Open center Closed center?

[medic0648]

You need a +20gpm valve that is closed center to work on that tractor. If you may need additional hydraulic functions in the future and have to get another valve I'd recommend upgrading if you can while you're at it.

 

[RickB]

Farmerford,

New guy here. Retired electronics tech and agree, hydraulics is a lot like an electronic circuit. I read with GREAT interest your explanation regarding "open/closed" center valves (spools) (bear with me here I'm still learning the ropes)

I have a JD401-C loader and 3 point hitch. The bucket and lift valves are of the "closed" type. (I have the manual) I am trying to adapt an "auxiliary" valve to control a grappling hook on my bucket. No joy so far. I tried 'inserting' my GB (grappling bucket) valve in 'series' with the bucket valve and while the bucket would work ok the GB did not. I believe the GB valve is of the 'open' center type. (when I pump compressed air into the feed ports and switch the lever to either an up or down position, air freely blows through those ports. Then when in neutral air goes in and then out through the hi side and the low side ports)

At this point I'm not sure of what question to ask next other than I would like to weld a plate just above my bucket valve and mount my grappling hook 'gadget' to my bucket in order to pick up tree limbs etc..) HELP, please.

You need a +20gpm valve that is closed center to work on that tractor. If you may need additional hydraulic functions in the future and have to get another valve I'd recommend upgrading if you can while you're at it.

Nothing about this grapple installation requires a 20GPM valve given that the system is closed center. Open center, yes. Closed center valving only has to flow enough to provide acceptable cylinder cycle times. A commonly available 12-15 GPM CC valve would more than likely be just fine unless the grapple cylinders were unusually large displacement.

 

[hydroholic]

Thanks for everyone's help, I think I'm getting a little closer to solving the problem. And J_J I will definitely try to convert or find out first about the 'array' of valves I do have on hand before I buy any others, real good advice for sure. (used to live in Jax, Fruit Cove on Roberts Rd., just above Switzerland)

hydroholic
(Living on the worlds' largest sandbar)

 

[hydroholic]

Whoops! Sorry, didn't see page 3 but here's a link to some pics I put up last night. (grappling hook)
Tractor Valve

hydroholic
Sandbar w/fl

 

[hydroholic]

OK, so now I'm getting a little more 'up to speed' regarding these valve types. I guess with some compressed air going into the "in" port what should I be looking for with the results I get? And with this information can I then determine "what" sort of valve I do, in fact, have in my hand?

Bottom line is this: In testing a valve with compressed air "what" are the results for each valve type, (open or closed)?

I really do appreciate all the info here from you guys, makes life a LOT easier.

hydroholic
Sandbar w/fl

 

[J_J]

If you can't find one to use, here is the smallest I could find, an 8 GPM valve that can converted to closed center.

Surplus Center - 1 SPOOL 8 GPM PRINCE MB11B5C1 DA VALVE

Hex screw converts the above valve to closed center.

Surplus Center - P-BEYOND & CLOSED CENTER PLUG 8 GPM MB VALVES

Closed Center Conversion
Convert to closed center by inserting the power beyond plug into the internal threads of port C then replacing the steel plug into port C.

Find a convenient place to tap into the main feed line for all the valves and add a tee. Then run a pressure line to the grapple valve and run a hose from the OUT port to tank. Connect cyl hose to work ports and you are now done.

If you wanted to go to solenoid valve, instant response , then use this valve with a DO3 subplate and connect it up and control the grapple using a button on the joystick loader valve.

Surplus Center - 12 VDC 10 GPM CC DA SOLENOID VALVE

DO3 subplate

Surplus Center - 1 STATION DO3 PARALLEL CC SUBPLATE

You will not have a fether capability, but you can add a needle valve and adjust the response to whatever speed you desire.

 

[J_J]

OK, so now I'm getting a little more 'up to speed' regarding these valve types. I guess with some compressed air going into the "in" port what should I be looking for with the results I get? And with this information can I then determine "what" sort of valve I do, in fact, have in my hand?

Bottom line is this: In testing a valve with compressed air "what" are the results for each valve type, (open or closed)?

I really do appreciate all the info here from you guys, makes life a LOT easier.

hydroholic
Sandbar w/fl

When you test an open center valve using air, air flow at the IN port should exit the PB or OUT port continuously.

If you work the lever one way, , air should exit one work port , and if the lever is moved the other way, air flows out the other work port..

If the valve is a closed center valve, lever in neutral, Air at the IN port will be blocked inside the valve. If you work the lever, air should exit the work ports.

There is really more to testing, such as moving the lever part way, and the results you might expect.

You have to know how the valve works before you can do a complete test.

The valve I posted above can be converted to an open center valve, a PB valve, or a closed center valve.

 

[duke7595]

Farmer;

Thank you for the very thorough explanation. Those of us still awake eagerly await your second installment

WAS THAT COMMENT NECESSARY ?

 

[hydroholic]

The cylinder I am using I'm told is a "double" action, i.e. pressure in to open, pressure on other fitting to close grapple. OK, so now I'm off to see if this one can be converted. I'll keep you all posted (probably a week) I'll even put up a u-tube video of the whole thing inaction when done. Yahoooo.

hydroholic
sandbar w/fl

 

[duke7595]

Farmerford

Thank you for your explanation it was very interesting and informative.

 

[hydroholic]

J_J again thanks for your patience with me and these 'basic' questions. Believe me I've asked around here but obviously not the right ones or possibly I'm not too clear in what I want. Anyway I'm going to really study your # 27 post to FULLY get it into my head what to do. (any comments on the picture link would be appreciated, pos or neg, I just want to see if I'm on the right track)

hydroholic
sandbar w/fl

 

[medic0648]

The need for the higher GPM valve is to prevent thermal breakdown of the hydraulic oil due to excessive friction when using the valves. I have a 301a with prince sv series valves that get so hot when using them that you will get 2nd degree burns if you touched them after 30-45min of moderate use. The pump will try to force all of its flow through the valves if no other functions are continually being used.

 

[J_J]

medic0648,

You only need to match pump GPM and valve flow.

Bigger is not always better.

An open center hyd system, the pump fluid is always flowing but at low or no pressure .

A closed center hyd system may have standby pressure at the valve , but no flow.

You should not be getting that much heat if there is no restrictions.

Put a hyd gage in the system and with all valve in neutral, tell us what you read.

Maybe a flow and pressure test is necessary on your tractor.

 

[medic0648]

0psi on output with valves closed. Pump puts out 23gpm. The stated GPM on tractor data is incorrect. It's OK if I don't use the loader much.

 

[medic0648]

The factory loader valve was a Cessna rated for 50+gpm

 

[RickB]

The need for the higher GPM valve is to prevent thermal breakdown of the hydraulic oil due to excessive friction when using the valves. I have a 301a with prince sv series valves that get so hot when using them that you will get 2nd degree burns if you touched them after 30-45min of moderate use. The pump will try to force all of its flow through the valves if no other functions are continually being used.

I understand the principles of closed center systems and respectfully disagree.
More than likely you have an unrelated internal high pressure leak that is causing the heat problem. Intermittent use of an undersized single spool valve isn't going to cause that much heat. It could be a 2 GPM valve and when not in use it may as well be a pipe plug. The user isn't likely to send the cylinder lock-to-lock at full speed anyway. Feathering the spool reduces its capacity.

 

[medic0648]

Notice I said it's OK when not being used. But under moderate use it gets hot.

 

[hydroholic]

OK, this is the way I had the grapple hook installed when my troubles BEGAN.
Break into the bucket/loader valve and insert grapple hook valve and cylinder (in series).
With grapple hook in neutral bucket/loader works as advertised.
Depressing either open or closed on the grappling hook STOPS the bucket/loader operation and the grapple never works. Releasing the grapple back to neutral restores the operation. I feel sure now that the grapple hook valve is of the OPEN CENTER type.

My next move will to convert (or buy) the valve necessary (closed center) and try it again. This time I will put 'T's' in the loader/bucket lines and run the grapple (closed center) hook in that fashion. If that does not work I'm considering installing a large thermal nuclear device and testing it on the back 4 acres. Works for me.

hydroholic
sandbar w/fl

 

[J_J]

Since your tractor is closed center, all valves should be in parrallel, and that means that the same line feeds all valves IN ports.

You don't need to break into the bucket lines for anything.

When you release the lever on a closed center valve, fluid from that valve stops flowing.

 

[hydroholic]

I think I understand you now J_J, i.e. don't break into the "bucket lines" but I will 'T' off the "IN" and "OUT" feeds to the bucket/loader valve and "PARALLEL" my new "CLOSED CENTER" valve to my grapple cylinder.

OK, let me try this and I'll get back to you guys with pictures and a "successful" sigh of "oh, yeah".

hydroholic
sandbar w/fl