Looking for the optimal solution to control flow through a pipe. 2

[cmcmcm]

We have a client that wants to install a system which does the following:

- Have a modulating control valve (for example a globe valve with a 4-20mA positioner).
- Has a flowmeter installed on the same pipe.
- Flowmeter sends the flow data to a PLC, and this PLC will send a signal to control valve's actuator to either increase or decrease flow.

The fluid that goes through the pipe is water, standard temperature.

Is this the best option to control the flow of water? Or is there a single equipment that could make the work of the system?
Thanks very much

 

[Compositepro]

You just described a generic flow control loop used in many chemical plants. It will be very expensive. Can you do it another way? Sure, but you have given zero details of what you want to accomplish. How accurate does the control need to be. Do you need remote operation and data logging? Will the setpoint be changed often?

 

[cmcmcm]

Well the control valve needs to have a linear behavior that's why I suggested globe valve, but maybe we could do it with pinch valve as well.
As for remote operation and data logging, it is more important to have remote control, data logging isn't a priority.
And the setpoint doesn't have to be changed often, let's say a few times a day.
Regards.

 

[dbill74]

Most any type of valve will work. Pipe/valve size will influence the type of valve. Globe and ball valves work well on smaller (<4") pipie.

With a physical meter with a wheel or vane in the flow, you will need to be mindful of the meter position. Either upstream of the control valve or far enough downstream to have smooth flow.

It is possible to get control valves with probe ports on either side of the ball/globe into which you can insert pressure probes. Connect these to a reader and measure flow on pressure drop.

 

[LittleInch]

Errrr " Most any type of valve will work." - Not to act as a linear percent control valve it won't....

"Is this the best option to control the flow of water?" To answer this you need to define "best" and "control"

What is important to you? accuracy of flow control within a certain percent - if so what percent?

How variable are the inputs which affect the flow, i.e. upstream and downstream pressure. big changes you'll need a good fast acting system. Very low changes you might get away with manual control.

Remote control really then needs an I/P controller to vary the opening of the control valve and respond to remote changes of set point - globe valve is probably Ok for your needs.

don't see why this needs to be that expensive, but if you're doing this as a process to last 20 yrs or more then you need to buy proper instruments.

You can get stuff like this

http://www.cla-val.co.uk/flow-control.html

http://www.cla-val.co.uk/flow-limiting-4-20ma-remote-set-point.html

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[cmcmcm]

Thanks for all the helpful answers, in this situation "best" would mean cheapest valve that can do the work, and "control", throttle the flow through with 10% error give or take and a delay of a few seconds.
I think this time I'll choose the globe valve.
Regards.

 

[gerhardl]

Where is the engineering perspective? Are we talking about 1-4 inch valves and a low water pressure or are we up to 12 - 24 inches or even higher?

As given by others we are talking about two (or three) separate but integrated items:
1. Valve to be selected by flow, pressure, and required accuracy.
2 A modern electrical actuator and PLS plus flowmeter to do the regulating. An up-to date el. actuator (or pneumatic) can have much of the necessary soft and hardware integrated.
3. To find the cheapest solution you will have to define minimum, normal and maximum pressure and flow conditions, required accuracy and response time. Quality valve producers and suppliers can give you an offer for integrated items or ful package if the engineering data is known.