2 detent valves in series?

[Rio_Grande]

Want to add a log lift to my current splitter is there any reason I can't connect two detent valves together? I saw it on a ebay splitter but that don't mean much.

 

[rswyan]

First valve in the series will have to have "Power Beyond" capability. Each valve will have it's own separate return line (which can be tee'd together at some point before the reservoir)

Also, I'd be disinclined myself to add a detent valve for a log lift ... personally I'd go spring-to-center rather than detent, but that's just me.

 

[Tx Jim]

First valve in the series will have to have "Power Beyond" capability. Each valve will have it's own separate return line (which can be tee'd together at some point before the reservoir)

I sure thought I've seen stack type control valves all bolted together with one return line.

 

[LD1]

I agree, I dont think they each need a return. First valve needs to have PB capability on the return. That gets hooked into the pressure port of the second valve. It dont need to have PB but does need to be tandem center.

First valve dont need a return to tank, it will return through the second valve (since its tandem center) when sitting idle. IF first valve also returned to tank, second valve wouldnt develop pressure to work.

What you need to know is what valve you have NOW. IT is most likely tandem center but may or may not be capable of PB. If it is not capable of PB, buy one that is and use it FIRST in the series. If the one you have now IS PB capable, you can buy one that dont have PB and use it second in series.

 

[aczlan]

First valve dont need a return to tank, it will return through the second valve (since its tandem center) when sitting idle. IF first valve also returned to tank, second valve wouldnt develop pressure to work.

I will have to disagree with this.
The point of the return to tank is so that if the OP wants to lower the log lift while extending the splitter ram, the excess low pressure "exhaust" fluid can return to the tank rather than having to come up to the pressure needed by the splitter ram.

Aaron Z

 

[LD1]

IF the valves have a pressure line in series, but you have a return line between the valves, effectivly making the return a parallel circuit, how will the log lift ever work? Fluid will take the path of least resistance.

If you have a return path that has no resistance between the valves thats where the fluid is going to go instead of making the log lift raise.

Lowering the log lift requires almost no pressure. So if you are extending the splitter ram, the fluid coming out of the rod end port would normally just pass through the tandem center lift valve and return to tank. If you actuate that valve, the returning fluid cycles through that cylinder. IF it is just lowering it wont take much if any additional pressure. If it is raising, the pressure is just additive. May require the pump to stay in second stage longer? or may not make enough and stall the rams, in which case you would just quit cycling the lift until the split finished. But I think it would be rare to be trying to lift the lifter while splitting.

 

[aczlan]

IF the valves have a pressure line in series, but you have a return line between the valves, effectivly making the return a parallel circuit, how will the log lift ever work? Fluid will take the path of least resistance.

If you have a return path that has no resistance between the valves thats where the fluid is going to go instead of making the log lift raise.

Lowering the log lift requires almost no pressure. So if you are extending the splitter ram, the fluid coming out of the rod end port would normally just pass through the tandem center lift valve and return to tank. If you actuate that valve, the returning fluid cycles through that cylinder. IF it is just lowering it wont take much if any additional pressure. If it is raising, the pressure is just additive. May require the pump to stay in second stage longer? or may not make enough and stall the rams, in which case you would just quit cycling the lift until the split finished. But I think it would be rare to be trying to lift the lifter while splitting.

With power beyond and a tank line, you have high pressure in, power beyond (high pressure out) and tank (low pressure return to tank)
The only time fluid uses the tank line is when you are moving a valve (such as lifting the log lifter), the fluid from the other side of the cylinder goes to the tank port.
When the valve is in neutral, fluid comes in via the high pressure port and leaves via the power beyond port. In that case, no fluid flows through the tank port.

Aaron Z

 

[muddstopper]

I always get confused with this type of conversation. Are we taking about adding another valve to the circuit or replacing the single spool valve with a double spool valve with detent on each spool. If replacing a single spool valve with a double spool valve with detent each spool, it will work, I am not going to ask why you want detent on each spool. If we are just adding an additional single spool valve to an already existing valve, then the first valve in the circuit would have to be power beyond capable. While not 100% sure I believe the first valve with power beyond would also have another port to tank. When the spool is shifted, it would direct fluid to either the a or b port and fluid from the opposite port would exit the valve and return to tank, not continue on down stream to the second valve. When the spool is in center, fluid would pass thru the valve and continue out of the valve thru the power beyond port, providing fluid flow for the second valve. Not allowing the fluid to return to tank and passing the return fluid thru the PB, could result in the action of the first valve not completing if the actions of the second valve required less pressure than the first valve, as which ever action required the least pressure would be the first to move. Why else would a PB valve have a plug or sleeve separating the return port from the PB port. With out the plug/sleeve, the fluid can pass straight thru the valve, the PB port and the tank port are connected and all fluid flows to tank. Install the plug/sleeve and you have separated the return and PB, so that when all spools are centered, all fluid flows from the IN port out the PB post. Once the spool is shifted, fluid flows thru the A or B port and out the opposite port thru the tank port. Any fluid that flows over the relief also flows back thru the tank port, it doesnt continue out the PB port. The tank port of the first valve can be tee'd into the tank port of the second valve to return to tank since all pressure will be low or no pressure.

 

[muddstopper]

With power beyond and a tank line, you have high pressure in, power beyond (high pressure out) and tank (low pressure return to tank)
The only time fluid uses the tank line is when you are moving a valve (such as lifting the log lifter), the fluid from the other side of the cylinder goes to the tank port.
When the valve is in neutral, fluid comes in via the high pressure port and leaves via the power beyond port. In that case, no fluid flows through the tank port.

Aaron Z

With two valves connected by PB, fluid can pass thru the tank port of the first valve, even if the spools are centered. If the first valve has a relief pressure set lower than the relief setting of the second valve, fluid will flow over the first relief and pass thru the return to tank. First relief should be set higher than the relief of the second valve.

 

[LD1]

I guess the first step that needs answered is what valve he has.

There are some valves that feed power beyond from the tank port as it is pressure rated to do so. That was my line of thinking when I replied. Some valves cannot do this as the tank port is for low pressure only. An acutal PB valve does need a separate return to tank. remove the PB plug and that is where the next valve will go.

Being a logsplitter valve, it may have PB, it may not. IF it doesnt, I'd use that valve for the lift and buy a PB valve to actually run the splitter. Or you could use the PB valve to run the lifter and have the lift the first in series.

 

[rswyan]

With power beyond and a tank line, you have high pressure in, power beyond (high pressure out) and tank (low pressure return to tank)
The only time fluid uses the tank line is when you are moving a valve (such as lifting the log lifter), the fluid from the other side of the cylinder goes to the tank port.
When the valve is in neutral, fluid comes in via the high pressure port and leaves via the power beyond port. In that case, no fluid flows through the tank port.

Aaron Z

Correct.

 

[muddstopper]

Want to add a log lift to my current splitter is there any reason I can't connect two detent valves together? I saw it on a ebay splitter but that don't mean much.

As LD1 pointed out, a log lifter wouldnt need much pressure. While I wouldnt want to be the one that tried this, It could be possible to connect the two valves together, even without PB. I would want to make sure I had the relief on the second valve set low enough that it wouldnt exceed the pressure rating of the tank port of the first valve. Even raising and lowering the log lift, it would be possible to hold the lever just long enough while raising or lifting to create full system pressure, with the relief set low enough, this could be avoided. I dont know what the pressure rating would be for tank port. Might be more than enough to handle a log lift and then again, it might not. I think if I had to purchase the second valve anyways, I would just buy one that I knew was PB capable.

 

[Tx Jim]

I'm curious what is the maximum pressure &//or flow before one needs PBY? I know older tractor hyd's back in the 50's & early 60's didn't normally have PBY.

 

[rswyan]

As LD1 pointed out, a log lifter wouldnt need much pressure.

But that's not necessarily the case ...

A lot of it has to do with the specifics of the design and the actual components used.

Things such as cylinder size, initial starting angle, weight of the lift itself, etc.

I'm running a 2" cylinder on mine (because it was what I had when I built the splitter/log lift) and have found it will not lift heavier rounds at full pressure (with the relief set @ 2000 - 2200 psi) Example: a 24" x 20" (long) fresh, green round of sycamore, which weighs about as much as oak when it's green and unseasoned.

I'm sure that it has something to do with the design and initial starting angle, which is slight.

When I get flush, I'll probably replace that cylinder with either a 2 1/2" or 3" bore cylinder.

 

[LD1]

Yep. Pressure required is based on cylinder bore and length. Shorter strokes are going to be designed different. Longer strokes have greater mechanical advantage requiring less pressure.

Larger bores require less pressure to get the same force of a smaller cylinder.

 

[muddstopper]

Does anybody know what the pressure rating is at the tank port???. I dont know that I have ever seen a rating for that port.

 

[aczlan]

Does anybody know what the pressure rating is at the tank port???. I dont know that I have ever seen a rating for that port.

Often its rated for 500 PSI. NOT something you want to put a valve after.

Aaron Z

 

[muddstopper]

Often its rated for 500 PSI. NOT something you want to put a valve after.

Aaron Z

500psi with a 4in lift cyl would do a lot of work, about 3 tons worth. I still wouldnt be comfortable doing it. Certainly wouldnt want to be in a position where the tank port would see system pressure.

edited to add, the 2in cyl @ 2000psi of Rswyan's will lift the same as the 4in cyl at 500psi. Just for comparison in case someone has a 4in cyl laying around and is now thinking they want to go that route. If its not enough for Rswyan, it probably aint going to be enough for anybody else either.

 

[aczlan]

500psi with a 4in lift cyl would do a lot of work, about 3 tons worth. I still wouldnt be comfortable doing it. Certainly wouldnt want to be in a position where the tank port would see system pressure.

edited to add, the 2in cyl @ 2000psi of Rswyan's will lift the same as the 4in cyl at 500psi. Just for comparison in case someone has a 4in cyl laying around and is now thinking they want to go that route. If its not enough for Rswyan, it probably aint going to be enough for anybody else either.

Until you deadhead the cylinder at the end of its travel and spike the system pressure to the system relief pressure...
I would NOT use the tank port as a power beyond port unless its rated for the system relief pressure.

Aaron Z

 

[Rio_Grande]

I figured I would need a power beyond. It doesn't need to be a detent, the log splitter detent valves are cheap. I have an old tractor valve that has power beyond, might just use it and add my detent to it. That way I would have another valve for an adjustable wedge or similar.