Like all other work related to offshore activities. trenching of pipelines seems to be more troublesome in the North Sea than in other parts of the world. This is either because more attention is paid to the results in this area, or because the environmental conditions make it more difficult to perform satisfactorily with the same equipment. The problem with conventional trenching equipment is that it does not perform well in clayey soils. and in several cases misoperation has resulted in damage to coating and pipeline (leading to rupture during pressure testing). This pipeline (leading to rupture during pressure testing). This possibility. taking into account the cost of trenching and possibility. taking into account the cost of trenching and pipeline repairs. should be weighed against the protection pipeline repairs. should be weighed against the protection provided by a trench towards natural and man-made provided by a trench towards natural and man-made hazards. This paper discusses the influence of trenching on pipeline safety for trunk lines with a diameter of more than pipeline safety for trunk lines with a diameter of more than 30 in. For smaller diameter pipelines the conditions may be different. Statistical analysis of pipeline failures show that the most important causes are corrosion and equipment fault. These types of failure can hardly be affected by trenching. Another important cause is anchor dragging, which also only to a limited extent can be protected for by trenching. For the major offshore pipelines constructed or planned in the North Sea over the last few years. great emphasis has been put on thorough investigation of the needs for protection of pipelines of the seabed. Based on our protection of pipelines of the seabed. Based on our knowledge of these investigations carried out by owners and operators of submarine pipelines. and on our experience as a certifying agency and consultants to oil companies. our evaluation of trenching as a safety pressure is given in this paper. A shore summary is given pressure is given in this paper. A shore summary is given below.
