The maintenance methods for seven types of tapered roller bearings (i.e. double row tapered roller bearings) need to revolve around lubrication management, installation adjustment, operation monitoring, environmental protection, and special working condition response. The following are specific instructions:
1. Lubrication Management
Lubricant Selection:
The lubrication method is determined based on the speed coefficient dn value (bearing inner diameter mm × speed r/min). When the dn value is less than 300000, grease lubrication is applicable, and when it is greater than 300000, oil lubrication is required. Lubricating grease containing MoS2 or extreme pressure additives (EP) should be selected for heavy-duty conditions, such as ISO L-XBCHB2 grade products, whose base oil viscosity should not be less than 100mm ²/s at 40 ℃.
Lubrication cycle:
The grease lubrication replenishment cycle can be estimated according to the formula T=10 ⁶/(60n √ d) (T is in hours, n is the speed r/min, and d is the bearing inner diameter mm).
. In practical applications, the lubrication interval should be shortened by 30% -50% in high-temperature environments.The amount of grease injection should be strictly controlled. Overfilling can cause stirring and heating. Generally, it is advisable to fill 1/3-1/2 of the internal space of the bearing.
. When using an automatic lubrication system, it is recommended to set the grease injection to 0.5-2cm ³ each time, with an interval of 4-8 hours.Lubricating oil monitoring:
Regularly take samples to detect changes in oil viscosity (should not exceed the initial value ± 15%), moisture content (<0.1%), and particle contamination (below ISO 4406 standard 18/16/13 levels).
. When abnormalities are found, the lubricating oil should be replaced immediately and the sealing system should be checked. The use of online oil monitoring sensors can real-time monitor the lubrication status and prevent bearing damage caused by lubrication failure.II. Installation and Adjustment
Preparation before installation:
The bearings need to be stored in their original packaging and can only be opened one hour before installation.
. The surface needs to be cleaned and inspected with gasoline. The roundness error of the journal should be ≤ 0.005mm, and the surface roughness Ra should be ≤ 0.8 μ m. When using oil bath heating installation, the heating temperature should be controlled at 80-100 ℃ (not exceeding 120 ℃), and the heating time should be calculated based on the bearing mass of 1.5 minutes per kilogram.Clearance adjustment:
Conical roller bearings need to maintain an appropriate working clearance, usually 0.05-0.10mm. If it is too small, it will cause excessive pre tightening and high temperature, and if it is too large, it will reduce system rigidity.
.Adjustment methods include measuring axial play (which should be 2-3 times the clearance value), torque method (suitable pre tightening when the rotational torque suddenly increases by 20%), or direct measurement with an ultrasonic feeler gauge.
.Anti micro corrosion:
In working conditions where micro vibrations may occur (such as fan gearboxes), it is recommended to use H7/k6 transition fit for the fit between the shaft and the bearing inner ring, and the fitting surface can be coated with molybdenum disulfide anti creep coating.
. The tightening torque of the locking nut must be strictly executed according to the standard, and effective anti loosening measures should be taken, such as double nuts and stop washers.III. Operation Monitoring and Status Diagnosis
Vibration Analysis:
Install vibration sensors in the vertical, horizontal, and axial directions of the bearing seat, with a sampling frequency of at least 10 times the characteristic frequency of the bearing fault.
. Focus on the acceleration envelope value in the high-frequency range (5-10kHz). When bearing fault characteristic frequencies (such as BPFO, BPFI, etc.) and their harmonics appear, it indicates early damage has occurred.Temperature monitoring:
The normal operating temperature should be below 90 ℃, and the temperature rise should not exceed the ambient temperature+40 ℃.
. The infrared thermal imager can detect abnormal hotspots, and a temperature gradient>15 ℃ indicates the possibility of poor lubrication or alignment issues. The intelligent bearing unit can integrate a PT100 temperature sensor to achieve real-time monitoring with an accuracy of ± 1 ℃.Oil abrasive particle analysis:
Regularly take samples for iron spectrum analysis. During normal operation, the abrasive particles should be<50 μ m and have a regular shape.
. The appearance of flake like abrasive particles or a large amount of oxides larger than 100 μ m indicates that the bearing has entered an abnormal wear stage.Online particle counters can monitor the number of particles>25 μ m in oil in real time, and sudden growth is often a precursor to faults.
.IV. Environmental and Special Working Condition Protection
Pollution Environmental Protection:
In dusty environments such as cement and mining, bearing units with triple lip seals (such as SKF's VA405 design) should be selected.
. The sealing material should be selected according to the medium: NBR rubber is generally used for dust, and FKM fluororubber is used for chemical corrosion environments. Intermittent operation equipment maintenance: For equipment that has been out of service for a long time, manually rotate it at least 2-3 times a month to prevent static corrosion of the raceway. Before reactivation, the lubricating grease should be replaced, and the first run requires a low-speed break in for 30 minutes.Precautions for high-speed working conditions:
When the dn value is greater than or equal to 1000000, light series bearings should be used and the clearance should be strictly controlled (C2 group is recommended).
. The retaining frame should be made of high-strength polymer materials (such as PEEK), and the lubricating oil should have good high-temperature stability (such as poly (alpha olefin) synthetic oil).