FORM 2
THE PATENT ACT 1970
(39 OF 1970)
&
The Patent Rules, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)
1 TITLE OF THE INVENTION :
A METHOD FOR REPLACEMENT OF SLEW BEARING FOR MOBILE HARBOR CRANE.
2 APPLICANT (S)
Name : JSW ISPAT STEEL LIMITED.
Nationality : An Indian Company.
Address : Geetapuram, Dolvi, Taluka Pen, Dist. Raigad, Maharashtra-
402107,India; having the Registered Office at The Enclave', 5th Floor, Behind Marathe Udyog Bhavan, New Prabhadevi Road, Prabhadevi, Mumbai-400025, State of Maharashtra, India.
3 PREAMBLE TO THE DESCRIPTION
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION
The present invention relates to a method of replacement of slew bearing for Mobile harbor crane by a simplified procedure using easy to use kit with less man hours, without usage of external cranes. More particularly, the present invention implemented a step by step procedure for dismantling the worn out/damaged bearing, removing it and inserting and assembling a new slew bearing carried out simply by involving the readily available undercarriage hydraulic systems. Advantageously, the advancement would enable for the first time bearing replacement for Mobile harbor crane without the need for removal of boom, tower and luffing cylinders thereby making the process of bearing replacement much simpler, faster and user friendly.
BACKGROUND ART
A mobile harbor crane has a top structure, a undercarriage which supports the top structure, a Slew bearing that is located between the bottom flange of the top structure and top flange of the undercarriage, tower which supports the boom and grab bucket, undercarriage cylinder which is used to lift and lower the undercarriage, support structure below tower, support structure below counter weight. During regular operation of the crane which handles heavy pay load, the slew bearing gets worn out and thus needs to be replaced with new bearing at periodic intervals.
Conventionally, when such slew bearing of mobile harbor crane needs to be replaced, large mobile crane, fork lift are essentially being used to dismantle the top structure and replacement of bearing and reinstallation of top structure. However in that case, very high time ranging approximately 25-30 days is required to perform such activities.
Conventional Practice for replacement of such bearing thus includes:
A. Dismantling of top structure which includes
i. Installing Hook on Ropes - and Boom down on the ground.
ii. Removing of all ropes from the crane. Requires drum, mechanical winch to wound
the ropes on drum iii. Removing of Luffing cylinder and securing of the same on tower.

iv. Removing of Boom, Counter weight, operator cabin, tower platform, tower, slewing platform and bearing from the crane.
B. Installation of new bearing and slewing platform
C. Torquening of the all slewing bearing/gear mounting bolts.
D. Reinstallation of top structure which includes
i. 1. Installation of Counter weight and Torque tightening of its bolts. ii. 2.Installation of the tower and torque tightening of it's mounting bolts iii. 3. Installation of the boom, luffing cylinder and wire ropes
E. Trial run and testing
To execute the above stated jobs, which take at least 25-30 days, the following machineries are essentially required.
1. 1 x 300 T mobile crane lifting height approx 35 meters
2. 1 x 120 T mobile crane -lifting height approx 35 meters
3. 1 x 5 T fork lift
There are some patent applications known to exist which discloses the bearing replacement and maintenance activities of wind power generator, although there is no knowledge of availability of any prior attempt to developing new method of replacement of slew bearing in mobile harbor crane, which adopted means and measures directed to avoid known limitations and disadvantages in such activity.
US 20120139257A1, discloses a method of replacement of yaw bearing in wind power generator wherein an external jack devise is mounted between the power generator main body and tower such that an opening is formed for removing the yaw bearing from inside or for inserting the new yaw bearing.
EP 2490975 Al discloses an apparatus for assembling a wind turbine by involving an external crane to lift the component during assembling of wind turbine. A control

mechanism comprising guide members are also required which is coupled to the crane boom for controlling the orientation of the wind turbine component.
EP2143936A1, discloses a method of replacement of main bearing of a wind turbine wherein at least one main bearing and the rotatable main shaft are moved relatively to the stationary part in the direction of stationary axis for replacement. Fasteners which comprise bolt holes, bolts and shim are used for fixing the wind turbine rotor to the stationary part during replacement of main bearing.
There has been therefore a continuing need in the art to developing means and method for faster and safe replacement of slew bearing in mobile tower crane avoiding the complexity of dismantling its top structure and without the use of any external cranes or lifting jacks. In the above stated prior attempts, bearing is removed following the basic approach of lifting/dismantling the top structure which required lifting/handling means like crane etc, while keeping bottom structure fixed, whereas in the bearing replacement procedure proposed by the present invention, top structure is fixed and bottom structure is moved up and down to create the required gap.
OBJECTS OF THE INVENTION
The basic object of the present invention is thus directed to providing a method for replacement of slew bearing in mobile tower crane in a safe and reliable manner, in less time with less manpower and needing no external crane or forklift/jack etc.
A further object of the present invention is directed to providing a method for replacement of slew bearing in mobile tower crane wherein undercarriage hydraulic cylinders of the crane itself would be used for lifting and lowering the undercarriage for creating space for replacing the bearing.
A still further object of the present invention is directed to providing a method for replacement of slew bearing in mobile tower crane wherein simple fixtures and gadgets produced in-house from readily available materials are used to facilitate disassembling and

removal of old bearing as well as insertion and assembly of new bearing with desired precision in positioning/alignment in a user friendly manner.
A still further object of the present invention is directed to providing a method for replacement of slew bearing in mobile tower crane wherein there is no need to dismantle the top structure which includes Luffing cylinder, Boom , Counter weight, operator cabin, Tower platform, Tower and Slewing platform, thereby reducing the time for dismantling and again assembling of said parts after replacement work is over.
A still further object of the present invention is directed to providing a method for replacement of slew bearing in mobile tower crane wherein stability to the top structure is provided during the bearing replacement work by providing support structures below boom, tower and counter weight and top of the tower tied with tension ropes from all four directions.
A still further object of the present invention is directed to providing a method for replacement of slew bearing in mobile tower crane wherein precise positioning and aligning of the bearing is carried out by providing simple ball/roller based support.
A still further object of the present invention is directed to providing a method for replacement of slew bearing in mobile tower crane wherein easy and safe removal and insertion of bearing is done with pulling of bearing out/pushing in using roller assembly over temporary structure.
SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided a method for replacement of slew bearing for mobile harbor crane comprising the steps of
i) lifting the top structure of crane to desired height such as to allow desired
gap between crane top structure and under carriage to facilitate the removing/inserting of said bearing during replacement;
ii) providing stable support to the top structure;

iii) removing all bearing inner race nuts such that top flange of undercarriage is detached and lowered from the bearing bottom surface to a desired level to create a workable gap;
iv) Removing all bearing inner race studs;
v) Placing roller assemblies involving guide pins across the top flange of undercarriage at said lowered position for supporting the bearing inner race;
vi) Lifting the top flange along with channel and roller assemblies such that the roller assemblies touch the bottom face of the bearing inner race with said guide pins inserted inside the inner race holes;
vii) removing all bearing outer race nuts and lowering the under carriage such that the bearing along with outer race studs is lowered down supported on said roller assembly so that said studs comes out of the outer race holes;
viii) Removing the bearing outer race studs from the bearing and removing the same through gap between top structure and undercarriage to a position beyond the top structure wherefrom the old bearing is removed;
ix) Placing a new bearing on said roller assemblies as per the earlier positions and inserting guide pins into the bearing inner race holes to avoid radial displacement of the bearing, fixing guide rods selectively on outer race holes to favor matching with corresponding holes on bottom flange on top structure;
x) Providing the bearing supported on said roller assemblies inside through the gap between bottom flange of top structure and top flange of under carriage;
xi) Aligning the bearing outer race holes with the holes of bottom flange of top structure after removing all guide pins from bearing inner race holes;
xii) Lifting the undercarriage till top of the bearing outerrace touches with bottom flange of top structure and bearing inner race teeth meshes with the pinion teeth while guide rods guide inside the bottom flange holes of top structure;

xiii) Fastening all the studs in to bearing outer race holes through bottom holes of bottom flange of top structure from top after removing all guide rods and fastening the bearing to bottom flange of structure using nuts with studs from top;
xiv) Lowering the under carriage and removing all roller assemblies, and support structure and fixing selectively equispaced guide rods with bearing inner race holes;
xv) Lifting the under carriage till the top flange of the undercarriage touches the bottom of the bearing inner race and simultaneously aligning the holes of the top flange of undercarriage with bearing inner race holes with said guide rods on bearing inner race holes guides in through the holes of bottom flange of under carriage;
xvi) Removing all guide rods and fastening all studs into the bearing inner race holes through holes of bottom flange of undercarriage from bottom and finally fastening the bearing using nuts on the studs to top flange of the undercarriage;
xvii) Releasing the special support of said top structure and restoring to its usual operative state involving the thus replaced bearing.
A further aspect of the present invention is directed to a method for replacement of slew bearing for mobile harbor crane wherein said lifting and lowering of said undercarriage is carried out involving the undercarriage cylinders of the carne and said method comprises in said step i) said lifting the top structure of crane to desired height using outward stroke of undercarriage cylinders of the crane, with packings inserted below the base of undercarriage cylinders to allow desired gap between crane top structure and under carriage for removing/inserting of said bearing during replacement.
in said step ii) said step of providing stable support to the top structure in said raised position with boom rotated at 90 degrees with respect to parking position of said crane and lowered to rest on grab bucket, using column support at selective locations under top structure as well as tying the tower from all four sides.
In said step iii) after removing all bearing inner race nuts lowering under carriage by inward stroke of undercarriage cylinder.

in said step v) said selected number preferably four number of roller assemblies involving
guide pins fixed thereon on web portion of two channels placed across the top flange of
undercarriage preferably parallel and equidistant from center at said lowered position for
supporting the bearing inner race preferably at equispaced circumferential locations.
in said step vi) wherein after said lifting of the top flange alongwith channel and roller
assemblies the roller assemblies touch the bottom face of the bearing inner race at four
points with said guide pins inserted inside the inner race holes.
in said step vii) wherein after removing all bearing outer race nuts the under carriage is
lowered such that the said bearing along with outer race studs is lowered down supported
on said roller assembly so that said studs comes out of the outer race holes.
in said step viii) wherein after removing the bearing outer race studs from the bearing the
bearing is removed by pulling out the bearing through said gap between the top structure
and undercarriage to a position beyond the top structure wherefrom the old bearing is
removed.
In said step ix) wherein for placing a new bearing on said roller assembly , balls are placed
in slots provided in the plate fastened to top of roller assembly and thereafter the new
bearing is placed on said roller assembly.
in said step xi) wherein said aligning the bearing outer race holes with the holes of bottom
flange of top structure is carried out using balls provided between roller assembly and
bearing after removing all guide pins from bearing inner race holes.
In said step xiv) comprising lowering the under carriage involving the inward stroke of
under carriage cylinders and removing all said balls, roller assemblies, channels and support
structure below channels and rubber pads from top surface of top flange of undercarriage
and fixing selectively said equispaced guide rods with bearing inner race holes.
In said step xv) wherein aligning of the holes of top flange of undercarriage with bearing
inner race holes is carried out by releasing the bake of the drive motor and rotating the
bearing inner race for said matching of holes.
A still further aspect of the present invention is directed to a method for replacement of slew bearing for mobile harbor crane wherein for said removal of said bearing by pulling, the bearing is joined by chain block through eye bolts being fixed on said outer race holes and thereafter it is pulled on a roller support by rolling over said channel web under pulling force applied through chain block.

Yet another aspect of the present invention is directed to said method for replacement of slew bearing for mobile harbor crane wherein said step of releasing the special support of said top structure and restoring to its usual operative state comprises removing all tie ropes and column support structure below boom tower and counter weight and lowering the undercarriage cylinders till the crane rests on wheels and the packings below the under carriage are removed , lifting the boom involving luffing cylinder and rotating the boom to carne parking position so that carne can be put on operation involving the new bearing.
A still further aspect of the present invention is directed to said method wherein said bearing replacement is carried out faster by way of avoiding the need for dismantling, boom, tower and luffing cylinder, thus minimizing time for replacement.
According to a further aspect of the present invention is directed to said method wherein lifting and lowering of the undercarriage during replacement of bearing is carried out involving crane's existing hydraulic system.
A still further aspect of the present invention is directed to said method wherein pulling out of bearing through the gap of top structure and undercarriage is facilitated by using roller assembly over temporary structure.
A still further aspect of the present invention is directed to said method wherein aligning of bearing outerrace holes with bottom flange holes of top structure is facilitated by placing balls between roller assembly and bearing bottom surface.
A still further aspect of the present invention is directed to said method wherein bearing replacement is carried out avoiding removal of drive pinion and simply by aligning of bearing innerrace holes with top flange holes of undercarriage achieved by releasing braking system of the pinion drive motor.
The various objects and advantages of the present invention are described in greater details with reference to the following non limiting accompanying illustrative drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 : is the schematic view of the mobile harbor crane in parking position for bearing replacement according to the present invention with the undercarriage and top structure lifted at desired height using four numbers undercarriage cylinder to assure sufficient gap for bearing removal/replacement, boom resting on grab bucket, and top structure is supported on suitable support structure from below and top of the tower tied with tension ropes from all four directions to ensure stability, during bearing replacement.
Figure 2: is the schematic view of the mobile harbor crane in parking position of Figure 1 along with the top view of the arrangement.
Figure 3: is the schematic view of the roller assembly with fixed plate having slots for inserting guide pin and balls for easy removal and inserting of the bearing during replacement.
Figure 4: is the schematic sectional front view of the assembled old bearing to be replaced showing removing all bearing inner race nuts and lowering the under carriage for removing the inner race studs so that the required gap for bearing replacement is created between the top structure and the undercarriage.
Figure 5: is the schematic sectional view of the one of the four locations of placement of the roller assembly with fixed plate(of Figure 3)and guide pin placed in slot of fixed plate, on a channel section placed on the top flange of undercarriage to support the bearing for removal.
Figure 6: is the schematic top view showing the ail four locations of the placement of four number roller assemblies on channel in relation to the slew bearing circumference.
Figure 7: is the schematic view of the under carriage top flange with roller assemblies raised to a position (using under carriage cylinders' inward stroke) to touch the bearing inner race, with the guide pin inserted into inner race hole.
Figure 8: is the schematic view of the slew bearing resting on the roller assemblies and removed from bottom flange of top structure by removing the all nuts from all bearing outer

race studs by lowering the top flange of under carriage structure (using outward stroke of undercarriage cylinders).
Figure 9: is the schematic view of the bearing removal procedure by pulling out the bearing (after removing all outer race studs) using chain and chain block and joining the bearing with I- bolt and sliding on roller assembly along channel web.
Figure 10: is the schematic view of placing the new bearing on the roller assembly with balls and guide pin placed in the slots provided in the fixed plate fastened to the roller assembly and another set of guide pins for fitting in bearing outer race tap holes, pulling the bearing inside through the gap between bottom flange of top structure and top flange of under carriage by sliding on roller assembly and keeping outer race guide pins aligned with the holes on bottom flange of top structure.
Figure 11: is the schematic view of positioning and assembly of the new bearing placed in position in relation to the bottom flange of the top structure, the top of bearing outer race touching the bottom flange of the top structure by lifting the under carriage using undercarriage cylinders, fixing the studs for all bearing outer race holes after removing the guide rods and fitting nuts on the studs.
Figure 12: is the schematic view showing the new bearing assembled on the bottom flange of top structure and the holes of top flange of undercarriage aligned with all the bearing inner race holes by selective use of guide rods fitted with the inner race holes and rotating the bearing inner race holes by releasing the brake device of drive motor.
Figure 13: is the schematic view of complete assembly of the new bearing(replacing the old one) between the top flange of bottom structure and the bottom flange of top structure after lifting the undercarriage using the under carriage cylinders so that the bottom flange touches the inner race of bearing, and duly fitting studs and nuts on all inner and outer race holes.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS
The present invention relates to a method of replacement of slew bearing for Mobile harbour crane by a simplified procedure using easy to use kit with less man hours, without usage of external cranes. More specifically, the present invention implemented a step by step procedure for dismantling the worn out/damaged slew bearing, removing it and inserting and assembling a new slew bearing carried out by utilizing the undercarriage cylinders which is used to lift and lower the undercarriage for creating required gap between the top structure and the undercarriage. Importantly also, in the above methodology the top structure along with the counter weight, tower and boom, is kept fixed by providing required structural support with due stability while the under carriage is moved up or down as per the need for dismantling of the old bearing and assembly of the new bearing. Moreover, customized tools and fixtures are designed and configured to suit the need for positioning, aligning, sliding out/in of the bearing during the replacement work enabling the entire work to be carried out at minimum time with less manpower in safe and reliable manner without the need for any external crane or forklift. The exact methodology and steps involved are now described in details with the help of accompanying drawings as under:
Reference is first invited to the accompanying Figure 1 which is the schematic view of the mobile harbor crane in parking position for bearing replacement according to the present invention with the undercarriage and top structure lifted at desired height using four numbers undercarriage cylinder to assure sufficient gap for bearing removal/replacement, boom resting on grab bucket, and top structure is supported on suitable support structure from below and top of the tower tied with tension ropes from all four directions to ensure stability, during bearing replacement.
In this procedure, top structure is kept fixed at a suitably lifted position and bottom structure is moved up and down, by the outward and inward stroke respectively of the undercarriage cylinders to create necessary gap to meet the requirement of pulling out the dismantled old/damaged bearing and inserting and positioning the new bearing replacing the old one.

At the first step packing 1 is placed below each of the 4 number undercarriage cylinder base 37 to assure sufficient gap for bearing 11 removal through the gap between top structure and bottom structure. Next, the under carriage 8 is lifted using outward stroke of 4 number undercarriage cylinder 2 in synchronization to maximum stroke. The boom IS is rotated by 90° with respect to parking position as shown in Figurel. Using outward stroke of Luffing cylinder 20, the boom 18 is lowered and rested on the grab bucket 21. To ensure stability of the top structure of crane in the lifted position, prefabricated column support structure 19 is placed below boom, and similar column support structure 7 is placed below the counter weight 4 and column support structure 5 below the tower as shown in Figure 1. The column supports are designed based on a dead load of 300T. Additionally, the top of the tower 3 is tied with tensioning ropes 22 from all the four directions shown in Figure 1. Accompanying Figure 2 is the schematic top view of the mobile harbor crane in parking position of Figure 1 showing the arrangement of tension ropes in relation to crane top structure.
Before dismantling the old bearing, a prefabricated roller assembly with a slotted fixed plate at top is made ready for supporting the bearing from below. Accompanying Figure 3 shows the schematic view of the roller assembly with fixed plate having slots for inserting guide pin and balls for easy removal and inserting/positioning of the bearing during replacement. This customized gadgets are configured and produced inhouse from readily available materials to suit the need for positioning, aligning, sliding out/in of the bearing during the replacement work to be carried out at minimum time with less manpower in safe and reliable manner. Also, guide pins and guide rods are prepared and used to align the bearing holes with flanges of crane structure during assembly.
In the next step, all bearing inner race lib nuts 13 are removed and the under carriage 8 is lowered by the inward stroke of the under carriage cylinders, top structure remaining fixed, untill all the bearing inner race lib studs 14 comes out of holes 14a located at the top flange of under carnage as shown in accompanying Figure 4. When sufficient gap between the top structure and undercarriage is created, all bearing inner race lib studs 14 are removed as shown in Figure 4.
Reference is now invited to the accompanying Figure 5 which shows the schematic sectional view of one of the four selective locations of placement of the roller assembly with fixed plate(of Figure 3)and guide pin placed in slot of fixed plate, on a channel section

placed on the top flange of undercarriage to provide sliding support to the bearing from below for easy removal.
Two numbers channel 27 of required length are placed in to the gap between top structure and undercarriage, rubber packing 26 is inserted between the channel 27 and top flange 7 of the undercarriage. Next, four number roller assemblies 28 (as shown in Figure 3) are placed in the web portion of the channel 27. Fix plate 29 with slot is provided at top of roller assembly for placing guide pin 30 to roller assemblies 28. The four number roller assemblies 28 are selectively positioned at equiangular spacing on the bearing circumference such that the axis of the guide pin 30 aligns with axis of the bearing inner race lib holes 14b as shown in Figure 5. Accompanying Figure 6 is the schematic top view showing the all four locations of the placement of four number roller assemblies 28 on channel in relation to the slew bearing 11 circumferences.
Reference is now invited to the accompanying Figure 7 which is the schematic view of the under carriage top flange with roller assemblies raised to a position (using under carriage cylinders' outward stroke) to touch the bearing inner race, with the guide pin inserted into inner race hole. To achieve this, undercarriage 8 is lifted using undercarriage cylinder 2 untill the top of the roller assembly 28 touches the bottom of the bearing inner race lib, the guide pin 30 will guide into the bearing inner race lib holes 14b as shown in Figure 7.
Reference is next invited to the accompanying Figure 8 is the schematic view of the slew bearing resting on the roller assemblies and removed from bottom flange of top structure by removing the all nuts from all bearing outer race studs by lowering the top flange of under carriage structure (using outward stroke of undercarriage cylinders). All the bearing outer race 11a nuts 16 are removed. The undercarriage 8 is then lowered using undercarriage cylinder 2 untill all the bearing outer race studs 13 comes out of holes 13a of bottom flange of top structure shown in Figure 8. Then all bearing outer race studs 13 are removed.
I-bolt 32 is then fixed into bearing outer race holes 13b and joined with chain 33 of chain block 34 with I-bolt 32 using chain block 34 as shown in accompanying Figure 9. The bearing is then pulled out through the gap between bottom flange 9 of the top structure and top flange 7 of undercarriage using said chain block. To locate Soft point of the bearing 11 in the position specified by the equipment manufacturer, old bearing positions are marked on the new bearing. Remove the guide pin 30 and take the bearing out. Channels 27 are

supported using columns 31. These columns 31 are temporarily fixed to undercarriage 8 as shown in Figure 9.
Reference is now invited to accompanying Figure 10 that shows the schematic view of placing the new bearing on the roller assembly with balls and guide pin placed in the slots provided in the fixed plate fastened to the roller assembly. Before placing the new bearing 11 on the roller assembly 28, balls 36 are placed in the slots provided in the plate 29 fastened to roller assembly 28. The new bearing 11 is placed on the balls as per the earlier positions(as marked).To avoid radial displacement of the bearing during pulling, the bearing 11 is locked by inserting the guide pin 30 into the bearing outerrace holes 14b.Guide pin 30 sits in the slot provided in the plate 29. Six number of guide rods 35 (with threading) are fixed equispaced in the bearing outer race tap holes 14b. The bearing 11 is then pulled inside through the gap between bottom flange 9 of the top structure and top flange 7 of undercarriage. The guide pins 30 are removed from the bearing innerrrace holes 14b. Using balls 36 provided between roller assembly 28 and bearing 11, the bearing 11 is aligned with holes 13a of bottom flange 9 of the top structure shown in Figure 10. The methodology allows bearing alignment without removal of pinion. Aligning of bearing inner race holes with Top flange holes of Undercarriage is also achieved by releasing braking system of the pinion motor.
Reference is now invited to the accompanying Figure 11 that shows the schematic view of positioning and assembly of the new bearing placed in position in relation to the bottom flange of the top structure. After aligning the holes, the under carriage 8 is lifted using undercarriage cylinders 2, guide rods 35 will guide inside the bottom flange holes 13a of top structure. The under carriage 8 is lifted by the outward stroke of the undercarriage cylinders till top of the bearing outer race 11a touches with bottom flange 9 of the top structure. Bearing inner race lib teeth meshes with the pinion 10 teeth shown in Figure 11. All the guide rods 35 are removed, and the studs 13 are fastened into bearing outerrace holes 13b through holes 13a from top. Nuts 16 are used to fasten the bearing 11 to bottom flange of the top structure 9 shown in Figure 11.
Accompanying Figure 12 shows the schematic view showing the new bearing assembled on the bottom flange of top structure and under carriage is in lowered down position. The undercarriage 8 is lowered by inward stroke of the undercarriage cylinders. Next, balls 36, roller assembly 28, channels 27, support structure 31 below channels 27 and rubber pads

26 are all removed from top flange of bottom structure as shown in Figure 12. Six number guide rods 35 are then fastened equispaced with bearing inner race holes 14b. Next, the undercarriage 8 is lifted by using outward stroke of the under carriage cylinders and the holes 14a of the top flange 7 of undercarriage 8 are aligned with bearing inner race holes 14b by releasing the brake of the drive motor 16 and the bearing inner race is rotated untill the holes 14a of the top flange 7 of undercarriage 8 aligns with bearing inner race holes 14b. The undercarriage 8 is lifted till the top flange 7 of the undercarriage 8 touches with bottom of the bearing inner race lib as shown in accompanying Figure 13.
All guide rods 35 are removed. Studs 14 are fastened into bearing innerrrace holes 14b through holes 14a from bottom. The bearing 11 is fastened to top flange 7 of the undercarriage 8 by using nuts 15 fasten. Next, the tie ropes 22 are removed. Also support structure 19 below boom 18, Support structure 5 below tower 3, support structure 7 below counter weight 4 and Packing 1 below the undercarriage 8 are removed. Lastly, The boom 18 is lifted using luffing cylinder and rotated to crane parking position. All hydraulic and electric connections are checked before putting the crane on trial.
It is thus possible by way of the present invention to provide a method for onsite replacement of the slew bearing of mobile harbor crane without dismantling the crane top structure including Luffing cylinder, Boom , Counter weight, operator cabin, Tower platform, Tower and Slewing platform and without using any external crane or forklift etc, but by using the undercarriage cylinders to create required gap between the under carriage and the top structure by keeping the top structure fixed at required height and moving the undercarriage up and down and using specially configured tools and gadgets for dismantling and removal of old bearing and inserting the new bearing as well as assembling it following simple sequential steps in a user friendly, safe and reliable manner with substantial reduction in bearing replacement time.

We Claim:
1. A method for replacement of slew bearing for mobile harbor crane comprising the steps of
i) lifting the top structure of crane to desired height such as to allow desired
gap between crane top structure and under carriage to facilitate the removing/inserting of said bearing during replacement;
ii) providing stable support to the top structure;
iii) removing all bearing inner race nuts such that top flange of undercarriage is detached and lowered from the bearing bottom surface to a desired level to create a workable gap;
iv) Removing all bearing inner race studs;
v) Placing roller assemblies involving guide pins across the top flange of undercarriage at said lowered position for supporting the bearing inner race;
vi) Lifting the top flange along with channel and roller assemblies such that the roller assemblies touch the bottom face of the bearing inner race with said guide pins inserted inside the inner race holes;
vii) removing all bearing outer race nuts and lowering the under carriage such that the bearing along with outer race studs is lowered down supported on said roller assembly so that said studs comes out of the outer race holes;
viii) Removing the bearing outer race studs from the bearing and removing the same through gap between top structure and undercarriage to a position beyond the top structure wherefrom the old bearing is removed;

ix) Placing a new bearing on said roller assemblies as per the earlier positions and inserting guide pins into the bearing inner race holes to avoid radial displacement of the bearing, fixing guide rods selectively on outer race holes to favour matching with corresponding holes on bottom flange on top structure;
x) providing the bearing supported on said roller assemblies inside through the gap between bottom flange of top structure and top flange of under carriage;
xi) Aligning the bearing outer race holes with the holes of bottom flange of top structure after removing all guide pins from bearing inner race holes;
xii) Lifting the undercarriage till top of the bearing outerrace touches with bottom flange of top structure and bearing inner race teeth meshes with the pinion teeth while guide rods guide inside the bottom flange holes of top structure;
xiii) Fastening all the studs in to bearing outer race holes through bottom holes of bottom flange of top structure from top after removing all guide rods and fastening the bearing to bottom flange of structure using nuts with studs from top;
xiv) Lowering the under carriage and removing all roller assemblies, and support structure and fixing selectively equispaced guide rods with bearing inner race holes;
xv) Lifting the under carriage till the top flange of the undercarriage touches the bottom of the bearing inner race and simultaneously aligning the holes of the top flange of undercarriage with bearing inner race holes with said guide rods on bearing inner race holes guides in through the holes of bottom flange of under carriage;
xvi) Removing all guide rods and fastening all studs into the bearing inner race holes through holes of bottom flange of undercarriage from bottom and finally fastening the bearing using nuts on the studs to top flange of the undercarriage;
xvii) Releasing the special support of said top structure and restoring to its usual operative state involving the thus replaced bearing.

2. A method for replacement of slew bearing for mobile harbor crane as claimed in claim 1 wherein said lifting and lowering of said undercarriage is carried out involving the undercarriage cylinders of the carne and said method comprises in said step i) said lifting the top structure of crane to desired height using outward stroke of undercarriage cylinders of the crane, with packings inserted below the base of undercarriage cylinders to allow desired gap between crane top structure and under carriage for removing/inserting of said bearing during replacement. in said step ii) said step of providing stable support to the top structure in said raised position with boom rotated at 90 degrees with respect to parking position of said crane and lowered to rest on grab bucket, using column support at selective locations under top structure as well as tying the tower from all four sides. In said step iii) after removing all bearing inner race nuts lowering under carriage by inward stroke of undercarriage cylinder.
in said step v) said selected number preferably four number of roller assemblies involving guide pins fixed thereon on web portion of two channels placed across the top flange of undercarriage preferably parallel and equidistant from center at said lowered position for supporting the bearing inner race preferably at equispaced circumferential locations.
in said step vi) wherein after said lifting of the top flange alongwith channel and roller assemblies the roller assemblies touch the bottom face of the bearing inner race at four points with said guide pins inserted inside the inner race holes. in said step vii) wherein after removing all bearing outer race nuts the under carriage is lowered such that the said bearing along with outer race studs is lowered down supported on said roller assembly so that said studs comes out of the outer race holes.
in said step viii) wherein after removing the bearing outer race studs from the bearing the bearing is removed by pulling out the bearing through said gap between the top structure and undercarriage to a position beyond the top structure wherefrom the old bearing is removed.
In said step ix) wherein for placing a new bearing on said roller assembly, balls are placed in slots provided in the plate fastened to top of roller assembly and thereafter the new bearing is placed on said roller assembly.

in said step xi) wherein said aligning the bearing outer race holes with the holes of bottom flange of top structure is carried out using balls provided between roller assembly and bearing after removing all guide pins from bearing inner race holes. In said step xiv) comprising lowering the under carriage involving the inward stroke of under carriage cylinders and removing all said balls, roller assemblies, channels and support structure below channels and rubber pads from top surface of top flange of undercarriage and fixing selectively said equispaced guide rods with bearing inner race holes.
In said step xv) wherein aligning of the holes of top flange of undercarriage with bearing inner race holes is carried out by releasing the bake of the drive motor and rotating the bearing inner race for said matching of holes.
3. A method for replacement of slew bearing for mobile harbor crane as claimed in claim 2 wherein for said removal of said bearing by pulling, the bearing is joined by chain block through eye bolts being fixed on said outer race holes and thereafter it is pulled on a roller support by rolling over said channel web under pulling force applied through chain block.
4. A method for replacement of slew bearing for mobile harbor crane as claimed in anyone of claims 1 to 3 wherein said step of releasing the special support of said top structure and restoring to its usual operative state comprises removing all tie ropes and column support structure below boom tower and counter weight and lowering the undercarriage cylinders till the crane rests on wheels and the packing below the under carriage are removed , lifting the boom involving luffing cylinder and rotating the boom to carne parking position so that carne can be put on operation involving the new bearing.
5. A method as claimed in anyone of claims 1 to 4 wherein said bearing replacement is carried out faster by way of avoiding the need for dismantling, boom, tower and luffing cylinder, thus minimizing time for replacement.
6. A method as claimed in claims 1 to 5, wherein lifting and lowering of the undercarriage during replacement of bearing is carried out involving crane's existing hydraulic system.

7. A method as claimed in anyone of claims 1 to 6 wherein pulling out of bearing through the gap of top structure and undercarriage is facilitated by using roller assembly over temporary structure.
8. A method as claimed in anyone of claims 1 to 7, wherein aligning of bearing outerrace holes with bottom flange holes of top structure is facilitated by placing balls between roller assembly and bearing bottom surface.
9. A method as claimed in anyone of claims 1 to 8, wherein bearing replacement is carried out avoiding removal of drive pinion and simply by aligning of bearing innerrace holes with top flange holes of undercarriage achieved by releasing braking system of the pinion drive motor.