Problem 11.6: A valvedoff 4inch branch line has been

From Chapter 11 Problem Set. Level 2: Applied Thinking.

Question

A valved-off 4-inch branch line has been stagnant for 2 years in a nitrite-treated chilled water loop.

Using the four questions, predict:

• what no longer enters,
• what no longer leaves,
• what may have accumulated,
• what chemical and biological transformations likely occurred

Then identify the dominant failure mode.

Answer

Show answer

Strong answers may include:

• What no longer enters: Fresh inhibitor, fresh water, oxidant, or meaningful flow
• What no longer leaves: Water, corrosion byproducts, or biological material
• What may have accumulated: Corrosion products, stagnant water, depleted chemistry, biomass
• What likely changed form: Dissolved oxygen is consumed, inhibitor residual is depleted, localized microbial communities may establish, and corrosion proceeds in chemically isolated conditions

Dominant failure mode: localized corrosion, often with significant MIC risk.