actuator and valve

[Dost]

I want open and close a valve(on 1 inch pipe) via actuator .Is it possible if yes how.i would appreciate if some body could guide me what other specjfication i should consider in selecting an actator for my requiremnt.

[Conseils]

Some ideas: -
a) How much force will be required in the worst case?
b) How quick the valve has to change state?
c) What power will be available locally?
d) What interface exists physically for connection of the actuator to the device?
e) What reliability are you looking for?
f) Do you need to know the state or position of the system?
g) Regulatory requirements?
h) Environmental conditions?
i) What command / control system will be used?

[Dost]

Thanks for the reply
I am planning to use NI E series card the actuaotr will drive the valve to open and close. i will be using pid loop to proprtionaly control the actuator though right now i dont have much knowledge about PID. i want to know how actuator work with NI card i mean how to programe actautor to drive a valve.

[MogaRaghu]

>> i want to know how actuator work with NI card i mean how to programe actautor to drive a valve.

Going by your query it generally appears that you are trying to design an actuator to control "something" that is passing through a 1" pipe. If your answer to this is "yes", then I suggest you watch out ! Designing a proportional control actuator and deploying it in a PID loop is not something you could term as simple / easy.

Controlling with a NI card is least of the problem :

If its going to be ON/OFF, then you use a digital output.
If its proportional, then use an analog output to drive the valve amplifier's 0-10V command input. Thats it.

You would be better off searching the net for ready made solutions. Key parameters would be : The fluid to be handled; expected minimum and maximum flow rate; working pressure; the temperature of fluid ; response time of valve; control resolution. This is just the begining and will help narrow down on the basic product group to choose from.

Raghunathan

[Dost]

Hi
Thank you for reply and good suggestion but i would like to take more help from u and it is about
"If its proportional, then use an analog output to drive the valve amplifier's 0-10V command input."
i mean in that case would there be no need of any actator could u please write more about this option i would really be thankful.
Nadeem

[MogaRaghu]

>> i mean in that case would there be no need of any actator could u please write more about this option

This term Actuator is very generic one. It could be a hydraulic cylinder, pneumatic cylinder, electric motor gearbox combo etc.

However when you want a proportional control the set up needs some basic elements :

> A user command interface that will accept 0-10V or 0-5V or 4-20mA etc as the signal to position the actuator infinitely from 0 to 100% open condition. ( 0 V signal => actuator fully closed ; 10V signal => actuator fully open )

> A power driver / amplifier to translate user commands to a level suitable to drive the actuator through some means like a proportional solenoid valve.

> A feedback element to "inform" the actual position of the actuator. It could be a LVDT / Encoder etc.

> A PID loop that finally does the position control taking the user command as the setpoint(SP) , the feedback as the process variable (PV) and generates the control output to minimize the error term in the shortest possible time.

As I continue further I have a feeling that I cannot conclude effectively as the subject is really vast.

But the above msut have given you some basic idea of what is involved.

Raghunathan

[Dost]

Raghunathan
Thank you once again for your kind help.I inquired about the proptional solenoid valve and i came to know from the vendors that solenoid valves are not proptional they are either fully open or fully closed if u know any company that makes proptional solenoid valve in uk please let me know.secondly is there any way that i can do this work with out using pid loop .I mean I am using NI E series card if i interface an actautor at its out put and send signal from PC to NI card using Labview with out any PID controller is it possible to proptionally control the valve.I really appreciate your interest and help in solving my problems.
Regards
NAdeem

[LV_Pro]

When you ask if you can control the valve proportionally what are you trying to accomplish? As for a proportional solenoid, as far as my experience, solenoids are "binary", in one position or in the other. There are a number of proportional valves, but they are not solenoids. Many of the ones that I have dealt with have their own electronics, which are controlled by varying a control voltage or current. There is also an extremely wide variety of valves, depending on what your fluid is, a gas, water, an oil? The need for PID control comes only if you are trying to control the flow, based on some feedback. If you need only to open the valve a certain percentage, then you don't need to have PID, just some way of knowing what control signal level relates to the valve being opened a certain amount. If you are trying to control flow, then you need: to have some means of determining the flow, some means to translate that into an amount of valve opening. This is where it gets interesting, depending on many factors. Your fluid is the first major variable. Compressible fluids (gases) will behave differently than fluids that are incompressible (oils, water) and developing a PID algorithm that will smoothly control one is different than for another. The "system" that the fluid is flowing through also will frequently behave in non-linear ways (is the system a hydraulic control system with variable loading, are you running pneumatics, etc.?). As a previous post mentions, the NI DAQ card is only a small, mostly trivial, piece of the puzzle. It is used to produce either the control voltage or current, which is easy, but determining what that control signal will be is less so.

Give the group more definition in what your application is, and we may be able to help a little more. We can't design the system, but there are experts in just about every technical field on this forum and we can give you pointers to help you find the answer.

Putnam Monroe
Senior Engineer - North Shore Technology, Inc.

[MogaRaghu]

Dear NAdeem,

I am by profession an engineer designing servo and proportional systems in oil hydraulics for my bread and butter. As such if only I know your application in detail, I can defenitely put you on the right track.

There is this general misconception that solenoids are only binary. There have been tremendrous development in this field and today you have solenoids that can position a spool in an infinite position betweem two extremes - these are called proprotional solenoids. If you want to know more on a typical proportional valve check here : http://www.boschrexroth.com/business_units/bri/en/products/overview/stetigventile/st_prop_stromventile/st_ps_2ws/index.jsp

And as I mentioned in a previous post, we need to know certain basic information before we can even talk about actuators. I will be happy to help if you can revert with your application details.

Raghunathan

[Dost]

Raghunathan
Hi
You are really helping me lot as iam new to this field of control engineering by profession iam software developer and i am doing my MSc Research project.about my project iam montoring the control rig via mobile device using WAP protocool.I have completed one part where i used a pressure tranducer interfaced it with NI E series card and recorded the Pressure than wrote some WAP pages to access this pressure on mobile.my second part is to open and close a valve proprtionally. speed is not very much important now i just want to show that a valve can be operated using mobile.the only information i have is that diameter of copper pipe is 1 inch and 120 cubic litre of air is passing to it. if u can guide me what else should i need to know for this process i would be thankful.and can u suggest me any company who sell proptional solenoid valve.i also wish to know what kind of solenoid valve should i use for my rig i mean pnematic or others.
i think if i got this than would interface it with labview card and pass signal please correct me if iam wrong.
iam looking to hear more from u.