DP techniques take upward turn Down Under

The dynamic positioning (DP) sector has been growing globally but oil companies in Asia have been slow to adopt this cutting edge technology. This is largely due to exploration activities in the region being restricted to relatively shallow waters. B...
Published 11th November 2015 by

The dynamic positioning (DP) sector has been growing globally but oil companies in Asia have been slow to adopt this cutting edge technology. This is largely due to exploration activities in the region being restricted to relatively shallow waters. But as the search for oil extends into deeper oceans, Asia is now beginning to catch-up. Currently, the choice is between chartering an offshore vessel positioned by manual control or anchors and a fully fitted DP vessel. The problem being that vessels relying on anchors or securing direct to the platform combined with anchors are at greater risk of causing damage to both the drilling platform as well as pipelines and wellheads. In general, Australia is making more use of DP technology than Asia and most pipelines and subsea work is undertaken using DP barges and vessels. Much of the associated supply activities in Australia is also conducted by DP fitted vessels whereas Asia still relies, in the main, on manual control.

Vessels must be fit for purpose

Until recently, many of the DP vessels operating in Australasia had tended to be those that were considered too old to cope with the harsh conditions of the North Sea in relation to the more modern vessels. But that is changing and the region is now seeing an influx of newbuild ships. When commissioning a DP vessel, good practice begins during the construction phase at the yard. Most new DP ships for service in the Asia Pacific region are now built in China and the days of questionable quality from these yards is long past. Many vessel owners are making the mistake of relying on the yard to ensure that the newbuild is class approved with the relevant DP notation. Doing this allows the yard the choice to select the DP consultancy to undertake the Failure Mode and Effect Analysis (FMEA) of the DP systems as well as the subsequent study and trials. Unsurprisingly, this often results in the yard selecting the consultancy that quotes the lowest fee. Not all FMEAs meet approved standards and the risk for the owner is that its vessel is considered unsuitable for charter or, worse, is involved in a DP related incident. Gap analysis provided by the Marine Technology Society (MTS) has now been adopted by most large oil majors and has proven to be a good tool to identify whether an FMEA meets industry standards.

Class societies require an FMEA for DP Class 2 and 3 vessels to prove redundancy in all DP related systems; and also for the vessel to maintain position in the case of a single point failure. This means that the vessel can suffer a failure in a complete system but should still be able to maintain position with the remaining, healthy system still operational. For DP Class 3 vessels this must also incorporate a fire and flood within a compartment and/or a failure of static components.  For DP Class 1 vessels, the vessel is allowed to lose position with a single failure occurrence, but this should only be a drift off and not a drive off. In addition, Class 1 vessels do not require a full assessment of the systems and their failure modes.

 

DP Vessel William E. Bright
DP Vessel William E. Bright operting in Australia at jack-up rig ENCO 104

 

Mitigating the risk

As many oil companies see this as a risk, independent consultancies are often asked to undertake FMEA proving trials on DP Class 1 vessels and for non-DP vessels, such as support craft for FPSOs. The aim is to identify and mitigate any risk of loss of total propulsion and to ensure that there are no failures that might result in a drive off by a thruster going full ahead or astern in the case of a control failure.

There are many DP fitted vessels – such as DP anchor handling tug supply vessels (AHTS) – operating in the Asia Pacific region that seldom use their DP capability.  Despite the fact that these vessels are provided with an approved FMEA, annual DP trials are often postponed until these ships are employed on a contract that requires DP activities. This results in a DP system that has not been tested or maintained adequately. Recent findings have included back-up batteries providing the uninterrupted power supply lasting just a fraction of the required 30 minutes, and unused independent joysticks failing to operate.

To help mitigate this risk, the oil majors operating in Australia have implemented stringent vetting procedures for every vessel operating in their fields. Some have stopped chartering DP Class 1 ships altogether and others are commissioning extended tests or placing age limits on the vessels they charter.

Fully competent crews

The growing requirement for DP capable ships has placed increased pressure on the availability of competent and trained DP mariners and marine engineers. Many recent DP related incidents might have been prevented had the operator been sufficiently trained to take immediate and correct action to safeguard the vessel. In Australia, vessels are required to be manned by Australian and New Zealand nationals and many operators now have established pools of DP qualified mariners to draw on. A number even have their own DP training facilities. An issue occurs when a non-Australian operator brings a ship into Australian waters and is required to swap the existing crew for locals. This is where well established policies, familiarisation programmes and drills are vital to ensure the operations remain safe.

Dynamic positioning in the Asia Pacific region is still a little behind some of the more advanced techniques being used in Europe and the Americas but with the search for oil reaching into more inaccessible waters, Australia and Asia will not be playing catch-up for long.

This article first appeared in International Tug & OSV