Skimmers tested in iceTest tank simulates Arctic broken sea ice conditions for recovering spilled oil
By Alan Bailey Petroleum News
With questions over the practicalities of responding to an oil spill in ice-laden waters at the forefront of a contentious debate over the merits or otherwise of Arctic offshore oil exploration and development, there is a pressing need to test equipment that might be used in the event of an Arctic marine oil spill incident. However, since the deliberate spilling of oil into the ocean for testing purposes is banned in the United States, the only U.S. option for testing spill response equipment is the use of simulated conditions in test tanks.
Between mid-February and mid-March the Bureau of Safety and Environmental Enforcement scheduled an “ice month” in its Ohmsett testing facility in New Jersey, to give the U.S. Navy, the U.S. Coast Guard and spill response organizations an opportunity to test equipment designated for the mechanical removal of oil from Arctic waters. Ohmsett consists essentially of a 600-foot long rectangular tank, holding saltwater and designed for the simulation of oil spills and the testing of spill response techniques. Skimmers According to the most recent Ohmsett newsletter, the organizations participating in the ice-month testing brought seven different types of oil skimmers for evaluation. Oil skimmers use a variety of techniques to gather oil from a surface oil slick, enabling the oil to be pumped into a barge or other oil storage vessel. Participants in the Ohmsett testing anticipate using the test results to improve mechanical response technologies and to initiate the development of standards for oil spill response equipment used in broken ice, the Ohmsett newsletter said.
“The Navy-owned skimmers selected for testing at Ohmsett are currently used in the Alaska response region,” said Stephanie Brown, pollution equipment lifecycle manager for the Navy’s salvage and diving organization, one of the organizations participating in the Ohmsett testing. “Demonstrations of the new Arctic-specific equipment brought in by vendors also proved to be a valuable tool for selection of future capabilities for the U.S. Navy.”
“Over the past two and a half years since the Deepwater Horizon spill response, the Coast Guard has been focusing on evaluating the need for and developing an Arctic oil-spill capability for skimming oil in ice,” said Mike Crickard, logistics management specialist for the U.S. Coast Guard National Strike Force Coordination Center.
Although some types of skimmers have been tested successfully in simulated oil spills in the Norwegian Arctic offshore, where the controlled spilling of oil is allowed for the testing of oil recovery techniques, questions have been raised in the past over the effectiveness of skimmers in broken sea ice, given the potential for the ice to clog the skimming mechanisms. Test procedure To conduct the Ohmsett tests, facility personnel installed a chiller in the Ohmsett tank, to cool the water to 35 F. They then placed eight-inch-thick sheets of sea ice of various sizes into the tank, to simulate sea-ice coverages of 30 percent and 70 percent. Previous tests have found that 30 percent coverage is a threshold above which ice starts to inhibit skimmer performance, while 70 percent coverage represents the maximum coverage in which a skimmer could operate, the Ohmsett newsletter said.
To conduct a test, skimming equipment was placed within a boomed area of the tank that had been pre-loaded with ice and a layer of refined oil. The skimmer was run until one-third of the oil had been removed, with a total of three tests of this type being conducted. The skimmer was then run for an extended period, to determine changes in the skimmer’s performance as the oil slick thinned.
Valuable experience Brown said that the testing had provided the Navy with valuable experience in operating its skimmers in oil and ice, and had provided opportunities for optimizing techniques for the efficient recovery of oil in ice-infested waters.
Crickard said that the U.S. Coast Guard had found from the tests that a particular type of skimmer fitted with a specific brush adapter had proved promising.
“Some additional tests and adjustments to system components will be completed over the next few months in order to harden up the current system design, making it ready to distribute a system to each National Strike Force Strike Team as a ‘ready load’ system for operational deployment,” Crickard said.
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