Abstract: the cylinder gasket was replaced twice in a row, and was washed out after being used for one month. After disassembly and inspection, it is found that the cylinder block and cylinder head are deformed. The flatness error of the cylinder block is 50 μ m. If the cylinder head is deformed by 0.20mm, the main reason is that the cylinder head is damaged by punching.
1. Repair of engine cylinder head deformation
Our company has two kld85z loaders from Kawasaki, Japan. The engine cylinder head is warped and deformed due to long-term operation under high temperature, high pressure, thermal load and alternating load, and the cylinder gasket is washed out from the water channel opening, resulting in reduced pressure in the combustion chamber, insufficient engine power and water gushing from the radiator water inlet.
The cylinder gasket was replaced twice in a row, and was washed out after being used for one month. After disassembly and inspection, it is found that the cylinder block and cylinder head are deformed. The flatness error of the cylinder block is 50 μ m. If the cylinder head is deformed by 0.20mm, the main reason is that the cylinder head is damaged by punching.
The repair method we adopted is that since there is no concave shape of combustion chamber on the machine cover, it is not necessary to consider the change of combustion volume (the change value of combustion chamber volume should generally not be greater than 4% of the original volume), and the plane of cylinder head is processed by plane milling; A red copper pad (the thickness of the copper pad is 1.2 times of the thickness of the concave platform of the water channel port) is installed at the water channel port of the joint surface between the cylinder head and the cylinder block to replace the rubber sealing ring on the cylinder pad, and then install the cylinder pad. At the same time, the method of cold tightening first and then hot tightening is adopted to firm the cylinder head bolts. The engine repaired by this method has no fault of overshoot cylinder gasket.
2. Emergency repair of dry thin wall cylinder liner
For a Komatsu wa420 loader of our company, due to long-term field work, the cooling water used by the engine contains more minerals, coupled with the negligence of the maintenance of the cooling system filter, the engine crankcase is pitted at cylinder II, and the thin-walled cylinder liner is also pitted, resulting in serious corrosion Φ 2mm hole, causing water to enter the crankcase oil pan. Considering that the machine was purchased in 1992, the crankshaft, camshaft and cylinder block of the engine have reached or approached the service limit, and it is worthless to invest a lot of money to repair, but the wear of the cylinder liner and piston of the engine still meets the technical standard, there is no burning of oil and black smoke, the engine works normally, the fuel consumption has not increased significantly, and the hydraulic system and chassis can still be used, And the efficiency is obviously higher than that of domestic similar machinery. To this end, we turn the original cylinder liner 180 degrees and block the cavity of crankcase body with AB glue, and then reassemble the engine. Running again shows that it works normally. With this lesson, it worked normally later. With this lesson, in the later work, the management and maintenance personnel attached great importance to the maintenance of the cooling water filter. It has been one year since the repair, and the machine is still in use.
3. Welding repair of bulldozer frame
Sh320 bulldozer has been used for 6 years. Due to the long-term bending moments and torques in different directions, the two support bolts were broken. In addition, they were not found in time, resulting in the fracture of the jib of the platform frame into two sections. Because it is difficult to repair, and we know that even if we buy the core, it will cost more than 10000 yuan. Therefore, we decided to repair it by welding technology. The specific method is to install the broken bolt according to the original state, assemble the bench frame, spot weld the crack, then remove and pull it back to the workshop, erect 30cm with a support, heat it with carbon fire within 1m around the crack (to prevent local heating deformation) to reach about 120 ℃, then cut the V-shaped groove with acetylene flame to make the groove depth reach 3 / 4 of the arm thickness, and then weld. The welding process is as follows: DC arc welding machine, reverse connection method (the weldment is connected to the negative electrode), J507 electrode (heated to 100 ℃ before use), and the electrode diameter is Φ 3.2mm, and the welding current is adjusted according to the arcing condition. After welding, eliminate stress (heat to 200-300 ℃ and slow cooling) and conduct grinding treatment. The installation and use after welding shows that the quality fully meets the requirements. The machine has been used for 10 months and works normally.
4. Loader power unit
Machining and repairing of piston cylinder
Double pipe pneumatic assisted hydraulic braking system is mostly used on loaders, and this braking system is also used on a kld85z loader of our company. Due to long-term use, once, the brake booster suddenly failed during use. According to the investigation, the cause of the failure is: the inner cavity of the booster hydraulic cylinder has been corroded by the brake fluid for a long time, resulting in the wear and failure of the rubber cup.
After inquiry, this product has no domestic parts, and the import price is 12000 yuan. Obviously, if you buy it, it will not be economically cost-effective. We found that the rubber cup in the BJ2020 Jeep clutch repair kit is similar in size to that of this machine, but the outer diameter is slightly smaller. After analyzing the size of piston cavity, it is considered that this part can be processed by lathe; Adopt fast and small feed machining to reduce the roughness of the inner cavity; When feeding, adjust the tool holder 2-3 degrees to make the inner wall have a certain slope; The inner diameter is determined according to the outer diameter of the cup and is 0.4-0.5mm smaller than its original size. After careful measurement and processing, it can be used normally after repair.
5. Welding repair of vulnerable parts of T815 dump truck
Our company has a total of 30 T815 self cylinder vehicles made in Czech Republic. During several years of use, it is found that due to the localization of the chassis part of the vehicle, the chassis quality can not meet the construction requirements, and some accessories often have malignant fracture, which has brought great economic losses to users. After long-term exploration, we have welded and repaired the vulnerable parts of the machine (such as steel plate lifting lug, steel plate clip, spring steel plate and half shaft sleeve, etc.), and achieved good results. Attention during welding: use DC arc welding machine and j506 welding rod, preheat before welding and keep warm after welding to eliminate local thermal stress and prevent stress concentration.
