ATF

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Bureau of Alcohol, Tobacco, Firearms and Explosives

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ATF Explosives Industry Newsletter Masthead
August
2002
Editor,
Gene Baker

further
questions on magazine construction standards or other storage
requirements, please contact the Public Safety Branch in Washington,
DC.

INDUSTRY
ALERT ON ANFO STORAGE

Spontaneous
combustion indicated in trailer fire

On
August 27, 2001, a fire was reported in a forty-foot long trailer
parked at an explosives plant operated by Golden State Explosives,
located about 40 miles east of Sacramento, CA. At the time, the
trailer was being used to store approximately 25,000 pounds of
pre-mixed ANFO (ammonium nitrate and mineral oil) in plastic bags/tubes.
The relatively small fire self-extinguished and no explosion occurred.
The investigation revealed that the fire was most likely due to
either some type of thermal decomposition of the blasting agent
product or its packaging caused by the ambient temperature conditions
or a self-heating/spontaneous combustion scenario in the product
or packaging.

Investigators
found several hundred 30-pound tubes of pre-mixed blasting agent
stacked in the trailer. The 36-inch long tubes were laid lengthwise
on the floor of the trailer (end to end) and covered the entire
deck from side to side, approximately three feet high. It was
packaged under the name of Tovan Extra, and the material
was reportedly made and packaged in 1998 by Cook Slurry Company
in Salt Lake City, UT, and delivered that same year to Golden
State Explosives. The Material Safety Data Sheet (MSDS) for the
product refers to it as a packaged emulsion known as CO-GEL
1150
. The material was designed as an 83 percent mixture of
Ammonium Nitrate prills emulsified with Mineral Oil (instead of
diesel oil).

As
the tubes were removed from the trailer, investigators discovered
that there had been substantial thermal decomposition in some
of the tubes that had the most direct sun exposure. Golden-brown
stains were visible along the bare metal sides and the lining
material near the front of the trailer. As the packaged tubes
of blasting agent were removed from the truck, a nearly clear
liquid was found leaking from of most of them. The liquid appeared
to have saturated the wooden floor and was dripping through the
bottom of the trailer onto the ground. In the stacks at the very
front of the trailer, the plastic covers had darkened, melted,
and,

in
some instances, split open. Damage to the tubes increased towards
the bottom of the stack until completely melted/burned material
was visible. There were also numerous holes, as big as 12 inches
in diameter, which had burned into and in some cases through both
the wooden decking and the wooden forward bulkhead of the trailer,
allowing additional air to enter the fire/smoldering environment.

During
the investigation, which occurred on the 28th of August, the outside
air temperature at the trailer reached 100-103 degrees. The metal
skin on the inside of the trailer facing the sun measured between
125 and 130 degrees. The metal skin on the opposite side of the
trailer facing away from the sun reached a temperature of 105-110
degrees. The plastic covers of the material, which came in contact
with the hot-side metal skin, was about 103 degrees Fahrenheit.
Blasting agent inside the tubes had a recorded temperature of
about 96 degrees Fahrenheit.

Analysis

Subsequent
analysis of why the material self-ignited revealed some possible
causes, but no specific reason for the self-initiation has yet
been determined. The heating process could have been initiated
from simple elevated ambient temperature conditions, coupled with
several years of natural decomposition, or it might have been
initiated or catalyzed by other chemicals.

A
background search disclosed that this is not an isolated incident
of self-initiation of similar products. In December 2000 the UN
Sub-Committee of Experts on the Transport of Dangerous Goods at
their 21st session held in Geneva, Switzerland discussed under
Agenda item 2(b), (in paper UN/CETDG/21/INF.14) a thermal stability
test for ammonium nitrate emulsions similar to the one involved
in the Golden State Fire.

All
personnel in the explosives industry who deal with ANFO,
particularly the ANFO mix from this incident, should be
aware of this self-heating situation. Any requests for additional
information should be referred to ATF Special Agent (Certified
Fire Investigator) Steve Carman in Sacramento, CA (916)
498-5100, or ATF Fire Protection Engineer Gerald Haynes
in ATF's Arson & Explosives Programs Division at (202)
927-7930.

 

     

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