Hello all! First off sorry for the long post. Last time I was here a year ago you guys did your best to help me through a fuel problem with my new to me dozer and it ended up being crud in the fuel tank. I sucked fuel through a hose I dropped in from the fill hole last winter and finally cut tank open last summer and cleaned it out. No prob since, thanks so much for all the good ideas! I will preface this with the fact that I don't know much about the hyd system on this dozer. It appears to be an open center system but looks to use load sensing also. Frankly I am not familiar with this system at all so bear with me. The primary job if this dozer is to pull a tile plow which is at this point being supplied with hyd oil through the ripper valve. Functionality of the plow is great but the hyd oil overheats and it seems the ripper valve is sending way more oil than needed to the plow and likely bypassing via the high pressure relief valve all the time. I fully understand this is not kosher but is the way it was set up when we bought it. What I'd like to do is install a priority valve somewhere between the hyd. pump and the control valves to feed the tile plow. I just need 11gpm to operate the tile plow. I am not familiar with doing something like this and am not sure if it will work or not with this particular system. I also am not sure how to be sure of what size or type of valve (concerning system flow) that I need. I will plan to return oil from the tile plow back to tank. Any help you guys are willing to give is greatly appreciated! Thank you.
Serial number? Photos of the current setup?
Here is the serial number. I don't have any good pictures of the way it's plumbed but I'll try to get some tomorrow. The ripper valve supplies oil to the valve block on the tile plow now. The ripper valve lever is held in the engaged position full time when running.
How do you set the depth with the tile plow control valve outside the machine cab? Your machine wasn't designed for power beyond capabilities. It is a unique system that has a gear pump for a hydraulic pump (usually used for open center systems) but a closed center hydraulic control valve with an unloader valve. The only way to get power beyond capabilities would be to have the attachment control valve be an open center design with the hydraulics from the pump going to it first and then the power beyond port going to the machines control valve second. When you can, figure out where the line coming off the main hydraulic pump is going to first.
The plow control valves are proportional electric over hyd. Grade control is ran by a Trimble gps system. So the system is open center with oil flowing at all times? I'm not familiar with the function of an unloader valve. Do you know the gpm of the dozer hyd pump? Not sure we could run a high amount through the control valve on the plow. This is my reason for thinking about a priority valve ahead of the dozer control valves to feed the plow. Plow only requires 11 gpm to operate. I have been waiting a week for the plow manufacturer to tell me if I have an open center valve. Thanks for your replies thus far!
850C hydraulic pump is rated for 35 - 42 gpm.
It does have a gear pump, so open center, if it does have a load sense valve, than maybe all you need to do is throttle back the ripper control to limit flow, don't stroke the spool the full amount. Worth a try. Next on the cheap trick is to put a flow divider at the plow on the pressure line from the ripper valve, set it for what the plow needs and run the excess flow back through an oil cooler with electric fan and tee it back in at the return filter maybe.
We tried running with the ripper valve only engaged just enough to operate the plow. Didn't make any difference, in fact it almost seemed the oil got hotter. Does anyone know if there is constant flow through the control valves on the dozer at all times? There have been a couple of comments about an unloader valve and/or load sense valve in this hyd system so I'm not sure how it works. I do know that the oil is going somewhere at all times as it is a gear pump.... The more I think about, the simpler it seems to install a flow divider BEFORE the control valves on the dozer and just siphon off 11gpm there for the plow and return it to tank. Do I assume 35-42 gpm is what my priority flow divider needs to be rated for? mg2361, is that total pump output, or what is flowing through the control valves? I suppose that the oil probably only goes to the control valves.... I know I don't want to impede the flow in any way. Sorry this feels like a scattered post, thank you!
That looks like a Danfoss PVG valve stack, if it's the 32 size (they make three sizes) it will flow roughly 33 GPM with no problem, IF it's built as an open center. You need to get that information from the plow manufacturer, what size it is, 32, 100, 120, and open or closed center setup as the valve can be built either way. Hell it can be built at least a dozen different ways, Danfoss is a bit insane at times. As mg2361 said, the dozer appears to have a constant flow pump with a closed center control valve with an unloader. The unloader dumps all the oil to tank until a spool is shifted then the load sense shifts the unloader valve and it builds enough pressure to move the load. It's an odd system, but it works, usually. Actually the problem may be the reverse of what we're thinking, you may not be able to get enough flow through the ripper section and lines, and since it's flowing constantly, the unloader valve is sending part of the oil flow back to tank constantly with a pressure drop, which is what's building the heat.
That is rated flow at 2000 rpm and with 2000 psi of pressure. Free flow at fast idle would be a little higher.
T hread from newagtalk that might help https://talk.newagtalk.com/forums/thread-view.asp%3Ftid%3D531193&sa=U&ved=2ahUKEwjohoe-s6nvAhWSHM0KHb9CCnA4ChAWMAN6BAgIEAI&usg=AOvVaw24npielQiWtiWKOOcf5iIA
Thanks a bunch, this will definitely help me figure this system out! I have searched and searched newagtalk but never came across that particular thread!
chum a achetr
Thanks for your input but I need it translated to English please!