(128a) Lessons Learned From Fire in Air Supply Ducts

ABSTRACT

Submitted for consideration to the 47^th LPS on Oct 31, 2012

Title: Lessons Learned
from Fire in Air Supply Ducts

Primary author: Al Waller, Principal Process Safety
Engineer, FMC Corporation

A significant fire occurred inside the air supply ducts to a
drying and milling operation.  Investigations
concluded that the interlocks functioned as designed on loss-of-airflow but were
not sufficient to prevent overheating the inlet air filters (including HEPA
filters) from the residual heat in the air heaters.  The two main lessons learned from this
incident apply to a broad range of operations in the CPI:

1)  Mundane unit operations such as air filters that
have combustible components must be evaluated as thoroughly as the rest of the
chemical process. 

2)  Designers and HAZOP leaders must recognize the
potential of thermal inertia of heaters (and coolers) to heat (or cool) a
stagnant volume of fluid when flow is interrupted.  Gas streams are particularly susceptible due
to the low heat capacity relative to the heat capacity of a metallic heat
exchanger.  Interlocking the supplies (to
steam and electrical heaters in this incident) is often necessary but may not
be sufficient.

Other lessons from the escalation aspects of this fire will
also be discussed.