pH Control

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.

PID 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 disturbances
  • 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...

pH respons with standard PID control
Figure 1 – pH response with standard PID control

pH respons with MANTRA 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:

AN 319 MANTRA for Scrubber pH and Oxygen Reduction Potential (ORP) Control
AN 320 MANTRA: Overcoming the Challenges of pH Control
EM08-08-01 Solving the Problem of pH Control
EM08-19-02 Neutralizing pH is Common But Can Be Difficult
  To receive a copy of one or more of the above Application Notes and Technical Papers, simply select the desired paper above and submit the form below. (* Required fields.)
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