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