Impact analysis

Causes and consequences

The principal causes of impact to subsea pipelines are from dropped objects and from interaction with fishing gear and anchors. Possible consequences to the pipeline include damage to the coating, denting and gouging of the pipe wall and excessive bending stresses caused by trawl gear or anchor pullover loads. These could result in immediate failure or subsequent failure from creep or fatigue depending on the size of pipe and type of impact.

Jee technology and experience 
Jee has been working in this field for many years and has accumulated experience and developed technological solutions in the following areas:

• Impact tests of coated pipes: produced impact test specifications.
• Development of dynamic FE models: these take account of the seabed boundary conditions, global and local pipe response and wall denting.
• Design of protective coatings: selection of type and thickness of material.
• Impact acceptability criteria: a Jee-led JIP developed acceptability criteria for trawl impact. These were subsequently incorporated in HSE publication OTH 561.
• Design of protection systems: tunnels, burial, rock dump and coatings.
• Pullover loads: assessment of effect of anchor drag and fishing gear.

What Jee offers

• Feasibility: development of protection philosophy and criteria.
• FEED: design of protection coating/structure. Risk assessment and consequence analysis. Determine requirement for burial/burial depths.
• Technical support: provide impact test procedures, test specification, management of tests. Perform fatigue assessments of damaged pipelines and provide recommendations for remedial action.
• R&D: development of protective structures – in particular, coatings.