Testing the Draft ASTM Skimmer Test Protocol at Ohmsett
Testing the Draft ASTM Skimmer Test
Protocol at Ohmsett
Over the past two years engineers at Ohmsett, The National
Oil Spill Response Test Facility, have been working with the American
Society for Testing and Materials (ASTM) F20 Committee on Hazardous
Substances and Oil Spill Response to draft a test standard to more
accurately determine skimmer nameplate capacity.
It is recognized that the current method is arbitrary and seldom
reflects the actual performance of a skimmer, as a system, to collect
oil. As a result, the U.S. Coast Guard derates nameplate capacity
by as much as 80% in estimating the Effective Daily Recovery Capacity
(EDRC).
“The goal of this standard is to develop a test that would
establish a realistic nameplate capacity,” said Ohmsett Senior
Test Engineer Dave DeVitis. “The test should be simple, inexpensive,
and yield reproducible data that can be used to compare skimmer
performance.”
During July and August 2007, researchers from SL Ross Environmental
Research, Ltd. were at Ohmsett to assist in testing the draft standard.
"The main objective in testing the protocol was to resolve
issues relating to the slick thickness for a valid test," said
Steve Potter of SL Ross and head of the ASTM committee. "We
were also looking at measurement methods, and the minimum tank area
required for the test."
During the tests, three generic skimmers types - disk, drum and
weir - were used to measure the oil recovery rates under simulated
conditions. The researchers focused on the testing methods, rather
than the results of the individual skimmers.
|
The skimmers were tested in an 8 ft. x 8 ft. x 2.5 ft. (1000 gallon)
portable open-top tank on the deck of the Ohmsett test basin. Oil
collected by each skimmer was pumped to an overflow tank until steady
state was achieved, then flow was diverted for 1 to 3 minutes, depending
on skimmer recovery rates, to collection tanks located above the
skimmer. Samples of the collected oil were analyzed to determine
water content. These values were used with the collection volumes
and collection times to calculate recovery rates and recovery efficiencies.
One recurring question about the test protocol is how much of
a difference is there between testing in all oil and testing in
an oil layer over water. Tests were conducted with the test tank
filled with oil only, as well as various thicknesses of oil on top
of a water layer. When testing with the oil water interface, the
water depth was typically 20" and the oil layer varied from
approximately 1" to 6".
Results from these tests were presented to the ASTM F20 Committee
meeting in October 2007 in Tampa, Florida. The draft test protocol
was revised based on the Ohmsett test results and in December 2007
was sent to the ASTM committee for final balloting.
|