Class will follow the Vestdavit standard

how-sea-state-is-linked-to-davit-performance

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