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Valve Type for controlling a Hydraulic Ram

J Tully

(Marine/Ocean)

(OP)

Good day all

This is not my specialty (Hydraulics) and I am finding it very challenging.

What I am trying to do is to pressurize a hydraulic cylinder in the pull direction (ram is always under tension) at a very slow speed from a electric powerpac. I need to control the speed and the max pressure which has not been determined as yet so that along with the flow rate will need to be adjustable. If I was to do it all with separate valves this is how it would go. First an inline check valve, next an adjustable throttle valve, next an adjustable pressure relief valve to the tank, then a 12v dc controlled pressure relief valve hosed to the tank. My question is can I get a manifold block with any of these components incorporated into one unit to simplify installation.

Any help would be appreciated

Regards, John.

Replies continue below

RE: Valve Type for controlling a Hydraulic Ram

TugboatEng

(Marine/Ocean)

Have you selected your pump yet? A pressure compensated variable displacement pump does everything you need without any additional valving.

RE: Valve Type for controlling a Hydraulic Ram

Serge_blr

(Mechanical)

I think this product catalog might help you. Look at page 33

• https://files.engineering.com/getfile.aspx?folder=af-949e--8c08-0

Good day!I think this product catalog might help you. Look at page 33

RE: Valve Type for controlling a Hydraulic Ram

J Tully

(Marine/Ocean)

(OP)

Yes I already have the power pack installed its a 12v watt unit. It is also used in the system to power two reversible winches. This is it

https://www.princessauto.com/file/general/_...

I will be taking the power off the bottom of the manifold block which I have mounted separately to power these two rams. I was thinking of using a poppet valve like this

Regards, John

RE: Valve Type for controlling a Hydraulic Ram

BrianPetersen

(Mechanical)

That is a fixed-displacement (although with two possible choices) gear pump.

Does the required speed of your cylinder motion coincide with the displacement of the pump (in either the high-volume-low-pressure regime, or the low-volume-high-pressure regime)?

Do you need "precision" motion control? (difficult to achieve with hydraulics in general)

Hydraulics with a fixed-displacement pump want to be "bang-bang". Either moving full speed one direction with all pumped fluid directed into one side of the cylinder and let the pressure float with whatever it wants to be in order to push the load or stopped with the pumped fluid being bypassed to tank at minimal back pressure and the fluid in the cylinders trapped by closed-off valve ports or moving the other direction full speed. They're unhappy with trying to modulate the flow or trying to split it partially bypassed and partially applying load. Possible, yes - but unhappy.

IMO wrong pump for the job. Should really be a variable-displacement pressure-compensated pump with an adjustable pressure setting. There are a multitude of control strategies for the displacement control.

'Course, the right pump is going to cost a lot more than that one ... (C$400-ish for a new one)

You may want to check the spec sheet at Princess Auto. There's a duty-cycle limitation, which isn't very long. One of the bad things about fixed-displacement pumps with a pressure regulator, is that they're really good at converting full motor and pump load into lots of heat and noise, and not much work.

RE: Valve Type for controlling a Hydraulic Ram

TugboatEng

(Marine/Ocean)

I'm thinking, what needs to be done here, is to put your control valve downstream of the cylinder kind of like a diesel fuel injector. A valve downstream would close to divert flow through a needle valve to control the extension speed. A regulator between the needle valve and cylinder with a return to tank would control max force. In order to actuate two cylinders independently, a selector valve upstream of the cylinder would divert flow to one cylinder or the other. A check valve on each cylinder outlet would allow them to be combined so each doesn't require a needle valve and regulator.

RE: Valve Type for controlling a Hydraulic Ram

TugboatEng

(Marine/Ocean)

This is probably an ideal pump for your application, a Metaris MHPVB5. It's 0.64 in^3/rev which should get you down into the ~ 2 horsepower range. Metaris makes cheap knock-offs of the brand names.

RE: Valve Type for controlling a Hydraulic Ram

PNachtwey

(Electrical)

Quote:

What I am trying to do is to pressurize a hydraulic cylinder in the pull direction (ram is always under tension) at a very slow speed from a electric powerpac.

So if the pressure goes away the rod will be pulled out?
If not how do you get the rod extended?

Quote:

I need to control the speed and the max pressure which has not been determined as yet so that along with the flow rate will need to be adjustable.

What are you really trying to do? Pulling requires force. That depends on pressure AND area. Do you know the pressure on the cap or blind side of the piston?
If the cap or blind side is vented to the tank then no problem. If not the pulling force will be
Force = Pressure_rod_side*area_rod_side-pressure_cap_side*area_cap_side;

Quote:

If I was to do it all with separate valves this is how it would go. first a inline check valve, next a adjustable throttle valve, next a adjustable pressure relief valve to the tank, then a 12v dc controlled pressure relief valve hosed to the tank.

This assumes the pressure on the cap side is 0 psia.
Relief valves are not control valves. They are safety valves.
Controlling speed will be a problem without position or speed feedback.

Peter Nachtwey
Delta Computer Systems
http://www.deltamotion.com
http://forum.deltamotion.com/
IFPE Hall of Fame Member

RE: Valve Type for controlling a Hydraulic Ram

J Tully

(Marine/Ocean)

(OP)

FAQ: Can you help me find the right hydraulic valve?

1. What is a hydraulic valve?

A hydraulic valve is a mechanical device that controls the flow of fluid in a hydraulic system. It is used to regulate the pressure, direction, and rate of flow of the fluid, which is typically oil or water-based.

2. How do I know which hydraulic valve is right for my system?

The right hydraulic valve for your system depends on several factors, including the type of fluid being used, the required pressure and flow rate, and the specific application. It is best to consult with a hydraulic expert or refer to the manufacturer's specifications to determine the most suitable valve for your system.

3. Can I use any hydraulic valve for my system?

No, it is important to use the correct hydraulic valve for your system to ensure optimal performance and safety. Using the wrong valve can result in damage to your system or equipment and may also pose a safety hazard.

4. How do I maintain and troubleshoot a hydraulic valve?

Regular maintenance is crucial for the proper functioning of a hydraulic valve. This includes checking for leaks, cleaning or replacing filters, and ensuring proper lubrication. If you encounter any issues with your valve, it is best to consult with a hydraulic expert for troubleshooting and repairs.

5. Can I adjust the settings on a hydraulic valve?

Some hydraulic valves have adjustable settings, such as pressure and flow rate, while others are fixed. It is important to refer to the manufacturer's instructions and guidelines before attempting to adjust any settings on a hydraulic valve. Improper adjustments can lead to system failure or damage.

For more hydraulic flow control valve information, please contact us. We will provide professional answers.