Probe uncovers source of Barton Solvents blast

Tag : normal hexane

W hile checking the rubble of the Barton Solvents storage-tankfacility in ValleyCenter last July, federal investigators found animportant piece of charred equipment -- a crucial clue to solvingwhat caused the huge fire.
It was the same kind of measuring-float equipment used in the15,000-gallon above-ground storage tank where the initial explosionoccurred.
Now, federal investigators have concluded that metal linking to thefloat allowed a spark to form, setting off an explosion in thetank.
It has far-reaching implications because it is the same type ofmechanism used in hundreds of thousands of chemical storage tanksacross the nation.
It works like this: To measure the level of the liquid in the tank,a metal tape measure extends down and connects to a float restingatop the liquid. When there is slack in the tape, a gap can occurbetween two pieces of metal that link to the float. Testing showedthat static electricity could spark across the gap.
The investigators concluded that is most likely what ignitedflammable vapors in the tank while it was being filled with VM&Pnaphtha, a widely used solvent, the U.S. Chemical Safety and HazardInvestigation Board (CSB) announced Thursday in Wichita.
The initial explosion shot the tank up, and it landed 130 feetaway. Large pieces of metal rocketed into the surrounding area,striking a mobile home about 300 feet away and a business about 400feet away.
Resulting explosions and billowing fire caused the evacuation ofabout 6,000 people. It prompted 11 residents and one firefighter toget medical treatment. It destroyed 43 storage tanks, each 15 to 40feet tall, with capacities of 3,000 to 30,000 gallons, the CSB andBarton Solvents said.
"It was fortunate that there were no severe injuries or deathsresulting from the accident," said CSB board member William Wark.
Barton Solvents president David Casten declined to provide a damageestimate.
Casten, who attended the CSB news conference, said the DesMoines-based company will modify the commonly used float mechanismthat was singled out by the agency. The modification basicallyentails installing a small wire.
Barton Solvents plans to build a new tank storage facility in theWichita area, possibly in Bel Aire or El Dorado but not in ValleyCenter, partly because of the proximity to homes, Casten said.
In seeking a new location, Barton Solvents will look for a sitethat will have plenty of buffer around it, he said.
For now, Barton Solvents continues to operate a warehouse at itsValley Center site.
Design questioned
Although the agency focused on how the tank exploded, CSB leadinvestigator Randy McClure said that if the tank farm had been"designed appropriately," the fire wouldn't have spread as it did.
McClure said that more spacing between tanks and better venting inthe tanks that subsequently caught on fire and exploded would havehelped contain the fire and made it easier to fight. The tanks werefive rows deep, he said.
Initial explosions sent about 20,000 gallons of flammable liquidinto the spill containment area, the CSB said.
In a fire, venting allows pressure from the heated liquid in thetank to be released, preventing the vessel from rupturing andlosing its contents.
Asked about McClure's saying that the design wasn't appropriate,Casten said, "That's a new one on us."
He said the venting was sufficient.
"There's no amount of venting that would have prevented the firstexplosion," Casten said. "The pressure built so rapidly. There's novent that would have been able to contain that pressure."
Last fall, the Occupational Safety and Health Administration finedBarton Solvents about $1,700 for failure to inspect vents at theValley Center plant as recommended by the manufacturer, Castensaid.
The CSB, an independent agency whose board is appointed by thepresident, said it is publicizing the Barton Solvents findings sothat handlers of commonly used solvents can check float mechanismsand take precautions to prevent sparks.
CSB does not have regulatory authority; it makes safetyrecommendations based on its findings.
Key findings
Although the float appears to be a crucial factor, it took acombination of conditions for the accident to occur, McClure said.
Other key findings in its investigation, the CSB said, were:
• The tank "contained an ignitable vapor-air mixture" in the spaceabove the solvent.
• The Barton employee pumping the solvent from a tanker-trailerswitched from one trailer compartment to another, allowing air intothe piping. The air caused bubbling and turbulence in the storagetank, resulting in a "rapid static charge accumulation."
• Required data sheets from the solvent manufacturer "did notadequately communicate the explosive hazard." The data sheets areknown as MSDSs.
The CSB checked 62 MSDSs for several "nonconductive flammableliquids that are widely used," such as VM&P naphtha, hexane andtoluene, and found that most did not recommend enough precautions.
"The accident at Barton Solvents emphasizes the need for accurateand detailed" chemical safety sheets, said Wark, the CSB boardmember.
The CSB said it has asked OSHA and six oil and chemical industryassociations to help push for better data sheets for liquidsshipped to distributors.
McClure said the investigation highlights a little-known hazard:that some solvents can ignite while being transferred even innormal temperatures, even within storage tanks and even whengrounded and bonded in the typical ways. Grounding safely divertsan electrical charge, and bonding prevents sparking.
Because of its findings, the CSB is recommending that peopletransferring solvents take additional precautions, including:
• Requesting more guidance from manufacturers
• Adding an inert gas, such as nitrogen, to the space above a tank'scontents. That process removes oxygen, a key element in a fire.
At a Barton Solvents facility in Kansas City, Kan., the companywill test a process to charge tanks with nitrogen, Casten said.
• Modifying, replacing or inspecting tank floats to make sure theydon't cause sparks.
Casten said Barton Solvents plans to modify about 135 tank floatsin Iowa, but the process takes at least a week per tank.
The current float mechanism has been the industry standard in wideuse for decades, Casten said.
• Removing slack in the metal tape measure connected to the float.The slack can allow a "spark gap."
• Reducing the speed at which the liquid is pumped, to preventstatic electricity
• Adding anti-static agents to liquids before they are transferred
Under a new law, prompted by the Barton accident, the state firemarshal will begin inspecting above-ground chemical storagefacilities.
The law requires the state office to develop regulations for thesites by Sept. 1.
The law applies to above-ground storage systems with a totalcapacity of 10,000 gallons or more. The fire marshal will berequired to inspect the facilities by July 1, 2009, then once everythree years. Facilities have until July 1, 2012, to comply with thenew regulations.

Contributing: Jeannine Koranda of The Eagle
Reach Tim Potter at 316-268-6684 or tpotter@wichitaeagle.com .