The industry's recognized authority for design, engineering and application of equipment and services in the global ocean community
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www.sea-technology.com July 2014 / st 11 Examples of specially designed winch solutions include underwater winches, Arctic winches, military specifcation winches and complete vessel moon pool handling systems. MacArtney also supports a full range of A-frames, integrated launch-and- recovery systems (LARS), winch ancillary prod- ucts, service programs, testing and offshore support. MacArtney specializes in electric winches and supports two primary winch ranges. The CORMAC range covers stainless steel portable and modular winches, and the MER- MAC range comprises advanced systems for ROV, subsea, oceanographic and general purpose equipment handling. One of the key features and benefts of a MERMAC winch is the combination of powerful electric winch drive and AHC. Electric AHC Winch Systems In essence, the purpose of AHC is to keep a load, held by a vessel, motionless with regard to the seabed, hereby allowing operators to sustain subsea equipment opera- tion, even during adverse weather conditions and higher sea states. AHC is enabled by using the data from a motion reference unit (MRU) to detect vessel displacement (heave, pitch and roll). A PLC control unit on the winch system then applies advanced algorithms to calculate how the winch system is to respond to and compensate for the movement. MacArtney was among the frst winch developers to pioneer AHC on electric winch systems. Electric winches are able to utilize power directly from vessel generators, whereas hydraulic winches must rely on the generation of fuid power in order to perform. Beyond being more energy effcient, easy to install, operate, maintain and signifcantly less noisy than their hydraulic counterpart, electric winches offer some clear advantages when it comes to AHC perfor- mance. While a hydraulic winch needs to spend time regu- lating cylinder oil fow to compensate for vessel movement, an electric winch system can simply drive the cable in the opposite direction at the same velocity as the wave motion, in real-time sync with MRU readings. AHC for ROV Operations Owing to this accuracy and effectiveness, electric AHC winch solutions are often preferred for ROV systems and for handling equipment that is to operate near or on the seabed. Within this context, MERMAC electric AHC winches are used extensively by major work-class ROV operators and service providers who aim to offer their clients optimal sys- tem safety and operational effciency. The following sections will offer a case-based illustration of how AHC tinuously involved in the launch and recovery of ROVs, towed systems, corers, drills, pumps, diving systems and many other equipment types under demanding conditions across the globe. While the company's winch and handling systems are among the most advanced, rugged and operator-trusted so- lutions available, the real strength of the MacArtney winch portfolio is its pedigree and heritage of underwater technol- ogy and solution expertise. With a portfolio spanning from electric wet and dry mate connectors, cables and termina- tions to telemetry, subsea fber-optics, cameras, ROVs and custom instrumentation platforms, MacArtney engineers know from experience what to demand from a winch when handling specifc equipment types under harsh marine con- ditions. Standard or Custom Winch Systems Most MacArtney winches are based on proven standard designs, and this offers many advantages to customers, in- cluding reduced delivery time, cost and spare-part stan- dardization. However, while standard winch and handling systems are suitable for most applications, certain jobs, equipment types or operational environments call for cus- tomized or even tailor-made systems. MacArtney has sup- plied a broad range of such systems and offers professional design and engineering support for all kinds of customer projects. The common denominator involves the close co- operation between winch engineers and the client to iden- tify the exact technical needs and expectations. (Top) All MERMAC AHC winches are subjected to extensive testing. (Middle) On board the RV Dorado Discovery, Odyssey will put the active heave com- pensation on their MERMAC winch to good use while operating an advanced deepwater seafoor drill for mineral ex- ploration. (Bottom) The SeaBotix CDS, complete with vLBV4000 ROV, TMS, LARS, control room and custom-engi- neered MERMAC AHC winch .