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hydraulic power pack question


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i might be in the wrong place with these questions. but im looking to build a hydraulic press. to use when forging . 
there are lots of designs’ out there on the web and i think i have most of it all figured out apart from the power pack i have acquired for free 
it came off a large road barrier system. operated by a key card system.
and im guessing that the hydraulic ram must had a spring return ram [ that and the Wight of the retractable barrier] 
as on the power pack i have there is only one hydraulic line going out .
i have got a photo here and just a have a few questions as the people at the local merchants weren’t much help at all 
SO FEEL FREE TO TELL ME I HGAVE IT ALL WRONG as im just trying to logically work it out from scratch

form the photo im assuming that that it operates this way
"D" is my line out , activated by
"C" a 24v solenoid
"E" is a return path to the oil chamber . the valve im told was so they could keep the barrier down during events
[leaving it open would create a bypass ]
"B" behind the cab there is a screwdriver slot? is that for adjusting pressure ?
"A" is another 24v solenoid and i have no idea what’s it does 
the gauge is stuck at 600spi but i imagine that’s the static amount of pressure when it’s all switched off
i have re pipeed it , so instead of "C" there is just a gauge on it . the pump ran and didn’t sound any different , i don’t know if there is air in the line and needs priming somehow. or it is something to do with solenoid A needing to be open ?

i intend to have a set up were the pump feeds a shuttle valve [ came off an old tractor ] that can feed a ram to open / close 
made with all new hoses and with some thick 15mm angle iron i have 
although the gauge only goes to 14000 psi i assume the adjustment on "B" will get me more ?
apart from the motor there is no spec on the unit.
i can find on line, a v simmiler unit for the same intended use inc motor ,has a small 1.1kw 3~ motor will run at 25000 which is more what i think need get ram with about a 4" diameter to be able to get me about 15 ton of force which is the min i will need really

if anyone can give me some advise on this it would be great



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If I'm reading what you wrote correctly - there is only one hose out of the unit? No separate return line? I'm no expert on this setup, But I would say the 2 solenoids are controlling flow to and from the pump and its direction of flow - probably with a spool valve in the pump body. Here's my opinion on this - I'm sure others will give you other ideas too.... I would disconnect all the existing hoses and blocks on the unit piping - and start from scratch - the application isn't what you want. You need a discharge line out of the pump - which you have, but you will need to figure out which position the solenoid on the pump needs to be in (power on or off of coil) to generate pressure. You will need to install a return line connection into the tank so you have 2 hoses - supply and return. Otherwise, you won't be able to operate a double acting hydraulic cylinder through a double acting spool control valve. Obviously this is a simplification of an answer - you will also need to add a relief valve with a hose that feeds into you return line you created to protect yourself, a filter, Etc.... The unit is small, but you should be able to make a small cylinder work hopefully as long as it generates a high enough hydraulic pressure. Do some research online on simple press piping diagrams - and modify your setup for that. 

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which part of the world are you in?

yes you can normally turn up the pressure relief valve to get more pressure but it will depend on the motor and what the rest of the system is made to take, you can gradually increase the pressure after checking hose ratings and watching the amount of current the motor is taking.

speed is more important than pressure and that will depend on the displacement of the pump.

how much force you get from your press will be dependent on the bore of the cylinder and the pressure.

what is the hp / kw of the motor, I use a 2.2kw at 200 bar and get about 10 ton on a 80mm bore cylinder at a good speed

the hoses on that wont go anywhere near 14,000 psi, that is nearly 1000 atmospheres, if your pump goes to that it would take days to move a 4" bore cylinder, 700 bar is normally considered very high pressure, 200 to 250 bar is more common and most excavators and farm machinery work at more like 100 to 150 bar.

make sure every part of the system will work at above the max pressure you set it to or you could have an accident

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thats good advise and yes at the moment there is just one hose leaving the  unit . i imagine that port E is a return on a bypass [ with the valve open i can blow down the hose, so the air has to be going some were]

and i imagine that solenoid A needs to be powered on , as the pump works it seems to do nothing with out the solenoid A active

[is there any need to even have a solenoid on the system . ]



the iron dwarf

im in hull.

if the 3 merchants i went to i was told to come back next week when the expert was going to be in

one seemed to think it was a large bit of kit and i could power what i wanted off of it

[when i have got my self a ram i was going to build the rest of the rig and get some new hoses made up

i think im planing things based on the spec i think it it . comparing it to outer simmiler set ups online  as with out more parts i cant realy test it 

looking online

eg , i dont know what flow rate t his will work at.  i think it will be about 2.3 L/PM and a max pressure of 210bar [3000PSI]

but i am i right in thinking if you set the pump to go for 200 bar for example it will affect the amount of flow you can get, and as you say. slow down the  ram so much it starts to become useless

at  1.1kw [1.5hp]  giving out 2.3 L/PM. its a bout half the figures compared to your 2.2, does that mean i should be looking at a smaller ram ? say 50mm bore?

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I'd re-think things and only use the current valve set-up for spare parts.  It appears to me that you have a pressure and return port so you should theoretically be able to use a standard 3 position, 4-way valve and have power to both stroke directions.  You should also find a way to get a filter into the system on the return line.

You can buy standard 4 way solenoid actuated electric valves either in higher voltage or as low voltage units (or manual, of course like a log splitter uses).  You can also get standard electric foot pedal controls (or roll your own).  Although others might have different reasoning, I would say a bypass center position is safer--take your foot/hand off the switches for move/retract and the automatic spring center position is pressureless on the cylinder lines and oil free flowing so there is a chance you could get your hand out.  Using a blocked center position will hold the ram in place and it aint moving without someone hitting the retract switch.

If you wanted, you could add an adjustable flow restrictor to the pressure stroke and slow movement down.  I'm not sure that would ever be used on a forging press but it can help for things like pressing out bearings or if a small metal brake feature is added to the system to bend bar and such.

There are lots of sites on the web which help explain what those complex hydraulic valve diagrams actually mean so I suggest you take the time to read up.  It's not that hard after you start getting the hang of reading the gobbledegook in those diagrams.  Once it starts making sense, you will start to notice examples of what a standard system for what you intend to do looks like in diagram form and can design around that standard.

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I don't think you can remove solenoid A - plus it's probably easier to just use it. You could always get a coil for it that matches the pump voltage and wire together through the on/off switch?  If port E is a return port and open when solenoid A is energized - I'd just connect the return hose to that port directly (possibly also a good location for a return line filter). B definitely looks like a relief / pressure regulator - but I would still pipe in a new relief (you can never be too safe with hyd pressure) into your pump discharge line D either through a control valve with one internal or an inline one . Pipe the relief outlet back into your return line with a tee. 

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