Updated 02/27/2023

Chilled water issues

Cause and Effect Chain #

The cold water closed loop is built from pipes, flanges, and fittings. The problem is that pH reduces. The corrosion is observed on some flanges as shown in the picture:

Use Cause and Effect Chain analysis to understand the root cause of the problem and find a solution.

The corrosion is related to the pH drop - metal corrosion results in the generation of H(+) ions

This occurs due to the electrochemical process:

  • corroded flange operates as an anode,
  • while not affected flange is a cathode.

There are at least two main reasons for this:

  • Water is an electrolyte
  • A potentials difference exists between two flanges
May 26 2022 3:35:52 pm
5 Whys #
Causes Chain
Root Cause Analysis

pH drop is observed


Replace the water when the parameters (pH and conductivity) got out of the spec limits


Corrosion occurs between metal parts (flanges)


Connect the flanges with wire to ensure equal potential


Electrical current occurs through the cooling water between the parts (flanges)


Replace the water continuously to ensure low conductivity of the water


Electrical potentials difference exists between the parts (flanges)


Ground all the metallic parts (pipes, flanges) to ensure equal electrical potentials


Parts made from different materials

This is the fundamental reason for the problem (FRP).

Replace all the metal pipes with plastic pipes

Jun 22 2022 2:27:34 pm
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