Flow Rate is propositional to penstock Opening

I have to implement Penstock Opening and Closing according the flow rate.

I get the Flowrate from Transmitter and I will make decision it.How i can control opening of Penstock.

For Example if flowrate is 1000 open penstock 10%
if Flowrate is 2000 open penstock 20% and vice verse also.

I am beginner.I think I have to use PID but how?Is there any other way.

Thanks

obi1987 said:

I have to implement Penstock Opening and Closing according the flow rate.

I get the Flowrate from Transmitter and I will make decision it.How i can control opening of Penstock.

For Example if flowrate is 1000 open penstock 10%
if Flowrate is 2000 open penstock 20% and vice verse also.

I am beginner.I think I have to use PID but how?Is there any other way.

Thanks

Click to expand...

Hi,

I work for a water company and we use this philosophy to control the flow across our sand filters. We don't use a PID loop.

We simply try to maintain a flow rate across the filter. For example:

FLOW SETPOINT = 100L/s (Litres a second)
ACTUAL FLOW = 90L/s
VALVE POSITION = 45%

In the above scenario, our control philosophy is to pulse the valve an open signal until it reaches flow setpoint.

In the ladder we have a "Greater Than" block which compares the set point to the actual flow, if it's greater it allows the rung to continue through a 1 second timed bit that switches every 5 seconds (ON for 1 second, off for 5). This pulses the valve open for 1 second every 5 seconds until the flow rate is achieved. This also the same for Less Than, but obviously closes the valve.

The actual position is NOT used by the PLC control. This is because the feedback pots in ROTORK valves tend to play up over time, causing the control of the valve to play up. This way, however, uses the flow meter to control, which is much more practical.

Hope this helps!

EDIT: Just thought I'd point out that we use a deadband for the setpoint against the actual flow, this is to help stop the valve from opening and closing continuously (although with this control method it's hard to avoid, flows tend to wander around)

I use the same method as SilverShotBee for most of my analog control loops. I find it is much easier to tune and a lot more stable than PID.

Thanks Silvershootbe and Tom Jenkins.
I am totally new with all these things.
I have to open valve according to rate of change in flow.
let say if rate of change is 500 then I have to open a Valve 10 then again if rate of change 500 then i have to open 10+10=20% valve.So i have to send the pulse for some duration to open valve for some percentage.
Also how i can find the rate of change?

SilverShotBee said:

Hi,

I work for a water company and we use this philosophy to control the flow across our sand filters.

Click to expand...

Out of interest which water company? I also work for a water company.

You don't adjust the valve based on rate of change, but on actual flow rate.
1) Compare measured flow rate to setpoint
2) If the difference exceeds your allowable tolerance "bump" the control device open or closed a small amount - amount to be field adjustable.
3) Wait an appropriate time for the new flow to stabilize, the time delay being field adjustable
4) Go to Number 1

Tom Jenkins said:

You don't adjust the valve based on rate of change, but on actual flow rate.
1) Compare measured flow rate to setpoint
2) If the difference exceeds your allowable tolerance "bump" the control device open or closed a small amount - amount to be field adjustable.
3) Wait an appropriate time for the new flow to stabilize, the time delay being field adjustable
4) Go to Number 1

Click to expand...

This is correct for a valve thats actually controlling the flow, but I am wondering if the OP is requiring some sort of additional draw off from a main.

For example, when 100ML/D is flowing through the flow meter, open a valve further down stream, possibly for flow division purposes ect?

What is the application in question exactly?