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Dredging Applications of High Density Polyethylene Pipe Virginia R. Pankow Hydraulics Laboratory U.S. Army Engineer Naterways Experiment Station Introduction Since its development in the early 1950s, high density polyethylene HDPE! pipe has gained wide acceptance as the material of choice in many applications. A combination of physical and chemical properties make HDPE pipe resistant to corrosion, abrasion, deformation, and water hammer effects. It is also lightweight and flexible and has excellent flow characteristics. One area in which HDPE pipe use is increasing is slurry discharge lines. Laboratory tests and actual field use have shown that HOPE pipe wiII outlast steel pipe for slurry transport under certain conditions. At the U.S. ArmyEngineerWaterwaysExperimentStation WES!,Vicksburg,Missa dredgingtestloopwasconstructed in the Hydraulics Laboratory. Two conditions of slurry velocity and concentrations homogeneous and heterogeneous! were tun with steel and HDPE pipe and elbows. The test results confirmed industry claims that depending on slurry flow and concentration, HD PEpipe is three to five times more abrasion-resistant than conventional mild steel, Although the test results were encouraging, field data were needed to determine the effectiveness of HDPE pipe in a full-scale dredging operation. With the cooperation of the Operations Division, U.S. Army Engineer District, Portland, and the Port of Portland, two 20-foot-long sections of 30-inch-inside diameter ID! HOPE pipe were installed in the land discharge line of the dredge OREGON, The pipe was installed on August 20, 1985, and waSin uSeuntil February 26, 1986, Wall thiCkneSSmeaSurementSwere taken tOrneaSurewear by the amount of wall thinning. After the pipe handled over 2.6 million cubic yards of dredged Columbia River material, wall thickness measurements taken at various points along the pipe length showed wear from 1.1 percent to 29.9 percent of the original thickness, Wear patterns were more closely associated with the material type, i.e., coarse sands and gravel, than with the amount of material dredged, ThispaperdiscussessomeofthepropertiesofHDPEpipethatmakeitespeciallyapplicabletodredging situations, the results of the Portland HOPE pipe field test, and some comments and views on HDPE pipe by dredge operators who use the product. The information in the following two sections, "High Density Polyethylene Pipe" and "Dredging Applications," was extracted from the manufacturers' literature listed in the bibliography. High Density Polyethylene Pipe High density polyethylene plastic is made from an extremely tough and durable resin with a very high molecular weight. These polyethylenes are formed by the polymerization of a group of straight chain, unsaturatedhydrocarbonsethylenes!into long-chainmolecules.Inthe late 1970san ultra-highmolecular weighthighdensitypolyethyleneproductwasdeveloped.Carefulprogrammingof the polymerizationreaction can control the density and molecular weight to obtain HDPE pipe compounds with desired characteristics. AmericanSocietyfor TestingandMaterials ASTM!StandardO 1248,"PolyethylenePlasticMoldingand ExtrusionMaterials,"althoughrevisedseveraltimesto meetthe needsof industry,was not adequatefor all HDPEmaterials.Asa result,ASTMD 3350,"PolyethylenePlasticPipeandFittingsMaterials,"waswritten especially for very high molecular weight materials. This new system uses cell classification rather than a material code to designate the polyethylene properly. Using the cell classification system of ASTM O 3350, a material classified as PE355434C available as Driscopipe 8600!, has the following properties the code "PE" indicates polyethylene: Property 1. Density, g/ccm base resin! 2. Melt Index 3. Flexural Modulus, psi 4, Tensile Strength @ Yield, psi Cell Classification 0,941 0.955 cell 3! Flow rate, 4.0 g/10 min. by condition F. Method D 1238, cell 5! 120,000 to 160,000 ceil 5! 3000 - 3500 cell 4!PDF Image | Dredging Applications of High Density Polyethylene Pipe
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