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Methodology for current day Aquaculture Systems
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GLOBAL AQUACULTURE www.unet.com.au Universal Nets Pty Ltd PROVIDINGCORE VALUE SOLUTIONS ENGINEERED MOORING ARRANGEMENTS
What are our Core Values • Socially Acceptable; Products and Technologies must help to mitigate social issues frequently associated with marine aquaculture operations. • Examples of social mitigation would be that of possible noise control and that of improved worker safety • Cost Effective; Products and Technology must be cost effective in terms of economic feasibility, covering such issues as ease of deployments, decreased maintenance efforts and be readily integrated with existing operations and stock density ratios • Eco-Friendly; Products and Technologies must help to reduce the Environmental impact associated with the operational footprint, benthic nutrient loading, and escape interactions with wild fish stocks, among other environmental issues • Professionally Managed and Engineered Solutions; Products and Technology needs to be professionally proven and Due Diligence site specific engineering engaged to protect the client. An appropriate Quality Assurance Regime needs to be in place • A well mapped implementation plan “Roadmap” managed jointly and cohesively between Industry and the designated Regulatory and Government bodies. This will ensure a positive prospectus to potential stake holders and Investors Financial Institutions and Sustainability • Robust for Survival and Adaptable; Products and Technologies must allow for expansion into “High Energy Sites” Fish welfare is therefore a priority consideration of Technology and Product as well as planning
The Engineered Difference • Universal Nets prides itself on its ability to provide the correct solution for all site conditions be it in sheltered inland water installation or in severe high energy sites • Our Systems are engineered off the back of our Mooring Anchors a purpose built anchor providing exceptional holding powers
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GOING AND GONE • 250KG Mooring Anchor 30.89 Tonne Ultimate Holding Power
Mooring vs Anchoring • UNIVERSALGLOBAL AQUACULTURE SOLUTIONS • ANCHORS vs MOORING • ANCHORS • Overview • The purpose of this document is to give operators a better understanding of • Anchors and their functionality, particularly in permanent mooring applications. • It is worthy of note that there are actually differences between anchoring and mooring. • Anchoring can be defined as the act of anchoring a vessel temporarily for the • purposes of replenishment or taking short term shelter from the weather or for • some other reason on a short term basis. • It is for this reason that Lloyd’s Register of Shipping makes the following statement in their rules for anchors for ships, • “The anchoring equipment specified in this section (of the rules) is suitable only for use in reasonably sheltered conditions or in emergencies”. • Boat or vessel anchors are not particularly efficient as they need to be able to be easily retrieved after use. • Mooring on the other hand is a very different application and can be defined as • connecting a vessel or floating plant to a piece of infrastructure that is, for all • intents and purposes permanently attached or embedded into the seabed. Hence the term “mooring” or “mooring system” when describing the infrastructure to which the vessel connects. • Permanent mooring anchors therefore have to be different from an anchor • designed as a vessel anchor for a number of reasons including; • The permanent mooring anchor has to be able to take the loads for a • much longer period of time. • Requires a very short drag distance. • Must be capable of holding the floating plant on station. • Has to be able to cope with a wider range of loads due to environmental forces. • Has to be able to be handled and transported easily and cost effectively. • Able to be for specific ground conditions.
Mooring vs Anchoring • There are three main types of anchors in use today • The Deadweight or Clump weight, • The Pile or Pin • The Drag Embedment Anchor. • Dead Weight • The Dead weight is probably the oldest style of anchor in existence. The holding power is generated by the mass of the material used and partly by the friction between the mass and the seabed. Common materials in use today include iron, steel and concrete. They have a very low efficiency. • Pile • The Pile is typically a hollow steel pipe, though pins from solid round bar can also • be used in smaller applications. These are generally installed by means of • hammers or drills. The holding power is generated by the friction of the soil along • the pile and lateral soil resistance. The pile normally has to be installed at a great • depth below the seabed to obtain the required holding capacity, • they can resist both horizontal and vertical loads. • Pile solutions are very expensive and the cost of installation usually exceeds the cost of the pile. • Drag Embedment Anchor • Drag Embedment Anchors are the most popular type of anchoring device available today. • The drag embedment anchor has been designed to penetrate into the • seabed, either partly or fully. The holding capacity of the drag embedment anchor • is generated by the resistance of the soil in front of the anchor. • The drag embedment anchor is very well suited for resisting large horizontal loads, but not for large vertical loads although there is some drag embedment anchors available today on the market that can accommodate some degree of vertical load. • The History of Drag Embedment Anchors • No one can be exactly sure when anchors were first used, though it is known that • anchors were used in ancient China as far back as 2000BC. • Typically they were large stones or baskets of stones connected to lines of vegetable fiber. • The weight of the stones and the degree of friction obtained on the seabed were what kept the vessel on station. • The introduction of iron into anchor manufacture saw new developments such as • teeth or flukes being built into the anchors, this allowed penetration into the seabed thereby offering improved stability and holding power. These anchors were primitive by any standards and as such often broke under the pressure of the loads. • Around 1813 curved “arms” were introduced to add further stability and • from 1852 onwards the “Admiralty Anchor” was introduced to service the ships of • the Royal Navy.
Mooring vs Anchoring • Further refinements continued throughout the 19th century including the elimination of the stock, this improved handling and stowing ability of • the anchors, qualities still valued highly today. • Many anchor types have been developed through the years, some have • prospered, others have fallen by the wayside. • The most recent designs are based on the vast amount of experience gained from the use of anchors through the ages as well as extensive testing programs designed to make the new generation of anchors much more efficient then those of past times. • The following brief overview of the types of anchors in use today is presented to • give users a wider understanding of how anchors have evolved and the relative • efficiencies of each. • Based on certain characteristics of anchors such as fluke area, shank design and • stability it is possible to classify the various types of anchors. To enable a • comparison of anchor types an indication of anchor efficiency is provided. • Efficiency, is based on the holding capacity divided by the weight of the anchor • and is expressed as a ratio, e.g. 33:1 = 33 x anchor weight. • The anchors are classed from A, best performing to G worst performing. • Class A • These are slender highly engineered anchors with ultra penetration in which the • holding power extends to the third power of penetration. Efficiency above 50:1, • examples include the Stingray F and Stingray HD anchors. Stingray anchors can • exhibit efficiencies up to 200:1. These types of anchors may also allow uplift angles at the mud-line, for example Stingray anchors can accommodate loads at up to 20 degrees above the horizontal. • Class B • Anchors with elbowed shank allowing penetration into the seabed. These anchors have an efficiency of between 17 and 25:1 and include the Bruce SS, Bruce TS and AC-12 Bruce SS • Class C • Anchors with open crown hinge near the centre of gravity and relatively short • shanks with stabilizers. Typical efficiency of 14-25:1 and include Stevin, Stevfix • and Flipper Delta. Stevin Mk3 Flipper Delta • Class D • These are anchors with hinge and stabilizers at the rear and relatively long shanks and stabilizers. Efficiency range 8-15:1 and include the Danforth, LWT, Moorfast- Stato-Offdrill and Boss anchors.
Mooring vs Anchoring • Class E • This class is for anchors with extremely short, thick stabilizers, hinge at the rear • and short basically square shaped shank. Typical efficiency 8-11:1 and includes • anchor types AC-14, Stokes and Snugstow. • Class F • Anchors with a square shank where the stabilizers are built into the fluke design. • These anchors have typical efficiencies of 4-6:1 and include Halls Stockless, US • Navy Stockless, Byers and Spek models. • Class G • These include anchors with a stock and small fluke area with the stabilizers at the front of the shank. Efficiencies are typically less than 6:1 and the anchor types include Single Fluke Stock, Dredger and Stock types. • Comparison • It is sometimes useful to compare anchor types based on the applications for which they were designed to see which specific anchor best suits a particular application. • The AC-14 or Admiralty Class 14 anchor for instance was developed to provide a • high holding power boats/ships anchor that would perform well in certain bottom • conditions but not necessarily give the absolute best performance in a permanent • mooring application. These anchors have proven themselves to be reliable for • ship’s applications, they are relatively efficient, easy to use and offer a reduced • weight over traditional boat style anchors. • During testing carried out by the British Admiralty the AC-14 was proven to be a • high holding power anchor when it demonstrated holding power efficiencies of • between 6:1 for soft bottoms to a maximum efficiency of 12:1 for the best holding • bottoms. • The Stingray anchor developed in Australia primarily for Pearling Long-line • applications and permanent mooring systems performs exceptionally well in all • bottom conditions except rock. This anchor exhibits considerably higher holding • power than the Bruce as it is designed for permanent mooring applications where • the primary consideration is the anchor holding capacity, not the ability to be used as a boat anchor. • Typically this anchor has holding powers as high as 200:1 in small sizes and around 100-150:1 for anchor sizes used in long-lines and most small to medium work-boat moorings. These holding powers were proven in field tests conducted in 1998 as well as tests witnessed by the Classification Society Det Noske Veritas (DNV) in 2002 when a five (5) kg Stingray was shown to develop over twice the holding power of a 28kg Danforth. • Other advantages of the Stingray include an ability to be stacked flat for pallet • loading thereby reducing transport and handling costs. They are of steel plate • fabrication and so are not prone to suffer from casting imperfections that can • reduce the structural integrity of any cast anchor.
Mooring vs Anchoring • The comparison then shows us that the AC -14 would be the preferred choice for a vessel anchoring application, but that a Stingray would be more effective for a long term mooring application. To complete the comparison then we should also look at the size of anchor required to perform a specific task. In this instance we will concentrate on a long term mooring application rather than a short anchoring of a boat. • To do this we must first ascertain what size of anchor is relevant to the application, the first thing we must do then is to compare the anchor efficiencies. • When we do this we see that the Stingray has an efficiency at least eight and up to 12 times higher than that recorded for the AC-14, therefore, for any specific • mooring application the AC-14 should be at least 8-12 times the mass of the • Stingray. • To put that into operational terms, if it was determined a Stingray anchor of 50kgs was required then a 400kg to 600kg AC -14 would be required to generate the same level of holding power. This is not to say that a AC-14 anchor is not a good anchor, just that there are other types that are better suited to these long term applications. • If on the other hand we were looking for a boat anchor then the AC-14 would • probably outperform the Stingray in areas such as stowage and the ability to self right. • Typically these are not highly valued qualities for a permanent mooring • anchor as they tend to be “installed” to a pre-determined pattern or position and • are not simply thrown over the side and allowed to drag until they eventually hold. • Some other advantages of Stingray permanent mooring anchors are their lack of • damage to the sea floor, whereas other anchor types tend to drag for rather long • distances and as such they carve great troughs into the seabed which is not good for the environment in that proximity. Stingray anchors have been approved by various Government departments and agencies as being friendly to the • environment and are being used in marine parks such as Ningaloo Reef, The • Rowley Shoals and Ashmore Reef for this reason. • Stingray anchors can accommodate far greater vertical loads than the AC-14 or • any conventional anchor. In field tests carried out the Stingray anchors has • demonstrated an ability to handle loads up to 30 degrees from the horizontal, • though the manufacturer claims no more than 20 degrees. • Stingray anchors are patented so you are getting the supply from the source, not • someone copying another anchor and selling it on price alone which inevitably • leads to reductions in the quality of the build as reductions in cost are investigated.
Mooring vs Anchoring • Conclusions • In recent comparisons performed for a major contractor Stingray anchors were determined to have a cost of holding power of around half that of the other major anchor types. It is this cost that users should concentrate on, not the actual cost of the anchor. • It has been demonstrated above that the weight of an anchor is not necessarily the best way to select the anchor required, it really is the holding power of the anchor that is important. • It can clearly be seen that there are a number of different issues that need to be addressed when selecting an anchor for a specific application. • It is important to understand the difference between anchoring and mooring as a first principle, then to establish the needs of the application. Once this has been determined then the anchor selection process can begin.
CONTACT DETAILS • Peter Phelan peter@unet.com.au • Geoff Wolfenden geoff@unet.com.au • Graeme Johnson graeme@unet.com.au • Visit our web site www.unet.com.au
