How to Completely Replace Excavator Hydraulic Oil

The lifespan of hydraulic oil in excavators is typically 4000-6000 hours, requiring replacement every two years. However, unlike engine oil or gear oil, only about half of the hydraulic oil in the excavator's hydraulic system is in the hydraulic oil tank, with the other half distributed throughout the pipes, pumps, valves, cylinders, and motors. Simply replacing the hydraulic oil in the tank would result in mixing old and new oil. So how can hydraulic oil be completely replaced?

First, gather the necessary materials: sufficient hydraulic oil (about 2.5 times the volume of the hydraulic oil tank), filter elements, flushing oil, cheesecloth, rope or iron chain, oil plugs, air pump, and various sizes of empty oil drums.

Extend the boom cylinder, arm cylinder, and bucket cylinder of the excavator to their maximum positions and then turn off the engine.

Next, begin cleaning the hydraulic oil tank. Drain all the hydraulic oil from the tank, remove the hydraulic filter element, disconnect the pipes between the pump and the tank, and drain the oil from the pipes. Flush the hydraulic oil tank and pipes with flushing oil, wipe the inside of the hydraulic oil tank clean with cheesecloth, replace the filter element, and close the cover.

Next, clean the hydraulic pump. Open the upper and lower oil drain ports of the hydraulic pump, drain the hydraulic oil from the pump, close the oil plug at the bottom of the pump, fill the pump housing with flushing oil through the oil port on top of the pump, and then open the bottom oil plug to drain the flushing oil. Repeat this process several times. Finally, use an air pump to blow out any remaining oil in the pump housing, fill it with clean hydraulic oil, and tighten the oil plug.

Also, replace the seal ring of the pump's inlet port, reconnect the oil tank to the pump's pipes, and fill the tank with clean hydraulic oil through the hydraulic filter element oil port.

For the hydraulic oil in the cylinders and motors, the "top-up" method needs to be used to replace the oil.

For the boom cylinder: Use a rope or iron chain to secure the boom of the excavator, disconnect the oil pipe from the boom cylinder's rodless chamber, and collect the discharged hydraulic oil in an empty oil drum. Then connect the disconnected multi-way valve to the boom cylinder's oil pipe and place it in an empty oil drum. Start the engine, and when new hydraulic oil flows out from the multi-way valve to the boom cylinder oil pipe, immediately shut off the engine. Reconnect the pipes and start the engine again to repeat the process until the boom cylinder is filled with oil. Pay attention to changes in the hydraulic oil level in the tank and add hydraulic oil as needed.

The process for replacing the oil in the arm cylinder is similar to that of the boom cylinder. First, disconnect the oil pipe from the arm cylinder's rodless chamber, collect the discharged hydraulic oil, and then connect the disconnected multi-way valve to the arm cylinder's oil pipe and place it in an empty oil drum. Start the engine, retract the arm cylinder piston rod, and then shut off the engine. Reconnect the pipes and start the engine again to repeat the process until the arm cylinder is filled with oil.

The process for the bucket cylinder is also similar to that of the boom cylinder. First, disconnect the oil pipe from the bucket cylinder's rodless chamber, collect the discharged hydraulic oil, and then connect the disconnected multi-way valve to the bucket cylinder's oil pipe and place it in an empty oil drum. Start the engine, retract the bucket cylinder piston rod, and then shut off the engine. Reconnect the pipes and start the engine again to repeat the process until the bucket cylinder is filled with oil.

For replacing the hydraulic oil in the swing motor, disconnect one of the two oil pipes leading to the swing motor from the multi-way valve. Close the oil plug between the multi-way valve and the swing motor, and collect the discharged hydraulic oil in an empty oil drum. Start the engine and slowly rotate the excavator until new oil flows out from the oil pipe leading to the swing motor. When this happens, immediately shut off the engine. Reconnect the disconnected oil pipe and repeat the process for the other side of the swing motor until both sides of the swing motor and the system are filled with hydraulic oil.

It is important to follow these steps precisely and manipulate only the corresponding parts to avoid operating errors. Additionally, any disconnected oil pipes must have their seal rings replaced.
 

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