Energy


The Tyre Filled Net Solution


Swan Net Gundry in collaboration with Norfolk Marine have developed the Tyre Filled Net or TFN to provide a sustainable solution to windfarm scour. The TFN’s utilise recycled tyres to replace non renewable natural resources.

Each TFN consists of 50 recycled tyres held inside a robust marine grade net. The tyres are tied together inside the net with ropes that provide a back up method of securing and recovering the tyres from the seabed.

The tyres inside each net trap material which is suspended in the tidal water flow and prevent it escaping so the seabed is reinstated with naturally occurring sediment.



The fact that the TFN’s are placed into the scour hole below the surrounding seabed level and the sediment is trapped within the tyres means that the problem of ‘Secondary Scour’ and the scour protection moving away from the turbine pile is eliminated. The TFN system has been designed and tested, to provide a product, proven to withstand the effects of the marine environment.

Scroby Sands

It is proposed to install 12 TFN units around 6 turbine piles to give a total of 72 nets using 3,600 recycled tyres. The TFNs will be secured to each other and around the turbine bases to ensure they remain in place.

The Numbers

To install scour remediation using Tyre Filled Nets at 6 turbines within the Scroby Sands Windfarm when compared to conventional aggregate solutions:

TFN’s

• 72 TFN Units
• 3,600 recycled tyres
• 360 m3 when filled with local sediment
• 32 Tonnes of materials
• 3 Truck deliveries
• Small installation vessel
• Permanent SolutionThe Numbers:

Aggregates

• 950 Tonnes of non renewable natural resources
• 48 Truck Deliveries or large capacity dredging vessel
• Large rock dumping or crane vessel
• Temporary Solution

TFN PRODUCT PAMPHLET

The Problem
When an object, such as a wind turbine, protrudes from the seabed it causes ‘Scour’ around it. Scour occurs when the water flowing around the object increases speed and picks up the seabed material, creating a hole.
Scroby Sands
 The sandy seabed found at the Scroby Sands site is particularly susceptible to this scouring effect, and large holes have developed around the turbine structures.
These holes around the turbines create a number of problems for the operation of the windfarm as there is a longer exposed length of the turbine piles and less penetration depth into the seabed. Key problems include:
• Stability • Vibration • Fatigue
• Safety
Existing Scour Solutions
Current methods of filling the scour holes around wind turbines use non renewable aggregate resources which are either quarried and transported or dredged from the seabed and then deposited into the hole. These aggregate solutions can be either rock, which is dumped into place around the turbines or sand which is placed inside geotextile ‘bags’.
Disadvantages
The impact of using natural aggregate resources includes: • Dredging, Quarrying & Transport Costs
• Dredging activity on Benthic substrates
• Disturbance of marine organisms
• Non renewable use of natural resources • Introduction of non indigenous species

The British Marine Aggregate Producers Association state that it can take 2 to 5 years for the seabed to recover from dredging activity.

The use of solid aggregates as scour protection around wind turbines is only a temporary measure as ‘Secondary Scour’ occurs around the edges of the material and draws it away from the turbine base.
Another consideration is, in order to access the power cables that exit from the base of the turbine, for maintenance or repair, the aggregate needs to be dredged out again with risk of damaging the cables.
The Use of Recycled Tyres
In order to responsibly manage our environment we need to recycle or re-use materials wherever possible. According to government figures 55 million tyres are replaced, and enter the waste system, in the UK every year.

The EU Waste Framework Directive ‘Waste Hierarchy’ states that reuse of waste is preferable to the recovery of materials or energy from that product. Recycled tyres have been used in the marine environment, in the form of artificial reefs and coastal erosion protection for many years. Environmental concerns have been raised in the past, particularly after vast quantities of tyres became loose from an artificial reef project in Florida US. Reports conducted following this incident identified engineering failures in the construction of the reef rather than the tyres themselves as the cause.

The other significant environmental concerns regarding the use of tyres in the sea are the release of chemicals or leachates and degradation of the tyre compostion.

A number of reviews and reports conducted or recognised by the ‘Department for Environment, Food & Rural Affairs’ and the ‘Environment Agency’ (Particularly the report ‘Sustainable Re-use of Tyres in Port, Coastal and River Engineering) conclude the following:
• Leaching of chemicals in marine environments has been reported as low risk, generally due to large dilution of any contaminants released.
• Underwater, tyres are protected from ultraviolet degradation and are in a neutral, stable chemical environment.
• Test Results indicate that tyres do not leach volatile organic compounds. Detection levels are 10 to 100 times less than regulatory limits for drinking water.
• The US National Artificial Reef Plan includes tyres as a reef construction material noting that no toxic effects attributable to leaching or decomposition have been demonstrated.

Helix Tag Line

Using a regular rope of poly, nylon or sisal has some inherent problems when used as tag line:

1. They tend to wrap around objects
2. They get caught in pinch points
3. The bottoms fray and are then knotted to stop the fraying causing the line to catch
4. They get slick when worn, wet or dirty with grease The HELIX TAG LINE solves these problems, as it is specifically designed for the application.

 

HELIX TAG LINES are tangle resistant as it is designed with a rigid core & stiff overbrading to prevent any turning on itself and wrapping around objects. We have added an additional factor which is the spiral effect (HELIX), which will dramatically increase grip in wet & slippery conditions. HELIX TAG LINES are designed not to catch on pinch points, as there are no knots or areas to snag.

Features

  • Made from DynIce SK 75 12mm with 6mm core (18mm) synthetic rope offering remarkable strength & light weight.
  • Weaved Over Braided cover to prevent abrasion.
  • Colour Coded Eyes and triple action karabiner with captive pin .
  • Specifically designed in conjunction with Major Drilling Contractor for the desired application.
  • Tangle resistant.
  • Designed not to catch on pinch points.
  • No knots.
  • High visibility yellow outer braid.
  • Available in four sizes, 15ft, 25ft, 35ft and 45ft

Patent Pending: IS 8691, EP13176751, US 14203127

Product Specification

MARINE ANTI-TANGLE TAG LINES are manufactured from DynIce SK 75 synthetic rope giving them exceptional strength and they are also lightweight for operator handling. Each tagline has a soft over braided cover to help prevent abrasion. This similar technology is used in tow lines and gives the product its anti-tangle properties. There are four current lengths 15ft, 25ft, 35ft and 45ft each coming with a relevant colour coded eye for length identification. In addition to this there is a triple action karabiner with captive pin.