Pipe Failure (Hydrogen Embrittlement)

  Sun 6/30/2013

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The tube carries very hot chemically treated water for generation of superheated steam to drive a turbine.  The small protrusions on the tube surface effectively increase the surface area for efficient heat transfer.  Failure occurred by ejection of a small irregular shaped piece of the tube wall.  The tube wall fracture lips are thick-walled, that is they have not thinned.  The microstructure of the tube at the fracture and away from it is similar without evidence of overheating.  Hydrogen is produced by a chemical reaction that corrodes the internal surfaces of tube.  At very high temperatures, the nascent hydrogen reacts with the carbon in the steel to form Methane.  The escape of methane thru the steel at high temperature causes grain boundary separation in the steel, resulting in embrittlement.  Hydrogen embrittlement was determined as the failure mode, and deficiencies in the water treatment as the root cause.

Contact/Location

Matt Keenan
CUSHING, WI
715.648.5000