What's the attention when replace,install and maintain slewing bearings?

Large slewing ring bearings

The excellent performance of slewing bearings is the equipment which can bear hundreds of tons, thousands of tons and even tons. They are able to operate smoothly, with axial and radial loads as well as extremely large impact loads and overturning moments. It is a unique skill of slewing ring bearings.

With the continuous improvement of design and technology and the accumulation of manufacturing experience, our product quality has reached or approached the international advanced level.However, as the user fails to pay attention to the transportation, storage, installation and maintenance of rotary supports, the phenomenon of the host performance degradation cannot be ignored.The common slewing ring of bucket turbine bearing is inclined, the noise of stack-reclaimer bearing is harsh, the large crawler type equipment has the sound of slewing ring during the test run, and the rotation is not smooth.

Steelworks metallurgical equipment swing bearing and rotary table equipment, flask machine bearings, filling machine bearings, a 24-hour equipment used 14 months after the slewing ring outer ring fracture, the reason is that the equipment has never checked the pre-tightening bolts, several bolts loose and similar events.

Then how to properly install and maintain the slewing bearings?If the bearing is repaired, what is the basis for reference? If the bearing is replaced, where does it start?

First,Transportation and storage
A series of big bearings, such as the slewing bearing of bucket turbine and the crane rotary bearing, have been coated with anti-rust oil before delivery and wrapped with film.The storage temperature should be in 20 plus or minus 10 ℃, and the relative humidity is not more than 60%, over the period of validity, should be timely maintenance.Grease should be added to the stock after one year and the flexibility of its rotation should be checked.

When the turntable bearings is delivered, it is usually fixed on the pallet or in the packing box.Transportation and storage shall be kept level, shall not collide and squeeze, shall not be wet, and shall be kept flat.There should be a smooth isolation between stacked slewing ring.

The slewing bearing generally has the hoisting hole, may screw into the lifting ring bolt to lift safely.Also can use condole belt triangle to hoist.

Second, Installation
First open the slewing ring package, check the certificate and label, and confirm that the type swing bearing used is correct.

1) installation plane
The mounting surface should be smooth and clean, removing all superfluous material such as paint residue, welding beads, burrs, etc.Care should be taken not to let the solvent infiltrate into the slewing ring during cleaning. Do not use solvents that damage sealing materials.The mounting surface should be dry and free of lubricant before assembly.Measures should be taken to protect workers and the environment.

The roughness of mounting surface of mounting bearing shall not be greater than Ra=12.5,6.3 displacement m, and the planeness error of mounting surface shall be tested for axial error and radial error.The axial planeness tolerance value has a corresponding standard value range with the diameter of the turntable bearing raceway (referring to the relevant standards specifically, the radial error is based on the actual width measurement of the flange, and the radial plane tolerance value takes half of the circumferential tolerance value).

In order to avoid partial overload of rotating support caused by unevenness of mounting plane or bearing deformation, the axial planeness error can only be undulated once within any 180 degree range, and changes gently.

2) positioning
The inner and outer ring raceways of the crane slewing bearing and the turntable bearing have a soft belt which should be placed on both sides of the main load plane.That is, with the main load area staggered by 90 degrees.There is a blockage or "S" mark in the soft band.

In addition, it is necessary to check the match between the slewing bearing and the mounting surface. The gauge is usually used to check. If the match is not good, it should be filled with appropriate materials.Welding operation on support is prohibited after slewing bearing installation.

3) Strong bolt
4-1 Selection of mounting bolts
Bolts and washers shall be installed using specified (size, quantity, strength grade, etc.).Another note:
1) do not use full threaded bolts
2) don't use old bolts, nuts and washers
3) do not use open gaskets such as elastic washers

4-2 Selection of bolts pre-tightening torque
The yield strength of normal metric bolts should be 0.6-0.7 times.Hydraulic fastening device is recommended for bolts larger than M27, and the pre-tightening force should not exceed 85% of the yield strength.

4-3 Fixing bolts
Slewing bearings should be installed without load.Note:
1) apply a little oil on the thread of the bolt to ensure the balance of friction resistance.
2) pre-tightening bolts: the three steps shall be staggered and pre-tightening, with the force of 30%, 80% and 100% respectively.
3) the strength grade of bolts is above grade 8.8, and 10.9 grade is chosen for large rotary bearing or rotary bearing.

5) Adjust the gear side gap
It is important to adjust the gear side gap correctly when installing a toothed slewing support.It can be measured and adjusted with a feeler at the highest point of radial runout of gear.If the side clearance is not within the specified value, the pinion can be moved to change the center distance.After the setting, turn the swivel support at least one full turn to confirm that there are no other gear high jump points, and check the side clearance again after the swivel support is finally fixed.The highest point of gear radial runout is marked in the gear groove with green paint.

6) First lubrication
6-1 Raceway lubrication
To ensure adequate lubrication, the grease specified in the drawing or product manual should be added again before initial use.Pay special attention to all nozzles being injected one by one into the grease, preferably by turning and rotating the supporting edge to fill the oil until the grease is seen extruding from the sealing ring.

6-2 Gear lubrication
When gear lubrication, tooth surface should be clean.It is recommended to brush the grease on the gear with a clean brush.

The third,Regular inspection and maintenance
1) first use 100 working hours, and check the bolt pretightening torque once.If more than 10% of bolts are loose, check again in the 200th working hour.
2) check every 500 working hours thereafter;The inspection interval should be shortened in bad working conditions.
3) after working for 2000 hours, if a bolt is found to be loose below 80% of the specified torque, the bolt and two adjacent bolts shall be replaced.If 20% bolts are found to be loose below 80% of the required torque, all bolts shall be replaced.
4) all bolts shall be replaced after working for 14000 hours.
5) add oil every 100 working hours for equipment with high rotating speed or continuous rotation or frequent operation.The time interval of filling lubricating grease should be further shortened under the bad working condition.

To replace the rotary bearing or rotary bearing, the manufacturer needs to make surveying and mapping according to the old bearing, so as to guarantee the complete and correct installation of the newly manufactured bearing.The repair technical agreement for the bearing repair shall be issued and accepted by both parties.

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Hi, how can I help you?debbie