First Subsea Pipeline Recovery Tools (PLRT) are utilised for laydown or recovery of subsea pipelines and interface with a wide range of API pipe sizes. They can also be used to seal or dewater pipelines to assist in retrieval, and have found a wide use both as contingency and in actual emergency situations.
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New PLRT Developments - Recovering Buried Subsea Pipelines
The challenge of removing subsea pipeline from under rock berms during decommissioning has led to the development of new pipeline handling technologies by First Subsea.
The complete decommissioning of subsea pipelines involves the removal of seabed and buried pipelines. Traditional techniques such as cutting the pipeline, strapping and pulling it to the surface, work well for pipeline lying on the sea bed. However, they are ineffective in removing pipeline buried under berms where the safe working loads and stresses on the pipe and recovery tool are too high. As a result, contractors are faced with either having to uncover the pipeline first and then lift it, a time-consuming and expensive process, or taking a new approach to extracting the pipeline from under the rock berms.
The First Subsea 2", 4" and 24" pipeline handling tools are designed for extracting rigid pipe buried under 1.5 m of rock berm. The pipeline tools are based on the ball and taper connection principle used in mooring systems and pipeline recovery tools.
Briefly, ball and taper works on the simple principle of a ball engaged in a taper. The male connector is inserted within a female receptacle – it is self-energising and self-aligning. As the male connector's balls roll up the tapers, the tightness of the grip increases in direct proportion to the load applied. In pipeline recovery and handling tools, the female receptacle is the pipeline.
The 4" and 24" pipeline handling tools use the male part of the ball and taper. Unusually for ball and taper technology, the balls on the 24" tool are hydraulically activated rather than spring activated. After the tool has been inserted into the pipe, an ROV 'hot stabs' the tool's hydraulics to release and drive the balls onto the pipe's inner surface. Once load is applied the balls 'bite' into the pipe wall, creating a tear-drop shaped tapered indent. After the pipe has been dragged out from under the berms, the hydraulic activator is then 'hot stab' deactivated, disengaging the balls, and the tool reused.
For smaller diameter pipes where the safe working load on the buried pipe is too great for a conventional ball and taper tool, First Subsea has reversed the normal ball and taper geometry in its 2"pipe extraction tool. The balls are positioned inside the tool. The company claims this is first ball and taper pipeline handling tool to grip the pipe on the outside rather than the inside. Protective external surface coatings often used on subsea pipelines can also be accommodated in the 2" tool design.
The 2", 4" and 24" tool designs are custom engineered reflecting the size, condition, and safe working load on the pipeline. This takes into account the hardness of the pipe material and maximum stress the pipe is able to withstand. The tools can be fitted with either a clevis head or padeye allowing recovery of the pipe to the surface ship or left in wet storage on the sea bed for subsequent removal.
The First Subsea 2",4" and 24" tools have already been used successfully on recent pipeline decommissioning projects including flexible pipes.
Innovative Pipeline Recovery Tool for external grip of pipeline