Oil cylinder replacement method for CAT 336 excavator
The hydraulic oil in the hydraulic oil tank of a used excavator is half of the total oil used in the hydraulic system of the entire machine, and the remaining half of the hydraulic oil is stored in the hydraulic pump, motor, multi way valve, hydraulic cylinder, and various pipelines When changing the oil, if only the hydraulic oil in the tank is replaced instead of replacing all the hydraulic oil in the vehicle's hydraulic system, this method only involves blending old oil with new oil If two grades of hydraulic oil are mixed together, it can also cause the oil to deteriorate.
For example, a Caterpillar 336D excavator uses about 520L of hydraulic oil for the entire hydraulic system, while the hydraulic oil in the hydraulic tank is about 325L, and the remaining oil is stored in the system. The ratio of oil used in the hydraulic system of excavators of various brands to the volume of the fuel tank is generally consistent.
Preparation work for replacing hydraulic oil
(1) When replacing hydraulic oil on an excavator, the following preparations should be made: purchase oil for the entire hydraulic system of the vehicle. (2.5 times the capacity of the hydraulic oil tank), filter element, wash oil, 3 kilograms of flour, rope, oil plug to seal the hydraulic oil pipe, (prepared according to the oil pipe on the excavator for oil change), one steam pump, and empty oil drums of different sizes. Prepare a normal excavator. Lift the excavator boom for oil change to the highest point, and when the boom and bucket reach the inner point, the engine will turn off (The cylinder rods of the boom cylinder, arm cylinder, and bucket cylinder are all extended to the vertex).
(2) Cleaning of hydraulic oil tank: Drain all the hydraulic oil in the tank, remove the hydraulic filter element, disconnect the pipeline between the pump and the oil tank from the pump interface, and drain the oil in the pipeline. Rinse the hydraulic oil tank and pipelines with wash oil. Clean the inside of the hydraulic oil tank with a medical sandpaper. Knead the flour until it can stretch and divide it into three parts. Use the dough to clean the inside of the hydraulic oil tank, especially the corners of the tank and the filter cartridge, three times. The hydraulic oil tank and filter cartridge must be thoroughly cleaned. Replace the hydraulic filter element with a new one and secure the cover plate.
(3) Flushing of hydraulic plunger pump: Each type of hydraulic plunger pump on the excavator has a flushing oil port (drain port). Unscrew the upper and lower oil ports to release the hydraulic oil from the pump housing, screw on the oil plug below the pump, fill the pump housing with wash oil from the oil port above the pump, then unscrew the oil plug below the pump to release the wash oil from the pump housing, rinse repeatedly, and finally use an air pump to blow off the remaining oil in the pump housing, fill it with clean hydraulic oil, and tighten the oil plug.
(4) Replace the pump inlet seal ring (O-ring), connect the hydraulic oil tank to the pump's oil supply pipeline, and fill the hydraulic oil tank with clean hydraulic oil from the hydraulic filter element oil port (with the replaced filter element in place).
2. Oil change method for topping out old oil with new oil
(1) Hydraulic oil replacement in the boom cylinder: Use a spare excavator to pull the boom that is ready to change oil with a rope (at this point, the boom that is ready to change oil has been lifted to the highest point), remove the oil pipes from the rodless chambers on the left and right boom cylinders, and use a spare empty oil bucket to catch the released hydraulic oil. Pay attention to environmental protection and prevent environmental pollution. Then place the oil pipe connecting the disassembled multi way valve to the boom in the spare empty oil bucket, start the engine, and the hydraulic oil flowing out from the multi way valve to the boom oil pipe is the old hydraulic oil in the multi way valve. The oil change personnel should pay attention to the color change of the oil. When the new hydraulic oil flows out, immediately turn off the engine. Connect the disconnected pipeline, untie the rope, start the engine, and repeatedly lift and lower the boom until the boom cylinder is filled with oil. Only this single action is allowed. Pay attention to the liquid level changes in the hydraulic oil tank and add the missing hydraulic oil in a timely manner.
(2) Hydraulic oil replacement in the stick cylinder: After lifting the boom to the highest point (only this single action is allowed), the engine is turned off (at this time, the stick cylinder rod is fully extended), the oil pipe with the rod chamber of the stick cylinder is disconnected from the multi way valve, the oil in the pipeline is drained, and the pipeline is reconnected. Remove the oil pipe from the rodless chamber of the boom cylinder at the back of the boom, and seal the opened multi way valve and rodless chamber of the boom cylinder with oil? Manage. Prepare a spare oil drum to receive the hydraulic oil released from the stick cylinder, start the engine, retract the stick cylinder piston rod, and (retract the stick into the cylinder) turn off the engine. After connecting the disassembled oil pipe, start the engine again, extend and retract the piston rod of the stick cylinder several times, place the stick at a vertical angle to the ground, and then turn off the engine to change the oil.
(3) Hydraulic oil replacement in bucket cylinder: Remove the oil pipe from the rodless chamber of the bucket cylinder at the back of the boom, and use oil to block the disconnected multi way valve and the hose oil port of the bucket cylinder. Catch the disconnected oil port on the forearm cylinder with an empty oil bucket, start the engine, and perform the bucket retraction action (the cylinder piston rod is fully retracted into the cylinder barrel), which can only be done as a single action. The new hydraulic oil enters the rod chamber of the bucket cylinder, and after the piston rod retracts, it causes all the hydraulic oil in the rodless chamber of the bucket cylinder to be discharged into the empty oil bucket. Turn off the engine and connect the disconnected oil pipe. Pay attention to the position of the oil level gauge on the hydraulic oil tank.
(4) Oil replacement for the rotary motor system: Disconnect either of the two oil pipes from the multi way valve to the rotary motor. Block the oil outlet of the multi way valve and the rotary motor with oil. Connect the spare empty bucket to the disassembled oil port of the rotary motor, start the engine, and operate the excavator to slowly rotate. If the oil pipe on the motor does not release oil when rotating in one direction, it must rotate in the other direction until oil flows out, which is considered correct operation. At the same time, pay attention to checking the color change of the flowing oil, and immediately turn off the engine when new hydraulic oil flows out. Connect the oil pipe of the disconnected rotary motor and replace the oil.
(5) Replacement of hydraulic oil in the left and right walking motor hydraulic system: Use the excavator boom to support one side of the excavator's walking track, and remove the side cover of the walking motor on its inner side. Disconnect either of the two inlet and outlet oil pipes of the walking motor, seal the disconnected inlet pipe with oil, connect a spare empty oil bucket to the outlet of the walking motor, start the engine, operate the walking control valve on the supported side, and the track begins to rotate until new oil flows out of the oil outlet of the walking motor. At this point, immediately turn off the engine, connect the disconnected oil pipe, and use the same method to replace the other side of the walking motor and hydraulic oil in the system. When replacing the hydraulic oil in the walking motor hydraulic system using this method, be careful not to make operational errors. If the track on the unsupported side is mistakenly rotated, the old hydraulic oil in the walking motor system on that side will flow back into the hydraulic oil tank.
