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Oil Change Steps and Precautions of Excavator Hydraulic System

Oil Change Steps and Precautions of Excavator Hydraulic System

Hydraulic excavators usually need to change hydraulic oil after 2000 hours of operation, otherwise the system will be polluted and the hydraulic system of the excavator will be faulty. According to the statistics, about 90% of the faults in the hydraulic system of the excavator are caused by system pollution. This article describes the process steps and precautions for excavator oil change.

1. Preparation
(l) Familiar with the working principle, operation rules, maintenance and use requirements of the hydraulic system of the excavator, so that you can know what is in your mind and not blindly.
(2) Prepare new oil according to the oil specified in the instruction manual. The new oil should be precipitated for more than 48 hours before use.
(3) Prepare tools for disassembling each pipe joint, oil filter for new oil, hydraulic system filter, etc.
(4) Prepare a cleaning solution, a brush, a silk cloth for wiping, and the like.
(5) Prepare oil drums for waste oil.
(6) Select a flat and solid site to ensure that the excavator can turn unobstructed under the condition that the bucket and the arm are fully abducted. The boom will not touch any obstacles after being lifted completely, and the distance from the wire should be greater than 2m or more.
(7) Prepare 4 sleepers so that the crawler can be blocked from front to back
(8) The operator must have at least 4 persons, including: the driver, one on-site commander, and two oil changers.

2,Method and Steps
(l) Place the excavator boom parallel to the direction of the track and stop after turning 45° to the left, so that the piston rod of the excavator bucket cylinder is fully extended, and the piston rod of the excavator arm cylinder is fully retracted. Drop the boom to place the bucket on the ground, then turn off the engine, open the tank bleed valve, pull the operating handles back and forth several times to release the system residual pressure caused by its own weight.
(2) Thoroughly clean the joints of the pipe joints, the pump and the motor, the drain plug, the fuel filler cap at the top of the fuel tank and the bottom drain plug at and around the gasoline.
(3) Open the drain valve and the drain plug at the bottom of the tank to allow all the old oil to flow into the oil drum of the waste oil.
(4) Open the fuel filler cap of the fuel tank, take out the fuel filter, and check whether the residual oil in the bottom of the tank and its edges and corners contains metal powder or other impurities. Thoroughly clean the fuel tank, first clean it with diesel oil, then blow dry the inside of the tank with compressed air. Check for residual sludge, impurities, etc. at the inner corners until they are cleaned, and then rinse again with fresh oil.
(5) Disassemble the following tubing:
1 Remove the oil pipes in the return line, such as the main control valve to the full-flow filter, the oil return filter, the filter to the oil tank between the oil tank and the oil cooler.
2 Disassemble the rotary control valve to the oil return pipe of the filter and the fuel supply pipe of the swing motor.
3 Remove the oil supply line of the hydraulic pump.
4 Disassemble the pilot system to return the oil pipe.
5 Disassemble the drain pipe of the main pump and motor. Thoroughly clean the tubing. The steel tube was cleaned twice with diesel oil, and the hose was washed twice with a cleaning solution, then blown dry with compressed air, and then rinsed again with fresh oil. The joints are blocked with nylon plugs, caps, or used for a net plastic cloth to prevent dust, moisture, etc. from entering and contaminating the system.
(6) Remove the filter element of all the filters in the system. When replacing the filter element, carefully check the filter for metal powder or other impurities to understand the wear of the parts in the system.
(7) Discharge the old oil from the main hydraulic pump, the swing motor, and the travel motor cavity, and fill it with new oil.
(8) Install the oil pipe that has been removed. Before installing each oil pipe, be sure to re-clean the pipe joints and wipe them clean with a silk cloth. It is strictly forbidden to wipe the pipe joints with cotton fabrics such as cotton yarn and towels. Sealing tape should be used when installing threaded joints, and should be applied in the opposite direction to the direction of rotation of the threads. The pipe joints shall be installed and connected in order according to the specified torque.
(9) Fill the fuel tank from the fuel filler. First install the fuel filter, then open the new oil drum, use the oil filter to fill the oil into the tank, add the oil to the upper limit of the oil mark, and cover the fuel cap.
(10) Replace the old oil in each of the following operating circuits. Before changing the oil in each circuit, the machine should be in the three states of the bucket cylinder piston rod fully extended, the arm cylinder rod fully retracted and the bucket freely placed on the ground.
1 pilot control system loop. Disassemble the control oil pipe joint of the left and right travel motor parking brakes, so that the selector valve is in the neutral position, use the starter motor to drive the engine to idle several times, so that the old oil in the pilot system supply line is discharged, and then the pipe joint is cleaned and then The connection is good; start the engine, idle for 5 minutes, then loosen the pilot oil pipe joints on the control valve separately, and operate each action back and forth until the new oil is discharged, then clean the pipe joints and connect them.
2 boom circuit. Place the bucket on the ground, pull the handles back and forth several times, disassemble the oil pipe joint of the boom cylinder without rod cavity, release the old oil in the rodless cavity of the hydraulic cylinder, and then operate the boom handle to move slowly. Slowly move the handle until the joint discharges new oil, then clean the pipe joint and connect it; loosen the oil pipe joint of the boom cylinder with the rod cavity, operate the boom handle, and slowly move the handle to the landing direction until the tubing Before discharging new oil; operate the boom handle, slowly pull the handle in the lifting direction to discharge the old oil in the rod cavity, clean the pipe joint and connect; operate the boom to raise and descend several times to discharge The air in the system.
3 bucket circuit. Loosen the oil pipe of the bucket cylinder with the rod cavity, operate the handle, slowly pull the handle toward the outer direction of the bucket, until the pipe joint discharges new oil, clean the pipe joint and connect it; disassemble the rodless cavity oil pipe joint, Slowly raise the boom to make the bucket about 1.5m off the ground, then slowly operate the bucket handle to make the outside turn to the top, drop the boom, and let the bucket touch the ground; operate the bucket handle, the shovel Slowly move the handle in the direction of the bucket to discharge the old oil in the oil pipe, clean the pipe joint and connect it; lift the boom to make the bucket 2.5m off the ground, turn the bucket inward and outward several times, To discharge the air remaining in the loop
4 stick circuit. Disassemble the oil pipe joint of the armless cavity of the arm cylinder, operate the handle, slowly pull the handle toward the inner direction of the stick, and discharge the old oil in the oil pipe until the new oil flows out, clean the pipe joint and connect it; The rod cylinder has a rod cavity joint, which discharges the old oil in the rod cavity, slowly pulls the handle toward the outer direction of the stick, and ejects the old oil in the tube until the new oil is discharged, and cleans the pipe joint and connects Lift the boom and turn the stick to the inner and outer forces several times.
5 swing system. Disassemble the right (rear) end oil pipe joint on the rotary control valve, operate the rotary handle, and make it slowly turn to the right one turn and then insert the rotary lock pin. When no old oil is discharged, clean the pipe joint and connect it. The same method is used to discharge the old oil in the left swing buffer brake valve,
6 walking system. To support the left track on one side, touch the ground with the round surface of the bucket and make the angle between the boom and the bull's pole 90°~110°; disassemble the front oil pipe joint on the left travel control valve, step on Move the pedal to the left and let the left track slowly move forward until the pipe joint discharges new oil, clean the pipe joint and connect it. The old oil in the right travel line is discharged in the same way.
(11) When all the oil is replaced and the joints are connected, the residual air in the system must be discharged again, because the residual air will cause poor lubrication, vibration, noise and performance degradation. Therefore, after changing the oil, the engine should be operated for at least 5 minutes, and then the boom, the stick, the bucket and the swinging motion should be operated slowly several times. If the walking system is in the state of unilaterally supporting the crawler, the hydraulic oil can be filled. Throughout the system, the remaining air is automatically discharged through the fuel tank after being moved. Finally close the bleed valve.
(12) Check the fuel tank oil level. Fully extend the bucket cylinder piston rod, the arm cylinder piston rod is fully retracted, and lower the boom to make the bucket land; check whether the fuel tank oil level is between the upper and lower limits of the oil level gauge, if the oil level is lower than the lower limit, ), oil should be added until the oil level is close to the upper limit.

3,Precautions
(l) During the oil change process, it is strictly forbidden to start the engine when the fuel tank is not filled and the hydraulic pump and motor chamber are not filled with oil.
(2) During the oil change process, the stopper must be placed before and after the crawler, and the lock mechanism should be inserted into the lock pin; when the bucket, the stick and the boom are in motion, it is strictly forbidden to stand underneath or within the range of motion.
(3) When disassembling each pipe joint, be sure to place the system freely on the ground and confirm that the pipe is free of pressure before it can be removed. When disassembling, people should try to avoid the direction of draining the joint; wear protective glasses when working.
(4) When the upper part of the excavator is turning or walking, the driver must press the horn to make a warning. It is strictly forbidden for the upper station, as well as the station members in the track and swing range.
(5) When disassembling, do not damage the joint surface and thread of each pipe joint of the hydraulic system.
(6) At the job site, smoking and open fire are strictly prohibited.
(7) When changing oil, it is best to finish it on the same day, not overnight, because at night or when cooling, the moisture in the air will form water vapor and condense into water droplets or frost, and enter the system to rust the metal parts, causing hidden troubles.

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