DeepWater Buoyancy has the finest international representative network for oceanographic subsea buoyancy. What follows is the next in a series of articles on our representative groups. This time we are highlighting our representative in the UK – Saderet. Founded and still led by Andy Smith, Saderet is another of our representatives who have many years of experience integrating our buoyancy solutions into subsea moorings and structures. Saderet services our customers in this region from the National Oceanography Centre in Southampton to the Scottish Association for Marine Science in Scotland, in applications ranging from ADCP deployment to monitoring of aquaculture to support of offshore oil and gas operations.
Since 1998 Saderet has successfully served the land and marine survey industry with leading products and solutions. Founded by Andrew Smith the company now employs 7 and is based in the Isle of Man. Geographically the company offers equipment worldwide with a particular emphasis on the UK, Europe including Eastern Europe, the Middle East and Russia.
The company specialises in representing manufacturers of complimentary equipment so that complete equipment packages can be provided from one source. An example of this is Deepwater Buoyancy whose sub-sea platforms are offered in tandem with oceanographic instruments also represented and supplied by Saderet.
In addition to Deepwater Buoyancy the company also represents the following offshore equipment manufacturers including:
Teledyne RDI Acoustic Doppler Current Profilers and associated oceanographic instruments including CTD’s.
Teledyne Odom single and multi-beam sounders for seabed mapping together with the associated speed of sound measurement systems.
Teledyne TSS gyro compasses, motion sensors and pipe/cable trackers.
Hemisphere GNSS. Saderet is the official HGNSS Distributor for Europe and the Middle East and has established a 45 strong dealer network to promote and support the navigation and heading systems product line. The company also offers OEM board level receivers and Saderet assists customers in the integration of these products into their own systems.
QPS software packages for hydrographic survey, dredging, rig moving and many other offshore engineering applications.
Edgetech acoustic release systems for subsea equipment recovery. Edgetech also offers side scan sonar and sub-bottom profiling systems for vessel towed or AUV/ROV mount.
Satel UHF and VHF radio modems for data telemetry, DGPS, RTK and vessel tracking applications such as rig moving operations.
Chesapeake Technology sub-bottom data acquisition and processing software for geotechnical studies including offshore site surveys.
Saderet also supports clients with installation, technical support and training services as required. This is backed by factory trained engineers with many years of offshore industry experience. The company also offers first line repairs to keep customers operational, and some product lines are offered from stock to help with fast mobilisations.
Principle markets for the company include land and marine survey companies, harbours, container ports, universities, Government marine institutes, fish farms, OEM system integrators, dredging contractors, superyachts, racing yachts, marine archaeology, ROV and autonomous underwater/surface vehicles, pilotage, TV outside broadcast, precision agriculture, and fellow marine equipment suppliers and rental organisations.
DeepWater Buoyancy creates subsea buoyancy products for leading companies in the oceanographic, seismic, survey, military and offshore oil & gas markets. Customers have relied on our products for over thirty-five years, from the ocean surface to depths exceeding six thousand meters.
For the next installment in our series of technical articles, Dean Steinke of Dynamic Systems Analysis Ltd., discusses the role of finite element-based simulation and visualization software in mooring design.
He demonstrates this capability with a video of the simulation showing an analysis of our three different ADCP buoy geometries – spherical, elliptical and the unique StableMoor® design.
Mooring System Numerical Modeling
“Don’t let the ocean knock you down.”
Using dynamic analysis software to assess mooring deployment, recovery, and performance in current and waves. By Dean Steinke, PEng – April 5, 2017
For many years moorings have been designed using basic mass-drag-buoyancy calculations, spreadsheets, rules-of-thumb, black magic scripts, and a dose of ‘salty-sea-dog’ experience. With these methods, we can frequently estimate a line size to use or an approximate anchor weight. But sometimes despite our experience we still have questions. This article looks at increasing the precision of mooring analyses using numerical modeling software designed for ocean engineers.
Software for single point moorings has come a long way in recent years. Finite element-based cable analysis programs have been tested and developed by oceanographic institutions and ocean engineers for various purposes (towed bodies, ROVs, moorings, etc.). However, their use has been typically limited to a few advanced numerical modelling specialists who had both the expertise and patience to wade through the complex analysis process. In recent years, increasingly-refined software has been developed. This software has benefited from increased computational power and advances in 3D graphics. We can now get a much clearer picture as to what is happening with our moorings subsurface through simulation and visualization.
The video below demonstrates an analysis carried out by my firm, Dynamic Systems Analysis Ltd, using our ProteusDS software. Based in Canada, we have cut our teeth over the last decade simulating many different types of ocean technologies, including single point moorings.
Analyzing Buoy Pitch and Knockdown in Current
The video shows four buoys of various styles (spherical, ellipsoid, and streamlined) being loaded by current. As the current ramps up to 3.6 knots, the knockdown and pitch of the buoys increase. There are two key forces at play – buoyancy and drag. The buoyancy provides a vertical restoring force that keeps the buoy from pitching. Conversely, hydrodynamic drag pitches the buoys about their mooring connection point.
A pitch of greater than 20 degrees is not recommended for ADCPs, as the inclinometers which allow for compensation of buoy pitch typically only have a range of 20 degrees. Mooring designers would try to limit ADCP buoy pitch to only a few degrees if possible. In addition to uplift and drag, buoy pitch also depends on the length of the mooring and weight of mooring equipment (chain, shackles, line, etc.).
The example shows that increased buoyancy is effective in preventing knockdown and limiting pitch, as the AF49-750 buoy has the lowest pitch and knockdown of the elliptical and spherical buoys. However, this buoy still pitches significantly at the higher currents, whereas the streamlined StableMoor® buoy, with its reduced drag and configurable connection point, is effective at maintaining low pitch and knockdown.
The ProteusDS model uses 6 degrees of freedom for the buoys (heave, sway, surge, roll, pitch, and yaw). Although this case is essentially 2D, the solver solves for the position in 3D. The effect of the attachment point and location of drag loading affect the pitch calculated by the software.
Figure 1 The ProteusDS software pre-processor is shown. This software allows users to add mooring elements such as shackles and swivels from a central library. Line types such as Amsteel Blue or wire rope can likewise be selected.
Transient Loading and Acoustic Release Damage During Mooring Deployment
One aspect not often considered by mooring designers is what happens during deployment. As shown in the video, the simulation allows for prediction of launch transients, which ensures that shackles and lines are properly selected to handle the deployment loads.
We’ve observed that acoustic releases get damaged during deployment when they are placed too close to the anchor. ProteusDS can be used to check that the acoustic release’s downward momentum will not cause it to crash into the seabed or anchor.
A few questions I’m asked from time to time are: How long will it take for the mooring to come to the surface? and, How far might the mooring drift as it comes to the surface? The mooring recovery section of the video shows how you can assess this.
In the case considered, the AF36-750 mooring rises at about 2.7 meters per second. If this mooring was deployed at 750 meters, it would take between 4 and 5 minutes to surface!
Although no current was applied in the example, current can be applied in the simulation to determine how far it might drift in the time it takes to get to the surface.
Figure 3 ProteusDS post-processing software showing rendered view of the mooring systems being tested.
Interaction of Waves with Subsurface Moorings
Much like current, waves can cause an ADCP mooring to pitch and move. The example in the video shows the impact of the subsurface orbital wave motion on the mooring line and buoy. A JONSWAP wave spectrum is simulated to check how much the buoy will pitch. Clearly, in this case, a bottom mounted ADCP frame would be preferred – but we don’t always have the equipment we need on hand. It’s good to have tools to check the impact of waves on our moorings.
DSA has carried out a series of simulations in consultation with DeepWater Buoyancy using our ProteusDS software. The software is designed to help mooring designers and builders to answer practical questions about mooring performance. Most would agree that the software’s 3D visualization capabilities shown in the video are really cool, but I believe that the real value of the software is that we don’t have to speculate what is happening subsea. We can now get a clear picture.
About Dynamic Systems Analysis Ltd.
Dynamic Systems Analysis Ltd. is an ocean engineering consultancy and software company based in Canada. DSA provides progressive and accessible dynamic analysis expertise and software to enable those working with vessels, structures, lines and technologies in harsh marine environments to reduce risk. DSA provides software and services to the aquaculture & fisheries, defence, marine renewable energy, naval architecture, ocean technology, and offshore sectors.
DeepWater Buoyancy creates subsea buoyancy products for leading companies in the oceanographic, seismic, survey, military and offshore oil & gas markets. Customers have relied on our products for over thirty years, from the ocean surface to depths exceeding six thousand meters.
DeepWater Buoyancy, Inc. has announced today that it has entered into a distribution agreement with ASL Environmental Sciences, an oceanographic products and service company located in British Columbia, Canada. ASL will act as sales representative and distributor of the DeepWater Buoyancy oceanographic product line in British Columbia and Alberta, Canada, as well as in Alaska, USA.
ASL Environmental Sciences is a world class company with more than 35 years of experience in oceanographic, acoustic, remote sensing, and ice research products and scientific consulting services. Their products include the well-known, industry standard Ice Profiler, deployed in hundreds of locations world-wide. They also provide clients with consulting services including: Flow Measurement, Numerical Modeling, Wave Measurement & Analysis, Sediment Transport and Ice Studies.
ASL is also a sales representative for Teledyne RD Instruments’ line of ADCP products in the same region. TRDI/ASL PR DeepWater Buoyancy’s reliable ADCP deployment products (former Flotation Technologies designs) have supported Teledyne ADCPs for survey and research clients around the world for decades.
DeepWater Buoyancy is exhibiting at the U. S. Hydro 2017 conference in Galveston, Texas. The conference begins on March 20th.
Please come visit us at Booth 41 and meet David Capotosto, Director of Business Development. David will be joined by Chris Kelly. Chris is from Waters and David, DeepWater Buoyancy’s Gulf Coast representative group.
DeepWater Buoyancy is exhibiting at Ocean Business 2017 in Southampton, UK. The conference is from April 4th to April 6th. Please come visit us at Booth W28 and meet Dan Cote, Sales Manager and David Capotosto, Director of Business Development.
Ocean Business is a hands-on ocean technology exhibition and training forum. Learn more here… oceanbusiness.com
DeepWater Buoyancy has acquired the rights and designs for legacy Flotation Technologies (Flotec) products. We have been building these products and serving former Flotec customers since 2013. We invite you to look around our site and contact us with your needs.