Submerged GRP pipe application



Superlit, a well known major Turkish GRP pipe manufacturer, supplied (DN) 3000mm GRP pipes which are installed underwater for the project “Cooling Water Supply from the sea for Metallurgical Factory in Turkey”. Total of 600m GRP Pipe lines are installed as submerged on the saddles anchoraged on a continuous horizontal steel beam, due to the fact that cooling water for the factory is absorbed 7m below the sea level.

To resist abrasion of both inner and outer layers of GRP pipes due to continuous exposition to salty working environment, pipes were manufactured with re-engineered recipe to reach an effective working life of at least 50 years. Temperature change of sea-water, underwater currency effects, “stick-spread-reproduce” nature of undersea organisms (such as muscles, oysters, seaweed, algae, etc.) which might penetrate through the pipe walls, resistance to underwater seismic movements, and several more possible casualties were studied by Superlit engineers during manufacturing and installation stages.

The most important advantage of GRP pipes compared to alternative pipes is having adequate weight for sinking. GRP pipes can easily be submerged and sit on sea bottom without a need for additional ballast or buoyancy.

For an easier pipe laying, pre-installation of multiple pipes on-shore is preferred in most cases. However, pre-installed pipes are subject to coupling slippage during submerging due to unstable sea currencies and water movements. The most common technique used for prevention of coupling slippage during submerging is to install Marine Lugs at the pipe ends. Marine Lugs are T-shaped steels profiles strongly attached on the pipe ends by lamination. After multiple pipes are joined with couplings, marine lugs are connected to each other with steel rods. Even though axial resistance of marine lug joints are greater than the axial resistance of pipe itself in many cases, the main duty of marine lugs is to protect axial continuity and to prevent coupling slippage during submerging due to unstable water movements.

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