Repairing of gear box with welding in the Kosovamont.
Ramaj, Vehbi ; Bytyci, Bajrush ; Osmani, Hysni 等
Abstract: The reparation of gear housing with welding has the
purpose to improve the geometrical form, and obtain again desirable fits
of the wearing and deformable housing. To achieve this, we have to go in
some capital phases: welding, controlling of fits etc. In our case we
will handle the reparation of the gear box which is used in excavator with rotor in open pit mining (Power 400 kW).
Keywords: Repair, gear box, welding, Kosovamont.
1. INTRODUCTION
Kosova Power Corporation (KPC) is using gear boxes mainly for
mining purposes. They are used at coal mines as part of transports
lines.
There are two main types of gear boxes which are used at open pit
mining's and have different functions.
Everyday hard work and bad working conditions are only some factors
that make gear boxes to get damaged. The high price of new gear boxes,
has forced the Corporation to repair instead buy or produce them. KPC
has a working unit, called; "Kosovamont" which repairs damaged
gear boxes.
There are many damages of machinery which "Kosovamont"
repairs. But, here we are going to talk about gear house repairing
through welding processes.
2. REPAIRING OF EXCAVATOR SRS 470 GEAR BOX (POWER 400KW)
Most problems at gear boxes appear because of overloading, working
without oil, bearing deformation, consumption of many parts caused by
friction etc. (Trbojevic, 1988). Due to the mentioned problems, gear
boxes do not work properly (Ibrahimi, 1989), which may cause many times
breakdown of their work and failure of entire system (including
excavators or transport belts).
Most problems appear at contact surfaces between gear houses and
bearings (as at Fig.1. and Fig.2.).
[FIGURE 1 OMITTED]
[FIGURE 2 OMITTED]
3. GEAR BOX REPAIRING PROCESS
After deciding that many parts of gear house are damaged, it starts
the process of repairing them. First the gear house is demounted, and
then comes the control of damaged pieces and the level of the damage
made. If there are damaged contact surfaces between bearings and gear
house, we will clean those surfaces at combined milling machine so
called BORWERK. So we are going to clean places where were shafts and
bearings are placed.
Through cleaning this process we are going to resize diameter of
bearings house at list 3mm more.
After this, we do surfacing-welding using HED welding method
(Bytyci & Osmani 2006.). Repairing of consummated gear house
diameters is done at horizontal, vertical and roof position. Kosovamont
has special equipments and team to perform this welding.
Usually gear house repairing is done at [PHI]600H7, [PHI]540H7 and
[PHI]340H7 diameters repairing.
After welding reparation gear box is sent at the milling machine to
do holes milling dimensions according to our sketch.
[FIGURE 3 OMITTED]
After this, we do surfacing-welding using HED welding method.
Repairing of consummated gear house diameters is done at horizontal,
vertical and roof position. Kosovamont has special equipments and team
to perform this welding.
Usually gear house repairing is done at [PHI]600H7, [PHI]540H7 and
[PHI]340H7 diameters repairing.
After welding reparation gear box is sent at the milling machine to
do holes milling dimensions according to our sketch.
4. BASIC MATERIALS
Gear house is made by steel Ck 45. The steel of this chemical
composition leads us to a conclusion that this steel is for improving.
The attributes of steel Ck 45 are given in the following table (Ramaj et
al., 2006):
5. FILL-IN REPAIRING MATERIAL
Fill-in repairing materials used on gear houses welding usually are
soft electrodes called E432RR22 with diameter [PHI] 3,25mm For this type
of electrode it is used current with intensity I=1001-20A.
Electrodes properties are presented through following tables.
6. REPAIRED GEAR HOUSE CONTROL
Usually repaired gear house control is done in welded surfaces
diameter.
The instruments that are used during measurement are Varner Caliper
and Subitor (inner measuring instrument). Through control it was
measured also the hardness of gear house material with hardness
measuring instrument MIC 10 (Ramaj et al., 2007).
[FIGURE 4 OMITTED]
[FIGURE 5 OMITTED]
Hardness before welding reparation was 26, 5 HRC.
Hardness after welding reparation is 27, 2 HRC
According to this measurement we proved that material hardness
after welding is growing up.
7. CONCLUSION
Because of the high cost of gear boxes it is necessary to repair
instead to buy them. Supply with new gear boxes, also takes much more
time than repairing.
Gear box reparation using welding technique is performed
successfully in Kosovo Power Corporation (KPC) factory by KPC workers
and with equipment at Kosovamont Factory.
Life of repaired gear boxes is enough long to compare its
performances with new gear boxes performances.
8. REFERENCES
Ibrahimi, N; (1989). Detalet e makinave (Elements of machineri),
FIM, Prishtine,
Bytyci, B. & Osmani, H. (2006). Saldimi I (Welding I),
University of Prishtina, Prishtine.
Ramaj, V.;.Bytyqi, B.; Osmani, H.; Kacani, J.; (2006) The heat
treatment of axis and shafts repaired with welding in the
Palaj-Kastriot, "Intellegent Manufacturing & Automation:Focus
on Mechatronics and Robotics", 8-11 November 2006, Vienna, Austria.
Ramaj, V.;.Bytyqi, B.; Osmani, H.; Kacani, J.; (2007) Impact off
Welding parameters at shaft or axes surfacing process, 11 International
research / expert conference " Trends in the development of
machinery and associated technology" TMT 2007, 05-09 September
2007. Hammamet, Tunisia.
Trbojevic, M. D. (1988). Reduktori (gear boxes), Naucna Knjiga,
Beograd, 1988.
Table 1. List of repaired gear boxes at mining equipment factory
"Kosovamont"--Palaj-Kastriot- KPC.
Nr. Name of repaired gear box
1 Repairing of SRS 1300 gear box of transport belt II and IV
2 Repairing of SRS 1300B gear box of transport belt II
3 Repairing of excavators E1.SRS 315.gear box
4 Repairing of SRS.650 gear box of transport belt I
5 Repairing of SRS.470 gear box and actuating drum
6 Repairing of SRS.650 gear box and drum of cleaning belt
7 Repairing of excavator SRS 470 gear box (400KW)
Table 2. Chemical composition
Material Chemical composition, %
DIN C Si Pmax Smax
Ck 45 0,42-0,50 0,15-0,35 0,035 0,035
Table 3. Mechanical properties
Material Mechanical properties
DIN Rv, N/[mm.sup.2] Rm, N/[mm.sup.2] A, % Z, %
Ck 45 360 600-720 18 45
Table 4. Chemical composition
Chemical composition, %
Electrode C Cr Mn Si Mo
EN 499; 0,008 0,01 0,55 0,3 0,02
E432RR22
Table 5. Mechanical properties straightening situation
Rv, Rm, A5 AV
Electrodes N/[mm.sup.2] N/[mm.sup.2] % J
EN 499; 450-500 510-610 22 [greater than or
E432RR22 equal to]60