LODIC
Trim, stability and ballast advisory program package for rigs
Figure 1. Geometry model of a semisubmersible rig |
LODIC may be used for daily trim and stability control as well as for planning of ballasting operations and simulator training. The program package is developed in close co-operation with rig operators. LODIC is approved by the Norwegian Maritime Directorate.
Computerised trim and stability control
Continuous trim and stability control is required in the operation of floating rigs. Stability has normally been controlled manually, - a time consuming process where errors are likely to occur.
LODIC advantages:
- Easy to use, fast and reliable
- Increased safety
- Weight accounting
- Assistance to operator during ballasting
- Simulation of damaged conditions
- Printer documentation
- Updating of previous conditions
- Storing of generated loading conditions
System description
The information describing each unit is loaded into the computer before installation. Thus, the stability and ballast advisory programs can be used on board platforms or drilling rigs of any type.
No formal EDP-knowledge is required of the operator. Man-machine communication is via display and keyboard. Considerable effort has been done to ease the operator’s work. One example of this is that the computer makes all checks against rule requirements.
Weight accounting
In addition to total lists of all weights on board, LODIC may sum up weight groups, for instance: Ballast water, fuel oil, potable water, drillwater, total barite, bentonite, cement, drillfloor loads, main deck loads, anchors and chains, drilling pipes on board etc.
System requirements
LODIC is a fast system, which exploits the computational power of a 32-bit processor. Minimum requirements are:
Updating of previous condition
In order to check trim and stability, the operator can update stored loading condition from yesterday.
Planning of ballasting operations
When specifying a new wanted draft, trim and heel, the system recommends a ballasting procedure, which is based on minimum internal transfer of ballast water. The ballast tanks in use are according to own set-up. This means that if one of the tanks is not in use due to maintenance etc., the system will still be able to perform the calculations. Furthermore, the ballasting procedure may be established with focus on maximum stability if wanted. A future version of the system will include recommended ballasting sequences according to accessible pump and pipe configuration.
Simulation of damaged condition
Different damaged conditions and the consequent behaviour of the rig can be simulated with LODIC. Together with the module for planning of ballasting, the system can recommend a new upright condition, and how to achieve this new condition.
Simulator training on shore
In addition to the daily use on board rigs, LODIC is well suited for training on shore. New crews can be given valuable insight into ballasting procedures, heavy lift operations, and in training how to handle a rig in damaged conditions.
Printer documentation
A complete documentation of loading condition, trim and stability data, as well as ballasting procedures and damaged conditions may be printed out.
Depending on type of printer, graphic presentation of calculated results can be incorporated.
Service program
Six service functions are included in the LODIC package:
- definition of new light ship weight
- definition of length and weight of replacement anchors and anchor chains/wire
- redefinition of item identification text
- change of item’s capacity
- change of item’s specific gravity or unit weight
- change of specific gravity of sea and mud
The use of these functions is limited to authorised operators.
Figure 2. Screen image for loading condition input.
User interface
Fig. 2 shows the image used to establish the loading condition. The very same image is used throughout the entire input process. On the upper left side, the different item groups are listed, the active one being Mooring. The main part of the image shows a list of the items connected to Mooring, with the different fields for input made available, such as Chain Out, Wire Out and Tension. In the lower part, equilibrium data including stability control is shown, automatically being updated.
Further use of LODIC
On-line connections to ullage and chain tension measurements make continuous stability surveillance possible. Instrumentation for measuring drafts and metacentric height (GM) may also be connected to LODIC to check the calculated equilibrium condition and the stability. If needed, MARINTEK may implement further functionality based on hydrodynamic calculations related to mooring, station keeping, and crane operations.
LODIC is developed at MARINTEK, - marketing and sale is handled by LODIC a.s
Contact: 