Accident Case Studies

Spontaneous Heating and Pyrophoricity

DOE-HDBK-1081-94

ACCIDENT CASE STUDIES

ACCIDENT CASE STUDIES

Silane Gas Cabinet Fire

A 6.1 x 9.1 m (20 x 30 ft) room with concrete block walls was used for distribution of

process gases to clean room areas. Silane cylinders were located in 12-gauge metal gas

cabinets. The ventilation system for the cabinets was in the process of being upgraded and

the cabinets were protected by automatic sprinklers.

The silane cylinder involved was installed about 30 minutes prior to the incident. Employees

in the area heard a loud "pop" from the process gas distribution room. Upon investigation,

they found the windows of the cabinet broken, the doors open, and fire coming from the

cylinder valve. The sprinkler activated properly and confined the fire to the cylinder head.

The escaping silane was caused by an improper connection of the cylinder to the distribution

piping. There was evidence that the connection was cross-threaded, allowing the leakage.

The flow of silane could not be shut off because of damage to the cylinder manifold

connections. The fire continued to burn for about 8-1/2 hours until all silane in the cylinder

had been consumed.

Recent Coal Fire at a DOE Site

In 1992, a DOE site experienced a coal fire initiated by spontaneous combustion. Because of

the nature of the fire and initial ineffectiveness of the means used to fight it, the fire required

more than 28 hours to completely extinguish from the time a hot spot was first detected in a

coal bunker. The initial strategy involved trying to remove coal from the bunker by feeding it

more rapidly to the boiler and by using a drag chain to move more of it to the field. The drag

chain failed in 30 minutes, however. Subsequent efforts to control the fire with carbon

dioxide applied through inspection ports at the bottom of the bunker and from the tripper

(switchgear) room high above the bunker were ineffective, and may have worsened the

situation. The drag chain emptying coal from the bunker worked intermittently after being

repaired, and finally stopped. Boiler plant personnel then began to remove burning coal by

hand shovel.

Twenty-one hours after the fire was discovered, it had involved a large amount of the

bunker. At one point, flames appeared at the tripper room windows, which were

approximately 75 feet above the seat of the hot spots. A strong concern for a steam

explosion delayed the application of water, but the decision was finally made to use water,

which was applied without incident and eventually ended the fire.

Zirconium Incidents (Smith, 1956)

Up to May 1955, no serious fires had been encountered during storage of scrap Zr turnings,

chips, plates, rods, etc. Such scrap had been stored (pending contemplated future recovery)

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Pyrophoricity