BY JEFF CHANDLER AND RICHARD SCALORA
Shortly after 11 a.m., ON February 7, 2010, an explosion occurred at the Kleen Energy Systems power plant in Middletown, Connecticut, during testing of gas lines. The plant was under construction and near completion.
The Middletown South Fire District command staff, Connecticut Task Force 1 urban search and rescue team (CT-TF1), and detectives from the Department of Public Safety Office of the Connecticut State Fire Marshal (CT FMO) requested the Connecticut Department of Environmental Protection (CT DEP) Emergency Response Unit (ERU) to assist with metering for confined-space entries and to determine whether the explosion caused collateral damage to other hazardous materials containers present on the site (photo 1).
|(1-2) Photos by Richard Scalora, ERU.|
The ERU is staffed with 13 emergency responders and responds statewide to approximately 1,600 hazardous materials emergencies involving oil, chemical, and weapons of mass destruction annually.
Beginning on the day of the incident, the initial focus of the ERU was to assist with confined space atmospheric monitoring. When operating on a site that has been devastated by seismic activity or an explosive blast, you must determine the likely atmospheric contaminants that may be present.
Generally, a four-gas meter will be sufficient in clearing an atmosphere, but you must determine whether chemicals are present that the standard confined-space entry four-gas sensor suite [lower explosive level (LEL), oxygen, hydrogen sulfide (H2S), and carbon monoxide (CO)] may not detect. Remember, on a 1:1 direct-read basis, your four-gas meter detects only the gases to which it is calibrated. In a postblast event, oxygen may have been consumed and high levels of CO may be present in void spaces.
In an industrial setting that is still under construction, it is likely that the force of the explosion may have compromised cylinders present that contain heavier- and lighter-than-air gases. These may be flammable, toxic, oxidizing, or asphyxiant gases. Since all but 13 gases are heavier than air, you must always monitor the atmosphere in situations where you must descend into a belowgrade confined space. However, don’t neglect appropriate monitoring in horizontal or elevated entries into void spaces such as lean-to collapses, which may trap those lighter-than-air gases. Lighter-than-air gases such as methane, acetylene, ammonia, nitrogen, and CO can be expected in industrial postfire and postblast events at construction sites.
Additionally, when oxygen (gaseous or cryogenic) is present on site, ensure that oxygen levels remain at a normal level (20.9 percent), since a leaking cylinder may increase the concentration to levels above the maximum safe limit of 23.5 percent, which may increase combustion rates to an explosive level. To ensure the safety of responders, maintain proper ventilation throughout the entry.
ASSESSMENT AND DOCUMENTATION
On Day 2 of the incident, the initial collateral damage assessment of the site revealed hundreds of acetylene, propane, argon, and oxygen cylinders as well as cryogenic nitrogen and argon containers. Many of these cylinders had been directly exposed to fire, were displaced by the blast and struck stationary objects, or were struck by substantial objects that the blast had moved.
Containers that are leaking, have been exposed to fire, or are dented cannot be shipped over the road in these conditions (photo 2). They must either be dealt with on-site or placed in a cylinder overpack. Because of the large number of cylinders that required on-site handling, the CT DEP required the responsible party to hire an environmental emergency response contractor capable of handling compressed gas cylinders. Clean Harbors, a firm that provides hazmat mitigation and disposal services, was hired and dispatched a high-hazard team from Texas to assist in processing the cylinders.
During the initial site survey, a 10,000-gallon anhydrous ammonia storage tank was observed on a site’s blueprint. The general contractor in charge of construction stated this tank was empty, which entry personnel confirmed. This was quite fortunate, since the blast had damaged the tank’s ancillary piping, and a release of this volume of anhydrous ammonia would have dramatically increased the number of victims because of its toxicity. Also, if such a release had ignited, it would have created a secondary fire hazard, which would have cut off escape routes.
The weather forecast called for a substantial snowfall, which would hamper assessment and mitigation efforts if the cylinders were hidden by a blanket of snow. The CT DEP requested that CT-TF1 document the global positioning system (GPS) coordinates of each cylinder after assessment. This later proved invaluable in locating the cylinders in the following two weeks.
South Fire District Chief Edward Badamo, the incident commander (IC), used an incident management team to track resources and document the incident as it unfolded. At the beginning of each work period, each stakeholder in the event detailed its specific tactical priorities, which were then prioritized so that hazmat activities requiring a greater isolation did not interfere with other law enforcement investigative activities.
Additionally, a fire department safety officer and a law enforcement liaison were assigned to each team operating on the site. The safety officer was responsible for clearing the work areas of overhead hazards such as failed structural components resulting from the blast. The law enforcement liaison maintained contact with the investigative/enforcement branch to ensure site integrity.
As cylinders were discovered, they were assessed for damage and risk. Undamaged cylinders were photographed and their GPS coordinates recorded and conveyed to the CT FMO. These cylinders were then relocated to a lay-down area for temporary storage and were subsequently returned to their owners. When considering a space for a lay-down area for cylinder staging, ensure the area is large enough to comply with the regulations for safe distances between oxygen and acetylene cylinders, and ensure that the cylinders are appropriately secured from falling or vehicular traffic.
Also, when working at an emergency involving cylinders at an active construction site, it is likely that the regulators will still be attached. It is recommended that you remove the regulators before moving the cylinders and install a protective cap to protect the cylinder valve. This adds an additional safety margin if a cylinder is accidentally dropped.
PROCESSING DAMAGED CONTAINERS
If a container was found to be damaged, ERU personnel identified the container type, performed a risk assessment, and relocated the cylinder to a remote area for processing. These data were recorded and conveyed to the CT FMO.
Clean Harbors was equipped to handle the voiding of the cylinders. With cylinders containing flammable gases, the contents was burned off or flared to safely control the gases. With cylinders containing nontoxic, nonflammable gases, the contents were discharged to the atmosphere. When depressurizing cylinders of oxygen-displacing gases, ensure you do not impact belowgrade spaces. Fortunately, the site had a remote area that was free of belowgrade areas. All but one of the cylinders had operable service valves. In the case of a 20-pound propane cylinder with a damaged valve, technicians hot-tapped the sidewall, installed an offloading valve, and subsequently flared the cylinder (photos 3, 4). In a hot-tap, a valve assembly is clamped to the sidewall of the cylinder and purged with nitrogen. The sidewall is drilled to allow the cylinder’s contents to enter the valve assembly, which is then connected to a flare torch and subsequently burned.
|(3-4) Photos by Brian Emanuelson, ERU.|
Numerous cylinders were located in elevated areas at the site, such as catwalks and scaffolding platforms, and were accessed using a tower ladder or cranes (photo 5). The Middletown (CT) Fire Department used high-angle rope systems to lower the cylinders.
|(5) Photo by Brian Emanuelson, ERU.|
In the end, the CT DEP hazmat response unit assessed 489 cylinders, of which 429 were deemed shippable and staged in the lay-down area. Clean Harbors’ high-hazard team processed 60, flaring 11 acetylene and 23 propane cylinders and depressurizing 16 argon and 10 oxygen cylinders. All cylinders were devalved after they were flared or depressurized. It took 10 days to assess and process the cylinders. The work essentially was done in 12-hour work periods with downtime for the crews overnight.
SPECIFIC SITE HAZARDS
The following is a brief synopsis of the risk assessment points for each of the hazards found at the site.
Acetylene.The acetylene cylinders presented the biggest safety concern. Acetylene is an alkyne hydrocarbon, which is a triple-bonded molecule also known as ethyne, C2H2. This triple bond characteristically creates the main hazards of acetylene, which are a wide flammable range (between 2.5 and 100 percent) coupled with its tendency to decompose if not handled appropriately. With the wide flammable range, this material is easily ignited and may be ignited even by a minor static discharge. Use the four-gas meter to assess your entry since acetylene may ignite explosively; evacuate if the meter alarms at 10 percent of the LEL. Know the correction factor for your particular meter.
Present-day cylinders have a silica lime filler to which some manufacturers add asbestos, charcoal, and other materials to provide a lightweight filler with a higher porosity. The filler materials must be correctly proportioned to provide a homogenous mass so as to completely fill the shell within the maximum clearances specified by the U.S. Department of Transportation to resist cracking of the filler during rough handling of the cylinder and to obtain the best acetylene charging and discharging capabilities. Additionally, acetone is introduced to the cylinder; it fills the porous filler, which will dissolve the acetylene to allow for safe storage.1
If a dent in the cylinder’s wall causes a void space in the porous filler, the acetylene can decompose at normal cylinder pressure (250 psi). This decomposition will occur in a cylinder that is void of oxygen, since its upper flammable range is 100 percent, and will likely result in a violent rupture of the cylinder. This hazard also prohibits the use of cylinder overpacks for acetylene. If the acetylene cylinder starts to leak into an overpack, which inherently has no porous filler, the resulting overpressure will decompose the acetylene violently.
An acetylene cylinder is equipped with fusible plugs; smaller cylinders are equipped with a valve with fusible metal. Do not plug a release resulting from a fusible plug failure, since this may create a void space that will be at cylinder pressure, which will cause decomposition. If you find a cylinder that has been exposed to fire and its fusible plug is intact, do not move the cylinder until it has reached ambient temperature. The acetylene may be decomposing internally, and the cylinder is still subject to violent failure.
When setting up flaring systems, use only steel or wrought-iron piping. Acetylene may react with copper piping and fittings and create acetylide, which can be explosive. Operating pressures of greater than 15 psi will decompose acetylene, so it is imperative that the regulator be set appropriately.
Propane. Propane is a flammable liquefied petroleum gas. It is liquefied by pressure; it returns to liquid phase at –44°F. The internal pressure of a cylinder at 70°F is approximately 110 psi.2 Use caution when dealing with a cylinder that has a rapid release from the gaseous phase of the system, since the liquid may go into autorefrigeration, which may give you the false impression that the cylinder has released its contents.
In cylinders that are sized by weight (in pounds) rather than volume (in gallons), there is no liquid withdrawal fitting when the cylinder is in its normal upright position. To expedite offloading, the cylinders can be inverted to place the valve in the liquid phase. Use caution when performing this maneuver, since you must use a regulator listed for both liquid and vapor.
Cryogenics. Cryogenics are extremely cold liquids (below −130°F at one atmosphere pressure) that can freeze human tissue. Additionally, they have extremely high expansion ratios; one cubic foot of liquid nitrogen produces 696 cubic feet of gas. Use the four-gas meter to ensure adequate oxygen levels, since nitrogen will displace oxygen.
These containers are essentially a container within a container with an insulating material in the interstitial space. The container is protected from overpressurization with a self-closing pressure relief valve set at 220, 230, or 350 psi, depending on the container’s specifications.
Additionally, a burst disc protects the inner container. These gases are processed in a heat exchanger rather than pressurized to change to a liquid phase. Unlike pressurized compressed gases, the liquid/gas does not reach homeostasis when contained within a cylinder. Rather, cryogenics continue to boil and produce vapor. This vapor produces pressure within a closed system, so pressure relief valves will operate regularly to vent this building pressure. Never attempt to plug or contain a venting pressure relief valve on a cryogenic system; the resulting pressure will cause the container to fail violently.
Use caution when approaching cryogenic containers that may be damaged. Use a four-gas meter while closely monitoring the sensor that is appropriate for the specific hazard present (increased oxygen for liquid oxygen, LEL for methane, decreased oxygen for nitrogen and argon). Look for signs that the container is leaking, such as frost buildup at areas that are dented or damaged (photo 6, arrow).
(6) Photo by Richard Scalora, ERU.
If a container must be emptied, ensure that all components used to accomplish this are listed for use with cryogenics, and control the rate of vapor discharge, since the extremely cold conditions may cause a system failure. Also, if a container cannot be moved from its location without first emptying it, direct the depressurization to a well-ventilated area.
Ensure that there are no valves in sequence without a pressure relief valve between them. If liquid is trapped between two valves with no relief valve, the system could rupture violently. When approaching a cryogenic container that may be physically damaged, listen for the sound of escaping gas and look for visible frost on the container’s walls. When approaching a container that is not in its normal upright position, use caution since the pressure relief valve may be in the liquid phase. If this is the case, when it opens to relieve the building pressure, it will release liquid, which can cause severe harm to responders.3
Gaseous oxygen. The main hazard of gaseous oxygen is that it is an oxidizer. Although this material will not burn, it will greatly increase combustion, even to explosive levels. Use great care when approaching a leaking cylinder while continuously monitoring oxygen levels. If the meter goes into alarm (23.5 percent), immediately leave the area and begin ventilation to bring the levels down to a normal ambient range.
1. Air Products and Chemicals, Inc., Safetygram-13, “Acetylene,” Pub. No. 310-721, 1994. www.airproducts.com.
2. Alternative Fuels Technologies, Inc., “What is LPG?” http://www.propanecarbs.com/propane.html.
3. Air Products and Chemicals, Inc., Safetygram-27, “Cryogenic Liquid Containers,” Pub. No. 320-9504, 2000. www.airproducts.com.
JEFF CHANDLER is the Eastern Region’s supervising emergency response coordinator for the Connecticut Department of Environmental Protection’s Hazardous Materials Emergency Response Unit, which is responsible for hazmat investigation, mitigation, and remediation. He has 17 years of experience as a hazmat technician, including work as an environmental contractor. A 25-year veteran of the fire service, he has served as a volunteer assistant chief and a career captain. Chandler is a volunteer firefighter with the Mystic (CT) Hook and Ladder Company and a part-time career firefighter with the Preston (CT) Department of Fire and Emergency Services.
RICHARD SCALORA is an emergency response coordinator II for the Connecticut Department of Environmental Protection Hazardous Materials Emergency Response Unit, responsible for hazmat investigation, mitigation, and remediation. He has 17 years of experience as a hazmat technician, including work as an environmental contractor. A 23-year veteran of the fire service, he is a lieutenant with the Berlin (CT) Fire Department, where he previously served as assistant chief.
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