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 1 M NaOH solution at 500 degree 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 FeO_4^2- 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: the O_2 inlet valve has been closed off, and an in-line O_2 detector shows 10^-26 atm O_2. 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

It is difficult to comment on inlet valve pressures because it depends upon the velocity of the flow of NaOH.
However the inlet valve pressure should be optimum, otherwise it might cause poor flow problems.
Hematite forms poor adhesive layers and are not so reliable since they do not form uniform layers
throughout the pipe. Looks like the hematite got deposited excessively at some spot and got clogged. This might have triggered the rupture in the tube.

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