Core tips: maintenance skills sharing of several parts in engineering machinery (excellent): engine cylinder liner and piston wear and tear are still in line with technical standards, no oil and black smoke, and the engine work is normal, oil consumption is not significantly increased, the hydraulic system and the chassis still can be used, and obviously compared to domestic The mechanical efficiency of the class is high.
1. Emergency repair of dry thin wall cylinder liner
A Komatsu WA420 loader in our company has been working in the field for a long time. With more minerals in the cooling water of the engine and the negligence of the maintenance of the cooling system filter, the cavitation of the engine crankcase at the II cylinder and the cavitation of the thin-walled cylinder are also caved into the hole of the size of 2mm, leading to the oil bottom of the crankcase. The shell is inflow. Considering that the machine has been purchased in 1992, the crankshaft, camshaft and cylinder of the engine have reached or close to the use limit, and it is worthless to invest a lot of money to repair it, but the wear of the cylinder liner and piston of the engine is still in line with the technical standard, no oil and black smoke, and the engine is working normally, and the fuel consumption is not Obviously, the hydraulic system and chassis part can continue to be used, and it is obviously more efficient than the domestic similar machinery. To this end, we turn the original cylinder sleeve 180 degrees, and in the crankcase body cavitation with ab adhesive plugging, and then reassemble the engine, re run to show that the work is normal. With this lesson, the later work is normal. With this lesson, in the later work, management and maintenance personnel attached great importance to the maintenance of cooling water filters. It has been one year since self repair, and the machine is still in use.
2, the repair of the deformation of the engine cylinder head
There are two Japanese Kawasaki KLD85Z loaders in our company. The cylinder head of the engine is warped under high temperature, high pressure, heat load and alternating load for a long time. The cylinder pad is broken from the mouth of the waterway, which causes the pressure drop of the combustor, the engine power shortage and the water outlet of the radiator inlet.
Two cylinder cushions were replaced continuously for a month and then washed away again. After dismantling, it was found that the cylinder block and cylinder head were deformed. The plane degree error of the cylinder body is 50 mu m, which is also in line with the technical requirements, but the plane degree error of the cylinder head is 0.20mm, which is the main reason for the cylinder cushion to be washed out.
The repair method we adopt is that, because there is no combustion chamber concave on the cover, it is not necessary to consider the change of combustion volume (the change value of the chamber volume should not generally exceed 4% of the original volume). The plane of the cylinder head is processed by the method of plane milling, and a copper pad is installed at the port of the joint of the cylinder head and the cylinder body (the copper pad. The thickness is 1.2 times the thickness of the channel hole, instead of the rubber seal ring on the cylinder pad, then the cylinder pad is installed, and the cylinder head bolts are used in the first cold tightening method. The engine repaired by this method has no fault of the cylinder liner.
3, welding repair of bulldozer stand frame
The SH320 type bulldozer was used for 6 years. Because of the effect of bending moment and torque in different directions for a long time, the two support bolts were broken, and it was not found in time. Because it is difficult to repair, and learned that even if the purchase of old pieces also get more than 10 thousand yuan, we decided to use welding technology to repair. The concrete method is to set up the broken bolt first according to the original shape, assemble the platform frame well, weld the crack first, and then remove and pull back to the workshop, use the support to build 30cm, add heat in the 1m range around the crack (prevent local heating deformation), make it reach about 120 C, and then use acetylene flame to cut out V shaped groove, The depth of the groove reaches 3/4 of arm thickness, then welding is carried out. The welding process is as follows: the DC arc welding machine is used, the reverse connection method (welding part is connected to the negative pole), the J507 electrode (heated to 100 C before use), the diameter of the welding rod is 3.2mm, and the welding current is adjusted according to the arc starting condition. After welding, remove the stress (heating to 200-300 degrees slow cooling) and repair it. After welding, the use of the installed machine shows that the quality is completely in line with the requirements. The machine has been used for 10 months, and the work is normal. W-Cr-B
Welding repair of 4, T815 type dump truck
Our company has a total of 30 T815 type auto cylinder cars produced in Czech. In the years of use, it was found that the chassis quality could not meet the construction requirements because of the localization of the chassis part of the car. Some accessories often occurred malignant fracture, which brought great economic losses to the users. After a long period of exploration, we have repaired the vulnerable parts of the machine, such as steel plate, steel plate, spring steel plate and half shaft casing, and achieved good results. During welding, attention should be paid to using DC arc welding machine, J506 electrode, pre heating before welding, heat preservation after welding, eliminating local thermal stress and preventing stress concentration.
5, loading mechanism power
Machining and repairing of piston cylinder
The double pipe pneumatic assist hydraulic braking system is used on loaders. This brake system is also used on a KLD85Z loader of our company. For a long time, the brake booster was suddenly failed during the use of the brake booster. The reason for the failure was that the inner cavity of the hydraulic cylinder of the booster was pitted by the corrosion of the brake fluid for a long time, resulting in the failure of the rubber bowl wear.
After enquiry, the product has no domestic parts and the import price is 12 thousand yuan. Obviously, it is economically uneconomical to buy. We found that the rubber cup in the clutch repair kit of the BJ2020 jeep is similar to the size of the leather bowl of the machine, but the outer diameter is slightly smaller. After reanalyzing the size of the piston cavity, it is considered that this piece is completely machined with a lathe; it is processed with a fast small size to reduce the roughness of the inner cavity; the inner wall is inclined to a certain degree by adjusting the 2-3 degree of the tool holder when the knife is entered; the inner diameter is determined by the outer diameter of the bowl, and is 0.4-0.5mm smaller than its original size. After careful measurement and processing, it can be used normally after repair.
