Dynamic Positioning: a philosophy of operation

Dynamic positioning (DP) is an automated heading and position control system. It is the key equipment needed so that the safety of men and equipment is guaranteed.

The performance of a DP vessel results from the combination of its ability to hold a position, which depends on available power among other things and on the built-in redundancy level. If one system fails, the second one takes over and the inertia of the system in question will make it possible to complete an operation safely. So, on a DP2 vessel, we find a multitude of duplicate systems, including two operating consoles and two DP monitors.

Since the International Maritime Organization (IMO) has established three redundancy classes, vessels may be DP1, DP2, or DP3. Maneuvering a nearly 100 meter-long vessel just few meters from a platform that weighs thousands of tons and can be as big as a football field requires great vigilance from the crews of supply vessels. When the weather conditions deteriorate, this type of operation becomes particularly delicate.

Instant course correction

"Being DP2 does not just mean duplicating the DP computers" says Antony Grande, DP Superintendent. "Aboard a DP2 vessel or higher, duplication and redundancy are more comprehensive and cover all systems critical to maintaining the vessel in position, such as propulsion and power generation and distribution. Redundancy affects all the systems and sub-systems that may be involved in holding the vessel in position."

Whether its used to remain in position for a cargo operation or maintaining a heading and speed for a cable laying operation, the DP system has the ability to react at any moment to information transmitted to it by sensors regarding the impact of wind on the hull, draft or an external force generated by towing, a submarine cable being installed, or an underwater pipe during a pipe-laying operation.

"If the vessel has to reposition herself during DP operations from point A to point B, or follow an ROV conducting a pipe inspection, the DP system continuously calculates the difference between the set location and the actual place where the ship is located. Then the correction is immediate. In the case of maintaining a fixed position, the principle is the same...", explains Antony.

A competitive advantage

Almost all BOURBON supply vessels are now equipped with dynamic positioning. For example, the Bourbon Liberty series, PSV and AHTS vessels, are DP2, while the IMR vessels of the Bourbon Evolution 800 series are DP3. As for FSIVs, they are mostly DP1 or DP2.

"Operations don't all require a maximum level of redundancy but the BOURBON philosophy on the subject is to maximize a vessel's capabilities and to guarantee continuity of service," continues Antony Grande. "When a ship is DP2, it therefore operates in DP2 configuration, even if the DP1 may be sufficient under recognized standards."

This is a real competitive advantage, strengthened by the standardization of the fleet, which on one hand facilitates familiarization and use of the systems that outfit BOURBON vessels for DP operators, while it also allows these same operators to work on a wide range of vessels.