Turbine compressor bearings are one of the frequently malfunctioning components and should be given sufficient attention in maintenance, installation, and operation. There are many types of faults, and common ones include frayed bearings, wear, and scratches; Bearing engagement, Babbitt alloy melting, and fatigue fracture of bearing shells. There are many reasons that can cause malfunctions, and the conditions are also different. Today, we will analyze some common causes of oil film sliding bearings.
1 Reasons for the fuel supply system
Insufficient or interrupted lubricating oil will cause an increase in bearing temperature, resulting in bearing biting and severe melting of Babbitt alloy. The reason for insufficient or interrupted oil supply may be: the main oil pump is damaged and the auxiliary oil pump fails to supply oil in a timely manner; Oil leakage or breakage of oil supply system pipelines and connecting flanges, and blockage of oil pipelines; The low oil level in the fuel tank causes the oil pump to have insufficient oil suction or unable to suck up oil.
Lubricating oil is not clean and contains foreign objects such as sand particles and impurities, which can cause scratches on the bearing shell and even increase the temperature of the bearing, leading to the melting of Babbitt alloy.
The lubricating oil cooler is malfunctioning, the inlet oil temperature is too high, the viscosity of the oil decreases, the heat of the bearing cannot be carried away in a timely manner, and a good oil film cannot be formed inside the bearing shell.
Lubricating oil contains water, causing damage to the oil film.
2. Reasons for the machine and bearings themselves
1) The vibration of the compressor rotor is caused by imbalance or excessive bearing vibration due to surge.
The bearing installation does not meet the requirements, the alignment is not good, and the clearance is not appropriate. For example, the installation of the thrust plate of the thrust bearing should be careful, and the end face deviation should not exceed the allowable value. If the end face deflection is too large and the load on the thrust block is uneven, it will greatly reduce the bearing capacity and may cause damage to the thrust bearing.
The quality of the Babbitt alloy casting for the bearing shell is not qualified, and the Babbitt alloy may have defects such as detachment, cracks, sand holes, etc., containing impurities such as iron filings and sand particles.
The bearing structure is unreasonable, and some components deform excessively during operation.
For thrust bearings, excessive axial thrust can cause tile burning accidents. The reasons for excessive axial thrust may be compressor overpressure, damage to wheel cover seals, inter stage seals, and balance disc seals.
From the reasons listed above, the normal operation of bearings depends not only on the quality of the bearing structure itself, manufacturing, installation, and maintenance, but also on changes in the operation of the compressor and the working condition of the oil supply system. Therefore, during maintenance, it is necessary to strictly comply with the maintenance process standards to ensure quality; During operation, special attention should be paid to monitoring the temperature of the bearing shell, lubricating oil temperature, axial displacement, and whether the oil supply system is working properly, whether the vibration of the bearings is too large, and whether there are any abnormal sounds. If there is any abnormality, it should be analyzed and judged immediately, effective measures should be taken to handle it, and accidents should be avoided.
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