![]() ![]() Besides a 40-foot mid-body extension, the conversion added a Kongsberg-Simrad DP system and two Thrustmaster 500 retractable combination thrusters, one in the bow and one in the stern skeg between the two shaft lines. The 218-foot Elkhorn River started out as a 178-foot twin-screw OSV. Often a vessel is completely renovated while the DP system is installed. The heart of the Thrustmaster system comprises deck-mounted, over-the-side thrusters with deck-mounted self-contained power units, a DP sensor suite, and all the interconnecting cables and interfaces. A packaged system using pre-engineered modules can convert an older OSV or barge to a vessel able to command the day rates that are normally reserved for far newer DP-equipped vessels. However, there is another way, according to Thrustmaster of Texas, a manufacturer based in Houston. The installation of a DP system normally would require extensive design work and time-consuming dry-docking. Many of them can be upgraded at a fraction of the cost of vessel replacement.ĭP systems typically use azimuthing thrusters with either variable-speed, fixed-pitch propellers or fixed-speed, controllable-pitch propellers. (Photo courtesy Gulf Craft)ĭP has become so important that existing vessels are being retrofitted with DP systems. The laser head of an MDL Fanbeam target-positioning system aboard the crew boat Joyce McCall. As a general rule, crew/supply vessels and shelf supply boats use DP1 systems, while deep-water supply vessels 220 feet and longer and construction ships equipped with moonpools and ROVs have DP2 systems. DP3 systems have the most redundancy and are reserved primarily for drilling rigs. The basic difference is system redundancy. Inputs to the system come from wind sensors, gyrocompasses and special devices such as vertical reference units.ĭP systems are rated DP0, DP1, DP2 and DP3. In a DP system, a computer coordinates the main engines, bow thrusters, rudders and propellers to keep the vessel in position. ![]() Many of these rigs lease for $500,000 a day or more. A collision or even a slight bump might invite disaster by moving the drilling vessel off station, causing considerable equipment damage and lost drilling time. While drilling, these rigs must stay directly over a precise spot on the seabed. The main reason is that oil companies, contract drillers and other owner/operators of drilling rigs and platforms insist that any vessel coming in close contact with their structures must have DP systems.ĭP is especially important for vessels approaching drilling rigs. Once used only on the largest offshore vessels working in the deepest parts of the Gulf of Mexico, these systems are now standard on smaller OSV vessels. (Photo courtesy Gulf Craft)ĭynamic positioning may be the most important shipboard navigation system since the compass. Manufactured by Kongsberg, the RADius system uses radar technology for close-in positioning situations in which GPS signals may not be accurate. A RADius 1000 distance-measuring transmitter on Seacor’s John G. ![]()
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