Issues Final Report on Barton Solvents Explosion
Wichita, Kansas, June 26, 2008 - The U.S.
Chemical Safety Board (CSB) today released a case study
and safety video on the July 2007 explosion and fire at
the Barton Solvents distribution facility in Valley Center,
Kansas. The CSB found the most likely cause of the explosion
-- involving what is known as a nonconductive flammable
liquid -- was a static spark resulting from a loosely-linked
level-measuring float within the tank. The spark ignited
the air-vapor mixture inside the tank as it was being
Nonconductive flammable liquids can accumulate
and maintain static electrical energy which discharges
more slowly than from more conductive liquids. In addition,
some of these liquids can form ignitable vapor-air mixtures
inside storage tanks which can explode if a spark occurs.
The CSB released a ten-minute safety video
which features a computer animation depicting the sequence
of events that led to the explosion and fire. The video,
entitled 'Static Sparks Explosion in Kansas' is available
for downloading free of charge through the agency's video
CSB Board Member William Wark said, 'Our
goal is to help companies understand the hazards associated
with the kinds of flammable liquids that were stored and
transferred at Barton Solvents. We believe our case study
and the safety video will help accomplish that goal and
The July 17, 2007 explosion and fire led
to the evacuation of 6,000 residents. Eleven residents
and one firefighter sought medical attention. Fire destroyed
CSB investigators found that on the day
of the accident a tanker-trailer arrived to transfer Varnish
Maker's and Painter's Naphtha (VM&P Naphtha) into
a storage tank. The CSB determined that the transfer equipment
from the truck tanker to the storage tank likely was properly
bonded and grounded to prevent the generation of static
electricity. However, the CSB found, the float device
inside the 15,000 gallon storage tank presented a hidden
CSB Lead Investigator Randy McClure said,
'When transferring liquids, it is standard industry practice
to bond and ground storage vessels, tankers, and other
equipment to prevent static discharges. But our investigation
illustrates how normal bonding and grounding may not be
enough to prevent ignition from static electric sparks.'
Inside the tank was a device used for
measuring the liquid level, a metal float linked to a
metal tape measure. The CSB determined that a static electrical
charge in the liquid was generated by the flow of the
solvent pumped from the trailer into the storage tank,
and by stop-and-start filling which introduced air into
the liquid, resulting in bubbles and turbulence.
At the same time, the space above the
liquid was being filled with an explosive mixture of vapor
and air. The CSB determined that the liquid flow and turbulence
created by the filling of the tank likely resulted in
the metal float accumulating a static electrical charge.
As the float moved, a gap is believed to have formed within
the linkage of the tape and the float. CSB investigators
said a spark likely jumped between the metal parts and
ignited the explosive mixture of vapor and air that had
accumulated above the liquid.
The explosion blew the tank 130 feet into
the air, and within moments two more tanks ruptured and
released their contents. As the fire burned, the contents
of nearby tanks were released and ignited, launching debris
into the air where some of it struck a mobile home and
a neighboring business.
Board Member Wark said, 'Several common
flammable liquids are particularly susceptible to ignition
by static sparks. Some of these flammable liquids can
produce the optimal amount of vapor to fuel an explosion
at normal temperatures inside a storage tank.'
Mr. Wark continued, 'While we found the
most likely cause of the Barton explosion was sparking
across the float linkage, we emphasize that explosions
can occur in tanks without faulty floats when there is
a discharge from the build-up of static in the nonconductive
flammable liquid itself.'
Material Safety Data Sheets, or MSDSs,
communicate hazard information on chemical products. The
CSB determined the MSDS for the VM&P Naphtha did not
adequately describe the explosive hazard or the precautions
necessary to prevent ignition from static electricity.
Most of the MSDSs for the flammable solvents supplied
to Barton indicated that the solvent could accumulate
a static charge, which could spark and ignite vapor. But
the MSDSs did not warn that the solvent could form a highly
explosive vapor-air mixture inside a storage tank.
The CSB reviewed 62 MSDSs for some of
the most widely used nonconductive flammable liquids in
industry, such as VM&P Naphtha, hexane and toluene.
Most failed to recommend specific precautions beyond bonding
'The accident at Barton Solvents emphasizes
the need for accurate and detailed MSDSs,' said Mr. Wark.
'We found that while most MSDSs for this category of flammable
liquids do warn about the dangers of accumulating static
electricity because the liquids are poor conductors, the
MSDSs do not warn specifically that they can be ignited
in storage tanks. Companies should be aware that some
of these flammable liquids can form an ignitable vapor-air
mixture inside storage tanks.'
The CSB issued recommendations to OSHA
and others to improve required information contained in
MSDSs to include addressing nonconductive flammable liquids
which are routinely shipped to distributors such as Barton.
The CSB also recommended that six major oil and chemical
industry associations ask their member companies to improve
the warnings on the MSDSs of flammable liquids because
these materials can accumulate static electricity.
The Board recommended companies handling
the liquids should take additional safety measures, such
Obtain more detailed additional technical
information on the liquids from manufacturers
that may not be found on MSDSs.
Purge storage tanks with an inert gas
to remove oxygen.
Add anti-static agents to the liquids.
Pump liquids more slowly.
Verify that storage tank level floats
are effectively bonded.
The CSB is an independent federal agency
charged with investigating industrial chemical accidents.
The agency's board members are appointed by the president
and confirmed by the Senate. CSB investigations look into
all aspects of chemical accidents, including physical
causes such as equipment failure as well as inadequacies
in regulations, industry standards, and safety management
The Board does not issue citations or
fines but does make safety recommendations to plants,
industry organizations, labor groups, and regulatory agencies
such as OSHA and EPA.
Visit our website, www.csb.gov.
For more information, contact Sandy Gilmour at (202) 251-5496
(cell, in Wichita, Kansas for the news conference) or
Public Affairs Specialist Hillary Cohen at (202) 261-3601
in Washington, D.C.