Dynamic Positioning for the offshore energy industry

The Kongsberg Maritime Walk-to-Work (W2W) application optimises the operation of offshore service vessels fitted with gangways engaged in installation, commissioning, inspection, maintenance, and repair operations at wind turbines or unmanned oil/gas platforms.

W2W is suitable for operations ranging from navigation inside congested wind farms to sailing between unmanned platforms located over a large area. The application offers several methods for transit between turbines or platforms.

The locations of turbines, platforms, buoys and other critical data are stored in the Planning Station or downloaded to the DP operator station.  

The application calculates the best route between the present position and next turbine/platform or a planned sequence of turbines/platforms, accounting for all known obstructions, arrival and departure sectors, gangway locations, etc. The transits can be done automatically with All Speed Track functionality or manually with All Speed Joystick or All Speed Autopilot Mode.

The location of the turbines and/or platforms, gate or landing platform info, safety areas, local buoys, approach and departure sectors, vessel and gangway data are downloaded directly to the DP Operator Station.

The renewable offshore industry requires DP-enabled Jack-up vessels, which move into position using dynamic positioning but work on location on their jack-up "legs". The transition between DP station-keeping and leg penetration or retraction is critical, as the legs can suffer excessive stress during deployment. 

To deal with this, Kongsberg Maritime has developed a specific DP functionality in the Jack Up Mode, the Freeze-Current Function, in collaboration with several clients that is based on IMCA guidance document M 223. This function assists DP operators by providing key information to perform a stable, accurate and safe jack-up operation sequence during the touchdown phase of leg extension. 

The Riser Angle Monitoring (RAM) function optimises a vessel’s position during drilling operations. 

The Blowout Preventer (BOP) is a fixed structure on the seabed. The angle between the centre line of the BOP and a vertical line is called the BOP angle, which is measured by sensors attached to the BOP. 

There are usually at least two riser and two BOP sensors monitoring the riser difference angle. The riser difference angle at the lower flexjoint, between the riser and the centre line of the BOP, needs to be kept to a minimum, and this angle is zero when the vessel is at the Advised Riser Position. 

The RAM function computes the Advised Riser Position for the operator. The Position Advisory function uses the riser angle measurements to calculate the vessel position that will bring the Riser Difference Angle to zero. The Position Advisory function gives one zero-angle position for each interfaced and enabled angle sensor set, and a composite position which is calculated using the average of the accepted sensors. 

In case of emergency in drilling operations, it is possible to do an emergency BOP disconnect of the LMRP from the BOP quickly. 

To reduce delays in initiating emergency disconnect, the Riser Disconnect Limit functionality can be used to provide a clear indication that it is time to initiate an emergency disconnect. This function is only available together with the DP Alert application.

To disconnect the LMRP from the BOP, the angle between the LRA and the BOP should not exceed a certain value. This angle depends on water depth, vessel position compared to BOP position, and currents shaping the riser between the vessel and BOP. If a vessel’s position exceeds the riser disconnect limit, the operator is given an alert. 

DP systems offer many advantages over mooring systems for heavy-lift crane operations. However, when a heavy-lift vessel is connected to a fixed or floating object via its hoist wires, forces acting on the vessel may cause instability for a regular DP control system. 

Kongsberg Maritime has developed specific Heavy Lift functions to offset these instabilities and let a vessel conduct heavy-lift crane operations on DP, both for topside and subsea lifts. This function increases precision during heavy-lift operations and improves the user interface. Various sub-modes are available to optimise station-keeping and heading control.

Features: 

• Operational support – the K-Pos DP Control System can monitor ongoing operations using crane data (upper block position, load, and payout length), with the operator able to define a global equilibrium position. 
• Setpoint control – this function adapts the DP systems’ setpoint and rotation point for better control during heavy-lift operations. The vessel rotation centre will compensate for heel and trim as well as position. If the DP system detects heel or trim change, the system will change setpoint accordingly. 
• Heading-change limitation – this function limits the size of heading change during heavy-lift operations to avoid accidental damage to equipment. 
• Cargo on-deck compensation – the DP system compensates for wind drag forces from on-deck cargo
• Barge moored alongside – this function allows the DP model to compensate for the effect of objects connected to the hull of the vessel

Kongsberg Maritime offshore loading DP applications are specially designed to focus on safety and fuel-efficiency, backed by more than 30 years’ experience in offshore loading operations. 

Our applications are based on the weather vaning concept to have the lowest possible carbon footprint and they are fully compliant with DP 2 requirements. 

These DP applications cover all main types of offshore loading buoys. The applications are built around a basic package that meets the needs of all shuttle tankers, with additional packages for operations on different buoy types. Additional offloading buoy / terminal points for specific field location must be ordered separately.