PDF Publication Title:
Text from PDF Page: 019
17 seabed of loose sand or weak clay. In any case the specific design chosen should be based on: a) Ease of fastening the anchors to the pipeline; b) Fasteners resistant to salt water corrosion; c) Ease of bending and placing the reinforcing steel and: d) Ease of casting the concrete. Figure 4 illustrates a common ballast anchor design for small diameter pipe that is illustrated in many plastic pipe. This common design has two rectangular collars constructed of concrete in a manner so that it can be clamped onto the outside of the pipe. It is herein referred to as the Type A design. This particular variation uses two bolts of saltwater corrosion resistant material. It is possible to also use fiberglass bolts, or polyethylene plastic pipe with heat formed ends as a means of fastening the halves together. It has two major shortcomings. 1) This design does not have a center of gravity that is lower than the systems center of buoyancy and it is therefore somewhat prone to rolling over in strong currents. 2) The bolts are long making them difficult to align with the top and bottom bolt holes during attachment to the outfall pipe and this also makes grouting of the annular space more difficult. Figure 5 illustrates the Type B ballast anchor design that has been successfully used for HDPE pipelines up to 20 cm diameter. The spacing of this type of anchor is usually limited by the class of handling equipment available rather than the deflection or strain of the pipe itself. The major drawback of this ballast design is there is not much pipe surface area in contact with the bars that hold the pipe into place and this has resulted in kinking of pipe with larger dimension ratios during launching and sinking of the pipe. Figure 5(A) illustrates the Type C ballast anchor, which is usually the easiest to install and has the least problems with corrosion because it requires no bolts to attach it to the outfall pipe. It is installed on the pipe by squeezing the HDPE pipe with two large clamps on each side of the pipe where the anchor is to be placed. The temporarily deformed pipe is then inserted through the narrow (0.7d) neck of the opening and then the clamps loosened to allow the pipe to snap back into the round shape. It may be necessary to rotate the clamps 90% to "encourage" the HDPE pipe to snap back completely. This is possible only with HDPE and polypropylene pipe. Larger anchors of this design should be constructed with lifting lugs cast into them, to facilitate their handling and fastening to the pipeline. Concrete ballast anchors may be factory cast and hauled to the outfall assembly site or cast at the assembly site by the same labor crew to be used for installing and assembling the HDPE outfall. Since many installers elect to cast the ballast anchor themselves, some suggestions and precautions are included. 10.4 Ballast anchors cast at worksite In casting the two halves of the Type A design, the form shown in Figure 6 is usually constructed so that both halves of the collar can be cast at the same time, using a short piece of the HDPE outfall pipe to achieve an exact fit. The two halves are separated by 1/2 cm (1/4 inch) plywood. This provides sufficient play to insure a tight fit when the two halves are bolted together when the anchor collar is attached to the pipe. The holes for the bolts are formed using thin wall PVC pipe with an internal diameter 50 percent larger than the diameter of the bolts to be used. They are held in place by a rod extending through the form so as to help assure bolt alignment.PDF Image | SMALL DIAMETER (HDPE) SUBMARINE OUTFALLS
PDF Search Title:
SMALL DIAMETER (HDPE) SUBMARINE OUTFALLSOriginal File Name Searched:
OPSCEPISPUB0060_eng.PDFDIY PDF Search: Google It | Yahoo | Bing
Development of a solar powered Electric Ship The Electricship website originally started off as a project to develop a comprehensive renewable, affordable, modular electric ship... More Info
Modular Boat Hull Composite The case for a unsinkable, modular composite hybrid boat hull... More Info
MS Burgenstock Hybrid Electric Catamaran Lake Lucerne Unique shuttle servicing Lucerne to the Burgenstock Resort... More Info
Ground Power Unit GPU Powered by Lithium Ion Batteries The goal of the Ground Power Unit is to provide a readily accessible, modular, ready-to-power solution for remote power... More Info
CONTACT TEL: 608-238-6001 Email: greg@electricship.com (Standard Web Page)