dump valve question

[LD1]

I understand the question completely, but agree that you probably wont see much difference. And if you put a tee in the base end, And put the valve on the line that returns to tank, you want that valve CLOSED when you extend. Otherwise you would never build pressure as the fluid going to the rod end from the valve would just return back to the tank. The open/closed test needs to be on the return only.

Dump valves are used on pneumatic cylinders ALOT to increase speed. I actually have used them on can crushers to increase cycle time.

IF the dump valves are similar, they are usually labled. They are like a tee with a check valve in them. And labled C (cylinder), E(exhaust) and P or I (pressure/In). In which case you would put cylinder to cylinder, P or I would come from the valve, and the E would be the return to tank.

A dump valve works the same way you are describing with the tee. In which when you are extending the cylinder, the pressure is comming from the valve and entering the P or I port of the dump, and coming out of the Cylinder port and into the cylinder. When retracting, and the pressure/flow is coming in the Cylinder port, the "check valve" inside closes off the P/I port and opens the Exhaust port and offers an unrestricted path back to the tank without having to go through the valve.

 

[muddstopper]

The whole ball valve thing would just to be for a test. I would manualy open and close the valve, before operating the control valve. I would only be timiing the retaction stroke of the cyliner, not the extention stroke. For the testing, I would just drop the return hose into the tank, but if I endup using a dump valve, it would be connected to the return filter.

Now i dont know if I will gain more speed doing this or not, but It cant hurt to try and wont cost me anything. If it does work, then I just have to buy a couple of fitting to plumb it properly. It will either help or it wont.

JJ, I know I can get more speed by increaseing pump size, replaceing the current ports on the cyl with bigger ports, bigger hoses, changing out the control valve, and I even have a accumilator laying around I could plumb in. I am not wanting to spend the money to do any of these things. I am just trying to see if I can get a little more speed out of what I already have, without spending a lot of cash.

oldnslo, What you suggested about the control valve being rated for 25gpm and the return oil being about 29gpm, makes me think that I might gain some speed by simply bypassing the return away from the control valve. I realize return pressure wont be great, but any restriction would increase pressure and reduce speed. Reduceing restrictions and pressure build up should also reduce oil temp.

 

[J_J]

You seem locked into this against all data given so far.

If this is a manual gate valve, you lose time just moving the handle, and you are going to do this on a repetitive basis. The valve doesn't even have to be pressure rated as long as you don't ever block the return line to tank.

Just seems like that will add more time for a full cycle.

The best you could do is to mount an oversize gate valve on the cyl port in a tee, and dump directly to tank.

 

[LD1]

You seem locked into this against all data given so far.

If this is a manual gate valve, you lose time just moving the handle, and you are going to do this on a repetitive basis. The valve doesn't even have to be pressure rated as long as you don't ever block the return line to tank.

Just seems like that will add more time for a full cycle.

The best you could do is to mount an oversize gate valve on the cyl port in a tee, and dump directly to tank.

I think he is just doing the manual valve to test it out, before he spends the money on a actual dump valve.

I know they do work on pneumatics. I dont know about hydraulics, or even if you can find them. Just a quick google search, and the biggest I could fine was 1/2" ports. If you can find them large enough, and if they work like the pneumatic quick exhaust valves, then there is no valve to switch manually. Its automatic.

But let me ask this question...Since you are in the quest for more speed, why did you up to the 5" cylinder?? Did the 4" provide sufficient splitting force?? IF so, why not use that cylinder, with a larger pump. Going with a larger cylinder AND a larger pump kinda defeats the purpose

 

[oldnslo]

Muddstopper,
is the pressure at which your hi-lo pump is set to switch from high flow low pressure to low flow high pressure. As long as the accumulated system loss is lower than this set point you will not see any speed change. As long as you guides on the splitting head are not binding and your lines, filters, etc. are sized for the 25 GPM flow rate I would not expect to see any speed change.

With 25 GPM flow into the rod end your retract speed is 5.8 inches per second or 4.1 seconds for 24" travel
with 28 GPM flow into the rod end your retract speed is 6.5 inches per second or 3.7 seconds for 24" travel

stop watch is easier than wrench flipping in this case. If you are close to these times it is as good as is gets.

Like LD1 stated,
If you looking for speed your options are limited to a different cylinder, or different pump.

A 5" bore with 3.5" rod cylinder would provide very fast return.

25 GPM would give 10 inches second retract speed
28 GPM would give 11.2 inches per second.

This would require some for of dump valve to achieve these retract speeds.

 

[Scooby074]

Have a look about 1/3 the way down here: A + Log Splitter parts hydraulic pumps valves cylinders

They are offering a 30gpm dump setup for $120.

Must be a viable option for a splitter. Maybe call them?

Prince also offers a LSR valve that offers a fast extend (not retract) that works with a fixed, single displacement pump so it likely is of no value to you. http://www.princehyd.com/Products/MonoBlockValves/RapidExtendLogSplitter.aspx

 

[LD1]

Have a look about 1/3 the way down here: A + Log Splitter parts hydraulic pumps valves cylinders

They are offering a 30gpm dump setup for $120.

Must be a viable option for a splitter. Maybe call them?

Certainly looks like it would work. Allthough I dont see why you couldnt mount it right at the exit of the cylinder as well. Less clutter up by the valve.

 

[J_J]

Maybe add some retract springs to the cyl.

If you don't need 24 in logs, add a 8 in plug and accept 16 in firewood. and that will reduce the cycle time.

What do you want, speed or force.

 

[Scooby074]

Certainly looks like it would work. Allthough I dont see why you couldnt mount it right at the exit of the cylinder as well. Less clutter up by the valve.

I guess they must have mounted it there to save money on hoses?

 

[George G]

My guess would be, They are using a pilot operated check valve. When the cylinder extends the check valve closes. When the cylinder is retracting, pressure from the rod end opens the check valve. Allowing the oil from the cap end to freeflow back to tank.