Sound Strategy and Tactics Avert Potential Hazardous Material Disaster
HAZARDOUS MATERIALS
FEATURES
Having the highest burning velocity of any gas, possessing a flammability range of 4.1% to 74.8%, and burning with a nonluminous flame that is often invisible in daylight, hydrogen has the potential to create a severe combustion explosion and related hazard when large volumes are released from containment at high pressures.
The Danbury, CT, Fire Department was faced with just such a situation last year when a tube trailer containing 100,000 cubic feet of compressed hydrogen gas leaked at the Cryo-Dyne Corporation.
A call was received at the fire department communications center at 7:24 P.M. on August 31, 1984, reporting “a loud hissing noise in the area of Payne Road.” Two engines were dispatched to investigate.
While the units were en route to the scene, a second call was received stating that a sound like “the roar of a jet engine” was coming from the Cryo-Dyne Corporation on Payne Road. The Cryo-Dyne Corporation is a distributor of bottled and bulk gases, both compressed gas and cryogenic liquids. The dispatcher notified the responding companies that they could possibly be facing a hazardous material situation. He also dispatched two additional engine companies and Shift Commander Joseph Gowel.
Area layout/exposures
The Cryo-Dyne facility is enclosed on three sides by a chain-link fence. The plant itself houses a large storage area of compressed gases, many of which are flammable. On the south side of the plant are three 3,000-gallon vertical tanks containing liquid hydrogen, liquid nitrogen, and liquid oxygen, all stored cryogenically. There were also tanks of carbon dioxide and argon, the latter being empty.
Immediately east and south of the facility are residential buildings; industrial/commercial structures are to the north and west.
Strategy and tactics
The first-arriving units stopped 700 feet north of the plant and surveyed the area with field glasses before moving in. The Danbury Fire Department is in the process of organizing a hazardous material response team, and the procedure of observing a potential hazardous material emergency scene is being instituted throughout the department. Field glasses are carried on all the pumpers.
Although firefighters noted hydrogen placards on the two trailers parked among the chemical tanks and an audible roar coming from the south side of the facility, there was no visual indication of anything wrong.
Two firefighters in full protective gear and wearing self-contained breathing apparatus (SCBA) entered the chemical facility for a closer investigation. Keeping a 75-foot distance from the tanks, they determined that the noise was coming from one of the two compressed gas hydrogen trailers adjacent to the liquid hydrogen storage tank.
A call was placed to the CryoDyne Corporation, who said that the noise was a normal pressure venting procedure that lasts about 10 minutes. Checking with the neighboring residents, firefighters were told that this was not normal and that the sound had been going on for close to 30 minutes. The potential for a problem was further amplified by the fact that all the gas tanks were within 50 feet of the venting trailer.
The incident commander decided that this situation was to be treated as a hazardous material incident and set up a staging area about a half mile north of the chemical facility. A hot zone was defined whose perimeter was a 1,000-foot radius from the plant center.
A command post was established right outside the hot zone. The close proximity of the command post to the incident was due to not having an independent radio channel. Communications were a problem because of excessive radio traffic during the incident.
Apparatus was used to block traffic and secure the perimeter of the emergency scene. This positioning also kept the trucks away from the immediate emergency area and removed the possibility of their presenting an ignition hazard. Extreme caution must be taken whenever fireground operations involve venting hydrogen gas. Any equipment used on or near leaking hydrogen containers must be of the non-sparking, explosionproof type, as hydrogen can react violently when exposed to heat, flame, or oxidizers. Anything that could cause a spark, such as a turnout coat buckle or an SCBA regulator was taped over to prevent them from contacting the trailer and creating a spark.
The first order of priority was to evacuate all civilians within 1,000 feet of the plant, and to minimize the number of emergency personnel inside the hot zone. Although not a heavily populated area, zoning allows for residential, commercial, and industrial occupancies to be adjacent to one another. Crowd control problems stemmed from curious onlookers, the media, and people trying to return to the restricted area. Civilians were evacuated through the joint efforts of the Danbury Fire Department, the Danbury Police Department, and the Bethel Police Department.
A Level 3 situation was declared, bringing in mutual aid and resources from outside agencies, such as the city health department, industry, the Environmental Protection Agency, etc. The power company was summoned to shut off all power to the plant, and Cryo-Dyne was apprised of the status of the situation. The corporation dispatched two employees to the scene within 45 minutes. Also arriving at the command post was Chief of Department Charles Monzillo.
Photos by Randall Morits
After a discussion with plant personnel, it was decided that two firefighters and one Cryo-Dyne employee in full protective gear and SCBA would attempt to stop the leak. A back-up team was also in place.
Because of hydrogen’s nonluminous flame and its low levels of thermal radiation, the three-man team approached the trailer with rags tied to the end of pike poles to prevent them from walking into the invisible flame.
Each of the trailer’s storage tubes has its own vertical relief valve pipe, and there is a frangible disk at both ends of each tube, designed to relieve pressure at 3,600 psi. This type of trailer has a second relief valve system involving a springactuated device operating at 2,450 psi.
To stop the leak, it was necessary to reach the hydrogen trailer’s valving, a cascade-type arrangement, enclosed in a metal cabinet at the rear of the trailer.
The first team moved in. However, it turned out that the employee did not know how to shut off the trailer’s valves and the team had to withdraw. A plant engineer arrived who, fortunately, knew how to close the valves. He entered the hot zone with the firefighters. This team successfully stopped the leak and the incident was declared under control.
Upon examining the trailer after the leak was mitigated, it was discovered that a bursting disk designed to fail at 3,600 psi was defective and failed at normal operating pressure. It was also learned that all the valving was left in the open position, causing not only the tube with the defective bursting disk to leak, but the entire contents of all the tubes.
Shortly after this incident, Cryo-Dyne instituted a policy requiring all parked hydrogen trailers to have their valving in the closed position.
Critique
Several significant lessons were learned from this incident, not the least of which is the importance of a thorough education and proper training procedures in handling hazardous materials. Responders must be sufficiently prepared and equipped to identify and mitigate a hazardous material situation. Identification of the chemical was a problem for the first-due engine because of hydrogen’s unusual characteristics.
Although the incident was brought under control rather smoothly, inspections and preplanning of target hazards would have aided in a more rapid identification and determination of the immediate and potential hazards and the tactics necessary to secure the situation. Also, a familiarity with truck piping, valves, and assemblies within the district would be of value.
It’s also important to have an expert at a hazardous material incident, someone who is familiar with the layout of the area and who knows how to operate any necessary equipment.
Good communications are of prime importance in any hazardous material situation. It would have been extremely helpful to have direct phone communications with the department dispatch center, who were in direct contact with a corporation engineer. In this way, information would not have had to been relayed through the radio network to the command post. Information was often difficult to understand with the excessive fireground radio traffic.
