5 days prior to the annual inspection cycle of your plant, an iron pipe transpor

Question

5 days prior to the annual inspection cycle of your plant, an iron pipe transporting 1M NaOH solution at 500°C to a storage tank ruptured.

Hearing of the failure, the chief chemist in your team runs in and states "this shouldn't have happened! The hematite should have protected the inside of the pipe! We inject 10^-10 molar (FeO4)^-2 into the system for a reason!"

You decide to do a walk-down along the section upstream of the pipe, and you notice 2 things:
1) the O2 inlet valve has been closed off, and
2) an in-line O2 detector shows 10^-26 atm O2.

You make a note of this value, then return to your window-less cubicle to write up the report.

What happened? What should the inlet valve have been set at? As the new-hire corrosion engineer, explain and justify your findings in a way that your supervisor would understand.

Explanation / Answer

The inlet valve pressure can be found out using Ellingham diagram which is around 10-2 atm for hematite conversion.
Hematite forms poor adhesive layers and are not reliable as they do not form uniform layers
throughout the pipe and tend to get deposited and clogged. This might have caused the rupture in the tank.

Related Questions

Navigate

• Browse (All)
• Browse 5
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.