Force Plus Force: Maintenance and Inspection Process Standards for Gear Reducers

Abstract: For Gear reducer Maintenance personnel have provided various assembly and inspection standards, optimized the reducer maintenance and repair procedures, and ensured the quality of reducer maintenance and upkeep. To further refine job operation standards, this operational procedure has been specially developed.

I. Preliminary Preparations:

1. Based on the operational status of equipment, submit requests for major overhauls and maintenance, which shall be reviewed and approved by company leadership.

2. Organize maintenance personnel to go to the site to inspect the equipment’s condition, ask operators about any current issues with the equipment, and record the details thoroughly.

3. Gradually analyze the issues existing in the equipment, estimate maintenance projects, and preliminarily determine the overhaul plan.

4. Return the preliminary proposal to the department’s leadership for consultation and finalization of the definitive plan.

5. Prepare the relevant drawings and documentation, as well as the spare parts expected to be replaced through procurement, and follow up on the delivery progress.

6. Notify the production department and coordinate to determine the downtime;

7. Clearly define the division of labor within the maintenance and upkeep team, refine inspection and repair tasks, and assign specific responsibilities to individuals.

II. Begin Maintenance:

1. Disassemble the device, carefully removing components step by step according to the equipment’s structure and keeping detailed records to prevent parts from getting mixed up.

2. Clean the gearbox housing and check for any oil leaks.

3. Inspect and measure the gears inside the reducer, paying particular attention to gear wear and meshing conditions, and record the inspection results.

4. Measure the bearing clearance and inspect for wear; measure the housing and check for signs of wear; record all inspection results.

5. Measure and inspect the input, output, and intermediate shafts inside the reducer, check for wear, and record the inspection results.

6. Summarize the inspection results outlined above, compile the dimensional deviations for each item, and identify the repair tasks to be carried out.

3. Maintenance Process Operation Procedure:

1. Disassemble the gearbox:

(1) Clean the exterior surface of the disassembled gearbox housing to remove scale, then wash it with kerosene.

(2) Drain the lubricating oil from the gearbox;

(3) Use a dedicated tool (puller) to remove the reducer pulley.

(4) Disassemble the output section of the reducer: Remove the end cover fastening screws, and use a push rod or crowbar to separate the end cover. Then, using a puller and a bearing press, remove the gear and bearing from the output shaft.

(5) Use the same method to disassemble the input shaft, gears, and bearings of the input section.

(6) Remove the intermediate shaft, gears, and bearings by pressing them out using a bearing press or by tapping them gently with a copper rod.

(7) Clean the components disassembled above with kerosene.

(8) Inspect and measure the removed gears, bearings, shafts, end covers, housings, and bearing bores, and record the dimensions in detail.

2. Inspect and maintain bearings:

(1) Remove the bearing using a puller or bearing press, and then clean it with kerosene.

(2) Inspect the bearing for signs of wear, gently shake the bearing, and measure the axial and radial clearances (0.02–0.2 mm). Then, rotate the bearing and listen carefully to its sound. Examine the surfaces of the balls and raceways for wear, check for any spots or signs of annealing. If the wear is severe, the bearing should be replaced with a new one.

(3) Inspect and measure with a micrometer the clearance at the mating interface between the bearing and the shaft, and record the measurement results. For standard-fit dimensions, the outer diameter should be increased by 0.02–0.05 mm; if the clearance exceeds this range, repairs should be carried out.

(4) New bearings must be kept clean before assembly.

(5) For bearings that require grease lubrication, the amount of grease to be added should be half of the bearing’s cavity volume.

(6) When assembling bearings using the press-in method, a dedicated sleeve or rod must be used between the pressing tool and the bearing housing; the same applies when installing by hammering, to avoid damaging the bearing.

(7) The end faces of the inner and outer rings of bearings should generally be close to the shaft shoulder and the inner bore shoulder. For tapered and thrust bearings, the clearance should generally not exceed 0.05 mm; for other types of bearings, it should not exceed 0.1 mm.

(8) After the bearing is installed, the outer circle should be in uniform contact with the inner bore of the housing; generally, the interference fit should be between 0.02 and 0.05 mm.

(9) When installing bearings by heating them with oil or using a bearing heater, the temperature should not exceed 120℃.

(10) Bearings without a specified orientation should be installed with the end bearing the model number facing outward for easy viewing.

(11) Radial non-adjustable radial bearings shall be mounted at both ends of the shaft. When axial displacement is restricted by end caps at both ends, one end must be tightly against the cap while the other end must have an axial clearance. The calculation formula is as follows: C = 0.000011 × (80 - t) L + 0.15 (Where L is the shaft length and t is the room temperature.)

(12) The axial clearance of angular contact bearings is generally between 0.04 and 0.1 mm, while the axial clearance of cylindrical (tapered) roller bearings is generally between 0.05 and 0.18 mm.

3. Inspection and maintenance of the gear shaft:

(1) Use a puller and a press to remove the gear and then clean it thoroughly.

(2) Measure the radial runout of the gear, with an allowable range of: 0.02–0.05 mm;

(3) Observe the wear condition of the gear tooth surfaces and check for any signs of deformation, annealing, spotting, or peeling.

(4) Parts with severe wear and measurement dimensions exceeding the allowable range shall be replaced.

(5) When assembling new gears, the gear bore must meet the specified requirements. The gear reference surface should be tightly fitted against the shaft shoulder (or the end face of the locating sleeve), and the gear reference surface must be perpendicular to the axis of the shaft.

(6) The axial misalignment of meshing cylindrical gear pairs shall comply with the standards: When the tooth width B ≤ 100 mm, the axial misalignment shall be less than 0.05B; when B ≥ 100 mm, the axial misalignment shall be less than 5 mm.

(7) Bevel gears shall be installed in pairs according to their matching numbers.

4. Inspection and maintenance of the reducer housing:

(1) First, clean the inside of the housing with kerosene and check for any cracks or flaking.

(2) Use a dial indicator to measure the inner bore dimensions of the bearing assembled inside the housing and record the measurements. Generally, the ovality and taper should be less than 0.03 mm, and the inner diameter should be within the range of 0 to -0.02 mm relative to the zero line (the tolerance for the outer diameter of a standard bearing is zero).

(3) Shell casings that exceed tolerance limits or are already damaged should be repaired or replaced.

(4) When installing the reducer, all components should be thoroughly cleaned, and the assembly sequence should be the reverse of the disassembly sequence.

(5) For the assembly of the output section, apply oil or cleaning agent to the outer surface of the shaft. After the bearing is press-fitted onto the shaft, the inner ring of the bearing must be tightly seated against the shaft shoulder or positioning sleeve, with a clearance no greater than 0.05 mm.

(6) When installing the gear, the clearance between the gear end face and the shaft shoulder shall not exceed 0.1 mm.

(7) The oil baffle shall be flat and intact. After the inner ring is properly fitted onto the shaft, the outer ring must maintain a certain clearance (2–3 mm) from the housing.

(8) For the intermediate shaft assembly, first press the bearing at the fixed end into the housing. Then, sequentially insert the gears and the intermediate spacer sleeve. Finally, align the shaft with the keyway of the lower gear after pressing the bearing at the other end, and then press the shaft into place all at once. Measure the dimensions between the fitted press cover and the end face of the bearing outer race; the typical clearance is given by: C = 0.000011 × (80 - t) L + 0.1, where L represents the shaft length and t denotes the room temperature.

(9) For the assembly of the input end, first install the press cap at the fixed end, then press in the bearing at that end. Next, sequentially insert the gear and spacer sleeve, and finally press in the shaft together with the bearing at the other end. Measure the dimensions at the other end and ensure that the normal axial clearance between the press cap and the shaft is no more than 0.05–0.1 mm.

(10) The contact patch of the gear teeth shall cover at least 45% of the tooth height and at least 60% of the tooth length, with uniform contact distribution and located near the middle portion of the tooth surface.

(11) When adding new oil to the reducer, ensure that the oil grade is consistent and do not mix different grades. The oil level should be at the middle of the sight glass on the gauge.

(12) Then, press in the pulley; the fixing bolts must be equipped with lock washers or bolt-retaining clips.

(13) The mating surfaces of the housing must be coated with sealant, and the tightening torque for the fastening bolts shall comply with the following standard values:

M10 50 Nm M12 80 Nm M16 190 Nm M20 420 Nm

M24 650 Nm M30 1300 Nm M36 2300 Nm

(14) When servicing and changing the oil in the reducer, completely drain all the old oil. The recommended oil-change intervals are as follows: the first time—every 500 hours; the second time—every 3 months; the third time—every 6 months; and the fourth time—every 1 year.