Dynamic Positioning: How it works and why the Offshore Industry needs it

What is the difference between “DP 1” and “DP 2,” and which challenges is the industry facing due to dynamic positioning systems? This article will try to answer these questions and will explain why DP is of utmost importance for the offshore industry.

The article is based on the presentation of the Managing Director of E.R. Offshore, given at the 37th ISF Conference at the Flensburg University of Applied Science, Germany (Conference on Vessel Operations Research).

What is Dynamic Positioning (DP)?

DP stands for dynamic positioning and is a vessel system, including different equipment and software, that enables the ship to hold its position even in stormy weather. DP systems are used especially in the offshore industry and by scientific research vessels. Traders and merchants do not really use such advances, which would involve high costs.

The possibility of holding a position to within a centimeter is what, e.g., support and services ships in the offshore industry need, as they may have to navigate dangerously close to rigs. Any collision between a vessel and an offshore platform is likely to end in a human and environmental disaster, disrupting production output and hurting market prices. The past shows that major offshore accidents lead to loss of reputation for the parties involved and to tightened regulations for the offshore industry.

Without DP, it is almost impossible not to kill divers hanging 80 meters below the ship. When a ship moves 4 meters, a diver 80 meters below would be dragged through the water, continuously swinging and thus being killed by the force or being smashed against the rig.

About DP 1 and DP 0 and why everything is complicated

Of course, systems of such importance are governed by certain regulations. Even when classes and IMO have a certain influence, the basis for all contracts and regulation is the I.M.C.A. (International Marine Contractor Association). These guidelines are almost 17 years old and will be renewed soon.

“IMCA helps its members to share information on potential hazards at the worksite and lessons learnt from follow-up investigations and, thereby, to avoid repeat occurrences elsewhere in the industry.” imca-int.com

However, how can a trade organization have more influence on safety regulations than a class? Well, the answer lies within the failure of the classes to agree on a common standard. The American Bureau of Shipping for example uses “DP 0” while other classes start with DP 1 and ask for different requirements. As contractors in the offshore industry need reliable standards, the parties agreed on IMCA. Using it as basis (minimum) for their own service contracts, e.g. with E.R. Offshore GmbH & Co. Kg.

How Dynamic Positioning is working

The dynamic positioning system consists of the DP navigation software and a terminal, which are installed on the bridge. Furthermore, there is technical equipment, like the switchgear, thrusters, tunnel thrusters, special propellers, and the automation.

Vessels that are DP enabled are called “DP 1” by most classes, but what happens when the system has a failure? If the ship is using DP to maneuver close to an offshore platform, a fatal accident is likely. Knowing that there are as many service ships using DP as trade ships without DP, the sheer number speaks for the likelihood of a fatal event.

To avoid a disaster caused by a single point of failure (e.g. a switchgear malfunction), vessels started to run redundant systems so they would be able to operate even when one system completely fails. Therefore, it is necessary to build ships that have two separated engine rooms, two switchgears, several tunnel thrusters, etc. As a logical consequence, the ship becomes bigger compared to a ship without DP 2 and the engine power is divided between two engines.

Service ships often stay months at sea before they return to harbor. Using two engines may allow avoiding a disaster but also doubles the maintenance needs and the likelihood of a malfunction. Additionally when one engine, or any other critical area, shuts down, the ship loses 50% of its operational power and would have to return to the harbor. To avoid problems, most shipping companies rely on sophisticated planned maintenance software such as CODie ISMAN. To assure a DP 2 vessel can continue to operate, they are built today with three or more complete redundant systems – as required by owners.

Learn Details: Guidelines for The Design and Operation of Dynamically Positioned Vessels (PDF, IMCA)

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