SLC Function SLC 5/05 PLC Program

[Ones_Zeros]

Mickey,
what i'm wanting to do is restrict how far the valve can open or close because of the dead space of travel from 100% open until it reaches 60%
so if i limit the valve from opening to 60% open it has less distance to travel
on the flip side I want the valve to close to 80% that will lease it 20% open

When the Control Output CV % (this is the % the valve is closing) gets to 80% I want the valve to stop, & when the CV gets to 40% closed I would like for it to stop

not sure on these settings

output limiting bit (OL) word 0, bit 3 of PID Control Block is
enabled (1), the CVH (Control Value High) you enter is the maximum output
(in percent) that the control variable attains. If the calculated CV exceeds the
CVH, the CV is set (overridden) to the CVH value you entered and the upper
limit alarm bit (UL) is set

I have not configured this

 

[Mickey]

So as I understand your request the valve at 0 % is fully open and at 100% the valve is fully closed.

If this is the case then set the output max at 80% and the output min at 40%.Also set the "OL" bit to enable output limits.

This will prevent the valve from fully closing at 80% (closed) and from fully opening at 40%(closed).

Edit: others please jump in if I have misread this.

 

[Ones_Zeros]

Mickey,
Thanks again

your the man!!

I got it working

 

[Mickey]

That was quick.

You're welcome.

 

[Mickey]

Just thinking out loud..

If this is your pressure control, it does seem a little odd that you have a valve that will fail open on a loss of signal and you do not want it to fully close. Hopefully there is no overpressure issues in your process.

 

[Ones_Zeros]

Thanks Mickey for asking,
with our process if the valve was to fail closed, then there would be a pressure
issue inside the plant, by having it to fail open in the event of a shutdown would allow the pressure to equalize.


Thanks again for your help!!