Gearbox acceptance criteria:
Visual inspection;
No-load and temperature rise tests;
Bearing clearance test;
Measurement and testing of box vibration;
Measurement test of shaft vibration displacement;
Installation and adjustment requirements;
Routine inspection and maintenance of the gearbox.
1. Visual inspection
1. Visual inspection is required. The appearance should be glossy, the paint should be evenly applied, and the joints should be intact. The end caps, top and bottom caps, and other studs should be complete. A nameplate should be affixed, and the information on the nameplate should be clear and correct.
2. No gaskets are allowed between the split surfaces of the enclosure, but sealant or water glass can be applied to ensure a seal.
3. During assembly, before tightening the box bolts, a 0.05mm feeler gauge should be used to check the sealing between the box cover and the box base mating surfaces;
4. Lubricating grease should be applied to the shaft extension seal. All sealing devices of the reducer should be installed strictly according to requirements.
2. No-load and temperature rise test
Add clean lubricating oil to the specified quantity and conduct a no-load test run in both forward and reverse directions at the rated speed. The test run should last for more than half an hour and should meet the following requirements:
1. All connecting parts and fasteners must be secure.
2. There shall be no oil leakage or seepage at any sealing or joint.
3. The reducer should operate in a balanced and normal manner, without any impact, vibration, or abnormal noise.
4. The oil pump is working normally and the oil circuit is unobstructed.
After the reducer passes the no-load test run, it should be subjected to a load test run. The load should be applied gradually at the rated speed in four stages: 25%, 50%, 75%, and 100% of the reducer's rated load. The running time for each stage should be determined by the stabilization of the lubricating oil temperature, and the oil temperature should not exceed 100℃ after 3 hours of continuous operation. If the reducer has its own cooling system, the oil temperature should not exceed 90℃.
3. Bearing clearance test
When adjusting the differential bearing clearance, a gauge can be used to measure the differential's axial momentum. The clearance allowance can be referenced from the relevant national or ministerial standards issued by the Ministry of Transport in recent years. If neither testing equipment nor reference data is available, the following methods can be used to adjust the bearing clearance:
First, tighten the differential bearing adjusting nut in opposite directions until the differential bearing cannot rotate, or add sufficient washers to the bottom of the thrust surface of the semi-floating rear axle housing differential bearing to prevent the differential bearing from rotating. Then, gradually remove or loosen the shims using 0.05-0.08 mm thin shims, allowing the differential to rotate freely in its position. Ideally, it should rotate 1-2 turns per hand rotation. However, it is crucial to ensure that the bearing clearance is based on the differential bearing cap or the semi-floating rear axle housing after tightening. If the bearing clearance changes after tightening the differential bearing cap after adjusting the nut, and the bearing cannot rotate, this is because the bearing outer sleeve is under pressure from the bearing cap.
Besides severe lack of lubrication, differential housing deformation, and bearing journal misalignment, the main cause of differential bearing wear is improper bearing clearance adjustment. When the bearing clearance is too large, the bearing play will increase, leading to accelerated wear of the transmission components. When the bearing clearance is too small, the bearing friction resistance is high, and the bearing housing cannot adequately support the bearing cap (meaning that after the bearing cap bolts are tightened, the bearing outer race cannot shrink or deform), and the bearing outer race cannot move within the bearing cap. High temperatures are generated during transmission; under poor lubrication and heat dissipation conditions, the bearing will burn out. Even under relatively good lubrication and heat dissipation conditions, the roller surface will still be damaged (commonly known as bearing wear).
In summary, adjusting the differential bearing clearance during warranty maintenance is key to extending the bearing's lifespan, so caution should be exercised when adjusting the bearing clearance and timely maintenance is essential.
4. Measurement and testing of box vibration
Measuring the vibration at the bearing housing yields the vibration intensity value at the measuring point. Since the measured vibration value is an absolute quantity, the support structure for the test should ideally be considered a fixed foundation structure. During the test, resonance of the support structure must be avoided, at least within the test speed range. The measured vibration intensity is a function of the dynamic coupling between the rotating parts of the gear assembly and the support housing. Coupling is very direct when using rolling bearings; when using sliding bearings, shaft vibration is more or less suppressed due to the damping effect of the oil film. Sliding bearings are significantly affected by speed, torque, load, and lubricating oil; the influence of these varying factors must be considered when evaluating the vibration intensity of the bearing housing. Vibrations (generally caused by imbalance and eccentricity) may not be strongly transmitted to the bearing housing of the gear assembly, but under heavy load conditions, the intensity of these transmitted vibrations can be very high. Furthermore, high-frequency vibrations caused by gear meshing are also strongly transmitted to the bearing housing and dominate the measured housing vibration signal.
When measuring the vibration of the housing, a velocity sensor or accelerometer can be used. The linear range of the velocity sensor depends on its type, generally ranging from 10 to 2500 Hz. When the frequency is lower than the meshing frequency of the gear teeth in a high-speed gear unit, an accelerometer with a measurement range of not less than 10 kHz should be used. The instrument needs to be adjusted during use. When converting the signal into a velocity signal, special attention should be paid to eliminating the influence of low-frequency noise. At the same time, it is essential to ensure that the installation method of the sensor used can ensure the linear measurement range of the instrument.
Measurement test of vibration displacement of 5 axes
It is recommended to use non-contact sensors to measure shaft displacement.
Non-contact vibration sensors come in various forms, each with a different measurement principle. The main types include capacitive, inductive, and eddy current sensors. Eddy current sensors are widely used in gear assembly measurements due to their advantages such as a wide frequency range, small size, and insensitivity to changes in environmental conditions.
Non-contact sensors are generally used to measure the relative motion between a gear shaft and a bearing housing. By placing two probes perpendicularly to each other on a specified measuring surface, the movement trajectory of the gear shaft can be displayed on an oscilloscope. Most non-contact sensors (primarily eddy current sensors) can be used to determine the position of the shaft within the bearing clearance.
Although eddy current sensors have a wide frequency response range (0–10 kHz), they can generally only detect a small amount of shaft vibration signals above 500 Hz. Therefore, non-contact sensors are not suitable for vibration evaluation above 500 Hz.
When operating in the low-frequency range, non-contact sensors can be used to determine vibration factors related to shaft imbalance and mechanical errors, such as gear radial runout and roundness. They can also determine the magnitude of additional loads caused by gear forces, torques, and misalignment forces on the shaft, and identify bearing-related problems and potential instabilities.
When installing non-contact sensors, ensure that there is no large relative movement between the sensor and the bearing or housing. It is best to use a rigid component to insert the sensor into the housing, and to allow external access to the sensor so that it can be calibrated and maintained without opening the housing cover.
The measuring surface should be concentric with the journal and conform to the requirements of the evaluation grade.
6. Installation and Adjustment Requirements
1. Installation of rolling bearings.
When installing rolling bearings, the inner ring of the bearing should be tightly against the shaft shoulder, and the gap should not be able to be filled by a feeler gauge with a thickness of 0.05mm.
2. Axial clearance of the bearing.
For bearings with non-adjustable clearance (such as deep groove ball bearings), the axial clearance is 0.25~0.4mm; for bearings with adjustable clearance, the axial clearance values are as follows. Click to view the axial clearance of tapered roller bearings; axial clearance of angular contact ball bearings.
3. Gear (worm gear) meshing backlash.
A feeler gauge or lead weight method can be used. Place a lead wire on the tooth groove, then rotate the gear to flatten the lead wire. Measure the sum of the thickness of the flattened lead wire on both sides of the tooth, which is the size of the tooth side.
4. Tooth surface contact pattern: Cylindrical gear tooth surface contact pattern 2-10-4; Bevel gear tooth surface contact pattern 2-11-4; Worm gear drive contact pattern 2-12-4.
7. Daily inspection and maintenance of the gearbox
Check the oil level, oil temperature and oil pressure daily to ensure they are normal. Check the output and input ends of the reducer and all pipe joints for oil leaks. Check the temperature of each bearing to ensure it is normal. Listen to the operating sound to ensure it is normal. If any abnormalities are found, eliminate them immediately.
1. Daily inspection items:
Is the oil temperature (temperature rise) of the speed reducer normal?
Observe whether the oil pump and cooler are turned on, whether the lubrication oil circuit is unobstructed, and whether the current and pressure of the roller press are normal.
Check if the speed reducer sounds normally and if there are any abnormal noises.
2. Weekly inspection items:
Clean the filter screen, magnetic rod, and filter housing cavity with kerosene or gasoline and wipe them clean. Foreign matter removed from the filter needs to be settled, stored, and analyzed. When copper shavings appear, clean the filter every two days and observe the changes in the copper shavings. If the number of copper shavings does not decrease, stop the machine immediately and open the box for inspection, as this is a sign of abnormal wear of the bearing cage.
After cleaning the gearbox filter, the lost lubricating oil should be added back. Make sure that the type and quality of the lubricating oil added is the same as that used.
Check all bolts for looseness; if any are loose, tighten them immediately.
Check the input and output shafts of the speed reducer for oil leaks, noise, and abnormal temperatures.
Check the bolts connecting the motor and the reducer monthly to ensure they are tight, and check the bolts connecting the reducer and the mounting base weekly to ensure they are tight.
3. Monthly inspection items:
Tighten all bolts connecting the reducer and the torque plate, as well as the bolts on the locking plate, ensuring that the tightening method conforms to the specifications.
Check if the heat exchange of the cooler is normal, whether there are any changes in water pressure and flow rate, and whether cleaning measures are needed.
Check the last oil change date and ensure that the oil is changed every 6 months (if deterioration or emulsification is found, replace it immediately).
4. Annual inspection items:
Shut down for maintenance, remove dust from the input and output ends of the reducer, clean the vent cap, and repaint any peeling paint.
Replace damaged components and replace easily damaged and consumable parts according to the problems that occur during normal use of the equipment.
Recheck that the locking disc bolts are tightened, and tighten them again with the rated torque.
Clean the cooler and remove scale from the circulation system pipes. When disassembling the pipes, wrap all joints with a clean cloth to prevent dust from entering the gearbox.
Every three years, the machine needs to be returned to the factory for a major overhaul, replacing damaged parts such as bearings and oil seals, and repairing or replacing individual worn parts.
Disclaimer: This article is a reprint. If it involves copyright issues, please contact us promptly for deletion (QQ: 2737591964). We apologize for any inconvenience.
Disclaimer: This article is a reprint. If it involves copyright issues, please contact us promptly for deletion (QQ: 2737591964). We apologize for any inconvenience.
