Seabed Scour Control System

SEABED SCOUR CONTROL SYSTEM

At the beginning of the 1980's Seabed Scour Control Systems Limited (SSCS) was established in the U.K. and using information and trials data published by Dupont, and in particular that provided by ICI's LCL and also by Royal Dutch Shell Chemicals began a period of extensive research and full scale development trials in conjunction with, and supported by, Shell (UK) in the North Sea, and later also with trials installations with Amoco, which culminated in multiple field trials successes. In 1984 SSCS commenced full production.

The SSCS Frond Systems remain the only field proven scour control product that reduces current velocity by providing a strong and unbroken viscous drag barrier.

SCOUR CONTROL PRODUCTS

  • Frond Mats (with pre-attached SSCS Anchors)
  • Edge Weighted Flexible Frond Mats
  • Fronded Concrete Mattresses
  • Fronded Moulded and Formed Structures
  • Anchors
  • Mat and Mattress Installation Equipment
  • Deployment Frames, Rigging and Slings

The Frond Systems are used to provide planned and preventative scour protection for new subsea installations and to rectify scour encountered at existing facilties. SSCS has been approved to ISO 9001 2000 by Lloyds Register Quality Assurance Ltd. The SSCS Frond Systems and Anchors have received DNV approval for the protection of subsea Renewables Energy Installations.

THE FROND SYSTEM
The SSCS Frond System comprises continuous lines of overlapping buoyant polypropylene fronds that when activated create a viscous drag barrier that significantly reduces current velocity. The frond lines are secured to a polyester webbing mesh base that is itself secured to the seabed by anchors pre-attached to the mesh base by polyester webbing lines.

The action of reducing current velocity immediately prevents seabed sediment in the immediate area of the fronds from being transported i.e. 'scoured out', and causes sediment transported across the fronded area to fall into, and collect, within the fronds.

The Frond System

WHAT IS SCOUR?
The Cause of Scour
Seabed soil types and a combination of current, tidal and wave forces combine to create an environment which leads to seabed sediment being lifted and transported. The result is the natural depletion of soil in one area and its aggradation in another. This natural occurrence known as scour, or erosion, is exacerbated when objects are placed on the seabed, such as pipelines, platforms, protection structures, umbilicals and cables.

Local Scour
Any fixed subsea installation will disrupt tidal flow, causing the current to first decelerate in advance of it then accelerate beyond it, to form vortices and eddies which cause sediment to be scoured, i.e. lifted from the seabed and transported.

  • Local Scour
  • Local Scour

Reversed tidal flows will cause scour to develop significantly on all sides of the installation to form steep sided scour pits, and in the case of pipelines, cables and umbilicals, beneath them, to cause free spanning.

A pipeline spanning the seabed

HOW THE SSCS FROND SYSTEM WORKS
By reducing current flow the SSCS Frond Systems prevent scour from occurring and rectify scour by reversing the effects that cause it. A planned and selective deployment of the Frond Systems will immediately prevent and remedy scour, and provide permanent scour protection. The following photographs, courtesy of Shell UK Exploration & Production Ltd prove and demonstrate the effectiveness of the SSCS Frond Systems. The originally installed Frond Mats have now been in place at this Shell site for some 23 years and continue to provide protection.

  • SSCS Frond System

    Initial sediment build-up covering mat base and the foot of the fronds

  • SSCS Frond System

    Continued sediment build-up in centre of the mat and sloping to and beyond the mat edges

  • SSCS Frond System

    Re-inforced sediment bank near full development with a few short lengths of fronds exposed

  • SSCS Frond System

    Diver inspecting fully developed sediment bank with short random fronds showing and a typical "ripple" pattern appearing on sediment surface

  • SSCS Frond System

    One year after installation at the previously scoured pipline with a fully developed sediment bank formed over the fronds with marine life colonies on the final bank

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