Guidelines for safe cable crossing over a pipeline

Abstract

High voltage submarine cables are increasingly being installed in existing and new offshore oil and gas fields for power supply and control purposes. These power cables are both large and with a high submerged weight, which poses a challenge when designing a safe, maintenance free (economical), and fit-for-purpose crossing over a pipeline. Damage to subsea pipeline crossings caused by deterioration of a crossing support, field joint materials and cover components is well known in the industry, particularly with old pipelines.Crossing cables over an existing pipeline should be avoided whenever economical and practical. However, it is inevitable in some situations to use the existing pipeline (unburied) as the crossing support to a new cable/umbilical. In these situations, crossing the cable/umbilical over the existing pipeline may be a cost-effective and worthy consideration. However, there are no explicit guidelines or criteria in the industry concerning the acceptable practice of design and construction of crossings. The only clear recommendation is relating to pipeline separation distances. This paper documents a recent case study of damage of a field joint coating at a crossing of an existing pipeline by a 132 kV subsea cable of 191 mm outside diameter. Investigation of the damage on site revealed that it was caused by lateral movement of the cable under the influence of hydrodynamic forces.Further to investigation and assessment of the damage of the case study presented here, the paper proposes some guidelines for the safe design and construction of cable crossing. Another objective of this paper is to invite further evaluation of the proposed guidelines so that appropriate crossing design requirements can be further developed and standardised.

Guideline for the Decommissioning/Abandonment of Subsea Pipelines

“…A pipeline refers primarily to an enclosed pipe system that extends between two or more process facilities (e.g., offshore platforms, pumping/compressor stations, tank farm/storage facilities, refineries, etc.) to convey bulk volumes of fluid or fluids between those process facilities [1][2][3][4][5]. There is demand by different oil and gas operators to utilise existing ageing offshore structures, which has led to the need for the development of new regulations [6,7].…”

Guidelines on Composite Flexible Risers: Monitoring Techniques and Design Approaches

“…In addition, offshore platforms are designed to have structural components and conduits for extracting oil and gas products to provide energy [1][2][3]. However, the structural strength of aeronautical structures, subsea pipelines\cables, and marine risers is subject to certain limits, which also affect their service life and useability [4][5][6][7]. Conversely, an engineering challenge faced by pipe designers includes sustainable design methods, safe operating procedures, and better monitoring techniques [8][9][10][11].…”

Design of subsea cables/umbilicals for in-service abrasion - Part 1: Case studies

“…Furthermore, the same reference highlights that it is essential to ensure that the cable has sufficient abrasion resistance to ensure that the outer sheath of the cable is not damaged. Reda et al [8,12] and DNVGL-RP-0360 [7] emphasize that the tubular products which are utilized to provide stability or protection for the pipeline should be designed to ensure abrasion resistance thereby increasing the cable life under the impact of harsh environmental loads. The outer surface of the cable and umbilical provides resistance against corrosion.…”