October 2, 2018
It’s all about the cable!
When the SS Great Eastern laid the first successful transatlantic cables it used a drum-wheel with four turns of cable. For the cable to enter and exit at the same positions it had to be fleeted, with the coil pushed sideways by a “knife”. 150 years later and that same layout is still widely used. The engineer of the Great Eastern hadn’t invented the concept; he was vastly improving the simpler rope windlass drums, including knives, familiar to old time sailors.
The drum is still the best way to hold a cable load but the knife pushing on the side is always an undesirable high side load contact – something that wears grooves – and when objects like repeaters and joints arrive, it is a skilled task to manipulate the coils and knife so the object can pass through cleanly.
Telecoms cables have become remarkably more resilient since those days but the gentler the cable handling during deployment, the lower the risk of an in-service failure. Our ever more digital lives depend on the quality of those cables and how they are laid.
SMD has supplied linear cable engines of up to twenty wheel pairs which are, of course, knife-free – but few ships can afford the length of deck space required. Linear engines also only work on the cable sheath which can limit the ultimate grip compared to drums. SMD has also supplied plain drum tensioners with knives where that was the client preference or budget but has always looked for better solutions.
The self-fleeting challenge
In the 1980s there were several industry attempts to develop a self-fleeting cable tensioner that did not need knives, a drum where the cable would simply enter and exit in a continuous stable running spiral. One of those systems had a series of transverse conveyors. There have also been modified knife concepts like fleeting rings.
A particularly interesting concept to SMD was a stave drum, where the surface of the drum is overlaid with a number of staves almost all gently moving to fleet the cable across the surface, counteracting the natural action of the cable to wind to the side of the drum. At the same time, a small number of staves are rapidly resetting in the opposite direction – all this being driven by a cam mechanism. However, the challenges of a cam and stave mechanism that can easily slide laterally while resisting high, unbalanced, radial and circumferential loads should not be underestimated – especially when that mechanism that has to operate continuously for months at a time in a harsh environment.
SMD accepted that challenge and as a first exercise built an ROV umbilical pre-tensioner which proved the mechanism – it is still in factory service today. SMD’s engineers realised that driving the fleeting mechanism independently could deliver other cable manipulations, especially for passing objects. The experience was applied to a cable drum solution that equipped three ships in the early 2000s. The new-build cable lay vessel market went quiet for many years. Then, in 2017, recognising the improving demand for telecoms cable lay and other related applications, SMD completely re-engineered the product as a high precision production item with state-of-art variable speed drive controls.
The first pair of new cable engines was supplied to KCS (Kokusai Cable Ship Co.) in July 2018. A repeat purchase for them – they also operated first generation machines.
A Mesmerising Sight
To see a 4m diameter, 40 tonne capacity drum cable engine rotating at high speed with the horizontal staves all moving in a subtle wave motion, is mesmerising. The cable sits in a gentle spiral around the drum, rather like a standing wave, and all the while the cable is arriving and departing at speed. Couple that with a fast reacting electrical drive for constant tension control and it makes for a system that gives the cable the gentlest transition from storage tank to seabed.
Cable drums are based on the classic “capstan equation”, where the drum tension capacity TD is given by:
TD = THB eμΦ
THB = Holdback Tension
μ = friction
Φ = number of turns (in radians)
The cable friction is usually just a given. Holdback tension and number of turns are the only factors that can be practically adjusted. The initial holdback is provided by a short (4-wheel pair) linear cable engine. A 50:1 multiplication of the holdback is easy to achieve with a few turns on the drum. The linear engine, as well as providing the holdback tension, also controls the cable entry on the drum and there is an adjustable guide on the other side for running in reverse when recovering a cable.
The lay tension resistance generated by the drum is dissipated in heat somewhere (the Great Eastern had wrought iron band brakes with wooden block shoes in a water bath). The generated power, from load handling by electric drive, can potentially be fed back to the ship but due to risks of power distortion most customers prefer to dissipate it into the resistor bank as heating.
Passing Joints and Repeaters
Joints and repeaters are another area of potential risk for lay operations and cable integrity. They are large objects relative to the cable and giving them the least stress as they pass from storage tank to sea significantly reduces the risk of something going wrong, either to themselves or to the adjacent cable wraps. Ideally the joints and repeaters should pass around the drum without touching the other cable wraps.
This is something that the self-fleeting drum can do very well because the cam mechanism can operate at different speeds to the drum. This can increase or decrease the fleeting effect – the coils can be as wide or as narrow as the user desires within the limits of the drum width. Also, if the cam ring rotates at the same speed and direction as the drum, then there is no fleeting effect and the net effect is a plain drum. Using a combination of these effects and moving the linear engine can set up an ideal spacing suitable for a repeater arrival. When the repeater arrives, the drum can stop fleeting and the repeater pass around a plain drum without landing on any coils. The whole process can take place without pause to the lay.
In deep sea lift operations, the self-weight of steel ropes negates their lift capacity at depth. Aramid type fibre ropes have been seen as the answer as they have low weight in water and excellent net lift capacity even at ultra-depths. However, fibre ropes do not hold their shape when under high tension on a multi-layered winch drum. Introducing a self-fleeting cable drum tensioner may be the answer as the main rope can then be reeled on a low tension storage drum.
Analogies with the transatlantic cable lay can be a bit tenuous now. Nonetheless, it is surprising how many things they got right on those first lays. However, the wisdom of putting the cable through the least possible handling risk always remains true and self-fleeting drums can certainly help to do that.General Deck Equipment
August 8, 2018
Soil Machine Dynamics Ltd (SMD) are pleased to announce that the QTrencher 1600 and its associated deck equipment package delivered in April 2018 to Van Oord, has commenced its first job at Borkum-2 wind farm.
Van Oord’s deck equipment for the QT1600, Dig-It, included a 48Te launch and recovery system (LARS) with A-Frame, cursor docking head, umbilical winch with snatch limiter and hydraulic power unit ensuring safe and reliable deployment of the QTrencher 1600 in higher sea states.
Paul Hatchett, Managing Director SMD Deck Equipment comments, “SMD have been delivering safe and reliable launch and recovery and cable handling equipment for over 35 years, and we have used our expertise to deliver a Lloyds Register approved system to our new customer, Van Oord. We have designed this LARS to offer flexibility and ease of maintenance to our customer. The compact design means that Van Oord are not restricted on the layout of their vessel, with the system being compact enough for operation across the beam and over the stern. Together with SMD’s QTrencher 1600 Van Oord will be able to increase their operational window, working in conditions up to sea state 6.”
The deck equipment comes equipped with a state-of-the-art cursor launch system which allows high sea state deployment using the lift winch. SMD’s cursor launch system protects the vehicle’s umbilical and ensures operational loads are within safety factors at all times, even when the air weight of the vehicle exceeds the safe working load of the umbilical.
Furthermore, the integration of the snatch limiting device means the system is able to handle transitions through the splash zone, from heavy-in-air to light-in-water without transferring shock loads to the umbilical. This function prevents the umbilical from becoming overloaded, and also handles slack umbilical to prevent damage during vehicle recovery which can be caused by vessel motion in high sea states.
The QT1600, Dig-It, has commenced cable installation work which should be finished in July 2018. Once completed in 2019, the Borkum-2 offshore wind farm will deliver green energy to an equivalent of 460,000 households. The offshore wind farm is located 54 kilometres off the coast of Lower Saxony, Germany.General Deck Equipment Trenching
June 21, 2018
World leading subsea equipment designer and manufacturer Soil Machine Dynamics Ltd (SMD) are pleased to announce that their Multi-Mode Pre Lay Plough, delivered to Greek offshore contractors Assodivers Ltd in Spring this year, has successfully completed its first offshore job in the Baltic sea.
The Multi-Mode Pre Lay Plough is the newest addition to SMD’s power cable installation and protection product range. This plough has configurations for boulder clearing, trenching and backfill. The boulder clearance pass clears a 13.0m wide route including surface and submerged boulders. The trenching pass creates an engineered ‘Y’ trench profile with a secure power cable pocket for subsequent lay process. The backfill pass moves the cut spoil excluding boulders back over the product for maximum cover. All three modes have responsive and controlled steering and a fully integrated sensor suite for as built survey of performance.
Managing Director for SMD’s Subsea Business, Paul Davison comments, “I am thrilled that we have been able to deliver the plough with all three configurations. Having multiple configurations available means this one plough can be set up to carry out a campaign of route clearance and power cable installation and cover processes making it economical in both cost and time, minimising lay risk and maximising lay speed. Assodivers are the first client who have this capability in a single vehicle. We have a longstanding relationship with Assodivers, they have two of our Atom Work Class ROV systems already in their fleet and we are pleased that they trust us and our equipment.”
The equipment was mobilised on board Assodivers’ DP-2 Construction Support Vessel, the Aethra, directly from SMD’s quayside access point.
Technical Manager from Assodivers, Aggelos Tziotakis comments, “We are excited with the opportunities that have arisen from the use of a unique tool such as the multi-mode pre-lay plough; The vehicle has already performed its maiden work in the offshore fields of the Baltic with very successful results.”
Offering a full turnkey solution, SMD delivered a 20ft Control Cabin and a 60Te stabilising frame operational in up to sea state 5 via their dedicated Deck Equipment business. The team were able to integrate the 60Te stabilising frame with Assodivers’ existing A-Frame.
The scissor type stabilising frame used in conjunction with the A-Frame is designed to maintain plough orientation and reduce side to side movement during launch and recovery; fore and aft motion is restricted by the tow wire.Deck Equipment Trenching
April 23, 2018
As price pressures continue in the ROV industry, the need for operators to reduce operational costs through the adoption of new technologies is increasingly apparent.
For areas such as seabed mapping and pipeline inspection, where traditional work class ROV systems remain the preferred choice, SMD has recognised the limitations of the current technology available and developed FLO, a new high-speed Survey and Inspection ROV system, capable of delivering higher quality survey data and significant time savings in offshore operations.
Traditionally, standard work class ROVs have speed limitations due to their size, weight and hydrodynamics. They can also be unsteady operating at higher speeds.
SMD engineered FLO, a high-speed variant based on proven SMD ROV fleet technology, to perform tasks faster and more efficiently. The new system has a top speed of 6 Knots and the ability to hold position in currents up to 4 Knots from any direction. FLO also boasts 50% faster survey times compared to conventional work class ROVs and is capable of significantly extending the operational window in areas where high currents are prevalent, especially within the renewables sector.
From concept to manufacture, the new high-speed ROV by SMD, has been designed around the latest sensor payloads it would be tasked to carry in order to perform offshore, whilst also providing the most stable and acoustically quiet platform possible to gather quality survey data.
In order to provide this level of performance, FLO uses SMD’s advanced ROV drivetrain technology in a low profile hydrodynamic package less than half the height and half the weight of a typical Work Class ROV. Coupled with eight open water vectored thrusters and SMD’s advanced ROV control automation, FLO is able to accurately navigate and remain stable at high speeds while close to the seabed.
FLO can also be operated in free swimming mode for shallow water and uses a tether management system (TMS) in deeper water. Although travelling at high speed creates drag on the ROV umbilical, in water depths of 500m in free swimming mode, FLO has the power to achieve speeds greater than 4 Knots.
To ensure optimised deployment and retrieval of FLO in difficult conditions. SMD has drawn upon its’ 45 years of Deck Equipment design to offer purpose designed LARS system which incorporates innovative functions including the auto cable render and a gimballing docking head.ROVS
November 2, 2016
September 2015: Following successful completion of factory acceptance testing, we are delighted to announce the delivery of a QTrencher 1000 ROV to long standing customer KT Submarine. The relationship between SMD and KT Submarine began in 1998, with the supply of a standard cable plough, followed by the supply of a latest generation MD3XT 500kW, jetting assisted telecoms cable plough in 2012.
The combination of the MD3XT and QTrencher 1000 illustrates a significant investment for KT Submarine as they continue to expand and become a key player in the submarine telecommunications and power cable markets.
At the customer’s request, delivery of the trenching system was brought forward by one month to coincide with the early completion of the refurbishment of KT Submarine’s cable ship, Responder. The whole system including associated control, LARS and spares package was then loaded directly onto the newly refurbished vessel at A&P Tyne, which is located directly across the river from our trenching production facility. SMD staff will then work with KT Submarine at their Korean base to mobilise the trenching system on board M/V Miraero, the multi-purpose vessel that will be mainly engaged in post lay inspection and burial (PLIB) works on telecom cables, power cables and smaller O&G pipes.
The QTrencher 1000 already has a proven presence in the trenching market with two of these vehicles already delivered and in service. Positive client feedback indicates the vehicle is the first choice for post lay burial and protection of power cables.
The 2000m rated ROV embraces the latest technologies in jet trenching and ROV design with 1000hp of total installed power and up to 940hp of variable jetting power. The vehicle has been supplied with new launch and recovery equipment including telescopic docking head which will be integrated with an existing A-Frame, and a fast response winch and umbilical cable protection system.
The QTrencher 1000 is capable of trenching rigid products, power cables and telecommunication cables up to three metres in the seabed. This will enhance and improve KT Submarines’ cable maintenance capability in this competitive market and allow it to enter the post lay power cable and rigid product installation markets with its ability to handle up to 500mm product (and upgrade options for 800mm product).
Paul Davison, MD of our Trenching, Mining and Renewables division is delighted to be supplying KT Submarine again: “KT Submarine is an excellent client to work with and we are delighted to support their operations and market growth. Their success with the latest generation cable plough has shown how innovation can be used to improve performance. We look forward to a similar transformation when the 1000hp jet trenching machine operates in Asian markets.”
WD Jung, MD at KT Submarine commented: “The new QTrencher 1000 system has been bought based on reliable support given on operation of our current SMD systems, as well as the QTrencher 1000 system’s track record. This new tool will allow KT Submarine to expand its capability on subsea trenching market, substantially.”General
November 2, 2016
May 2015: SMD has recently delivered a Q-Trencher 400 telecoms vehicle to United Arab Emirates based company E-Marine. The vehicle is to be installed on the company’s new build CS Maram; E-Marine’s dedicated Submarine Cable Installation and Maintenance Vessel which is currently undertaking dock trials ahead of its maiden voyage later this year.
SMD has supplied E-Marine with the full trenching system, including control system and gantry style telescopic Launch and Recovery System, and has worked closely with E-Marine to integrate the bespoke gantry system into the state-of-the-art cable ship. The Q-Trencher vehicle is rated to 2500m water depth and, with high specification Curvetech thrusters, capable of operations up to 4.0knots.
The last cable maintenance machine of this size was delivered over a decade ago. The Q-Trencher 400 marks a new generation, equipped with SMD’s DVECS IITM vehicle control system. Based on proven industrial technology this offers both huge reliability and ease of maintenance. Operators benefit from powerful yet intuitive task based user interface which offers extensive control as well as status and diagnostics information, designed to reduce their workload such that operations can be performed with increased accuracy and reliability, driving down task based operational costs.
Established in 1984, E-Marine is the principal provider of submarine cable installation and repair solutions in the Middle East and Sub-Continent region; offering services in the field of Marine Project Management and Consultancy, Marine Route Survey, Cable Freight Management Storage and Chartering. Besides the Telecommunication field, E-Marine provides a complete range of solutions to the offshore Oil & Gas Industry. This expansion will help to strengthen E-Marine’s presence in the high growth subsea cable market, and undertake activities to satisfy demand from telecoms and energy sectors.
As a world leading manufacturer of remote intervention equipment, SMD has been building trenching ROVs for two decades. Its product portfolio includes the world’s largest range of subsea remotely operated vehicles (ROVs) such as work-class and specialist trenching vehicles; and its subsea engineering expertise results from over forty years of experience.
Paul Davison, Deputy MD responsible for SMD’s subsea trenching business commented “E-Marine already owns a number of SMD built vehicles, built over a decade ago and its returning custom is testament to our machines’ performance and reliability. We are delighted to be working with E-Marine again and hope to contribute to its continuing success”.
Omar Jassim Bin Kalban, Managing Director & Chief Executive Officer of E-marine said: “Our commitment to providing cable owners in the region with optimum solutions is significantly enhanced by the installation of the Q-Trencher 400 vehicle on CS Maram. Its ability to work closely with us to develop and install the bespoke gantry LARS made SMD the obvious choice for supply and one that we believe will help to increase our market share in the region. SMD also offers us access to its global customer support network, as well as excellent simulation and training facilities.”
November 2, 2016
February 2015: SMD are delighted to announce a contract award with KT Submarine for a QT1000 high powered cable installation and maintenance ROV.
The relationship between SMD and KT Submarine began in 1998, with the supply of a standard cable plough. This was followed by the supply of an MD3XT Plough in 2012; the latest generation 500kW jetting assisted, telecoms cable plough.
The combination of the MD3XT and this latest award illustrates a significant investment for KT Submarine as they continue to expand and become a key player in the submarine telecommunications and power cable markets.
The 2000m rated ROV embraces the latest technologies in jet trenching and ROV design with 1000hp of total installed power and 940hp of variable jetting power. The QT1000 is capable of trenching rigid products, power cables and telecommunication cables up to three metres into the seabed.
With two of these vehicles already delivered and in service the QT1000 already has a proven presence in the trenching market, and positive client feedback indicates that the vehicle is the first choice for burial and protection of power cables.
The scope of work includes integration of a telescopic docking head onto an existing A-Frame on the M/V Miraero with an option for installation on a new power cable installation vessel. The new launch and recovery equipment, including fast response winch and umbilical cable protection system will widen the M/V Miraero’s operational weather window.
The trenching ROV will be delivered in Q3 2015, with installation and sea trials planned for Korea.
Paul Davison, Deputy MD at SMD commented, “KT have been a loyal customer for SMD and we are delighted our equipment is helping their business develop and expand. We are particularly pleased to convert KT to SMD jet trenching technology and help their growth into the power cable and oil & gas installation markets in Asia.”