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Help with Hydraulic Design

Johnny SolidWorks

Hot Rolled
Joined
Apr 2, 2013
Location
Rochester
Good Morning Gang

I'm looking for some guidance (or maybe just a sanity check) on a really simple hydraulic system.

I've got a double acting cylinder (3" bore x 60" stroke) I need to power. Max cylinder pressure is 3000 PSI, but I'll never need it all. The only reason I'm using a hydraulic cylinder is because it's about the only thing readily available and cost effective in this stroke length that's still double acting. And the usage of this is going to be really minimal - think of it as a long-stroke positioning system, manually controlled.

To fully extend the cylinder will take ~1.84 gallons of fluid, so a 1.4 gpm hydraulic power unit will take ~1.3 min to fully extend this cylinder, correct? Or, since I'm not going to be anywhere near the pressure rating of the power unit, will it actuate faster?

Next up: I'm looking at a power unit (really needs to be single phase) that's rated for 2000 PSI and 1.4 gpm (2 HP) with a 5 gallon reservoir. I'm happy with the reservoir size (~3.6X the rated flow) and "Unit comes fully assembled with filler breather, fluid level gauge with thermometer, pressure gauge, relief valve, and a manifold block for mounting a valve. Fixed-clearance pump. Manifold is for direct pressure and tank (P&T) plumbing."

So if I put a 4 way manual control valve on the manifold block (called out as D03 - I'm guessing that's a standard valve mounting of some sort?) and run a hydraulic line to each end of the cylinder from the valve....that should be good - but I just have this feeling I'm forgetting something obvious. I'm looking for typical log splitter operation: push the handle forward, the ram extends. Let off, the handle springs to center and the ram holds. Pull the handle back, the ram retracts. Let off, the handle springs to center and the ram holds. That said, I do want the cylinder to hold position with the handle in the center position, even with the hydraulic power unit switched off, which means a closed center valve, correct?

Tell me how I'm stupid? (In relation to this, please.)

Thanks!
 
Just be sure the valve has the right configuration. ie closed center open center ect. There are a couple others.
 
"Will it actuate faster" ?

sounds like a simple squirrel cage (induction) motor on the standard gear pump.
If so, I would say No.

If an "Enerpac style" universal motor, I would say yes (read the chart),
you can change out the cartridge pressure relief valves for your
lower pressure requirements.

If you use a load sensing variable displacement pump (not likely on
a simple, low cost system) then YES, it can run as fast as you Have
motor H.P.

The log splitter crowd runs a 2-stage gear pump, that would get you more
speed when un loaded, coupled to a standard induction (squirrel cage) motor,
would get you a "2-speed" system. Might be a workable compromise.

You can also get (IIRC Prince makes one) a valve with "regeneration"
to speed up the extension speed, until you hit the load.
 
closed center has nothing to do with the cylinder side of things, that refers to whether oil flows freely through the valve from P to T with valve in center. Spool type will determine if cylinder ports are blocked in center position. I would go with an open center valve on that type of setup, that way when cylinder is not being moved the pump does not have to build pressure, but just flows oil through the valve and back to tank, less heat buildup and less electric.

Will it actuate faster with no load on cylinder, yes and no. No as the pump is more than likely a fixed displacement pump load should not affect output. Yes in the aspect of there wont be as much leakage in the pump, valve, cylinder, at lower pressures and the motor will have easier time spinning at full speed, not bogged down but probably not very noticeably faster.
 
D03 is a standard subplate for mounting either solenoid or manual valves.

Your power pack is probably going to use a gear pump, which pumps a specific amount of fluid regardless of the pressure (unless you are overloading it). Gear pumps require open center valves. Open center valves allow fluid to go back to the tank when you aren't putting it through the cylinder, so the pump can run with no load. If you use a closed center spool, you will force the pump to pump fluid through the relief valve, which basically results in idling at pumps maximum power. (This also heats the hydraulic fluid very rapidly). If you need the cylinder to move quickly under no load and then slow down under load (to limit the required power, typically) you either need a variable displacement pump, or a two stage (log splitter type) that pumps very fast when less than around 600 psi, then switches over to about 20% of maximum pumping speed when greater than 600 psi.

If you want the cylinder to stay in place in the center position, you are looking for what is known as a cylinder spool valve (this is the most common). The opposite of this is a motor spool valve, which is designed to allow a motor to coast freely in the center position. (A motor spool valve on a cylinder results in a cylinder that doesn't hold position, and a cylinder spool valve on a motor often destroys the motor because the motor suddenly locks solid but the inertia of what it was driving keeps going).

This place has a lot of fittings and hydraulic parts if you need:
Hydraulics | www.surpluscenter.com

And has a handy technical help section with lots of hydraulic calculators:
Surplus Center

The best way for any of us to help you is to link to everything you are buying and we can make sure it all checks out.

EDIT: Gear pumps produce a flow directly related to motor rpm. So if you have a variable speed motor, you will have variable cylinder speed. If it uses a DC series wound motor or a universal motor, this will be pretty much automatic because of the speed/torque curves of these. If you were to, say, put a motor on a vfd, you would be able to control the flow but if it hit a load it would try to continue at its current speed regardless of how high the pressure goes and how much power it has to draw.
 
IMHO,you can buy a chinese hydraulic log splitter cheaper than two new hydraulic hoses......and your machine will need four hoses,unless you put the valve in the tank and let the return overfow direct inside the tank..I have tons of hydraulic stuff,valves cyliners pumps, motors,what have you...But even with free parts ,hose costs make most projects uneconomic.
 
IMHO,you can buy a chinese hydraulic log splitter cheaper than two new hydraulic hoses......and your machine will need four hoses,unless you put the valve in the tank and let the return overfow direct inside the tank..I have tons of hydraulic stuff,valves cyliners pumps, motors,what have you...But even with free parts ,hose costs make most projects uneconomic.

Example please ?
 
Hose cost here are extreme....for instance ,prices were set in the dark ages when all fittings and hose were locally made.Now everything is Chinese,including bulk hose.....3/8" crimp fitting cost 25c each,and bill out at $5 to $15 each....Hose that costs $2/meter bills at $25-30 per /m...Average for a 3/8" hose with standard JIC or DIN fittings would average $125,so use four new crimped hose assys,looking at $500.....Chinese hydraulic splitter with electric or gasoline power sells under $200....Consequently no one builds anything ,and the unemployed fitters are Uber drives,or Food2Go jockeys.....The lucky ones have pizza delivery jobs,with regular shifts......And a rising resentment in the young for anyone who owns a house or land....Easily exploited by politicians.
 
Hose cost here are extreme....for instance ,prices were set in the dark ages when all fittings and hose were locally made.Now everything is Chinese,including bulk hose.....3/8" crimp fitting cost 25c each,and bill out at $5 to $15 each....Hose that costs $2/meter bills at $25-30 per /m...Average for a 3/8" hose with standard JIC or DIN fittings would average $125,so use four new crimped hose assys,looking at $500.....Chinese hydraulic splitter with electric or gasoline power sells under $200....Consequently no one builds anything ,and the unemployed fitters are Uber drives,or Food2Go jockeys.....The lucky ones have pizza delivery jobs,with regular shifts......And a rising resentment in the young for anyone who owns a house or land....Easily exploited by politicians.

The OP is not building a gas powered log splitter.

As far as an electric Chinese version, please note the OP's requirements of a "60" stroke".

The OP is making a product "Like a log splitter".

And here in the "Territories"..... my local "hose supplier" crimps up
Aeroquip hose with 2 standard ends for much less than you quoted "$125"
 
D03 is a standard subplate for mounting either solenoid or manual valves.

Your power pack is probably going to use a gear pump, which pumps a specific amount of fluid regardless of the pressure (unless you are overloading it). Gear pumps require open center valves. Open center valves allow fluid to go back to the tank when you aren't putting it through the cylinder, so the pump can run with no load. If you use a closed center spool, you will force the pump to pump fluid through the relief valve, which basically results in idling at pumps maximum power. (This also heats the hydraulic fluid very rapidly). If you need the cylinder to move quickly under no load and then slow down under load (to limit the required power, typically) you either need a variable displacement pump, or a two stage (log splitter type) that pumps very fast when less than around 600 psi, then switches over to about 20% of maximum pumping speed when greater than 600 psi.

If you want the cylinder to stay in place in the center position, you are looking for what is known as a cylinder spool valve (this is the most common). The opposite of this is a motor spool valve, which is designed to allow a motor to coast freely in the center position. (A motor spool valve on a cylinder results in a cylinder that doesn't hold position, and a cylinder spool valve on a motor often destroys the motor because the motor suddenly locks solid but the inertia of what it was driving keeps going).

This place has a lot of fittings and hydraulic parts if you need:
Hydraulics | www.surpluscenter.com

And has a handy technical help section with lots of hydraulic calculators:
Surplus Center

The best way for any of us to help you is to link to everything you are buying and we can make sure it all checks out.

EDIT: Gear pumps produce a flow directly related to motor rpm. So if you have a variable speed motor, you will have variable cylinder speed. If it uses a DC series wound motor or a universal motor, this will be pretty much automatic because of the speed/torque curves of these. If you were to, say, put a motor on a vfd, you would be able to control the flow but if it hit a load it would try to continue at its current speed regardless of how high the pressure goes and how much power it has to draw.

Thank you Strostkovy - lots of good information there. I understand what you're saying about a closed center valve, but considering the duty cycle of this mechanism (which I hadn't talked about before and will likely be the hydraulic power unit running, at most, once or twice an hour to make a position change of 1-2 minutes, and not even on a 40-hour schedule at that) I'l have to take a look.

Any chance you could link me to a 4-way/3-position cylinder spool valve? (which could be open center, and still hold cylinder position with the hydraulic power unit off, correct?) Maybe I just don't know where to look, but I'm having a hard time finding anything called out as such. The prices on that surplus website are decent, but I'm having a hard time finding things. Thanks!
 
Thank you Strostkovy - lots of good information there. I understand what you're saying about a closed center valve, but considering the duty cycle of this mechanism (which I hadn't talked about before and will likely be the hydraulic power unit running, at most, once or twice an hour to make a position change of 1-2 minutes, and not even on a 40-hour schedule at that) I'l have to take a look.

Any chance you could link me to a 4-way/3-position cylinder spool valve? (which could be open center, and still hold cylinder position with the hydraulic power unit off, correct?) Maybe I just don't know where to look, but I'm having a hard time finding anything called out as such. The prices on that surplus website are decent, but I'm having a hard time finding things. Thanks!

The tough part is finding a manual valve for a D03 subplate, which is typically used for solenoid valves. They exist, but aren't very common surplus and aren't cheap elsewhere.

Can you link to your power pack? You may be able to remove the subplate and plumb the valve in directly, which will get you to around $120 a valve if memory serves.

And yes, open center cylinder spool valves will hold position with no hydraulic power.
 
The tough part is finding a manual valve for a D03 subplate, which is typically used for solenoid valves. They exist, but aren't very common surplus and aren't cheap elsewhere.

Can you link to your power pack? You may be able to remove the subplate and plumb the valve in directly, which will get you to around $120 a valve if memory serves.

And yes, open center cylinder spool valves will hold position with no hydraulic power.

I had planned on using one of these: MONARCH Power Unit,1 Stage,115'/'23VAC,2 psi - 36NE3'|'M-455-151 - Grainger

The manufacturer says you can remove the manifold to obtain P&T which means I plumb the outlet port ("B") to the power in port on the valve, and the center would be a return line to the reservoir?

Image 26.jpg

I think I'm looking at a valve like this: Prince Standard 4-Way Control Valve, Model# RD2575T4ESA1 | Northern Tool + Equipment

In comes from the pressure port on the power unit, out goes back to the reservoir, and the A and B work ports are the rod end, and piston end ports on the cylinder. Or am I all twisted around somewhere?
 
I had planned on using one of these: MONARCH Power Unit,1 Stage,115'/'23VAC,2 psi - 36NE3'|'M-455-151 - Grainger

The manufacturer says you can remove the manifold to obtain P&T which means I plumb the outlet port ("B") to the power in port on the valve, and the center would be a return line to the reservoir?

View attachment 226322

I think I'm looking at a valve like this: Prince Standard 4-Way Control Valve, Model# RD2575T4ESA1 | Northern Tool + Equipment

In comes from the pressure port on the power unit, out goes back to the reservoir, and the A and B work ports are the rod end, and piston end ports on the cylinder. Or am I all twisted around somewhere?

Nope I read that the same way.

"P" = Pressure
"T" = Tank
"A" is cylinder extend
"B" is cylinder retract

The prince valve, normal, or one with "Kickout" ?
1 Spool 25 GPM Log Splitter Valve w/Auto Detent | Directional Control Valves | Hydraulic Valves | Hydraulics | www.surpluscenter.com
 
I had planned on using one of these: MONARCH Power Unit,1 Stage,115'/'23VAC,2 psi - 36NE3'|'M-455-151 - Grainger

The manufacturer says you can remove the manifold to obtain P&T which means I plumb the outlet port ("B") to the power in port on the valve, and the center would be a return line to the reservoir?

View attachment 226322

I think I'm looking at a valve like this: Prince Standard 4-Way Control Valve, Model# RD2575T4ESA1 | Northern Tool + Equipment

In comes from the pressure port on the power unit, out goes back to the reservoir, and the A and B work ports are the rod end, and piston end ports on the cylinder. Or am I all twisted around somewhere?

That seems like it should work, though if cost is any concern I would highly recommend surplus center, especially if you have to take apart the other power pack. I get all of my hydraulics from them.
AC Power Units | Hydraulic Power Units | Hydraulics | www.surpluscenter.com

I can't say for sure what is under that subplate though. Make sure there is a specification with what type of port it uses. If they don't have that you pretty much have to use the subplate.
 
You can easily buy a 3' stroke double acting pneumatic cylinder quite cost effectively if you don't really need hydraulic.

For example, a 2" double acting bimba round line cylinder, brand new, 2" diameter and 3' stroke is $202 with delivery in two weeks.
 
That seems like it should work, though if cost is any concern I would highly recommend surplus center, especially if you have to take apart the other power pack. I get all of my hydraulics from them.
AC Power Units | Hydraulic Power Units | Hydraulics | www.surpluscenter.com

I can't say for sure what is under that subplate though. Make sure there is a specification with what type of port it uses. If they don't have that you pretty much have to use the subplate.

Cost is always something of a concern, but not the main one. Being able to source replacement parts, or replace the entire unit (if necessary) without having to re-design anything is more important in this case.

Thanks for all your help with this!
 
You can easily buy a 3' stroke double acting pneumatic cylinder quite cost effectively if you don't really need hydraulic.

For example, a 2" double acting bimba round line cylinder, brand new, 2" diameter and 3' stroke is $202 with delivery in two weeks.

5' stroke, not 3' - Bimba maxes out as 50" of stroke on most of their stock cylinders. The other reason I'm not going pneumatic is because this system will be switched on, moved, then switched off. If I factor in the wait time for a compressor to generate enough air pressure and volume to move a 3" bore cylinder 60" under some load, the overall cycle time is significantly longer than hydraulic.

I'm with you though - I prefer pneumatic in most cases. This is just a standalone system that's relatively unique.
 
Normal valve - I think the 'kickout' ones are called detent valves (but I'm learning a lot on this one.)

There are valves that will stay in the "on" postions, and then the ones that don't. Various detents are available.

The one I linked to is actually cheaper (and more flow than your linked)
Because it's for the logsplitter crowd.

The "kickout" has a special detent
on the retract, it will stay on "retract" until the cylinder bottoms out
(or hits something like a custom stop) causing the pressure to rise above the
"kickout" point.


At this point, it will automatically move the lever (or kickout) to the neutral
position.

It has no detent on the extend side, and must be held to work,
let go of the handle, it springs back to center.
 
There are valves that will stay in the "on" postions, and then the ones that don't. Various detents are available.

The one I linked to is actually cheaper (and more flow than your linked)
Because it's for the logsplitter crowd.

The "kickout" has a special detent
on the retract, it will stay on "retract" until the cylinder bottoms out
(or hits something like a custom stop) causing the pressure to rise above the
"kickout" point.


At this point, it will automatically move the lever (or kickout) to the neutral
position.

It has no detent on the extend side, and must be held to work,
let go of the handle, it springs back to center.

Gotcha - I think that makes sense if for no other reason than an operator-proofing. Thanks!
 








 
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