Auto Refrigeration and Metal Embrittlement

Abstract AIChE Housten Conference April 1-4 2012

Loss Of Containment Protection

Auto Refrigeration and Metal Embrittlement

Tys Koerts

Sr. Process Safety Consultant

Auto-refrigeration occurs on adiabatic expansion of gasses and boiling of liquids. The resulting low temperature can bring metals like carbon steel below there ductile-brittle transition temperature resulting in metal embrittlement. This has resulted in complete rupture of vessels and pipelines with loss of containment and gas explosions.

In this paper the predominant root causes are identified and some best practices for equipment and process design basis is described. Also the key operating aspects on how to react upon a "chilling event", including the options for inspection of static equipment, will be mentioned.

Further the mechanism of embrittlement is discussed including materials that are less susceptive and can be used at low temperature.

The combined lessons learned are put in a practical format. They are relevant for all operating units that have compressed gasses or pressurised liquids with boiling points below ambient temperature.