Maintenance skills of the hottest construction mac

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Tips for maintenance of construction machinery parts

the engine cylinder head of two Kawasaki kld85z loaders in Japan from a company warped due to long-term work under high temperature, high pressure, thermal load and alternating load, and the cylinder gasket was washed out from the water channel mouth, resulting in a decrease in pressure in the combustion chamber, insufficient engine power and water pouring out of 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 was found that the cylinder block and cylinder head were deformed. The flatness error of the cylinder block is 50 μ m. It also meets the technical requirements, but the flatness error of the cylinder head reaches 0.20mm, which is the main reason why the cylinder pad is damaged

the repair method adopted is that since there is no concave shape of the combustion chamber on the machine cover, it is unnecessary to consider the change of the combustion volume (the change value of the combustion chamber volume should generally not be greater than 4% of the original volume), and the plane of the cylinder head is processed by plane milling; A red copper gasket (the thickness of the copper gasket is 1.2 times of the thickness of the water channel recess) is installed at the water channel mouth of the joint surface between the cylinder head and the cylinder block to replace the rubber sealing ring on the cylinder gasket, and then the cylinder gasket is installed. At the same time, the method of cold tightening first and then hot tightening is used 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-walled cylinder liners

a Komatsu wa420 loader of a 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 has pitted at cylinder II, and the thin-walled cylinder liner has also been pitted, resulting in 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 oil and black smoke, and 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

for this purpose, we turn the original cylinder liner 180 degrees, and use AB glue to block the cavitation of crankcase body, and then reassemble the engine. Running again shows that it works normally. With this lesson, it worked normally later. With this lesson, the management and maintenance personnel attached great importance to the maintenance of the cooling water filter in their later work. It has been one year since the repair, and the machine is still in use

3. Welding repair of bulldozer platform frame

sh320 bulldozer after six years of use, the platform frame was subjected to bending moments and torques in different directions for a long time, and the bolts of the two supports were broken. In addition, it was 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 use welding technology to repair it

the specific method is to install the broken bolt timer according to the original state, automatically save the test time, assemble the platform frame, spot weld the crack first, then dismantle 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), make it reach about 120 ℃, then cut the V-shaped groove with acetylene flame, 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 (weldment is connected with negative electrode), J507 welding rod (heated to 100 ℃ before use), and the diameter of welding rod is Φ 3.2mm, and the welding current is adjusted according to the arcing condition. After welding, eliminate stress (heat to ℃ and slowly cool), and conduct grinding treatment. The installation and use after welding show that the quality fully meets the requirements. The machine has been used for 10 months and works normally

4. The loader power unit

the loader mostly adopts the double pipe pneumatic assisted hydraulic braking system, which is also used on a kld85z loader of the company. Due to long-term use, once, the brake booster suddenly failed during use. The cause of the failure was found to be: the inner cavity of the booster hydraulic cylinder was corroded by the brake fluid for a long time, resulting in pitting, resulting in the wear and failure of the rubber cup

after inquiry, this product has no domestic parts, and the import price is 1. Compared with the advantages of traditional methods: 20000 yuan. Obviously, it's not economical to buy. It is found that the size of the rubber cup in the BJ2020 Jeep clutch repair kit is similar to that of this machine, and it is proposed that the outer diameter is only slightly smaller since that year. After analyzing the size of the piston cavity again, it is considered that this part can be processed by lathe completely; Adopt fast machining with different problems and small feed to reduce the roughness of the inner cavity; When feeding, adjust the tool rest degree to make the inner wall have a certain slope; The inner diameter is determined according to the outer diameter of the cup, which is 0 5mm. After careful measurement and processing, it can be used normally after repair

5. Welding repair of vulnerable parts of T815 dump truck

a company has a total of 30 Czech T815 dump trucks. During several years of use, it was found that due to the localization of the chassis part of the vehicle, the chassis quality could not meet the construction requirements, and some accessories often suffered malignant fracture, which brought great economic losses to users. After long-term exploration, the vulnerable parts of the machine (such as steel plate lifting lugs, steel plate clips, spring plates and half shaft sleeves, etc.) have been welded and repaired, and good results have been achieved. 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

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