DP AND CLASS 2 RULES
Dynamic Positioning (DP) is a computer-controlled system to automatically maintain a vessel’s position and heading by using its own propellers and thrusters. Acoustic position reference sensors, combined with wind sensors, motion sensors and gyrocompasses, provide information to the computer pertaining to the vessel’s position and the magnitude and direction of environmental forces affecting its position.
The International Maritime Organisation (IMO) categorises vessels into different classes depending on the type and duties it will be carrying out. A Class 2-equipped DP vessel has redundancy so that no single fault in an active system will cause the system to fail. Examples of DP Class 2 vessels operating with the offshore oil and gas sector include; survey vessels, ROV suport vessel, cable lay and repair vessel and rock dumper
External factors have always driven companies to look for ways to increase the efficiency of vessel operations. Choosing the right Ultra-Short Baseline (USBL) position reference (sometimes known as HPR) will deliver efficiency savings for both the owner and contracting oil company by reducing the number of seabed transponders, reducing overall system maintenance requirements and employing the vessel’s acoustic reference system to perform survey, construction and monitoring tasks as well as DP.
Extending DP performance
It is important that efficiency savings are delivered without compromising the integrity of the DP reference. Wideband digital technology delivers the highest possible accuracy and reliability but easy to use software is equally important so that DP operators can make full use of its potential. All USBL systems need to be precisely corrected for vessel pitch and roll in order to provide accurate position. A high performance, combined gyro / MRU can be a cost effective way of extending USBL accuracy into deeper water, especially when the calibration can be verified offshore with the sensor still installed on the vessel.
Operationally, it is important to choose a USBL that is compatible with subsea survey, construction and ROV operations as well as considering requirements for DP. Compatibility with our subsea equipment that is used in 95% of deepwater projects is an important consideration.