pH controler tuning

[all2win]

Hi guys,
Has anyone has ideas about tuning Ph controller .(The pH is maintained by dosing caustic}
We have a split control valve for this purpose.The fine controller is PID based.I can make the control valve slow and steady .But It collapses when slight disturbances in the flow or load.
CAn anyone helpme out?.

Thanx

 

[hacksaw]

sounds about right for pH.

you can use feed forward to increase the caustic flow with increased inlet flow and use outlet pH to trim the dosage.

good mixing, pH control with two sep. mixing tanks, etc all help.

good luck,