My Zaxis 120 swing motor seal fail the third time. The excavator run for a few hours only before the new seal broke. Obviously, the casing has been overpressure. The internal has no obvious damage, what could be the reason for overpressure in the casing ? The casing has a drain hole which is plugged, how the swing motor maintain the casing pressure ? In older Hitachi model, the casing drain is routed back th the storage tank.
Welcome to HEF Chaibf . Next time you are apart (if you haven’t done so already) ,With the head off the motor ,blow air through the case drain port and also the case drain hose to confirm they are clear. The brake piston o-rings are good ? When back together,Perform the swing motor leakage test.
The swing motor seal has been replaced the forth time, an additional drain hose routed back to the hydraulic storage was install, run for one hour seal blown again. The seal seemed to be blown when the travel motors were running, oil was blowing out from the swing motor gearbox. Is it possible that the oil return from various motors are sharing the same return route ? This time I am pulling out the hydraulic cooling coil checking for blockage/ cleaning.
Sounds like your swing motor is worn inside and sending pressure to the face seal.
The swing motor case drain and propel motors case drain share the same return tube back to the hydraulic filter in the tank. See screenshot below . Is the hydraulic filter plugged ? Did you perform the swing motor leakage test from post #2 ? .
No, I haven't do the leakage test, we dissemble the swing motor today, the seal is definately blown, upon inspecting the valve plate, the valve plate has two small rings of contacting evident, other parts looks dull in colour meaning that it doesn't contact with the rotary head. We plan to replace the seal, valve plate and the rotary head. I also plan to do leakage rate test on the casing after reinstall. Thank you for the help.
The hydraulic filter looks okay.
We check the oil leakage rate from the swing motor today after replacing the seal fifth time. We check the leak from the casing drain during idling, swing left then right, with bucket from it swinging for 10 minutes, approx 2 liter of oil collected. No level increase in the gear box. We then run the tracks at full speed for 50 yards, the oil level in the gear box rises up to the neck ! Thanks for the kind info, by the way, what is the meaning of the running condition " With the motor relieved" ?
The case drain port and hose were checked and look clear without obstruction last time when we replace the seal
The bucket in the ground , swing motor stalled over relief valve.
Are the swing motor case drain hose and the propel motors case drain hose installed in the locations shown in the picture below ?
Remove the oval plate between the boom cylinder mounts (see screenshot below) and check the swing gear cavity for any sign of oil.
Status update: After replacing the swing motor valve plate and the rotor, the swing motor casing pressure and the seal appear to be okay after a few hours operation. Thanks everyone for the help.