Published on 10 Apr 2019 by Emma Leoni
All subsea facilities, including structures, jumpers, spools, flowlines, risers and umbilicals, should be designed considering requirements for protection against potential accidental damage resulted from typical offshore hazards as listed below:
- Construction risks
- Dropped objects
- Anchor dragging due to construction vessels or marine traffic
- Snagging loads
- Fishing interaction
- Seismic events
- Hydrodynamics and subsea currents
- Subsea operations
Protection requirements must be based on a risk assessment, consisting of an estimation of the frequency of end events and evaluation of consequence of end events. All hazards, including external interference, accidental events and the resulting protection requirements must be identified, assessed and managed in accordance with:
- Company Safety in Design
- DNVGL-ST-F101 - Submarine Pipeline Systems
- ISO 13628-15 - Subsea Structures and Manifolds
- ISO 13826-1 - Metallic and other inorganic coatings
- ISO 13828-1 - General principles on the design of structures for durability
Protection design must meet the following requirements:
- Flowlines and umbilicals crossing the canyon area must be designed to be protected against hydrodynamic currents, material deposition, seismic events and possible scouring.
- Risks from dropped objects, fishing gear interaction and collision must satisfy the technical requirements stated in Design Standards mentioned above.
- Risk treatment using only procedural control of the construction and operational activities (e.g. demersal fishing interaction, vessel traffic, collision mitigation methods, drilling, pipelay and installation vessels, offtake tankers and workboats) must be used only when more effective treatments are not practicable. The selected risk treatment measures must be in accordance with ALARP . If the risk is not ALARP, then additional protection or risk reduction measures must be taken.
- The subsea structures (e.g. Christmas trees, riser bases, umbilical terminations, flowline structures, etc.) must be designed to protect critical pressure containing hardware and control system components housed within their structures, in accordance with the mandatory references above.
- Interconnecting flying leads and spools must be designed as the weakest part of the system in the event of snagging to avoid / minimize damage to inboard structures, such as inline tee, subsea trees and umbilical distribution units.
Protection products include (but not limited to) the following:
- Concrete mattresses / pads
- Revetment mats
- FRP Node Protection Covers
- FRP Shroud Protection System