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 filled.
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 10-minute safety video that features a computer animation depicting the sequence of events that led to the explosion and fire.
"Our goal is to help companies understand the hazards associated with the kinds of flammable liquids that were stored and transferred at Barton Solvents,” CSB Board Member William Wark said. “We believe our case study and the safety video will help accomplish that goal and prevent accidents."
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 the facility. 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 danger.
"When transferring liquids, it is standard industry practice to bond and ground storage vessels, tankers, and other equipment to prevent static discharges,” CSB Lead Investigator Randy McClure said. “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 filling the tank likely resulted in the metal float accumulating a static electrical charge. As the float moved, it is believed that a gap 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.
"Several common flammable liquids are particularly susceptible to ignition by static sparks,” Wark said. “Some of these flammable liquids can produce the optimal amount of vapor to fuel an explosion at normal temperatures inside a storage tank."
"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,” he added.
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 and grounding.
"The accident at Barton Solvents emphasizes the need for accurate and detailed MSDSs," Wark said. "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 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 to take additional safety measures, such as:
- 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 practices.
Cement Plant Sued for Hexavalent Chromium Exposure
California Attorney General Edmund G. Brown Jr. and District Attorney Rod Pacheco sued TXI International, a Riverside cement plant, for exposing people to the potent carcinogen hexavalent chromium without providing warnings to the community as required by law.
“Dust, which contained elevated levels of cancer-causing hexavalent chromium, escaped into the air in violation of state law,” Brown said. “California is suing the company to get them to stop their practices, which cause chromium exposure.”
In late 2007, the South Coast Air Quality Management District discovered that ambient quantities of hexavalent chromium, a potent carcinogen, were up to 50 times the level that would trigger a mandatory public warning under Proposition 65, the state’s Safe Drinking Water and Toxic Enforcement Act. Investigators traced the source of the chromium to dust piles on a four-acre plot at a cement factory operated by TXI International.
Since 2006, the company knew that there were four acres of uncovered and unwetted dust piles that contained chromium at a cement plant it operated. The company knew that fugitive emissions from the dust piles were spreading into the surrounding areas, including the nearby Fleetwood Motor Homes facility, where the emissions caused exposure to hexavalent chromium to persons living, working, or otherwise present in the area.
Proposition 65 was enacted to protect California citizens from chemicals known to cause cancer, birth defects, or other reproductive harm, and to inform citizens about exposures to such chemicals. Businesses that expose people to those chemicals must give clear and reasonable warning to the people being exposed. The law requires a warning for chromium if exposure would create a 1 in 100,000 risk of contracting cancer. The Air Quality Management District estimated the chromium levels near the cement plant were up to 50 times that amount.
In the lawsuit, Brown asserts that the exposures occurred because defendants allowed uncovered piles of dust to remain on a property owned by the cement manufacturer. The company’s deliberate and intentional acts have resulted in the hexavalent chromium emissions getting into the air where it has been inhaled by people near the area.
The piles of chromium-containing dust are a by-product of grinding and heating raw materials, such as limestone, clay, and silica, in a kiln during preparation to create concrete. After heating these materials, the resulting pebble-like particles, called clinker, are stored for long periods before other materials are added to create the final cement product. Investigators found that the company maintained approximately 80 tons of unwetted dust on four acres at a cement plant.
When wind or atmospheric conditions raise dust from the piles into the surrounding air, this results in emissions of the material contained in the dust. These emissions are called “fugitive emissions.” Defendants have known since at least 2006 that the dust at the cement plant contained hexavalent chromium.
Brown and Pacheco filed the lawsuit in Riverside County Superior Court in Riverside for violations of the state’s Safe Drinking Water and Toxic Enforcement Act. Under the act, also known as Proposition 65, businesses must provide a clear and reasonable warning before exposing individuals to dangerous chemicals. Brown is also suing the company for violating the state’s unfair competition laws, a statue which allows up to $2,500 per violation. The state is seeking an undisclosed amount of penalties and restitution.
Hexavalent chromium is a known carcinogen that was identified as a chemical known to the state to cause cancer on February 27, 1987.
Recently, the company agreed to pay the local air district $600,000 in penalties and spend $400,000 toward site improvements as part of an agreement to reduce the amount of toxic cement dust escaping from a factory north of Riverside. That settlement requires the company to eliminate outdoor storage of unprocessed cement, which was found to be a source of dust carrying hexavalent chromium into neighborhoods near the plant in the Rubidoux area.
Defendant TXI Riverside, Inc. is a Delaware Corporation that operates a cement plant at 1500 Rubidoux Blvd. in the City of Riverside.
New DOT Rule Makes Cheating on Drug Testing Harder
U.S. Secretary of Transportation Mary E. Peters announced a new rule that will make it more difficult for transportation workers to cheat on their required drug tests. The new rule will require drug-testing labs to analyze every test for tampering.
“We want to make sure there are no doubts about the ability of anyone working in transportation (to) do their job as safely as possible,” Peters said. “There is no margin for error when it comes to the safety of the traveling public.”
The Secretary said the new rule would cover the nation’s approximately 12.1 million transportation employers, safety-sensitive transportation employees, collectors, labs, and medical review officers. Under the terms of the rule, labs would no longer have the option of testing urine samples for signs of cheating, but instead would be required to test every specimen for possible adulterants and urine substitutes.
For example, observation procedures will include checking employees for items designed specifically to cheat the test. The rule also requires collectors to observe all tests for transportation workers who return to their jobs after a previous test failure. Secretary Peters added that the Department would treat any invalid test results as the same as a refusal to be tested by any employee who admits to tampering with or adulterating their test.
The U.S. Department of Transportation regulates drug and alcohol testing of safety-sensitive transportation employees in the aviation, motor carrier, railroad, transit, pipeline, and maritime industries. DOT publishes rules on who must conduct drug and alcohol tests, when to conduct those tests, and what procedures to use when testing.
The Drug and Alcohol Testing Final Rule was published June 25, 2008, in the Federal Register. The effective date of the Final Rule is August 25, 2008.
OSHA Cites Konie Cups International for Ignoring Fire Department Warning
OSHA is proposing $64,250 in penalties following an inspection of Konie Cups International's Medley, Fla., manufacturing plant, which revealed 12 alleged safety violations.
OSHA is proposing one willful violation with a $49,000 penalty. Despite an earlier warning given to the company by local fire officials, OSHA discovered during its inspection that an exit door was locked and the key was not easily accessible to all employees in case of an emergency. OSHA defines a willful violation as one committed with plain indifference to or intentional disregard for employee safety and health.
The company is receiving seven serious safety violations with penalties totaling $12,750. Employee safety was at risk because liquid propane tanks were stored near an exit route and too many tanks of the explosive gas were stored inside the building. Other problems included electrical hazards, slip and fall hazards, lack of eye protection, lack of a hearing conservation program, exposing employees to amputation hazards, and lack of an established lockout/tagout program to prevent machines' unintended startup.
OSHA also has cited Konie Cups International for four other-than-serious violations with proposed penalties of $2,500.
"If a fire occurred in this plant, employees could die because this employer chose to ignore basic safety precautions," said Darlene Fossum, OSHA's area director in Fort Lauderdale.
OSHA Fines KMA Manufacturing $119,400 After Fatal Accident
OSHA has cited KMA Manufacturing LLC for numerous alleged safety and health violations following a fatal industrial accident in December 2007.
OSHA initiated its investigation of the Beaver County facility, which employs 49 people, on Dec. 27, 2007, in response to an accident where a six-ton piece of stainless steel became dislodged from a crane and fell onto an employee. The investigation resulted in 42 serious violations and four repeat violations.
The serious violations include the company's failure to ensure that a swivel hook, which was used on an overhead crane to lift annealing furnace covers, was equipped with a safety latch. Employees were observed operating overhead cranes without proper training. KMA Manufacturing failed to ensure that overhead cranes were not used to lift materials beyond their rated load capacity. The company also failed to conduct a personal protection equipment workplace assessment. A serious citation is issued when death or serious physical harm is likely to result from a hazard about which the employer knew or should have known.
The repeat violations include failure to provide machine guarding and required training in hazardous energy sources. OSHA issues repeat citations when an employer previously has been cited for similar hazards and those citations have become final.
"Without the proper safety precautions, KMA Manufacturing continues to put its employees at great risk for potential injuries or death,” said Robert Szymanski, director of OSHA's Pittsburgh Area Office. "Employers have a responsibility to provide a safe and healthy work environment.”
OSHA is proposing $119,400 in fines for the combined violations.