Valve Type for controlling a Hydraulic Ram

Author: Daisy

Sep. 23, 2024

Valve Type for controlling a Hydraulic Ram

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Valve Type for controlling a Hydraulic Ram

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Valve Type for controlling a Hydraulic Ram

J Tully

(Marine/Ocean)

(OP)

4 Jan 21 21:12

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 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. 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

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RE: Valve Type for controlling a Hydraulic Ram

TugboatEng

(Marine/Ocean)

4 Jan 21 23:03

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)

5 Jan 21 09:03
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)

5 Jan 21 14:32

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

Thanks for the reply'sYes 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 itI 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 https://www.hydraforce.com/products/valves/solenoi... and when powered it would dump the pressure into the tank instead of just back to the pump side so it would have to have a 3 way block .Regards John

RE: Valve Type for controlling a Hydraulic Ram

BrianPetersen

(Mechanical)

5 Jan 21 22:29

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)

5 Jan 21 23:33

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 down stream 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)

5 Jan 21 23:50

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)

6 Jan 21 02:00

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 vales. They are safety valves.
Controlling speed will be a problem without position or speed feedback.

So if the pressure goes away the rod will be pulled out?If not how do you get the rod extended?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 beForce = Pressure_rod_side*area_rod_side-pressure_cap_side*area_cap_side;This assumes the pressure on the cap side is 0 psia.Relief valves are not control vales. 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)

6 Jan 21 20:20

https://www.navtechydraulics.com/vangs/

They are charged with nitrogen as the reverse force and holds up the boom.

As for duty cycle on the pump the most it will run is one minute .

I figure in order of operation the pump would first see an adjustable pressure relief valve then a check check next there would be a tee there that has a poppet valve going back the tank (for releasing pressure) then the last thing would be a adjustable needle valve (for very slow movement) then the cylinder .

What do you think ?

Thanks for all the help guys

This is what I am movingThey are charged with nitrogen as the reverse force and holds up the boom.As for duty cycle on the pump the most it will run is one minute .I figure in order of operation the pump would first see an adjustable pressure relief valve then a check check next there would be a tee there that has a poppet valve going back the tank (for releasing pressure) then the last thing would be a adjustable needle valve (for very slow movement) then the cylinder .What do you think ?Thanks for all the help guys

RE: Valve Type for controlling a Hydraulic Ram

BrianPetersen

(Mechanical)

6 Jan 21 21:40

That's a picture of the cylinder. What about a picture of what you are actually trying to do with that cylinder?

Probably someone (maybe even myself) has experience with trying to move something similar to what you're trying to do?

RE: Valve Type for controlling a Hydraulic Ram

hydtools

(Mechanical)

6 Jan 21 21:46

https://en.m.wikipedia.org/wiki/Boom_vang

Is this the application? Boom vang?

Ted

RE: Valve Type for controlling a Hydraulic Ram

J Tully

(Marine/Ocean)

(OP)

6 Jan 21 23:10

Yes sorry , that&#;s the right application . Forgot you guys are not all sailors.
There is always a compression force on the cylinder. It uses a nitrogen charge inside the cylinder to counteract the compression and hold up the load . When pressurized with hydraulic pressure the cylinder is pulled down against the nitrogen counter force and moves the boom downward .

Regards John

RE: Valve Type for controlling a Hydraulic Ram

TugboatEng

(Marine/Ocean)

6 Jan 21 23:14

J Tully, the reason I suggest putting all control valves between cylinder and tank is that the cylinder itself will act as a bit of an accumulator when the system is operated. This will eliminate some of the jerking associated with the bang bang operating of fixed displacement systems.

If you put the reliefs and needle valves before there will be a large shock as pressure instantly builds relief. It will also always run under relief when the isn't moving. If you put the controls downstream there will be minimal loss until the system is moving or has stalled.

I'll try to draw it shortly.

RE: Valve Type for controlling a Hydraulic Ram

BrianPetersen

(Mechanical)

6 Jan 21 23:51

Pick a pump that is small enough that its full displacement moves the cylinder at the rate that you want it to move. If you use that dual-displacement pump and are able to control which mode it is in, you can have a fast and slow speed. Then you need only a three-position center-open (pump shorted to tank, A port blocked, B port blocked) directional valve and NO flow controls, and the pump will not be operating on the pressure regulator.

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Can you help me find the right hydraulic valve?

Want more information on Hydraulic pressure valve? Feel free to contact us.

Thread starter

William123
Start date
Jul 31,
Tags

Hydraulic Valve

In summary: . . but it would be neater if there was a spool valve that could be controlled electronically (and proportionally).

Jul 31,

William123

: 39

: 0

Hi

I'm a novice when it comes to hydraulics but I want to be able to make use of it in future projects. I thought building a small scale excavator might be a fun project to start with. However I'm a bit confused when it comes to the valves that will control the different motions. From what I've seen, excavators use spool valves. If I understand correctly, a spool valve will allow slow and fast movements depending on how much you pull or push the corresponding lever.

I have found cheap lever type spool valves on ebay that would probably work, but I would be interested in controlling the excavator with joysticks. The electronic spool valves that I have seen so far are either open or closed (in either direction) and don't allow slower movements. I'm quite good with electronics so I'm considering hacking the lever type spool valve but it would be neater if there was a spool valve that could be controlled electronically (and proportionally).

If you can think of a good (or bad!) solution to this, please share it because I don't really know what kind of equipment is available out there. Cheaper is better!

Thanks

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Aug 1,

OCR

: 994

: 934

William123 said:

. . . but it would be neater if there was a spool valve that could be controlled electronically (and proportionally).

I know exactly what you want to do. . .I have a used Cat 312BL, which is larger than the project you are proposing, but the

principle is the same. . .

To bring your system to a new level of control, precision, and timing, Bosch Rexroth Industrial Proportional and Servo valves will improve your system&#;s functions by smoothing transitions and giving more control over the speed and forces applied by your actuators.

And that's where it gets real ugly, real fast. . .

Proportional and Servo Valves
The prices are horrendous !BTW, if you get this popup, just click Stop it.

I know exactly what you want to do. . .I have a used Cat 312BL, which is larger than the project you are proposing, but theprinciple is the same. . .And that's where it gets real ugly, real fast. . .The prices are horrendous !BTW, if you get this popup, just click Stop it.

Aug 1,

William123

: 39

: 0

Wow, that's expensive. I think I could motorize regular lever type spool valves for a lot less. That seems to be the only reasonable solution at this point. I have seen some current controlled flow control valves, but they take a long time to adjust so it's not a practical solution for this project.

Aug 1,

OCR

: 994

: 934

William123 said:

Wow, that's expensive.

Yeah. . . it's a shame, too. . .

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.

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

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