Hydraulic oil is like the blood in people’s blood vessels. Hydraulic oil is the blood of construction machinery. Its quantity and cleanliness are directly related to whether the entire mechanical operation is reliable and an important part of the operation according to instructions. The oil tank is the container of hydraulic oil. The amount of oil can be checked by checking the hydraulic oil level in the oil tank. The liquid level is at two-thirds of the level gauge.
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The recommended anti-wear hydraulic oil grades are: Winter: L-HM32; Summer: L-HM46. If it is missing, you can add it according to this grade, but you must remember the date when the crane was purchased and whether to use winter or summer oil. Ensure that the new oil is compatible with the oil in the hydraulic pipeline. It is forbidden to use oil containing molybdenum and sulfide, because they will damage the supporting mechanism to avoid mixing and changing the oil quality, and it cannot continue to be used.
1. Daily observation of hydraulic oil
The following are some reasons and hazards of hydraulic oil deterioration:
1. The color turns white and emulsifies, and the hydraulic cylinder becomes weak. Reason: Hydraulic oil is mixed; water enters the hydraulic oil tank, causing the oil to emulsify and deteriorate.
2. If the color of the oil becomes darker, the oil becomes dark yellow or brown: it may be due to long-term high-temperature operation and oil oxidation.
3. If there is a problem with the quality of the oil, the wear resistance is poor, causing the oil additive to deteriorate, and it will corrode the moving components in the hydraulic system and aggravate wear.
4. Observe whether there is precipitation in the hydraulic oil tank and whether the oil tank is tightly sealed. If impurities enter during use, it will also cause the oil to deteriorate.
2. Replacement of hydraulic oil
If the hydraulic oil is deteriorated, it must be replaced completely. The steps are as follows:
1. After the crane is fully retracted, drain all the hydraulic oil in the tank from the screw plug at the bottom of the tank and put it into a large recycling container. At this time, care should be taken to prevent environmental pollution;
2. After draining the hydraulic oil in the tank, disassemble the return oil pipe, clean the tank and oil filter with a chemical cleaning agent with a solid particle pollution level not exceeding 21/17/13, and dry it;
3. After adding new oil of the same brand, start the engine, run it at a low speed, start the oil pump, operate each mechanism separately, and use the new hydraulic oil to discharge the old oil in each circuit of the system one by one. The discharged old oil must not flow into the hydraulic oil tank until new oil flows out of the return oil pipe and the oil pump stops rotating;
4. Connect the return oil pipe to the oil tank, and finally put each component in the initial working state, and add hydraulic oil to the oil tank to the specified liquid level position.
Note: When changing the oil in each circuit, you should pay attention to continuously injecting new oil to prevent the oil pump from sucking out. Of course, you should also pay attention to safety and prevent oil leakage from polluting the environment. Waste oil should also be specially handled.
3. Cleaning and inspection of the hydraulic oil tank suction and return oil filter
The oil tank suction and return filter is a line of defense to ensure the cleanliness of the oil. Some small iron filings and impurities in the system are intercepted and filtered by it. After a period of use, small impurities will naturally be adsorbed on it, and it will often block the passage of the oil circuit, so regular disassembly and inspection to remove impurities is also an important project.
4. Inspection of hydraulic system pipelines
The hydraulic pipeline is the passage of hydraulic oil, mainly connected by hoses and hard pipes. Checking whether the connecting pipes are firm and leak-free is also an easy-to-check item to ensure the normal use of the crane. Hoses are afraid of exposure to the sun because they are prone to aging, which will shorten the service life of the hoses and may cause cracks due to aging and reduce the pressure resistance to form a burst pipe.
Note: Service life of hydraulic hoses: According to DIN20066:2002-10, the service life of the hose assembly and the hoses used shall not exceed 6 years.
5. Inspection of hydraulic valves and locks
Its function is to control the fluid pressure, direction and flow in the hydraulic system, thereby controlling all functions of the entire hydraulic system, such as the working pressure of the system, the action program of the actuator, the movement speed and direction of the working parts, as well as the conversion frequency, output force and torque, etc. Its reliable use plays a role in safety. During routine inspection and maintenance, pay attention to whether there is oil leakage, whether the bolts are loose, and whether the “O” sealing ring is damaged. Find the corresponding parts from the sealing package equipped with the vehicle for replacement, but be sure to pay attention to the release of residual pressure during the disassembly and assembly process, and then cover it with something like a towel to prevent the pressure oil generated by the pressure leakage from hurting yourself.
6. Hydraulic cylinder part
Hydraulic cylinders are an important part of the interconnected structural parts to produce a certain range of motion. Inspection items: Check whether there are oil stains and hard scratches on the surface of the main cylinder piston rod; whether there are oil stains on the valve lock installation surface and hard pipe connection of the cylinder; whether there are oil stains on the guide sleeve position; whether the cylinder stops working halfway through the movement and whether there is an automatic recovery or extension phenomenon, so as to judge whether the cylinder is working normally. In addition, the leaking part of the cylinder rod can be protected by applying butter.
