We have Bucyrus RH90C E, and we have problem with the bucket cylinders. When the cylinders are fully Retracted and when controls are in neutral, cylinders bucket begin to extend on one portion of his stroke. We checked servo sistem and relief valve. we have 300 bar on both sides of cylinder on max hp. When it freely move, pressure in work line decreases on 0 bar to its stop point, when it stoped pressure begin to increases to ~12 bar. We suspect on cylinders, If someone knows another option ?!?!?
That would be my guess, piston seals are bypassing, weight of the bucket pulling until it finds balanced spot. Since the rod end has less displacement than the piston end, when the cylinder begins to extend it actually will create vacuum and the check valves in the main valve will open and keep the cylinder full with oil.
Hi Husika , Is your cylinder falling both ways.? ie Falling out after the bucket is crouded in full and then Falling in after it is crouded out full.? If it is only falling one way then it may not be your cylinder. Secondaries give trouble on the 120's and allow the oil out of the cylinder via the valve. Check first if falling one way or both. If only one way then take a look at your secondary relief for which ever side it is bypassing on. Regards Ciaran