Use welding technology to restore heavy equipment gears and hydraulic cylinders


1The repair of the slewing reducer gear The main accessory of the QUY80A hydraulic crawler crane is the imported one. The hydraulic system uses advanced load sensing technology. The engine uses a Cummins QSL9 engine with a power of 209kW/2000r. The maximum rated lifting weight is 80, the mass of the whole machine is 79.5, the grounding pressure is 0.082MPa, and the weight is The 24,t track width is 960mm, the center distance is 4200mm, and the height is 1116mm. The hydraulic pump is driven by the diesel engine. The pressure oil output from the hydraulic pump is transmitted to the various devices through the control valve for operation. The rotary device is operated by the hydraulic rotary motor.
During the work process, the crane appears to be unstable, and a squeaking sound will occur at a certain position. The operator stopped the inspection and found that the gears of the rotary reducer were broken and injured. The broken part has fallen on the platform, and only 20 remains on the original gear. The broken teeth are old and the injured teeth are new ones. It can be seen that the broken teeth are caused by severe impact loads. The device has experienced a rollover, which may be the direct cause of broken teeth.
Generally, the heavy-duty mechanical rotary device has straight teeth, which is a low-speed working device with a high speed of 3r/min and a low speed of 1.8r/min.
This speed of rotation is a uniform load and can be repaired by a welding process. This not only ensures the operation of the equipment, but also saves the foreign ordering time (generally more than two months). The repair process is: (1) restart the reducer so that the broken teeth and the injured teeth stay in a prominent position for the welding operation, Make sure the welding process is completed successfully.
(2) Make a pattern that can measure three teeth according to the good teeth of the driving gear, and check the tooth shape frequently.
(3) Carefully clean the grease and stains on the working teeth around the active teeth and the left and right sides of the driven teeth to expose the metal luster of the base to ensure cleanliness.
(4) Protect the gear unit oil seal. Because the driving gear is downward, the shaft and the reducer housing have oil seals to seal the working oil of the reducer. The heat generated during welding has an effect on the oil seal, so it is insulated by winding the shaft with a wet towel.
(5) Preheat the teeth around the broken teeth and the teeth with oxygen and acetylene flame.
Since the rotary reducer is installed in the center of the crane, the rotary ring gear forms a protection for the preheating portion without wind interference.
(6) Select 3.2mmJ807 welding rod to make the base, weld the basic tooth shape, and reserve 2mm3mm of surfacing for the tooth core surfacing, so as to weld the wear layer and then weld the toothed surface with D256 electrode.
These two electrodes should be baked at 300 for 1h2h.
(7) The principle of narrow bead, small current, and short arc should be followed during the welding process, so that it can be welded tightly. Since the tooth profile is 80mm wide, the tooth height is 70mm, the tooth top is 30mm wide, and the tooth length is 100mm, when the welding is carried out, the first layer starts from the root of the tooth to the top of the tooth, and then the tooth is moved first. Side, then two sides in the middle. When the first layer is surfacing, the slag is compacted by hammering. The second layer goes from the top of the tooth to the root of the tooth, first on both sides, then in the middle, then on both sides and then in the middle. This layered multiple layers of layers up and down until the basic tooth profile is welded. Each layer must be struck and the welding direction of each weld is reversed.
(8) After the basic tooth shape comes out, clean the surface with an angle grinder.
The toothed surface of the D256 electrode is used to weld the toothed surface, and a wear layer is added.
(9) After the surface of the tooth surface is welded, the basic shape of the tooth is first polished by an angle grinder. During the grinding process, the convex part is continuously inspected by the toothed template. After the shape is determined, the stone is refined. At this time, we must be careful and meticulous, follow the principle of Ning slow, not thin, no fat, first high back, compare up and down, until the tooth surface is smooth.
The above process can also be used for the tooth, but the amount of welding is reduced.
This repair process took two days from preparation to completion. After the equipment was repaired, it has been used for more than 1000 hours, which not only saves time and effort, but also saves a lot of money.
2 Hydraulic cylinder crack repair Our Hitachi original EX750 front shovel excavator has a bucket capacity of 3.6m3. The engine adopts American Cummins N14C engine with rated power of 324kW and the whole machine weight is 75t. The cylinder of the hydraulic cylinder is 240mm. The inner diameter is 200mm, the total length is 1700mm, and the crack length is 1450mm. There is no crack at only two cylinder heads. After analysis, it was decided to repair the hydraulic cylinder by welding process so that the excavator left the working surface as soon as possible. The repair process is as follows:
(1) Since the weld is too long, two pairs of semi-circular clamps must be made to radially contract the cylinder to return to the original state.
(2) Use two pairs of semi-circular clamps to tighten the clamps at 1/3, 2/3, respectively, so that the cracks are basically closed.
(3) Use an angle grinder to open a longitudinal groove along the crack direction, the depth of which is 80 cylinder wall thickness, and the angle is between 6070.
(4) Select 707 electrode and dry, section welding, the length of the section should not exceed 200mm. In each welding process, each weld should be cleaned, and the weld is hammered and reground with an angle grinder. The non-porous seamless state, and then the second weld, this will ensure the welding is compact. The welding section is first in the middle, the last two, and the last section is selected in a cylinder head until the seam is welded.
(5) Since the slag may enter the inner wall of the cylinder during the welding process. When the compression is tightened by the semi-circular clamp, the inner wall of the cylinder tube is slightly displaced up and down, so the inner wall must be polished with a 100 mm diameter wheel boring oil, and the smoothness is not suitable for shaving. Since the depth of the cylinder is about 1450 mm, the grinding wheel must be fixed on a steel bar with a length of about 2000 mm and a diameter of 20 mm. The fixing method is very simple. A bolt is welded on the steel bar. The diameter of the bolt is equivalent to the inner hole of the grinding wheel. The length of the bolt is larger than the thickness of the grinding wheel. The external nut and the flat pad can be compacted. Manually honing from the inside to the outside, the honing process ensures a sufficient oil film, and the edge grinding is checked, both the longitudinal smoothness of the crack and the smoothness of the circumferential direction are checked.
(6) After honing, clean it, remove the clamp, and install the piston and piston rod. When the piston is installed and enters the cylinder, it must be ensured that there is sufficient hydraulic oil. Due to the corresponding shrinkage of the cylinder welding process, the piston entering process will not be as smooth as the original cylinder, so that it will not affect the installation, and the hammer can be used.
(7) After the hydraulic cylinder is installed, it can be hoisted and filled with hydraulic oil to the calibration position. Do not do the action first, do the work after a while, and observe whether there is oil leakage. Generally, oil leakage does not occur. In this case, there is no problem for ten days of continuous work, even if there is a problem, it is caused by high-pressure cavitation in the later stage.
The purpose of this repair is to let the excavator leave the work surface. It is completely feasible to take such repair measures.

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