Marine library

A Thruster refers to any propulsion unit on a vessel that is not part of the main propeller system. These auxiliary units are critical for maneuvering and precise positioning, particularly in operations requiring Dynamic Positioning (DP). Thrusters come in various configurations, such as bow thrusters, stern thrusters, azimuth thrusters, and tunnel thrusters, each serving specific roles in enhancing a vessel's control and mobility.

The Taut Wire system is a position reference system (PRS) used in Dynamic Positioning (DP) operations. It employs a tensioned wire that extends from the vessel to a weighted anchor or clump on the seabed. Sensors monitor the wire’s length and angles, enabling the DP system to calculate the vessel’s precise position relative to the seabed.

Sway refers to the movement of a vessel in the transverse (side-to-side) direction, perpendicular to its longitudinal axis. It is one of the six degrees of freedom in vessel dynamics and is actively controlled by Dynamic Positioning (DP) systems to ensure precise station-keeping and operational stability.

Surge refers to the movement of a vessel in the fore-and-aft direction, aligned with its longitudinal axis. It is one of the six degrees of freedom in vessel dynamics. Unlike motions like roll or pitch, which are monitored but not controlled by Dynamic Positioning (DP) systems, surge is actively managed to maintain precise station-keeping and operational stability.

The STCW (Standards of Training, Certification, and Watchkeeping) is an international protocol established by the International Maritime Organization (IMO) to ensure uniform standards of competence and training for seafarers worldwide. Adopted in 1978 and amended in subsequent years, the STCW Convention sets minimum requirements for seafarers in various roles, enhancing safety at sea and protecting the marine environment.

SSBL (Super Short Baseline) is another term for USBL (Ultra-Short Baseline), a position reference system commonly used in Dynamic Positioning (DP) and subsea operations. It employs acoustic signals to determine the position of subsea targets relative to the vessel by measuring the distance and angle from a single transducer mounted on the hull.

A Simplex system in Dynamic Positioning (DP) refers to a non-redundant configuration that relies on a single computer to manage all DP functions. This setup is typically found on vessels where the operational and safety requirements do not mandate redundancy, such as in DP Equipment Class 1 vessels.

Settling Time refers to the period required for a Dynamic Positioning (DP) system to achieve stable and optimal performance in maintaining the vessel's position and heading after activation or a significant change in conditions. This time is influenced by the speed at which the mathematical model of the vessel and environmental conditions is built and refined by the DP system.

In Dynamic Positioning (DP) systems, the Set-Point refers to the desired value of a controlled variable, such as the vessel's position, heading, or other operational parameters. The DP system continuously adjusts the vessel’s thrusters and other control mechanisms to maintain or achieve the specified set-point, ensuring precision and stability during operations.

Sea Force is a term used by some Dynamic Positioning (DP) system manufacturers to describe the residual vector of unknown forces acting on a vessel. This term is often synonymous with “Sea Current” but highlights that the vector may encompass multiple contributing factors beyond just water movement, such as inaccuracies in sensor data, unmeasured environmental forces, or system limitations.