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Potential Flammability Hazard Associated with Bulk Transportation of
Oilfield Exploration and Production (E&P) Waste Liquids
Safety and Health Information Bulletin
On January 13, 2003, a vapor cloud ignited, leading to a fire at an oilfield waste disposal facility (hereafter, disposal facility) near Rosharon, Texas, south of Houston. The fire occurred as two vacuum trucks were off-loading liquid wastes from oil and gas production wells.
The trucks arrived at the disposal facility within a few minutes of each other and were parked approximately 16 feet apart. The two drivers got out of their trucks, left the engines running, and told the disposal facility employees that the trucks were to be drained and rinsed out. Both drivers then went to the drivers’ shed to complete paperwork and to wait for the washout to be completed. (1)
The fire was caused by the ignition of hydrocarbon vapor released during the off-loading of basic sediment and water (BS&W) from the two vacuum trucks into an open area collection pit. BS&W is an oil/gas exploration and production (E&P) waste liquid. The BS&W was contaminated with highly flammable condensate. During the off-loading, vapor off-gassed from the BS&W and was drawn into the air intakes of the vacuum trucks’ running diesel engines. As a result, the engines began to race and backfire. The flammable vapor cloud ignited. (1)
The post-incident investigation documented five possible vapor cloud ignition sources – the vacuum trucks’ diesel engines, vacuum truck electrical systems, static electricity discharge from the off-loading liquid, (although equipped with a grounding cable, the trucks were not grounded during the off-loading), personnel smoking, and facility electrical wiring. The investigation determined that the diesel truck engines were most likely the ignition source based on physical evidence and the supporting eyewitness testimony. (1)
Two disposal facility employees and one tank driver, employed by the transport company, were killed in the fire. Three other disposal facility employees and one truck driver suffered severe burns. The fire destroyed the two 50-barrel vacuum trucks (each tank truck = 2,100 gallon capacity) owned by the transport company and heavily damaged waste liquid off-loading equipment and structures at the facility (See Figure 1). (1)
Figure 1. Layout of Open Area, Gravity Feed, Disposal Pad, with Vacuum Trucks
Positioned as on January 13, 2003, When the Fire and Deflagration Occurred. (1)
Purpose of SHIB
The purpose of this Safety and Health Information Bulletin is to alert other facilities in the oil and gas industry about:
Because of the deaths and injuries caused by this incident, OSHA and the U.S. Chemical Safety and Hazard Investigation Board (CSB) conducted investigations. CSB’s investigation sought to determine the root and contributing causes, and to issue recommendations to interested parties in an effort to prevent similar occurrences. (1)
In its investigation report, the CSB pointed out that "the oil and gas industry disposes of many thousands of barrels of E&P waste liquids annually, including potentially flammable BS&W." (1) "E&P wastes can have flammability characteristics that meet the definition of a flammable liquid in both OSHA and DOT regulations, thus posing a significant physical hazard to personnel." (1) The CSB found inconsistency within the oil and gas industry in managing the potential flammability hazard of BS&W. In some cases, the flammability hazard is not identified or recognized, and work practices are inadequate for safe handling of the potentially flammable liquid.
The CSB investigation revealed the following root causes of this incident:
Contributing causes of the incident reported by the CSB are summarized below:
Based on the listed root causes of this incident, the following aspects of the incident and their associated OSHA standards are identified below.
Hazard Determination and MSDSs
Vacuum truck owners must ensure that vacuum truck operators are trained and qualified for their work assignment. The following Standards address the issues necessary to provide appropriate training.
Hazard Materials Awareness
Vacuum truck owners must ensure that vacuum truck operators are aware of the physical and chemical characteristics of flammable, combustible, toxic and corrosive materials. Trace amounts of flammable and combustible liquids and gases, hydrogen sulfide gas, acids, caustics, spent acids, sour water and other liquids, materials and gases present in the petroleum industry may cause serious injury, illness or death if not properly handled. (2)
MSDSs need to provide correct information on hazardous materials in tanks or vessels, but occasionally, for various reasons, they do not accurately reflect the hazards associated with comingled and waste products, tank bottoms, contaminated catalysts, spent acids or other materials that are being transferred. (2) Therefore, employers should be aware that in these cases a flammable or toxic hazard could exist even though its MSDS does not identify this hazard.
CSB found that the majority of those industry personnel questioned during the investigation did not believe that BS&W poses a flammability hazard, even though it can contain highly flammable condensate. "CSB analysis of nine tank BS&W samples from six production wells, including one of the wells involved in the BLSR incident, indicated flashpoints below 30ºF in eight of the samples. For comparison, the flashpoint of condensate is about -36ºF, and the flashpoint of gasoline is about -45ºF. OSHA classifies any liquid with a flashpoint below 100ºF as a flammable liquid." (1)
"Care must be taken to ensure that the materials being loaded into the cargo tank are compatible with materials previously loaded and that the mixing of these materials will not create hazards such as fire, explosion, heat, toxic gases or vapors. Unless the vacuum truck has been thoroughly cleaned and inspected, it should not be used to load materials which are not compatible with those previously handled." (2) The same principles apply when the cargo tank contents are off-loaded – the contents must be compatible with the materials presently or previously contained in the receiving container. (2)
Safe Vacuum Truck Operations
Vacuum truck owners and operators, as well as facility personnel, should be aware of numerous potential hazards associated with operating vacuum trucks in petroleum facilities, including, but not limited to the following:
"The areas where vacuum trucks operate must be free of hydrocarbon vapor concentrations in the flammable range." (2) "If there is any question of whether the area is free of flammable vapor or toxic gas, atmospheric testing must be performed by a qualified person using properly calibrated and adjusted combustible gas indicators, appropriate toxic gas testers, or hydrocarbon analyzers. Testing should be conducted anytime there is uncertainty about the safety of the surrounding atmosphere, including prior to starting any operation, and during operations." (2)
Bonding and Grounding
"The complete vacuum transfer system should be bonded to ensure a continuous conductive path from the vacuum truck through the hose and nozzle to the tank or source container." (2) Bonding ensures that there is no difference in electrostatic potential between vacuum trucks and pumps and the source or receiving tank, container or vessel. (2) "This reduces the likelihood of a spark being created in the vicinity of flammable vapors when the suction nozzle or discharge hose is removed from the source or discharge container and/or is disconnected from the vacuum trucks, or when any conductive connectors are disconnected." (2)
Grounding is also a must. Prior to starting transfer operations, vacuum trucks need to be grounded directly to the earth or bonded to another object that is inherently grounded (due to proper contact with the earth), such as a properly grounded large storage tank or underground piping. Grounding ensures that any electrostatic charges that might be generated can be "bled off" to the earth, bringing all parts of the system to zero electrical potential. (2)
As stated earlier, vacuum truck personnel working in petroleum facilities must be trained in the safe operation of the vacuum equipment; be familiar with the hazards of the petroleum products, byproducts, wastes, materials being transferred, as well as any comingled wastes; and be aware of relevant government and facility safety procedures and emergency response requirements. (2)
MSDSs for the products being transferred must be available to vacuum truck operators, and a qualified person must be able to assess the potential exposure to unsafe air contaminant levels as well as any potential or existing flammable atmospheres. (2)
When loading and off-loading, all personnel must leave the truck cab and shut off the engine if flammable vapors are generated at or above 25% of the Lower Explosive Limit (LEL). However, when transferring flammable liquids or hazardous materials, vacuum truck operators should stay within 25 feet of the vacuum truck (between the truck and the source or receiving tank, vessel, or container) throughout the operation. (2) In practice, the vacuum truck operators will be positioned upwind and to one side of the truck within the line of sight of the operation.
Vacuum truck operators must monitor the transfer operation and be ready to quickly close the product valve and stop the pump in the event of a blocked line or release of material through a broken hose or connection. (2) Vacuum truck owners must develop emergency procedures that conform with OSHA requirements found in 29 CFR 1910.120(q) and 29 CFR 1910.38(a), and must train all vacuum truck operators in the use of those procedures. In the event of a fire, spill, release, or other emergency, operators must be knowledgeable about emergency reporting and appropriate emergency response actions.
During loading and off-loading, position the vacuum truck on level ground, at least 25 feet away from (50 feet if in a diked area) and preferably upwind or crosswind of the source or receiving tank, vessel, or container. (2) Smoking must not be permitted within at least 100 feet (depending on local procedures and atmospheric conditions) of the truck, the discharge of the vacuum pump, or any other vapor source. (2)
To prevent future accidents like this, the hazard of exploration and production (E&P) waste liquids must be recognized, communicated, and controlled by employers in the oil and gas production industry. Oil and gas waste liquids can be highly flammable and need to be handled appropriately.
OSHA recommends that employers engaged in the production, transport, and disposal of waste liquids take the following action:
Edwin G. Foulke, Jr.
Occupational Safety and Health Administration
*OSHA requires written emergency procedures [1910.120(q) or 1910.38(a)] except in the case where employers have ten or fewer employees and chose to comply with the emergency action plan requirements of 1910.38.
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