New Burial Techniques for Effective Burial for the Protection of Pipes

Abstract

This paper outlines recent developments which have been undertaken to improve techniques for effective cable burial and protection of subsea pipes.

Traditional methods of burial for subsea pipework have involved the use of towed plough systems, subsea dredging units, or mechanical or jetting based trenching systems. Recent vehicle developments as undertaken by BT (Marine) Limited (BT(M)) have embodied new techniques which will allow more efficient solutions for the pipeline owners. New vehicles now offer a hybrid of solutions depending on the local conditions which may prevail. For example, the new BT(M) Eureka vehicle has the ability to interface to four separate burial devices. There is a new advanced dynamic jetting system which maximises available power for efficient trenching. There are two separate mechanical tools; a rockwheel cutter for work in very hard seabed materials, and a chain excavator where very deep burial, in excess of 2m, is required. There is also a jet assisted plough which combines the benefits of water jetting with ploughed systems. All of these burial devices are controlled from the same host vehicle which is fitted with the latest sensing and tracking devices. Product handling is of prime importance and the new vehicle systems operate with either a non-product engagement system during burial, or an auto eject facility which ensures that in the event of hydraulic failure the product is safely ejected from the vehicle.

At present the burial vehicles have been designed to handle small diameter rigid pipes and flexibles. However, R&D studies have already proved the concept can be extrapolated for larger diameter pipes.