Understanding Hydraulic Circuits

Happy13

New member
Lifetime Member

Equipment
L3600 GST, LA680, Bradco 509, Barfoot Welding 84" Snow blower, Mott 60" Flail
Jan 13, 2022
6
0
1
Massachusetts
I have an L3600 with an LA680.
A local Kubota Dealer installed a Bradco 509 backhoe about 10 years ago.
The Power Beyond from the Loader block gets disconnected from the 3 point lift line (via quick connects) to power the Backhoe. Works great.
The 3 point lift is disabled but isn't needed when the backhoe is attached.
I recently acquired a Barfoots Welding Snow blower with hydraulic chute movement.
I bought a 2 spool valve and utilized the connections meant for the backhoe to power the remotes.
Works great.
I do need to use the 3 point lift to raise and lower the blower.
Thinking that both the remotes and the 3 point lift need high pressure I installed a tee from the Power Beyond at the Loader block.
Nothing.
Connect one at a time and they both work great.
Second try:
I suspect that the "Vevor" 2 spool valve which has an N (neutral) is from what I've gathered online is their term for Power Beyond.
I subsequently tapped into that and fed it back up front to complete the 3 point circuit.
No Dice.....Blower remotes still work fine.
I would like some Pro advice.
Can someone expand on what I am not seeing.
 

Dave_eng

Well-known member
Lifetime Member

Equipment
M7040, Nuffield 465
Oct 6, 2012
4,444
536
113
Williamstown Ontario Canada
Simply put you cannot Tee into a pressure line on an Open Center hydraulic system. The pressure will take the path of least resistance and not do any work for you.

Most hydraulic valves do not like pressures over 450 psi on their return or tank port. some tolerate it but it is not the correct way.

See if a power beyond sleeve or plug can be added to your Vevor valve

Dave
 
  • Like
Reactions: 1 user

TheOldHokie

Well-known member

Equipment
L3901/LA525, B7200DT/B1630, G2160/RCK60, G2460/RCK60
Apr 6, 2021
1,139
462
83
Myersville, MD
Simply put you cannot Tee into a pressure line on an Open Center hydraulic system. The pressure will take the path of least resistance and not do any work for you.

Most hydraulic valves do not like pressures over 450 psi on their return or tank port. some tolerate it but it is not the correct way.

See if a power beyond sleeve or plug can be added to your Vevor valve

Dave
Vevor is just an online retailer that rebrands and sells everything from donuts to doillies. They know nothing about the products they sell.

I believe the Vevor valves are a Chinese made version of the P40 and they dont offer a conversion sleeve for it. The N port thread on them 1/2" BSPP (G thread). No gaurantee but it may accept one of the BSPP sleeves from other manufacturers. Summits P40G valves have G thread power beyond ports and they sell a P40G sleeve for them. You could contact them and ask. Or just risk $22 and buy one to test.

Dan
 
Last edited:

Happy13

New member
Lifetime Member

Equipment
L3600 GST, LA680, Bradco 509, Barfoot Welding 84" Snow blower, Mott 60" Flail
Jan 13, 2022
6
0
1
Massachusetts
Simply put you cannot Tee into a pressure line on an Open Center hydraulic system. The pressure will take the path of least resistance and not do any work for you.

Most hydraulic valves do not like pressures over 450 psi on their return or tank port. some tolerate it but it is not the correct way.

See if a power beyond sleeve or plug can be added to your Vevor valve

Dave
Hi Dave, Thanks for the input.

I'm learning a lot but there's more to go.

Jim
 

Happy13

New member
Lifetime Member

Equipment
L3600 GST, LA680, Bradco 509, Barfoot Welding 84" Snow blower, Mott 60" Flail
Jan 13, 2022
6
0
1
Massachusetts
Vevor is just an online retailer that rebrands and sells everything from donuts to doillies. They know nothing about the products they sell.

I believe the Vevor valves are a Chinese made version of the P40 and they dont offer a conversion sleeve for it. The N port thread on them 1/2" BSPP (G thread). No gaurantee but it may accept one of the BSPP sleeves from other manufacturers. Summits P40G valves have G thread power beyond ports and they sell a P40G sleeve for them. You could contact them and ask. Or just risk $22 and buy one to test.

Dan
Hi Dan,

I appreciate the advice.

I will look into the sleeve you mentioned.

Best Regards,

Jim
 

TheOldHokie

Well-known member

Equipment
L3901/LA525, B7200DT/B1630, G2160/RCK60, G2460/RCK60
Apr 6, 2021
1,139
462
83
Myersville, MD
Hi Dan,

I appreciate the advice.

I will look into the sleeve you mentioned.

Best Regards,

Jim
Hi Jim,

I have used the European P40 valves in a number of products I sell. and been happy with them. Summit has been selling them for years and they have pretty good product support. I have no hands on experience with the ones coming out of Asia.

I recently purchased a P40 direct from Poland to evaluate and all of the ports on it are G thread so I happen to have a power beyond sleeve from it to compare with the SAE sleeve out of a Summit P40 valve. I have no way of knowing who the actual OEM is on these valves but I based on the castings I suspect they come from different sources.

Here is a pictures to illustrate the differences and similarities of the HPCO sleeves - SAE-10 sleeve on top, BSPP 1/2G sleeve on bottom. The key dimension is the distance from the base of the port thread on the plug to the o-ring on the end. That oring is what seals the tank core off from the center core. As you can see that distance is the same on both sleeves leading me to think the only difference is the thread itself and the design of the port o-ring seal. The o-ring on the SAE port fits inside a chamfer in the casting. The BSPP o-ring fits in a recess in the head of the plug and seals against the face of the casting. But when screwed in tight the cavity o-ring depth and bore on the end of both plugs is in the same position inside the casting leading me to believe the chances are good (99% ???) a Summit P40G sleeve will work in your Vevor valve.

Dan

PS> N and C are both used as high pressure carry over (power beyond) port labels and probably stand for "next" and "carryover"

p40HPCO.jpg
 
Last edited:
  • Like
Reactions: 1 user

Happy13

New member
Lifetime Member

Equipment
L3600 GST, LA680, Bradco 509, Barfoot Welding 84" Snow blower, Mott 60" Flail
Jan 13, 2022
6
0
1
Massachusetts
Well Dan, I can thank you enough for the attention that you offer here.
I know that the N port on the valve is a 1/2" BSPP.
I ordered the sleeve this morning but wasn't sure why it would work.
I constantly seek the engineering down to the last detail (which drives most people crazy) and this is it. I see now that the adapter that I installed didn't have a function other than hose to valve.
So refreshing.
I will receive the part next week. I look forward to testing it out.
I will keep you informed.

Thx

Jim
 

TheOldHokie

Well-known member

Equipment
L3901/LA525, B7200DT/B1630, G2160/RCK60, G2460/RCK60
Apr 6, 2021
1,139
462
83
Myersville, MD
Well Dan, I can thank you enough for the attention that you offer here.
I know that the N port on the valve is a 1/2" BSPP.
I ordered the sleeve this morning but wasn't sure why it would work.
I constantly seek the engineering down to the last detail (which drives most people crazy) and this is it. I see now that the adapter that I installed didn't have a function other than hose to valve.
So refreshing.
I will receive the part next week. I look forward to testing it out.
I will keep you informed.

Thx

Jim
I share your obsession with scientific and engineering details. A greater depth of understanding makes problem analysis a lot easier. So here is open center high pressure carry over (aka power beyond) in a nutshell.

In an open center hydraulic system a directional control valve has two main flow paths. The center core is the one that conveys pressurized oil from the pump past the spools and out the other side. The tank core actually consists of two parallel cores and is used to convey oil returned from an actuator (e.g. cylinder or motor) to the hydraulic reservoir.

Those three passages normally merge together at the outlet on the valve where the entire flow goes to the reservoir. If you are going to use the valve to feed another downstream valve the center cores and tank cores need to be kept separate. That's where the sleeve comes in. When it is installed in the HPCO port it acts as a little pipe separating the outflows. The high pressure center flow goes through the sleeve and out the HPCO port to the next valve. The two low pressure tank core flows go around the outside of the sleeve where they merge and go out the tank port and directly to the reservoir

Dan

HPCOcrossection.png
 
Last edited:

Happy13

New member
Lifetime Member

Equipment
L3600 GST, LA680, Bradco 509, Barfoot Welding 84" Snow blower, Mott 60" Flail
Jan 13, 2022
6
0
1
Massachusetts
Really good stuff Dan, I understand the concept. This makes sense.
If I were to find this schematic and section I would say "hey that's not my valve" but it is.
Just the way I absorb stuff. The way I learn best is by watching an example and seeing it work. All of my mentors are gone now, unfortunately.
In the attachment, the top connection on the left is the N port. To cold (-8 F this morning) in MA. to goof around. The sleeve will go before the right angle adapter.

I think I'm getting there.


Thx again

Jim
 

Attachments