flow divider

[ke4mns]

hey i built a portable back hoe and put two joy sticks toady i started the system and the vlvs wouldnt work unless i open the other vlv.(example) if i wanted to move the bucket i opened the bucket valve on the right and had to pull back on the left vlv to get it to work,this system is coming from one pump to 2 joy stick vlvs via a tee do i have to go to a flow divider or make the vlvs closed please help mark

 

[hydromech]

It sounds like you have valves that are connecting the pump to the tank in the normal position.

Without moving the joysticks, what pressure does the pump generate? If I am right there will be no pressure.

To stop the oil going to the tank...you have to operate both valves to close off the line back to tank.

What does the second joystick control? Does that work properly?

Do you have any technical information about the joysticks...are they electronic or hydraulic joysticks?

Let us know what you find...

Hydromech

 

[ke4mns]

they are prince vlvs and only one work s good the other is speractic how do i fix this thanks mark

 

[hydromech]

DO YOU HAVE THE PART NUMBER FOR THE PRINCE VALVE?

 

[ke4mns]

the part # is rd522gcga5a4b6 oc, this is a open vlv what would happen if i closed the centers would this work or can you give me a idea with out closing the vlvs,the plans for this back hoe says to use a open center vlv put that is vlvs that are all in one unit thanks for all the help mark

 

[hydromech]

THE VALVE YOU HAVE SELECTED IS A 4 PORT, 4 POSITION VALVE.

IN THE NORMAL POSITION THE PRESSURE PORT IS GOES STRAIGHT THROUGH THE FIRST SPOOL VALVE AND INTO THE SECOND VALVE AND THEN STRAIGHT THROUGH THAT VALVE. IN THE NORMAL POSITION WITH NO VALVES OPERATED THE OIL WILL GO STRAIGHT BACK TO TANK...THIS IS ON OPEN CENTRE VALVE.

THREE POSITIONS ARE USED TO MOVE THE CYLINDER.

NORMAL POSITION...NO MOVEMENT...THE CYLINDER IS LOCKED IN THIS POSITION.
POSITION 1...EXTEND CYLINDER
POSITION 3...RETRACT CYLINDER


THE FOURTH POSITION IS A FLOAT SECTION...THIS SECTION CONNECTS BOTH CYLINDER LINES TO TANK AND ALLOWS THE CYLINDER TO "FLOAT"...THIS SECTION SHOULD BE DETENTED...I.E IF YOU PUSH THE VALVE ALL THE WAY OVER IT SHOULD STAY THERE.

THIS VALVE IS DESIGNED TO ALLOW ONLY ONE SECTION TO WORK AT A TIME...YOU CANNOT MOVE TWO CYLINDERS TOGETHER.

IF THE FIRST VALVE IS OPERATED, THE PRESSURE LINE TO THE NEXT VALVE IS SHUT OFF.

YOU MENTIONED IN YOU FIRST NOTE THAT YOU HAVE 1 PUMP AND A TEE...THIS VALVE SHOULD ONLY HAVE 1 PRESSURE LINE GOING INTO IT...1 TANK LINE AND 4 SERVICE LINES COMING OUT. YOU DONT NEED TO SEPERATE THE FLOW FROM THE PUMP.

I THINK YOU NEED TO RECHECK THE PIPEWORK TO THESE VALVES.

THIS LINK WILL TELL YOU WHAT YOU NEED TO KNOW.

http://www.princehyd.com/products/valves/catalog/ValvesRd5000.pdf

REGARDS

HYDROMECH

 

[kcj]

Apparently he has two open center valves teed together from one fixed gear pump. Since valve number 2 has open center,when valve 1 is operated all the flow goes through valve two in the center.

With a fixed pump there must be an open path for unused flow, else it goes across relief all the time creating heat.

Therefore, options:
1. Use 'power byeond' first valve in which flow out of one vave goes into the second. However, the first one takes prioroty, and the second one will not operate if the first one is being used.

2. Parallel valves that have the unloading/relieving in the beginning of the first valve. That section unloads until either section is shifted. Interupting a pilot flow causes the inlet to stop unloading and go to high RV setting.

3. Get two spools in the same valve and toss the two existing single spool valves. Try

http://www.surpluscenter.com

kcj

 

[ke4mns]

kcj,you are correct that is what is happening i did by these vlvs at surplus center can i close these vlvs off and just use the releif vlvs and the dump to keep a flow through the vlvs i understand it will heat up but i'll be working the hoe i should get plenty of flow but have to shut it down if it sits for any time,now on this parallel option can i see a diagram i will send you my e-amil address later mark

 

[kcj]

1. How many spools in each valve stack?

2. No, I would NOT modify them to closed center. Even if this is physically possible to drill and tap, (possibly the valve is machined for aplug, but usually the lost cost valves arenot), the application will heat up rapidly. The entire engine/pump hp goes to heat.
Plus you would be attemtping to start engine against full blocked pressure each time.

3. The parallel connection I referred to uses different valves than what you have. Pumpe tees to each valve, as you have done, but there is a power beyond or sensing line from V 1 to V 2. Relief unloading is done in V1. V2 is a closed center spool. Any time the sensing line is interrrupted by shifting a spool in either valve stack, the relief unloading in section 1 goes to high and the flow is available to the work spools. I have tried to find a parker example web page to no avail in the quick search I did.

4. You may have to combine both functions in one stack valve and run linkages from joysticks to the common stack. Or, Surplus City had a joystick control for a two section vave from one liever. I think it was Prince. Prince is a common low cost mobile valve.

5. I don't see any way you can realsistically use the two valves you have. Granted its money wasted, but if you have made the entire backhoe, the cost of new valves is small compareed to overall project cost, and why compromise the design or performance at the very end due to a couple hundred dollars more.
Sell the single spool valves to buddies to use on their woodsplitters.


k

 

[ke4mns]

k,these are 2 spool prince vlvs just like you seen in supply center on pg 4 of the double acting vlvs,i dont beleive they were low end vlv the set cost me 500.oo they do have a closed and open plug on them,i didnt build the vlv they were bought that way now in metkit they refer to a joy stick application but dont give you no info,now i have the vlvs sent up in parellel,im getting good info from you and i'm tring i'll keep tring things thanks mark

 

[kcj]

-I went on the prince site referenced above. That should help you understand things much better.

-$250 per valve is not bottom of the line, but it is fairly cheap in the hydr world. Prince is actually a good mobile valve, but by 'low end' I mean not electric proportional, not sectional, and not usually machined for a lot of conversion options. It is not unusual to spend 500 or 1000 for similar valves in other applications.

-The prince literature shows these are capable of power beyond, and in fact may be set up that way now. That may be your easiest way out at the moment, although you will have to decide which function needs to be priorities in valve 1. When V1 is actuated it cuts off flow to 2. There is a small chance, depending on how the valve is cut, that operating both valves together at part flow MIGHT, not for sure, move each load together at a very limited speed. It is not normally the way PB works, but if the spools metering is cut just so it might happen. Its worth a try. and I think your only option at the moment.

-PB is different than series. Simply putting two valves in series doesn't work with most situations, as the pressure created by the load on the second valve is applied to the tank line and all ports of valve 1. Loads may act funny, or the spring cap cavity may also blow up from the pressure. It also defeats the relief valve function in certain situations.

-Power beyond isolates the tank/return line in valve 1 from the center gallery/pressure supply that goes on to valve 2. Thus, Valve 1 takes priority and flow coming out of 1 goes directly to tank, not to the downstream valve.

-Decide which functions you want as priority to be in valve 1. Also, since both valves probably have relief valve inlet sections, you can have V2 RV set lower than V1 and limit the pressure to say the bucket or clamp thumb. Ex: set main RV in V1 to 2500, set RV in V2 to 1500. When V1 is shifted, the first two spools will see 2500 maximum before relieving, because V2 is out of the circuit. When V2 is shifted, the spools will only see 1500 before relieving in V2. V1 always needs to be at equal or the higher setting.

-So, if the priority situation is acceptable, put the two valves in series. First verify that the PB plug is internally correct in Valve 1. Blow air in the P port, and it should come out the PB port. Shift a spool and the air should come out the tank port. For the second valve, remove the internal PB port, and plug the external PB port. Air in P should come out tank port in neutral, and when the spool is shifted. Actually either T or PB might be used as tank connection, depending on the valve, as they should be connected together just inside the casting.
Now, plumb pump to V1 inlet P port. Plumb the Tank/return port of V1 to your return filter. Connect the PB port of V1 into the inlet P port of V2. Outlet of V2 goes to return filter.

-There is apparently a float position on section one of each valve. This could be dangerous if float is connected to boom or jib on one side. If moved into float, the load could drop unexpectedly. Once you sort out the plumbing, take the float end cap of that section apart and disable it by putting some sort of stopper in there.

-I do see from the literature that the two sections in each individual valve are in parallel. That means even with valve 1 taking priority over valve 2, both sections in valve 1 can be operated together. Also, with valve 2 operating, both spools in that valve can operate together.

-The only other options I see using these valves to get true parallel function is to convert to variable piston pump, block the center core of the valves to make them closed center, and run in parallel. That is the most versatile, but I would not go there. Piston pumps need much more care and filtration, you are lookintg at $500-1000 more, and the valve catalog notes that in closed center operation, there can be cross port leakage. There is no internal spool drain connection. If the machine is parted at idle, there is tiny leakage from P port to each cylinder port equally. The cylinders could slowly move in rod extend direction. I have seen this happen, (not my machine) and had a boom move out slowly (20 minutes) until it got hit by a passing train.

kcj