Class will follow the Vestdavit standard

A new voluntary certification standard covering the davits used to launch and recover workboats and tenders is in its final review with DNV GL. For Vestdavit, the new standard promises not only clarity on davit performance, but recommendations that align closely with some of the design features that we have long argued lead to safer and more efficient boat handling.

The new set of standards was circulated for comment by DNV GL in April. Its scope includes a verification process for davit materials and systems, as well as components design and fabrication. We firmly believe that the consistency that runs through the new approach will bring benefits across the industry.

In line with Vestdavit`s own thinking

The need for these standards has been brought into focus by the development of smarter, more complex davit designs, where lack of clarity on documentation can lead to incorrect use, and potentially accidents.

‘DNV GL-ST-0498 Launching Appliances for Work and Tender Boats’ observes that existing certification approaches for non-lifesaving launching appliances are “ad-hoc based on the LSA standard”. In line with Vestdavit’s own thinking, it is an approach which the class body does not believe meets market or customer requirements.

IMO acted on a known LSA hazard in 2011, tightening rules failures in on-load release hooks, with all existing ships to comply by 1st July 2019. However, the review by the European Maritime Safety Agency (EMSA) covering the period 2011-2014 reconfirms accepted industry wisdom by tracing 67% of marine casualties or incidents to human error. DNV GL-ST-0498 thus includes provision for (non-LSAs) davits that seek to reduce or eliminate errors and equipment failure by recommending solutions that are “more forgiving” of system and human single failures.

Consequently, the new standards demand redundancy in critical components, control and monitoring systems, painter arrangements, launching cradles and radio remote control systems. They also include criteria on where to position the davit on a mothership, and for winches themselves (single or dual) and release mechanisms. In addition, though, the standards move with the times by opening the way for fibre rope use in the davit fall operation, instead of insisting on wire ropes.

In line with Vestdavit’s existing range of products, the new standards also recommend inclusion of an efficient shock absorber to dampen forces on boat launch and recovery, to limit the dynamic effect caused by the interaction with the waves.

Vestdavit is also delighted to see that the standards accept the direct connection between equipment performance and different sea states; today, IMO SOLAS requirements offer only minimum handling speeds for davit lifting and lowering operations – regardless of conditions. In higher sea state, boats also need to be hoisted clear of the water quickly enough to avoid being lifted by a following wave, because of the risk posed to crew when that wave subsides, the rope is slack and the boat drops. We have consistently argued that basing operations on the sea state in which the vessel is operating is not only favourable, but essential for safe boat handling.

DNV-GL envisages evaluations being carried out of work boat davits operating in sea state 4 or above (above 2.5m wave height) to see whether they need an anti-pendulation system (docking head or boat guiding system), or lifting hook(s) onboard the craft with a lifting ring on the fall. The assessment would also consider whether offload release devices that feature an interlock should be fitted to the workboat to ensure simultaneous release of the lifting mechanism.

We applaud these developments. Those seeking guidance on Vestdavit recommendations with respect to boat lifting and lowering speeds in relation to sea states can visit www.vestdavit.no/how-sea-state-is-linked-to-davit-performance/ or  Vestdavit-print-how-sea-state-is-linked-to-davit-performance (PDF).

For further information, please contact Atle Kalve, Development Director / Naval Architect, Tel: +47 90 89 39 39; Send e-mail: atle.kalve@vestdavit.no

 

Docking head advantages seen and believed

As an aid to boat launch and recovery the davit docking head remains innovative and, with its triaxial anti-pendulation device and compact design, the head used for Vestdavit’s latest PAPH-type, single point davit for fast rescue daughter craft is certainly state-of-the-art.

However, we are also mature enough to acknowledge that as a concept, the docking head is by no means new, which makes a recent surge in interest in the equipment type all the more intriguing.

A docking head fits over a cone on the boat to ‘lock’ it steady and in the right orientation when moving between the stowed position and the ready position at the ship’s side, whether as part of the launch or recovery operation. This prevents the boat from damaging itself or the ship’s structure, or hurting the crew, without requiring the extra hands the task would otherwise take.

Docking heads since the late 1990s

Vestdavit has been offering docking heads since the late 1990s and today its PAPH-design davits accommodate loads ranging from 3-16 tons and come complete with hydraulic shock absorbers, line pullers and self-tensioning systems. To dampen swinging loads, even in rough seas, its docking head feature hydraulic actuators which compensate movements triaxially and can engage with boats at inclines of up to 30 degrees.

Originally, though, the docking head was thought to be of most use when handling was too far from the ship’s side for guiding arms to perform effectively. Until recently, its use has been largely limited to North European navies and offshore operators handling fast rescue daughter craft.

A new version of Vestdavit’s docking davit

However, our latest experience is that it is increasingly being considered by surface forces across Asia and in the Americas and tenders being issued by government agencies today frequently include such phrases as “shall include docking feature”, or similar wording.

In response to the rising demand, Vestdavit has been developing a new version of its docking davit, with the first example set to be the PLD-5000. Developed with cost efficiency firmly in mind, the 5-ton capacity Navy’s PLD-5000 unit is expected to make its debut onboard a undisclosed Coast Guard in Asia.

We have every faith that the cost-efficient PLD-5000 will meet a warm reception in the wider market.

 

 

Adventures with MissionEase

If cruise ship orders have been the icing covering an otherwise uninspiring orderbook cake, then expedition ship orders have surely been the cherry on top. More than 20 ‘adventure’ cruise ships or yachts were reckoned to be on order at the end of 2017.

Expedition cruisers may be topping up calories at a shipboard bistro or burning them off in a gym, yoga room, sauna or Jacuzzi, but the ship’s ‘entertainment’ largely revolves around getting up-close-and-personal with the wilderness. While the view from the observation decks can be stunning, that only happens when the cruiser disembarks and boards the RIBs, dinghies, kayaks, Zodiacs and waterjets with which expedition cruise ships are generally brimming.

Vestdavit TSB-2500 davits

Mostly, passengers step onto these ‘daughter’ craft from ship staircases, but getting these vessels onto the water in the first place is another matter. A typical solution from Vestdavit is to be found on the Lindblad expedition vessel Quest, where Vestdavit TSB-2500 davits deploy and recover Zodiacs and kayaks astern.

However, Vestdavit’s super-efficient MissionEase multiple-boat handling system  for hangars and mission bays adds a new option to the expedition ship mix, and it was certainly one which had visitors beating a path to the Vestdavit stand at Nor-Shipping 2017.

Mission bay

Where conventional multi-boat handling solutions on deck use deck cranes or overhead gantry cranes to transfer boats to a waiting davit for launch, MissionEase turns conventional thinking on its head: it locates the boat transfer system in the floor of the mission bay. Here, a multi-boat cradle system transfers boats from their stored position at the rear of the mission bay to a transverse rail connecting to the maintenance, preparation or launch areas, while the patented feeding system links seamlessly with dual or single-point davits on either side of the vessel.

First delivered to an offshore customer at the end of 2016, MissionEase is equally at home in the luxury passenger vessel setting, where it can stow, launch and retrieve up to 24 ribs (typically of 7-8m in length), kayaks, waterjets and similar equipment.

Norwegian shipbuilders have had significant successes in replacing their offshore vessel construction business by attracting expedition ship orders during 2017. It is also interesting to note that several of the polar cruise ship designs to emerge have featured hull shapes familiar in the offshore support vessel market.

MissionEase delivers the type of stable, dry environment that owners and operators of expedition cruise ships will surely value.

For further information please contact our Development Director/Naval Architect Atle Kalve

Safety first with hook-in-boat

Boat launches and recoveries in high sea states are among the most dangerous activities a boat’s crew are likely to encounter. Any of a nervous disposition will feel no more confident knowing that the entire davit weight relies on the performance of a single metal hook.

Unsurprisingly the hooks used to engage the lifting and lowering davit are closely regulated and need to be certified to international safety standards. However, the Safety of Life at Sea Convention is a minimum requirement and, in heavy seas when the mothership is in motion, a swinging sling-mounted hook can be a hazardous thing.

One option that has been gaining traction, and also one which is strongly favoured by Vestdavit, is the ‘hook-in-boat’ solutions. Here, the hook is a feature of the boat rather than the lifting gear, and can be attached to the (lighter weight) lifting ring and davit wire. Vestdavit believes that the solution makes sense for safety and efficiency reasons, but also that the advantages go beyond that part of the operation where the lifting wire in coupled/decoupled.

One of the riskiest things that can happen during boat lowering is for the painter line keeping the boat parallel to the ship’s hull to be released before the lifting hook. A mothership towing a boat by its lifting hook alone can lead to catastrophic consequences, depending on the sea state and the speed of the ship. If, however, both the lifting and painter hooks are in-boat rather than part of the lifting equipment, actuations can be integrated so that it is not possible to release the painter line hook first, until the crew is ready.

Hook-in-boat solutions are available in mechanical versions, where the painter hook can be unlatched using a release bar, or with electric ‘push button’ actuators, where in-boat cabling can be of lower complexity and less prone to damage than comparable crane-hook cabling.

Either way, when hook-in-boat solutions are selected, crews do not need to risk their safety by struggling to detach the crane-mounted boat hook in heavy seas, while boat release can be achieved remotely and more efficiently by fewer personnel.

Check out this short animation from our partner Henriksen Hook systems: 

Of UPS and HPUs

The hydraulic power unit (HPU) used with a davit system can feature separate or integrated power packs, while electric motors can be mounted as standard on top of the tank, or ‘submerged’ inside. In either case, the preferred solution represents a straight choice and the market is split roughly but firmly 50/50 between the options.

User preference and experience influence the market share each solution commands, but it is always worth asking how the benefits of any ship’s equipment are shared between the vessel’s operator and its shipbuilder. One owner will prefer a submerged electric motor, for example, due to the superior protection it offers the HPU against weather and corrosion. Another might conclude that, since electric motors fail without warning, a top-mounted motor offers better access for maintenance.

Decision Making

These decisions are clearly for owners, irrespective of yard of build. However, a third decision facing specifiers is closer to first principles: choosing a dedicated power unit or drawing power off the ship’s hydraulics involves a clear divergence in approach. Shipbuilders far prefer the latter but, in what is no longer a suppliers’ market, perhaps it is time for shipowners to ask themselves whether yard preferences should continue to hold sway.

Vestdavit recommends separate HPUs

In most cases, Vestdavit supplies separate HPUs to work with our davit systems and, while we don’t say it’s definitively the superior option, what we can say is that those choosing this option show a very strong preference. A standalone unit is configured to supply hydraulic power to the specific davit, and is more likely to be up and running if there’s a man overboard or if there’s a problem with the main ship, they point out.

More significantly, any ship’s hydraulic system is likely to feature sizeable pumps and, while that means plenty of power to work the system, there are several “users” fighting for the same hydraulic power from time to time. Also, there may be issues with high pressures and the risk of overload. Our recommendation is for davits to be fitted with HPUs working at pressures of around 250 bar.

Also, working in the standalone solution’s favour is that some launch operations require stealth; some of our customers need to ensure that noise levels are no more than 80 dB in the engine room, let alone anywhere else. Our customers may be keeping quiet on the benefits of the separate HPU; but as experts in safe boat handling for life, there’s no reason we should.

For more information, contact:

thomas.nordin@vestdavit.no

Comfort and constant tension

The perpetually changing sea has often brought the best out of poets, but its constant motion is of more than romantic interest. For their own safety, seafarers must move beyond SOLAS and learn to work with the elements day by day, rather than against them.

As an expert in safe boat handling for life, Vestdavit’s equipment is being deployed in harsher conditions and on ship designs of greater variety than ever before, yet the safety of boat lifting and lowering operations cannot be compromised.

Ensure personnel safety at sea

A slack hoisting wire caused by the wave uplift of a boat being prepared for hoist, for example, represents a hazard for personnel and equipment on board. Again, personnel being transferred on and off ship have no appetite for swings, sways or jolts to be part of their daily routine.

It is for both safety and crew welfare reasons, then, that we are increasingly being asked to deliver davits that include Vestdavit’s innovative wave-compensation solution, achieved via our constant-tensioning system.

Constant-tensioning system – How does it work?

The self-tensioning system can only be active when a boat is waterborne where it is activated by the operator using a straightforward push-button, then joystick controlled to pull the boat towards windward and bring tension into the wire. With tension in the wires, the boat can rise and fall with the waves, up to a maximum applied tension pull of up to one third of the davit’s safe working load (minimum tension pull app. 300 kg). The operator can then judge the best time to hoist, which will be at that moment when the dynamic forces and the pickup force are as low as possible. In general, Vestdavit does not envisage using the self-tensioning system in the boat launching mode.

Preference for the solution is a result of customers seeking wider operational windows and greater scope of duty for the boats being handled in harsh conditions, while also satisfying the need to maintain the highest possible safety standards. If the self-tension function were to be actuated before the boat reached the sea, an override would kick in to disable its operation.

Innovative solutions designed for optimum performance

The self-tensioning principle may not be new, but Vestdavit is unique among boat handling specialists in the way it continues to refine its innovative solution. Most recently, we have improved the system by building more features into the winch block, reducing the amount of piping, and the number of valves so that Vestdavit’s self-tensioning solution is more reliable and robust with less maintenance requirement. Today, we recommend wave compensation at all times where crew safety and comfort are prerequisites, and the Vestdavit system is designed for optimum performance up to sea state 6.

For more information contact:

per.christian.mogster@vestdavit.no

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