on the surface of the shaft neck, and then process it to restore the original size. This repair process is more suitable for severe neck injuries.

 

2.4 Thermal spraying (spray coating) repair method

Aerobic acetylene flame spraying is widely used in thermal spraying. Oxygen acetylene flame spraying is achieved through an oxygen acetylene flame spray gun. The spray gun introduces acetylene (which can also be gas), oxygen, or compressed air through a gas valve. Acetylene and oxygen mix to produce a combustion flame at the nozzle outlet. The introduced metal coating material is heated and melted in the flame, forming mist like small droplets under the action of the flame flow, which are sprayed onto the surface of the shaft neck to form a coating. The two linear coatings used in arc spraying are automatically introduced by the wire feeding wheel. When a large current is passed between the two linear coatings, an arc is generated. The linear coatings quickly melt under the high temperature of the arc and are compressed into small droplets by compressed air, which are sprayed onto the surface of the shaft neck to form a coating layer. The thermal spray repair process is introduced as follows.

 

(1) Surface pretreatment

The surface of the treated journal can be further activated by methods such as organic solvent cleaning, heat degreasing, threading, rolling, and electric pulling to improve the bonding strength between the coating and the journal surface. For some coating materials that do not bond well with the pump shaft, nickel based materials can be sprayed on the surface of the shaft neck as the bonding substrate first.

(2) Preheating

The purpose is to eliminate moisture and dampness on the surface of the journal, increase the interface temperature between the sprayed particles and the journal surface, improve the bonding strength between the coating and the journal, and reduce the cracking of the coating caused by the thermal expansion difference between the pump material and the coating material. The preheating temperature is generally controlled between 60-120 ℃.

(3) The spraying method used mainly depends on the selected spraying material (such as self melting welding powder, stainless steel), the working conditions of the workpiece (such as self weight, speed), and the requirements for coating quality. When spraying, pay attention to the rotation speed of the pump shaft, the movement speed of the spray gun, the spraying distance, and the air pressure of the spraying.

(4) Post spray treatment

After spraying, the rear axle neck should be treated with oil leakage to allow more lubricating oil to penetrate the coating, making it easier for turning processing. After the oil leakage treatment, the pump shaft is machined on a lathe to achieve the required journal size and smoothness. After Z, roll with a rolling cutter or grind with grinding paste to improve the smoothness of the journal surface.

 

2.5 Sleeve repair method

The shaft sleeve is generally made by rolling stainless steel plates or iron plates, or by turning castings. Insert the whole set. The integral sleeve is suitable for situations where one end of the shaft is smaller than the inner diameter of the shaft sleeve. After fitting the shaft sleeve and pump shaft machining parts, heat the shaft sleeve in engine oil. After the shaft sleeve expands due to heat, insert it into the pump shaft from one end of the shaft while it is still hot. After cooling, tighten the shaft sleeve around the main shaft, and then turn the shaft neck to the specified size and smoothness.

 

2.6 Spot welding repair method

Draw four straight lines evenly on the surface of the shaft neck in the axial direction, and use electric welding to spot a welding point every 1 centimeter on the four straight lines. Use a hand file to evenly file the height of the welding point. When installing old bearings, in order to facilitate work, a ring must be prepared, and equal pressure must be applied on the circumference of the ring end face to evenly press the bearing in through the sleeve. In the case of small interference fit, a sleeve can be used to press the end face of the bearing ring at room temperature, and the sleeve can be hammered with a hammer to evenly press the ring through the sleeve. When the interference fit is large, the oil bath heating bearing method can be used for installation, with a heating temperature range of 80-100 ℃ and a Z-height not exceeding 120 ℃. This method of repairing the shaft neck is relatively simple and ensures its service life. We use this method more frequently in our work.

 

3. Summary

Running the inner ring of the bearing is a common problem that occurs during the operation of the water pump. It is difficult to distinguish the inner race of the bearing during operation by checking the sound, temperature, and vibration of the bearing. Therefore, to prevent and correct the phenomenon of bearing running out of the inner ring, we need to strengthen inspections, master the rules of pump bearing running out of the inner ring, and conduct disassembly inspections if necessary. Ensure that the water pump is working properly.

 

2024 October 2nd Week VAFEM Product Recommendation:

Linear Motion Guide-LM Guide

A linear-motion bearing or linear slide is a bearing designed to provide free motion in one direction. There are many different types of linear motion bearings. Motorized linear slides such as machine slides, X-Y tables, roller tables and some dovetail slides are bearings moved by drive mechanisms. Not all linear slides are motorized, and non-motorized dovetail slides, ball bearing slides and roller slides provide low-friction linear movement for equipment powered by inertia or by hand. All linear slides provide linear motion based on bearings, whether they are ball bearings, dovetail bearings, linear roller bearings, magnetic or fluid bearings. X-Y tables, linear stages, machine slides and other advanced slides use linear motion bearings to provide movement along both X and Y multiple axis.

 

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2024-10-15

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