one more hydraulic question

[bmw63]

one more question, as I prepare to add an additional valve to my tractor. am I correct in assuming it is ok for the valve to have a higher gpm, than the tractor system, i.e. it will still work,and not restrict anything, and the relief pressure should be the same as existing system ?
thanks,brent

 

[RonMar]

That should be fine as long as it is not a gross missmatch(6GPM pump and 200GPM valve). The only place this would be an issue I think would be with the safety. 2000PSI is 2000 PSI, so the safety will open at the correct pressure, the problem on a really large valve is that when the safety cracks open, it is expecting to flow large GPM. It will quickly flow the small GPM from the small pump, drop pressure and slam shut, pressure will build and the valve will burp again. This rappidly pulsing pressure felt back to the pump can be hard on things. A large valve spool is also built to flow a large ammount of fluid to/from the work ports so if too large a valve is used, valve operation may be very sensitive. If the difference is only a few GPM, it should work OK. For instance, My 20+ GPM loader valve on my 5GPM tractor pump works just fine.

 

[bmw63]

ronmar, I was going to use a valve that is 11 gpm, on my 5gpm tractor, however I spied a 5gpm valve that is a little more space saving I think will be a better choice. thank you for your response.
brent

 

[gotrocks]

Kub B-2910 book states pump 6.4 GPM , max pressure 1920 - 1992 psi

Would a valve listed at 5 GPM 2500 psi be Ok?

If not would a valve rated at 25 GPM be satisfactory for T&T addition?

 

[MJPetersen]

Gotrocks, The 5gpm valve would work, but you are in effect closing your system down to the 5 gpm level. Since everything is in series the worst restriction determines the flow for the entire system. Your valve in this case will flow less than the pump will produce (at rated RPM) and therefore will restrict the flow to other hyd events like the 3pt.

I personally do not think that a 25 gpm valve belongs on a 6.4 gpm tractor. It would work mind you, but as explained before not as it should. For a T&T it would be too sensitive and big and cumbersome. Normally they run 1/4 inch lines on a T&T to slow down the sensitivity anyway. You would be better off finding a 8-10 gpm valve.

Mike

 

[gotrocks]

Thanks Mike,
I plan on using an optional cap to hook hyd. lines up and will not be changing any connectons to 3 pt. or FEL.

The addition will only be for Top & Tilt.
Does this make any difference in your reply?

Thanks again,
Norris

 

[MJPetersen]

You going to use a pto pump? What is its gpm rating? Why a pto pump for only T&T? You have plenty of flow for T&T without aux pump and it would be a WHOLE lot more usable hooked into your tractors hyd.

More ?? than answers huh?

Mike

 

[gotrocks]

As you can tell I'm not "hydraulically educated".

I should have stated a 2 spool valve in the beginning.

Not planing to using a PTO pump,
plan to "tap" into the tractor auxiliary hydraulics.

Kub B 2910 has a mid and rear outlet.
The diagram shows "A" to implement inlet max. flow 6.4 U.S. gal/min
"B" from implement outlet
I understand implement to mean the control valve, then the other 4 hoses would connect to the two double acting cylinders and the each valve would activate the individual cylinders one for each valve.

Am I getting close?

 

[RonMar]

Where does that port "B" go to? IF "B" goes back to the resovoir, then you may have a workable plan. However, most small tractor hydraulics do not "TAP" into the hydraulic system, they install control valves in series into a hydraulic stream. These valves are open center so the flow passes thru the valve unimpeded untill a lever is moved and work is being performend.

"Tapping" into a system usually implies the use of a diverter or flow sensing valve. Imagine a 3 port metal block. The flow is normally in on port 1 and out on port 2. Port 3 feeds the tap. When flow is detected leaving on port 3, the fluid is diverted to port 3 denying flow to port 2. This allows pressure to be built(need pressure to perform work) on whatever port is flowing fluid and one port will have priority over another. IF your system works like this, you may need a closed center valve for your added accessory. If you add a open center valve, the diverter will always sense flow to that port thru the opencenter valve and deny fluid to any devices downstream on the diverters other path.

It might be good if you could scan and post the diagram of your system so our answers can be on the same page as your plans.

 

[gotrocks]

Thanks Mike and Pat,
On another thread Bird had given a lot of helpfull advice, then I jumped on this one. Bird told me about the rear outlet on my B 2910 and said I need "open center valves".

I jumped in here because I had read somewhere else about heat build up and was concerned about my pump 6.4 gal/min and a valve I was looking at that was rated 5 gal/min.

Since everyone on this site is so pleasant and helpfull let me keep this going with a scan of my Kub manual and a drawing of what I thought would work for me.

After checking the two pics please tell me if I'm on the right track or all wet.