Part 2: What Are The Internal Treatment Programs Used Within Steam Generators

February 24, 2022

Author; E. S. Beardwood, The Analyst, Winter 2022 Edition, Volume 29, Number 1, pages 24-33


In this article, we examine internal chemical treatment programs that are available. Some programs we will look at include all-volatile treatments, oxygenated treatment, caustic treatment, phosphates, polymers, chelants, and carbonate + polymers.

There are a number of internal chemical treatment programs available for use in the control of corrosion and deposition within steam generating equipment. A common aspect of all these programs is the need for pH, alkalinity, silica, iron and hardness control in the boiling waters. These programs can be described as follows:

  1. All Volatile Treatment Reducing (AVT – R).
  2. All Volatile Treatment Oxidizing (AVT – O).
  3. Oxygenated Treatment (OT).
  4. Caustic Treatment (CT).
  5. Phosphate Treatment (PT) subdivided into a)Coordinated Phosphate Treatment (CoPT), b)Equilibrium Phosphate Treatment (EPT; modification of CoPT), c) Congruent Phosphate Treatment (CPT; modification of CoPT).
  6. Residual Phosphate + Polymer; precipitating, crystal modification and dispersing program.
  7. All-Polymer; lots of polymer, crystal modification, sequestration (weak chelation), threshold inhibition and dispersing program.
  8. Chelant; solubilizing / stoichiometric chelant program.
  9. Chelant + Polymer; solubilizing / chelant, crystal modification and dispersing program.
  10. Chelant + Polymer + Phosphate; solubilizing / sub- stoichiometric chelant , crystal modification, sequestration, threshold inhibition and dispersing and precipitating program, Engineered Competition.
  11. Carbonate + Polymer; precipitating, crystal modification and dispersing program.

The first five programs were designed for high-pressure steam generators (greater than 900 psig) that have high purity make-up water in use.