Hi I have a late 90's Hyundai 210-3 excavator which has been running a hammer but i want to convert the aux lines over to double acting and run a hydraulic thumb. The current flow is unrestricted from the option spool with just ball valves on the stick to close flow. From memory the bucket i was looking at had 1/2 inch hoses so the piping on the machine is massive over-kill so im wandering what the standard flow control valve looks like for these conversions on older machines. I would of though a 3 port valve block with drain to tank would be the go but also thought a simple inline flow control valve with reverse check would work with the excessive pressure going over the option spool relief valves. I know this isnt the best option but in essence it would work right? On the hammer pressurized line i put a half inch reducer fitting on with ball valve wide open and machine at high idle and got 3800 psi. Im not exactly sure of the flow rate but the piping is large at least 1 inch inner diameter with the return line even bigger, could even be 1 1/2. cheers
Oversize piping won't make any difference on operation of the thumb. You can only put so much flow through the valve in the first place. Generally you want a larger pipe on the return to keep return pressure at a minimum on the outflow of a hammer. If your machine doesn't have it, you will need a three way valve on the return so you can shift flow from the tank to back into the valve bank again to use the thumb. I used to use a simple cross over valve block mounted on the boom for pressure control. It had a relief valve for each flow direction and a small relief drain line that went back to tank. Since you have a hammer already, it is likely that there is one port relief installed in the main control valve. If so it would likely be easier and cheaper to install a port relief in the other port of the main control valve. There are a few ways to control speed of the thumb if that is a problem. I don't know how you are going to actuate it from the cab so will stop here. Good Luck
Thankyou John C, i failed to mention that i will be ditching the hammer......for good, i never want to break another piece of cement again and taking away this option will prevent me from being lured into any more hammer jobs. In lieu of this, would i still need this 3-way valve on the return line you speak of? There are port reliefs on both of the MCV option spools so thats good. Yes what im concerned about is the speed of the thumb and what is the best method to reduce flow is. Thumb actuation will be electronic via joystick and solenoid directional control valve, ive installed these before on smaller jobs however on small cylinders with low flow. From memory this machine puts out somewhere between 35-40 gpm @ 3900PSI at the MCV The cylinder i have for the thumb has a 4 1/2 inch bore, 2 1/2 inch rod and 42 inch stroke. Cheers Noah
I'm not familiar with your model of machine so not sure if your stated flow of 35 - 40 GPM is two pump flow or one pump flow and don't know if your system can put two pump flow into an auxiliary valve. I wouldn't worry about the flow rate until you get the thumb set up on the machine and see what you have before working on limiting flow. You can just run back to the main valve with your return hose to get two way flow and don't need the three way if not going to use the hammer or something else with a motor. You will have to see if the circuit reliefs will dial down to about 2,100 PSI which is what most thumbs run at for pressures.
I was able to dial in the relief to 2000psi no problems however I was miles off in terms of pressure settings. I’ve got 4800psi at 8 gpm which is one pump flow according to the manual.
I would guess that the 8 GPM is the destroke setting when something is going over the relief and not moving. It's probably a lot more at 2,000 PSI.