Concern has sometimes been expressed about the particular requirements of DP vessels in layup and issues involved in reactivating them, but reactivation could be an opportunity, not just a challenge
Reactivation of a dynamic positioning (DP) vessel is different to other vessels, M3 Marine’s managing director Joey Fisher told the Asian Offshore Support Journal Conference in September.
Mr Fisher, who is also on the International Marine Contractors Association’s DP Committee, said he sees reactivation of a DP vessel as an opportunity to enhance a ship’s DP capability. Much of what is ‘different’ about reactivation of a DP vessel relates to mission-specific equipment. “What does – or should – a reactivated DP vessel look like?” Mr Fisher asked delegates.
Essentially, said Mr Fisher, reactivation of a DP vessel, should return the DP equipment on board to the same condition it was in when it entered layup, in accordance with flag state and class requirements. Systems need to be checked to ensure each redundant group is single-fault tolerant. Ideally, on completion of the process, the DP system on a reactivated vessel would be in a better condition than when it entered layup.
Layup places a number of stresses on a vessel. These include chemical stresses from moisture and humidity and the potential for damage to batteries. Depending on where a vessel was laid up, security and – potentially – theft could be an issue. The hull could also experience problems due to corrosion and marine growth. Thermal mechanical stress can lead to loose wires, and it is essential to carefully assess the state of electrical contacts, circuit breakers and protective functions.
“Management of change is an issue,” Mr Fisher suggested. Moreover, whilst a vessel has been in layup, skills fade, costs increase and revenue “disappears” – all of which have the potential to adversely affect a DP system and its operators if management of change isn’t prioritised. “The negatives of layup may well lead to premature component/equipment failure,” Mr Fisher said. Mean time between failures could be adversely affected, as could the expected time to failure of a non-repairable system/component.
One way of ensuring that vessels and their DP systems remained in good condition would be to rotate them in and out of service, although this would add to costs. Another is to replace suspect/obsolete equipment as required, but should one use new or used equipment as a replacement? Is it sufficient to use other laid-up vessels as ‘live stock’? “The standard approach would be to follow the layup plan, conduct an initial layup survey and establish preservation and maintenance routines to avoid deterioration, then conduct annual layup surveys,” Mr Fisher said. When reactivation is warranted, an owner should carefully follow a reactivation plan, complete planned maintenance, check equipment change report, prove that the system is fully operational using a DP audit and trials and have statutory certificates reissued.
Reactivation, he suggests, should also be used as an opportunity to consider reliability, availability, maintainability and safety, introduce more advanced maintenance techniques and improve the design of systems whilst keeping failure modes and effects analysis and other DP-related documentation updated. It is also an opportunity to introduce additional standby redundancy (using capital spares), assess and improve reliability and improve management of change.
“Getting the manning aspect correct is vital,” Mr Fisher told the conference. “Questions that need to be asked include is the crew the same as the one that put the vessel into layup? Is this a new crew for the shipmanager? Are crew members familiar with company procedures? Is a crew competency assessment required? Is additional familiarisation training needed, and should DP trials/drills and simulation be used as learning tools too?
Overall, Mr Fisher continued, the reactivation process should be used as an opportunity to re-educate crew on company management structure and procedures and allow them to refamiliarise themselves with equipment and systems, improve skills and implement and validate an improved redundancy concept. If looking for guidance on how to manage the process, sources are classification societies, the vessel’s flag administration, original equipment suppliers, internal procedures and experience and trade associations, he concluded.