[Music]
Off Screen Voice: We continue to follow the 
breaking news out of Valley Center this morning.
A huge explosion ... Newscaster: Tremendous 
amount of heat, smoke.
Officers and authorities are worrying about getting 
traffic rerouting, getting people out of the area.
Narrator: On July 17, 2007, at about 9:00 a.m.,
an explosion in a flammable solvent 
storage tank at the Barton Solvents facility
rocked the town of Valley Center, Kansas, 
about 15 miles north of Wichita.
Off Screen Voice: This is no longer a safe area; 
we are requesting that you evacuate.
Narrator: After the explosion, the fire spread, 
igniting the contents of other storage vessels
and eventually destroying the entire tank farm.
Wark: The CSB issued a case study on the accident.
Our goal is to help companies understand the 
hazards associated with the kinds of flammable liquids
that were stored and 
transferred at Barton Solvents.
McClure: At Barton, several factors 
combined to produce the initial explosion.
Our investigation shows the need for companies 
to take extra precautions when handling
what are known as nonconductive flammable liquids, 
which tend to accumulate static electricity.
[Music]
McClure: Based on equipment testing, 
laboratory analysis and interviews and documents,
here's what the CSB believes most 
likely happened on July 17, 2007.
Narrator: Barton Solvents was located 
on the edge of a residential community.
The facility was a wholesale distributor 
of solvents and other industrial chemicals,
which were stored in large outdoor tanks.
About 8:30 on the morning of the accident, a tank trailer 
arrived to transfer a nonconductive solvent,
known as varnish makers and painters 
or VM&P naphtha, into a storage tank.
Because liquid flowing through pipes 
and valves generates static electricity,
which can ignite flammable vapor,
the tank farm supervisor connected a cable 
between the truck and an electrical grounding station.
In addition, all the equipment involved 
in transferring the liquid was bonded,
that is, connected together with 
electrical conductors and grounded.
Inside the 15,000 gallon storage tank there 
was a device for measuring the liquid level.
A metal tape, which was grounded,
was suspended from pulleys and connected to a 
metal float by a loose, flexible linkage assembly.
This linkage presented a hidden danger 
during the filling of the tank.
The solvent was pumped from three 
tank trailer compartments into the tank.
As the hose was switched from one 
compartment to another, air entered the line,
creating bubbles and turbulence inside the tank.
A static electrical charge built up 
in the nonconductive liquid.
Meanwhile, the space above the liquid was 
filled with an explosive mixture of vapor and air.
The swirling turbulent liquid caused the float to 
drift and rock, creating slack in the metal tape.
This allowed a gap to form intermittently in the 
linkage assembly, interrupting the grounding of the float.
The metal float accumulated 
a static electrical charge.
About 9:00 a.m., a spark from static electricity 
ignited the vapor-air mixture.
[Sound of explosion]
Narrator: Causing a massive explosion.
The blast sent the storage tank 
rocketing into the air.
Two more tanks quickly ruptured and released 
their contents into the rapidly expanding fire.
As the fire raged inside the tank farm, 
other tanks burst and ignited,
launching heavy steel tank lids,  
ten to twelve feet in diameter, into the air.
Twenty thousand gallons of flammable liquid 
were released into the spill containment area.
[Sound of explosion]
Narrator: Valves, pipes and other heavy steel objects 
were hurled offsite and into the adjoining community.
One tank lid struck a mobile home about 300 feet away.
A pressure valve hit a 
neighboring business 400 feet away.
Narrator: Six thousand residents were evacuated.
Eleven residents and one firefighter 
required medical treatment.
[Music]
McClue: When transferring flammable liquids,
it's 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.
Holmstrom: Our investigation found several conditions
likely increased the accumulation of static electricity 
inside the storage tank at Barton.
Narrator: The CSB concluded that 
repeated starting and stopping of the pump,
air in the transfer piping and the likely 
presence of water and sediment in the tank
all contributed to rapid 
static charge accumulation.
Because VM&P naphtha is a 
poor conductor of electricity,
the static charge accumulated faster than it could dissipate, 
even though the tank itself was grounded.
Holmstrom: A lot of common flammable liquids are 
particularly susceptible to ignition by static sparks.
At normal temperatures inside a storage tank, they can  
produce the optimal amount of vapor to fuel an explosion.
Narrator: That's not so with gasoline,  
which is highly volatile
and usually produces a vapor-air mixture 
that is too rich to ignite inside storage tanks.
But the CSB noted that less volatile liquids 
like VM&P naphtha, hexane, heptane,
toluene, xylene and benzene 
form vapor-air mixtures
that are within the flammable range 
and can ignite readily.
Wark: Because most material safety data sheets  
do not communicate
all the hazards of 
nonconductive flammable liquids,
the CSB recommends companies take additional 
safety measures when handling these materials.
Narrator: The CSB said companies should consider 
purging storage tanks with an inert gas to remove oxygen,
adding anti-static agents to nonconductive liquids, 
pumping liquids more slowly
and contacting manufacturers for additional 
safety information that may not be found on MSDSs.
And the CSB case study also urges 
special precautions for tank level floats
that have a loose linkage assembly 
like the one at Barton.
Companies should replace or modify these floats, so that 
they remain properly bonded and grounded at all times.
[Sound of explosion]
Narrator: The CSB cautioned that while the 
most likely cause of the Barton explosion
was sparking across 
the float linkage,
explosions can occur in tanks without floats  
when there is a static discharge from the liquid itself.
Companies should consult the CSB case study 
and its references for additional information.
McClure: The CSB determined that the material safety 
datasheet for the solvent involved in the explosion
did not adequately describe the 
explosive hazard or the precautions necessary
to prevent ignition from static electricity.
Narrator: Material Safety Data Sheets or 
MSDSs are required under federal OSHA regulations
to warn workers about the 
potential hazards from chemicals.
The MSDS for the 
naphtha supplied to Barton
indicated the solvent could accumulate a static charge,  
which could spark and ignite vapor,
but the MSDS did not warn that the naphtha could form a 
highly flammable vapor-air mixture inside a storage tank.
And apart from normal 
bonding and grounding,
the MSDS did not include any special 
precautions against static ignition.
CSB investigators said the lack of 
warnings reflected a broader problem.
Holmstrom: We reviewed Material Safety Data 
Sheets for 62 nonconductive flammable liquids
that are widely used in industry.
The CSB found that the vast majority 
of these MSDSs had significant gaps.
Narrator: Of the 62 MSDSs covering a 
number of widely used nonconductive liquids,
most failed to recommend specific precautions 
beyond bonding and grounding to prevent static sparks.
Only three included electrical conductivity testing data  
and only one of the 62 MSDSs
warned of the danger of an ignitable 
vapor-air mixture forming inside a storage tank.
Wark: The CSB recommended that OSHA 
improve the information required in
Material Safety Data Sheets for 
nonconductive flammable liquids.
Narrator: The CSB recommended that OSHA 
advise MSDS preparers to evaluate each product
to determine its potential for 
accumulating static electricity
and to form an ignitable vapor-air mixture 
inside a storage tank.
Each liquid should be tested for electrical conductivity 
and the results included in the MSDS.
The CSB also recommended that six major 
oil and chemical industry associations
ask their member companies to 
improve the warnings on their MSDSs
for flammable liquids that can accumulate static electricity.
Wark: We hope the CSB investigation  
helps increase awareness
about the hazards of 
nonconductive flammable liquids,
so accidents like the one at 
Barton Solvents will not be repeated.
Thank you for watching 
this CSB Safety Video.
Wark: For more information 
about the CSB investigation
and to view the case study on the accident, 
please visit our website at CSB.gov.
[Music]
