Since the early 1960s, and shortly after the first introduction, polyethylene pipes have been increasingly used for offshore applications. Fluid discharge, fluid transfer from under the river or lake, and getting fresh water and saline water are the major applications of polyethylene pipes in the sea. In addition to the main applications mentioned above, they may be used at sea, in cases such as temporary pipelines floating on the water surface, installation on marshy land and using in dredging operations. Here, it has been attempted, while introducing the potential of producing polyethylene pipe by Tadbir `Novin Sazan Company, to take a small step towards using new products.
For installations that are mainly built by the seas and lakes and require large scale cooling systems, using seawater is the cheapest and most convenient solution. Double-wall polyethylene pipes with core-tube play a major role in transferring large volumes of seawater to the pumping part of the cooling system. With the development of the country’s industry in nearshore areas such as Assaluyeh, there has also been a growing need for the big diameter pipes for large petrochemicals and refineries.
How to place on the seabed
Double-wall polyethylene pipes up to 4000 mm in diameter can be easily welded into pieces of varying lengths and can be placed on the seabed by the Float & Sink method. Also, due to the modern capabilities of the company to produce an integrated “Stub ends” in large diameters, each piece can be attached to the next parts by using a flange and mechanically on the sea floor. High flexibility of pipes, high quality and above standard welding in joints, complete sealing and engineering facilities and design to offer optimum conditions to the client, are the advantages that have made the double-wall polyethylene pipe with core-tube on top of marine projects in Iran.
Insofar as, for the first time in the world, the company has sunk polyethylene pipe size 2500mm in diameter, with 1700 meters’ length, at 25 meters’ depth in the Persian Gulf.
In Germany, almost all marine wastewater outputs were built between 1970 and 1985, which the bauku company had been working closely with the project’s executives and the result is the experience that now this company enjoys.
High quality floats can be manufactured with double-wall polyethylene pipes. Its raw material is high density polyethylene (HDPE) with its specific weight of 960 kg/m3 which is lighter than water and makes the pipe float on the water. If the openings of the pipes are closed, their buoyancy will increase and they can withstand heavy loads.
If these floats are used in mooring at the seawater, the HDPE will have more advantages. They are resistant to saline water and unlike steel pontoons they will not be corroded.
Tadbir Novin Sazan Company cares about solving such problems. So, these floats are the best products of this company. They do not run out of water too much (the contact line with the waves) and do not dive too deep into the water to be covered with it.
The various chambers within the pontoons control the water level.
Separate chambers prevent complete flooding during damage to the floating body and prevent it from sinking into the water.
In Germany, most of the marine basins were built between 1970 and 1985. The basins were taken to the North Sea, the East Sea and the Elbe and Rhine rivers. Since then, the foreign partner of Tadbir Novin Sazan has acquired the knowledge of how to work with static structures and install pipelines.
Collaborating with construction companies is important because such projects require more work than ground pipe technology. Tadbir Novin Sazan double-wall polyethylene pipes with core-tube are connected without any problems over long lengths. The maximum length depends on the type of profile used in the double wall pipe and how it is installed in the water.
How to connect
External welding is used to connect the pipes. Because of the mechanical strength of the pipes, it is possible to move them in the water and they can be slept on the sea floor without causing any damage.
Of course, Tadbir Novin Sazan also uses special connections that can be built by divers under the sea. Only in this case it is possible to connect to buildings or multiple pipelines. The company uses a plastic connector to do this.
Due to the light weight of polyethylene pipe profiles than water, there is no problem in moving them in water. Placing the pipes on the seafloor is possible by applying more pressure from outside on the pipe or by creating anchor, or by filling the hollow chambers of the pipe profile, for example with cement.
The basin not only needs a good pipe, but it must also have a complete system, the output buildings are very important, the cross section of the pipe is enlarged, and it must be hydrodynamic. HDPE systems are also manufactured by the company and delivered to the construction site.