pH Control Systems

Automated Controls for
pH Neutralization

Automated pH Control Systems

It is far too easy to underestimate the complexity of pH control. The vast majority of the systems that we install are replacing existing systems that never worked properly. It is common to think that all I need to do is purchase a pH probe, controller, a couple of metering pumps and I am done. Far from the truth this is. Within this article we will investigate pH control and the required algorithms for a successful pH adjustment system.

At Digital Analysis we design, build, install, and maintain the world's most capable pH neutralization systems. While our systems are custom built for a specific application they are typically based upon one of four basic models and these include our pHASE, labTREAT, batchTREAT, and hydroTREAT pH families of pH Neutralization Systems. All of these Systems incorporate our state-of-the-art PLC central control system with a graphical HMI.

pH Control Applications Include

  1. Continuous Flow Through pH Neutralization:
    1. One, Two, and Three Stage Systems
  2. Batch pH Adjustment
    1. Simplex, Duplex, and Triplex Batch
  3. Sequential Batch pH Adjust
  4. Fluoride Reduction Systems
  5. Heavy Metal Reduction
  6. Effluent Monitoring Systems
  7. Supervisory Control And Data Acquisition (SCADA)
  8. Collection / Transfer Systems

 

System Features

  1. Completely Automated
  2. PLC Based, typically Allen-Bradley
  3. Ethernet Communications allow for access to all programmable Variables, Tuning Parameters, and Alarms.
  4. Remote Monitoring, Alarming, and Communications via an optional Internet Connection
  5. All panels are UL 508A inspected and listed
  6. OSHA LOTO Disconnect on all systems.
  7. NEMA 4X, 4 or 12 Enclosures.
  8. Explosion Proof.


pH Control Curve

pH Control Curve showing our control response to changing pH
Typical pH Control Curves used with all of our pH adjustment systems. For each pH control stage within a system the tuning parameters for the acid and metering pumps (and bulk assist pumps if used) are independently controlled with non-linear tuning algorithm that can be programmed to any curve, such as a titration curve.


pH Titration Curve

pH Titration Curve showing the titration of a strong acid
pH response is not linear and cannot be controlled as such. Most pH "controllers" on the market are not truly pH controllers because they use simple on / off control or linear control provided by a PID algorithm which is far too simple to account for the ever changing control gain encountered with the logarithmic reaction of pH to control input.

A true pH controller MUST have the ability to control to a logarithmic and non-linear response such as the typical pH titration curve shown here.


The curve above is the actual titration results of the pH Adjustment of an acid (HCl) with a beginning pH of 2.0 and an ending pH of 11.0. For a more complete and in depth discussion of pH and the control of pH see our technical article pH Adjustment - The Basics



Control System Design

AutoCAD Electrical Drawings
Our team of control engineers design all of our control systems using state of the art CADD technology that is compliant to all applicable standards including UL 508A, NEC, NFPA, IEEE, NEMA, OSHA, and etc.

All systems come equipped with thorough documentation packages in both hardcopy and electronic format. These documents include detail Sequence of Operations, Bills of Materials, instruction manuals for all of the individual components used and detailed design drawings including P&IDs, Mechanicals, and Electrical drawings.

All systems are PLC based, typically Allen-Bradley and the PLC programs are fully documented and provided with the drawing package.


Control Panel Fabrication

pH System Main Control Panel
We fabricate all of our control systems in house with our team of seasoned electricians and technicians. All control systems are subject to our rigorous quality plan which includes thorough testing, simulation of actual process conditions, 24 hour burn in, and more.

Electrical panels are all built to and certified by the UL to UL 508A standards and our shop and our systems are subject to routine inspections by UL engineers. 

Ready to discuss an application? Call 1-877-685-0760 or mailto:info@digital-analysis.com