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
November 3, 2016
September 2016: Shanghai Salvage Company (also known as China Offshore Engineering Shanghai, Co), a state owned entity who have a long history in diving and salvage have signed an order with SMD for a Quasar MKII 6000m remotely operated vehicle (ROV). Scheduled for delivery in the first half of 2017, the system will include a full suite of equipment suitable for both deep sea salvage and oil and gas operations.
“We are delighted that Shanghai Salvage have chosen SMD as their ROV equipment supplier,” said Mark Collins, Managing Director of SMD ROV Systems. “This system includes some new innovations in ROV modularity that will enable the client to operate across a wider range of markets, maximising revenue potential from their SMD asset. We believe that modular systems, which can be quickly optimised for a particular operation, will become important as clients continue to seek reductions in their operating costs. SMD’s ability to offer innovative products coupled with a strong global service network will support Shanghai Salvage as they expand.”
The ROV is a deep water version of SMD’s standard Quasar which has an extensive track record across various industry sectors. It will be one of the most powerful and capable systems to operate down to 6000m.
Deck equipment for the project, which will be designed and manufactured by SMD, includes a dual use 3000m/6000m winch and two cursor launch and recovery systems, one of which will be hanger mounted, the other mobile. The umbilical winches will be electrically driven with an axial fleeting configuration and active heave compensation, and provide the ability for interchangeable drums to accommodate steel wire armoured and aramid umbilical.
SMD’s deck equipment capability has been developed and refined over decades of experience. Leading the deck equipment business, Paul Hatchett explains “SMD has a long track record of designing and building more than four hundred systems with highly capable deck equipment for a broad range of subsea vehicle and cable handling applications. By holding this experience and capability within a dedicated unit in SMD we offer operators such as Shanghai Salvage a reliable and bespoke solution, which is seamlessly integrated with the subsea vehicle system.”General ROVS
November 3, 2016
April 2016: SMD have acquired a Heavy Duty Multi-Depth Plough HD-200 which is now available for sale or lease. This is one of the first offerings of SMD’s new Services division which is focused on making it easier for customers to purchase, own, maintain, upgrade and repurpose SMD assets.
The HD-200 is a 1500m rated plough with 300kW jetting, surface control system and umbilical winch, cable and spares.
The equipment was delivered in 2013 and put immediately into service, completing a long ploughing campaign on the Polar Prince, at the Gwynt y MÙr wind farm for RWE Innogy. The equipment was then de-mobilised in early 2015 and is currently at SMD Works in Wallsend, UK.
The asset has understandable wear to the ground engaging parts. The control system, umbilical winch and cable are in excellent condition. The plough is available in its original configuration needing only minor refurbishment for as-new condition.
Options are available to re-purpose the plough for suitability to the submarine telecommunication cable market, and also for protection of medium to large size power cables. Support from SMD is experienced six man operating crew is also available.
The equipment will be supplied after a full workshop test program and with SMD is Original Equipment Manufacturers warranty. A full spares package is included.
The equipment is available for outright purchase, or for lease with an option for outright purchase, and is available ex-works Newcastle upon Tyne, UK.
Re-purpose options have a delivery time 12 to 26 weeks depending on final specifications. Lead time on the refurbishment only option is 6 weeks.General
November 3, 2016
September 2015: Over the last year we have developed a new training course aimed directly at experienced freelance ROV technicians who want to broaden their portfolio of work class ROV skills. The course provides delegates with in-depth knowledge which can be applied to over 150 SMD ROV systems which are in the field.
Traditionally, SMD training has been aimed at corporate customers, who typically send staff to gain a better insight into their newly purchased vehicle. With requests from freelance personnel for training on SMD systems indicating a demand in the market for freelance personnel with the correct skillset we have decided to extend our world class offering beyond this market.
While this course provides an opportunity for freelance ROV pilots to gain expert training direct from the OEM, it will also allow SMD customers to identify potential freelance contractors with the relevant skills and experience required to operate their SMD ROV systems.
The new seven-day course has been carefully developed to provide training on the key elements comprising an SMD WROV system. This includes the operation and maintenance of control and electrical systems, and high voltage and hydraulics circuits across all SMD ROV systems.
Greg Brown is the Head of Training at SMD “We are hearing from the market that in these challenging times, opportunities will arise for technicians with the right skillset. Investing in training now will give two benefits: it will be a positive addition to their CV and put them in a strong position when market demand for technicians picks up.”
The first course was completed last week, with attendees travelling from as far as Australia looking to develop and broaden their skillset. The typical attendee for this course has worked in the offshore business on other ROV systems but has little or limited knowledge of SMD ROV systems.
Feedback from the first course was very positive with all delegates agreeing that they would recommend the course to others. Freelance ROV Supervisor Steve Bostock described the course as “…a valuable course delivered well by a knowledgeable instructor.”, while freelance ROV engineer Daniel Rainbow said “…a lot of what I have learned will help me offshore, minimising down-time.”
Two more seven day courses are already scheduled to start on 19th October 2015 and 30th November 2015 at SMD’s dedicated training facility in Wallsend, Newcastle upon Tyne.General
November 2, 2016
September 2015: SMD are pleased to announce that they are set to contribute to a major offshore wind research project lead by The University of Dundee. The project will look to determine whether cheaper, more environmentally friendly and more effective foundations can be developed for the offshore renewables industry.
The project, funded by a £1million grant from the Engineering and Physical Sciences Research Council, will look at the use of screw piles for offshore installations. These are foundations which are screwed into the ground and currently widely used onshore, for example, to support motorway signs and gantries.
Currently, the main foundation solutions being considered for offshore wind installations are driven piles, large monopiles or concrete gravity-based structures (GBS). Driving of piles in large numbers offshore causes concerns over plant availability and impact on mariScrew fas e mammals. There are also concerns over the limit of practical monopile development and the high material demands of GBS. Screw piles have the potential to overcome these issues and are scalable for future development from current onshore systems which have relatively low noise installation and are efficient in terms of both tensile and compressive capacity.
The research has the potential to make it easier to deploy screw pile foundations for offshore renewables. This project will develop foundations able to deal with current water depths and will provide understanding of the behaviour of piles as water depths and the demands on the foundations increase.
“The UK has challenging targets for expansion of energy from renewables with the potential for over 5000 offshore wind turbines by 2020,” said Dr Mike Brown, Senior Lecturer in Civil Engineering at the University of Dundee who is leading the project.
“The necessary move to deeper water will increase cost and put greater demands on subsea structures and foundations. There is already cost pressure on the offshore sector as people wait to see if it can be made more affordable, so we really need to find better solutions for how we develop capacity.
“Screw piles are potentially very attractive as a lower cost and more environmentally friendly option. However, there are significant challenges to be addressed. If we are to develop them for offshore use they will likely be larger than those used onshore, and face different pressures, so our work will look at whether they can meet the performance and efficiency issues.
“By harnessing the installation and performance benefits of screw pile/anchor technology, the results of the project will hopefully contribute to an overall cost reduction in electricity generated by renewable means and increase the public’s confidence in the future viability of this energy source,” said Dr Brown.
“We have a long-history of supporting industrial academic partnerships, said SMD’s Ian Bryan, Business Development Manager for their Trenching, Mining and Renewables business unit. “Much of intellectual property and many of our product features originate from research, and our customers benefit from the insights these bring into design of efficient and effective solutions. When compared to piling, screw piles offers significant potential benefits such as a reduction in noise during installation and lower costs. We look forward to developing an understanding of how this well proven approach can be adapted at scale for use in the construction of offshore wind farms, and to passing the associated benefits on to our customers.”
The project will also include contributions from the Universities of Durham and Southampton and also private sector partners Cathie Associates Ltd, Screwfast Foundations Ltd, and SeaRoc Group.General