By Bob Durstenfeld
Texas City lies within the Port of Houston, a 25-mile long complex of shipping docks. The port is ranked first in the United States in foreign waterborne commerce, second in total tonnage, and eighth in the world. The cargo in the shipping channel is primarily petroleum products, steel, and organic chemicals.
The traffic in the channel has grown to about 160 million tons and accidents are frequent. Over the past decades, the channel has been the site of a series of oil spills, explosions, and collisions between tankers, freighters, and barges.
In November 2003, a barge owned by American Corporate Barge Line and leased to Martin Product Sales LLC was carrying 235,000 gallons of sulfuric acid. As the barge was being pulled into a dock at Sterling Chemical in Texas City, it capsized and began leaking.
The Coast Guard and Federal and Texas Environmental Protection Agencies were notified and sprang into action. The agencies began actively monitoring the site, established a safety zone around the leaking ship, and working with the Texas Parks and Wildlife Department, began taking readings of the pH levels around the ship to gauge potential effects on sea life.
As the barge continued to leak, safety crews determined there was an explosion hazard and after review options that included moving the sulfuric acid to another barge and transporting it away in rail cars, decided to pump the sulfuric acid into the water.
During the draining operation, crews that were spraying down the barge to keep it cool heard pinging noises and saw a bulge that had formed in the hull as a result of a hydrogen gas build up. When surrounding water leaked into the barge, it mixed with the acid remaining in the barge and caused a cloud of sulphuric acid steam to form.
The EPA, recognizing that the situation remained hazardous and needing around-theclock monitoring of the site, deployed three wireless AreaRAE gas sensors to provide real time data on the acid cloud. The AreaRAE is manufactured by RAE Systems of Sunnyvale, California and is a one-to-five sensor gas detector equipped with a wireless, radio frequency modem that allows the unit to communicate and transmit data on a realtime basis with a base controller located up to two miles away.
"Wireless monitoring of the acid cloud probably saved air monitoring crews from serious injury," said Scott Harris of the United States Environmental Protection Agency. “As the cloud was moved around by prevailing winds, the AreaRAE monitors continued to send us valuable data about the nature of the cloud until they were finally destroyed by intense exposure to the sulfuric acid.”
Wireless, integrated sensing networks will play an increasing role in keeping people safe, economic assets in production and symbolic targets protected. Powerful handheld sensors and wireless sensing networks are already being deployed at many industrial, public venue and transportation sites, providing a critical safety net. Some monitors are able to detect concentrations of volatile organic compounds (VOC) such as chlorine, phosgene and ammonia in the parts-per-billion range, and in this way are providing an effective early warning system to workers and first responders. Fixed and wireless sensing networks are putting nodes of monitors around fence lines and security checkpoints at sites such as nuclear power plants, offshore oil platforms and at a variety of public venues such as arenas and subways.
Bob Durstenfeld is director of corporate marketing at RAE Systems Inc. He has published numerous articles on port security and wireless gas detection technologies. Durstenfeld received his master's degree in engineering management and master's degree in international marketing from Santa Clara University, Santa Clara, Calif. He holds two Bachelor of Science degrees from U.C.L.A., Los Angeles, Calif., one in engineering and the other in biology. He can be reached by telephone at (408) 585-3534 or by e-mail at [email protected].
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