(72b) 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.