Don't Let pH and ORP Problems Wash Away Your Profits!
One of the toughest loops to control can be pH, mainly due to the non-linear
nature of the pH signal. Since pH scale is logarithmic in nature, a change
of 1 unit of pH means a 10x change in the strength of the acid or base!
Add significantly long deadtimes, high potential for input flow disturbances,
and the need to coordinate multiple process variables and controller
outputs simultaneously (especially for pH and ORP), and you get a process
loop that will send most control professionals heading for high ground.
Controllers are not for pH!
Many people try to tackle pH and ORP loops with standard PID control,
but PID algorithms are better suited to linear applications where the
process gain and response time remain relatively constant. With pH, the
process gain can vary by orders of magnitude depending on the operating
range of the pH. PID is simply not robust enough for these situations.
Look to ControlSoft for your pH Control Solution
ControlSoft is an industry leader in advanced process control (APC)
solutions. Our MANTRA APC software is designed to handle even the most
difficult pH and ORP control situations with the use of our advanced
Coordinated Controller (CC) and Internal Model Controller (IMC) technology,
which allow you to:
- Detect strong interactions between process variables (i.e.
pH and ORP) and compensate accordingly
- Coordinate individual
control outputs to make overall control more effective
- Handle long
dead times of both pH and ORP control
- Provide bumpless transfer
from IMC to actual PLC controller
- Tune different regions of nonlinearity
using different parameters and controller speeds
- Handle influent flow
- Maintain your existing control system. With MANTRA, there
is NO need to add or replace existing hardware or adjust any wiring
on your current control system!
The proof is in the pH...
Figure 1 – pH response with standard PID control
Figure 2 – pH response with MANTRA control
How we do it
The application note available at the end of this page outlines the
design and implementation of MANTRA advanced process control software
for control of the pH and oxygen reduction potential (ORP) in scrubber
water. The particular system had troubles with input disturbances, long
deadtimes, and simultaneous control of pH and ORP due to strong interactions
and non-linear behavior.
Request Application Note 319 below to learn how the MANTRA APC software
was able to:
- Eliminate ORP excursions
- Stabilize pH control
by improving the predictability of the ORP control
- Use model predictive
control to robustly handle non-linearity in the process
ControlSoft APC technology can improve your pH control while saving
time, effort, and money.
Select from the following application Notes and Technical Papers:
See other applications.