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Updated 02/11/2025
6

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

Why?

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

2

Corrosion occurs between metal parts (flanges)

Why?

Connect the flanges with wire to ensure equal potential

3

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

Why?

Replace the water continuously to ensure low conductivity of the water

1

Electrical potentials difference exists between the parts (flanges)

Why?

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

4

Parts made from different materials

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

Replace all the metal pipes with plastic pipes

0
Jun 22 2022 2:27:34 pm
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