The Magazine for Underwater Professionals
Martin Slade, managing director of UK-based Divemex, writes about the problems commonly encountered when setting anchors and explains why his company's radical new omni-directional claw anchor ensures accuracy of placement and delivers costs savings
It has been recognised and agreed that the choices available for the accurate setting and positioning of anchors have been limited by the technology of the anchor design. Despite there being many recognised manufacturers and designs, the principle for anchor setting remains a constant.
Divemex has gained a wealth of experience in this field over the years and has been responsible for positioning everything from floating construction barges for the construction of the First and Second Severn Crossing bridges through to the placement of 100-tonne floating flare stacks for gas rigs at the Zafiro oil terminal in Equatorial Guinea, West Africa.
It is difficult enough to manage your construction projects on dry land, but when you have tides, currents and bad weather, these ever-changing conditions are not helped by having to repeatedly attempt to get the securing anchors in exactly the right position to enable the activity above sea level to take place. In some situations it has taken weeks to set anchors that are only budgeted to be set within days. Delays equal rising costs on every level. So how can you deliver projects not only on time, but also within budget in these testing applications? This is the pressing question that Captain David Beatty of Divemex has not only addressed but has solved.
Captain Beatty has developed an anchor that can be placed and set accurately into the position required. The Divemex claw anchor is an omni-directional device that sets within its own length. Traditional anchor designs are a single direction type that are dragged and pulled into position. These can be single anchors or multiple anchor (“piggy-back”) configurations. Whilst recognised as being reliable and dependable these designs all have one thing in common and that is that they can take time to set when accuracy is the prime requirement for placement.
Other traditional solutions to the placement of navigation buoys for example are outdated and potentially environmentally unfriendly and potentially dangerous at low tide or in shallow waters. Some of the well tried and tested solutions for navigation buoy placement include concrete anchor blocks, chain and old wagon/train wheels – all of these solutions are not exactly high tech. Concrete blocks not only are heavy to reposition, they also stand proud of the seabed and can potentially prove to be highly dangerous, particularly to deep-draught vessels. Steel chain and wheels, if left, can not only rust and contaminate the sea, they can also prove hazardous to dredging vessels if not correctly marked on maps and charts.
The new claw anchor will ensure that navigation buoys are not only held directly in an accurate position, it will also bury itself into the seabed so reducing the potential as a dangerous obstruction in shallow-water and low-tide moorings. The anchor can also be recovered easily by vessels with heavy duty winches in applications that would have previously required a high tonnage concrete anchor block. Divemex has been involved in the re-positioning of navigation buoys where concrete anchors have been used and the only way to accurately reposition them has been conducted using expensive support vessels such as floating cranes and their associated crew. The new anchor negates the need for this and can be recovered easily and within a timely manner.
So what makes Divemex’s claw anchor so different I hear you say? The radical anchor can be constructed in a wide range of materials that can enable it to be used across a range of applications. These include standard galvanised plate steel, 4130 chrome alloy (for high-hold applications), stainless steel and aluminium (military/minefields). The anchor will be made available in three core anchor designs. The entry level will be a type that is suitable for small dinghies through to 70-foot (21-metre) power cruisers and yachts. The classic claw design is available across a wide range of weights and sizes and will be suitable for navigation buoys and floating structures. Finally, there is an embedment claw anchor that will be provided in configurations and weights up to a maximum 70 tonnes for offshore oil and gas rig applications.
The anchor can be easily deployed and when settled upon the seabed it rocks itself in a “see saw” type motion into the seabed and embeds itself offering high holding power and accurate placement.
Typical applications for the Divemex claw anchor include: navigation buoyage systems; single point moorings; pontoons; port heaving anchors; barges; pilot boats; tugs; commercial and leisure vessels; deep-sea anchorage (beam/ embedment anchors); floating structures; flare stacks; and dredging – to name but a few. In addition to this, the claw anchor can be used in tidal areas and rivers and estuaries. With the ease of deployment and recovery, the anchor’s high performance design is highly flexible and is easily adapted for any application.
Testing to date indicates an improvement of vessel/structure holding power when compared with competitors’ equivalent designs. Divemex has been working closely with the Cardiff University, UK, ASTUTE (Advanced Sustainable Manufacturing Technologies) project, as well as conducting extensive beach and sea trials, in order to validate the claw anchor in anticipation of its commercial availability into the global maritime markets later on in 2016.