Double Acting Piston Actuator with Percentage Opening

Yes, it is.

Hi puat133,

To expand slightly on the previous correspondent. Various criterion have to be considered depending on the application, size etc. But yes they can be controlled remotely when fitted with a proportional actuator. These have a Main air supply to operated the valve and a 3 to 15 psi control signal that will give fully open to fully closed operation. Look at the Kinetrol web site, they are just one of the many manufacturers.

Best regards,

John

This can be a solution:the 4-3 valve is used for the remote control the spool being controlled either with solenoids or by pneumatic pressure with the 2-2 valve in the blocked flow position.when the 4-3 valve is in its centered position thus closed it is possible to free the cylinder with the 2-2 valve hand controlled for instance on the spot and act by hand the main valve. A logic has to be set so that the 2-2 can be actuated only with the 4-3 in centered position and that the 4-3 cannot be active if the 2-2 is open.

Simple and good solution...

Hi Jesw55 and nick, thanks for your answers. What I found before is closely similar to nick solution, like this

@Jesw55, how you feed 3-15 psi air for proportional control into double acting actuator design similar to this? Or the design is different to this.

Thanks

What you show does NOT allow a manual position change since ram is in the centered valve position closed thus BLOCKED.

The ONLY similarity is that the valve is 4-3 but for a bidirectional control it is the solution if only one valve is used.

To make constructive suggestions we need more information.

1 How accurate/repeatable do you want the position to be?

2 What is the current time taken to move the cylinder from full closed to full open and also the time taken to move the valve from full open to full closed? The two times will be different.

3 Can you afford to slow the movement down to increase the accuracy?

Subject to the answers to the above questions it may be possible to use your current valve configuration¹ to achieve your goal.

One way is to add feedback in the form of an electrical resistance (potentiometer) that changes corresponding to the position of the cylinder². Feed the signal into one input of a twin input/twin output "comparison relay"³ and a signal from a graduated potentiometer mounted on your control panel into the other input. The relay will have an adjustable dead band that needs to be set according to the speed and response time of your cylinder. This dead band will determine the accuracy that you can achieve.

¹Your may need to slow the speed down by adding one or more flow restriction valves. A single valve placed before valve 17 in your diagram will work if you only need crude positioning. For a more accurate solution place a valve in each line between valve 17 and cylinder 18 and adjust each so that the time for a full stroke is the same in both directions. Unless this is done, any given intermediate position will display a difference depending on the direction of approach. (If the response time time from each direction is the same the piston will have travelled further in one direction because it is travelling faster).

Finally, the diagram shown will drift off any intermediate set position if the load is not balanced. I would recommend adding pilot operated check valves to the inputs of cylinder 18 to counter this.

² The feedback should be attached as close as possible to the actual load so that tolerances in intermediate linkages are not added to the total tolerances of the system.

³ Google Murr Elektronik, Voltage Comparator Module or similar as an example, but there are many on the market, some in the form of a panel mounted controller with position display and digital position setting.

Do you mean manipulated as in from 0 to 100 percent open?If so , the actuator operating pressure needs to be given.If it is 3-15 psi,then a simple I/P will work with a couple of 4 way solenoid valves and a positioner.

If the operating pressure is supply pressure, for instance 60 psi, then you will need a pneumatic multiplying relay to boost the 3-15 psi to operating pressure, and a biasing relay to subtract the 3 psi before the multiplier.

If I remember correctly, Fairchild makes the Bias and Multiplier relays.

I have used this type system on a water treatment backwash system with no problems.

Been a long time, over 30 years ago, so technology has probably improved since then, and there may be a better way.

Use a proportioning valve.

http://www.ascovalvenet.com/pdf/LiteratureRequest/proportional.pdf

other companies probably make them.

Hi

What you require is a proprietary item so I do not understand why you asked the question. The common units are pneumatic and only switch to hydraulics for very large ball valves. As you do not say what size of ball valve you are looking at or what forces you are dealing with no further useful advice is possible. Do a Google on hydraulic/pneumatic actuated Ball valves and you should be swamped in suppliers.

Oliver Dunthorne

When I read the counsels you get I have the feeling that I did not understand your request so please explain clearly what you want:

do you want to have a possibility to use either a remote control for the valve or in case of need a local manual control ? or do you want to have a manual control override to the automatic control in the remote control room ?

My suggestion considered the first possibility.

If you want a possibility from the remote control room to manually control the valve you need only a logic with interlocking and use same command to the 4-3 valve but with manual buttons. Since your valve is ON-OFF I presume (you did not mention any intermediate opening) that your cylinder makes what is called a bang-bang i.e. it goes from one end position to the other. If it is so you do NOT need any proportional control which is used ONLY in case of intermediate positioning, to maintain the end position the valve has to be closed cylinder side in the middle position.

You can also use 2 valves in parallel with same configuration and use one for the automatic control and the other for the manual but in this case the free pump return has to be in series so that ONLY when both valves are in middle position the flow free to tank is available.

You should consider as well a solution with 2 x 3-2 valves which has some advantages in comparison to the 4-3.

Sorry for vague question resulting from my bad english. What I want to know is whether there is a possibility to have a valve installed with double acting piston actuator that suppose to be behave as on/off only to be opened/closed proportionally (eg. 60%,80%), since the requirement is to have this percentage manipulated manually from control room (not for throttling application).

Many thanks

Hi

You can get actuators on ball valves with micro switches on. However as a oil hydraulic engineer I would say never use a ball valve to attempt any sort of metering as they are very poor metering devices. In my experience ball valves are either open or closed.

Regards

Oliver Dunthorne