Hydraulic help needed

[r8f1k]

I have an old (1900-1910) hydraulic cider press. The ram comes up through the floor and presses upwards on a large frame. We pressed about 1000 lbs of apples on Saturday and I could not get the ram to hold under real pressure. It would easily push up with the pump running and then push back down once I shut the pump off. You could then hear a chatter like it was spinning the vane pump backwards and allowing fluid to head back to the tank. What do I do to get it to hold pressure? Do I need a check valve of some kind? Further enhancing the problem is that this is a single acting, gravity down, hydraulic cylinder that uses the same hose for pressure and return. Its about 10" in diameter and 38" long. I am running a Vickers vane pump and using typical hydraulic fluid. Any advice as how to get this animal working the way it should is welcomed. I should add that once upon a time, this press operated with gate valves where I think it was easier to open and close the path back to the tank. I am not using that anymore......thoughts?

 

[Zebrafive]

What are you using to control the cylinder instead of gate valves?

 

[loggin]

I have an old (1900-1910) hydraulic cider press. The ram comes up through the floor and presses upwards on a large frame. We pressed about 1000 lbs of apples on Saturday and I could not get the ram to hold under real pressure. It would easily push up with the pump running and then push back down once I shut the pump off. You could then hear a chatter like it was spinning the vane pump backwards and allowing fluid to head back to the tank. What do I do to get it to hold pressure? Do I need a check valve of some kind? Further enhancing the problem is that this is a single acting, gravity down, hydraulic cylinder that uses the same hose for pressure and return. Its about 10" in diameter and 38" long. I am running a Vickers vane pump and using typical hydraulic fluid. Any advice as how to get this animal working the way it should is welcomed. I should add that once upon a time, this press operated with gate valves where I think it was easier to open and close the path back to the tank. I am not using that anymore......thoughts?

Some pictures would help greatly!!

 

[r8f1k]

I have a few things doing the work of the valves.
1) I have a 12 volt Hydraforce selector valve which is used to drop the cylinder and close the path into the tank.

(SAE 12 15 GPM 12 Volt DC Hydraforce Selector Valve | Selector Valves | Hydraulic Valves | Hydraulics | www.surpluscenter.com)

2) I have a three phase wash down motor that spins a Vickers vane pump, which is plumbed into the above valve.

3) I use a couple ice cube relays to control the whole apparatus with a 6 button control station. UP ON/ UP OFF, JOG UP/JOG DOWN, DOWN ON/DOWN OFF.

That's it right now.

 

[oldnslo]

R8
How do you have the the Hydraforce valve plumbed? I do not see any way to make that valve work. with some addition valving.

 

[r8f1k]

Just like this:

https://www.surpluscenter.com/_MoreSpecs/I9-7986.pdf

I have it just like the instructions.

 

[oldnslo]

Which port is connect to what?

Port 1?
Port 2?
port 3?

What is the control logic or sequence of operation?

If port 1 is tank, Port 2 pump & port 3 press the only way you can lower is by spinning the pump backwards without some other form of valving in the system.

 

[ericm979]

I'd think port 1 would be connected to the pump, 2 to the cylinder and 3 to tank. So the pump would flow to the cylinder when the valve is not energized and when energized it'd go to the tank. If your pump can't hold pressure when it's not running then you'd need a check valve between the valve and pump. I'm assuming that like my apple press you crank the pressure up and then let it sit for a while for the juice to drain. You could swap 1 and 3 so you'd energize the valve to raise the cylinder and to hold it with the pump off but that'd also need a check valve, and more control logic.

 

[LouNY]

If the pump is supplying port 1, with port 2 to the cylinder, and port 3 to the tank.
When the pump is running with the valve de-energized the cylinder will receive pressure.
With the pump off the pressure would then back feed the pump and operate as described.
A check valve in the pump supply line before the valve would allow the system to hold pressure when the pump was shutoff.
The cylinder would then retract when the valve was energized.

That valve has free flow between 1 and 2 when not energized,
and free flow from 2 to 3 when energized.

If you plumb the pump to port 3 and to the cylinder to port 2 with the return to tank on port 1;
With the pump and valve energized you would apply pressure to the cylinder,
de-energizing the valve may dead head the pump and will allow flow back to the tank from the cylinder.
Again a check valve between the pump and the valve would provide the desired results I believe.

 

[r8f1k]

Let me make sure my plumbing, I'll take some shots of it tonight.

 

[oldnslo]

In reading the specs on the valve Port 1 is not intended as pressure port.

 

[LouNY]

OK, from the hydraforce website;
A solenoid operated, two position, three way, direct acting spool valve. When de-energized, the SV12-
34X allows flow from port 2 to port 1, while blocking flow at port 3. When energized, the spool shifts to
open from port 3 to port 2 while blocking port 1. While port 1 may be fully pressurized, it is not intended
to be used as an inlet

So port #2 as the pump or pressure port,
port#3 as the cylinder port,
and port#1 as the return to tank
and adding a check valve before port #2

a copy of the pdf from Hydraforce;

 

[oldnslo]

OK, from the hydraforce website;
A solenoid operated, two position, three way, direct acting spool valve. When de-energized, the SV12-
34X allows flow from port 2 to port 1, while blocking flow at port 3. When energized, the spool shifts to
open from port 3 to port 2 while blocking port 1. While port 1 may be fully pressurized, it is not intended
to be used as an inlet

So port #2 as the pump or pressure port,
port#3 as the cylinder port,
and port#1 as the return to tank
and adding a check valve before port #2

a copy of the pdf from Hydraforce;

Lou,
how do you get the cylinder to lower now? Port 3 is never connected to tank.

This valve could work if he teed it into the cylinder port and installed a check valve between the pump and tee. Plumb the 3 way with cylinder to port 3 and tank port 2. Port one 1 would not be used. He also needs a system relief between the pump and check.

 

[LouNY]

OK, from the hydraforce website;
A solenoid operated, two position, three way, direct acting spool valve. When de-energized, the SV12-
34X allows flow from port 2 to port 1, while blocking flow at port 3. When energized, the spool shifts to
open from port 3 to port 2 while blocking port 1. While port 1 may be fully pressurized, it is not intended
to be used as an inlet

So port #3 as the pump or pressure port,
port#2 as the cylinder port,
and port#1 as the return to tank
and adding a check valve before port #2

a copy of the pdf from Hydraforce;

Whoops;
corrected the port numbering above.

so supply to port #3
cylinder to port#2
return to tank port #1
With a check valve before the input of port#3
With the pump running and the valve energized flow would be port #3 to port #2,
with a check valve prior to port #3 with the pump shut off the system should hold in that position,
after time the pump could be bumped on to repressurize the system or increase the pressure to further stroke the cylinder,
when the valve is de-energized the fluid will return to tank allowing the cylinder to retract.

 

[oldnslo]

Lou,
agree that the corrected porting would work.

 

[r8f1k]

So I have the following:

Port 1: to pump
Port 2: to cylinder
Port 3: to tank though a filter

Now what do I need to buy?

 

[LouNY]

So I have the following:

Port 1: to pump
Port 2: to cylinder
Port 3: to tank though a filter

Now what do I need to buy?

nope, follow the below

so supply from the pump to a check valve then to port #3
cylinder to port#2
return to tank from port #1 thru your filter
Add a check valve before the input of port#3
With the pump running and the valve energized flow would be port #3 to port #2,
with a check valve prior to port #3 with the pump shut off the system should hold in that position,
after some time the pump could be bumped on to repressurize the system or increase the pressure to further stroke the cylinder,
when the valve is de-energized the fluid will return to tank allowing the cylinder to retract.

 

[r8f1k]

Recommendations for a check valve?

 

[oldnslo]

Recommendations for a check valve?

Any check rated for pump flow and pressure should work

I doubt that you can put a filter in tank line for lower since pressure drop through the filter could prevent the press from opening.

I recall another post on similar sounding system where we calculated there was less than 10 PSI to open the empty press and seal friction was causing his press to not open fully. A 10 inch bore is 78.54 square inches so 10 PSI will lift 785 lbs.

 

[etpm]

So I have the following:

Port 1: to pump
Port 2: to cylinder
Port 3: to tank though a filter

Now what do I need to buy?

You need a check valve between the pump and the cylinder. I am not the first person to tell you this. The check valve should really be right after the pump and before anything else. The reason for this valve is because the pump design will not allow it to hold pressure. This is because of the way a vane pump works. The rotating part of the vane pump has slots in it that hold the vanes. This rotating part is off center to the bore of the pump. As this rotating part rotates the vanes will be contacting the bore. Since it is off center the vanes must move in and out of the slots. Of course they don't come all of the way out of the slots. The vanes must maintain a fairly tight fit against the bore in order to seal against the bore and deliver the fluid being pumped at the desired pressure. Usually this tight enough fit is accomplished by the vanes being forced against the bore by centrifugal force. This of course requires the pump to be spinning. So when the pump is stationary it will not seal very well, hence the inability to hold pressure and the need for a check valve. I hope this helps you understand better what is happening with your system and why you need a check valve.
Eric