Dynamic Positioning
While the advantages of DP operations for deepwater are well documented and understood, station keeping while under DP is still a complex and evolving science. Understanding the basics of DP, the ABS Classifications for DP and the questions to ask can avoid misunderstandings and potential offshore problems.
- Comparison of different ABS Classifications for DPS
- Typical Class 0 System
- Typical Class 1 System
- Typical Class 2 System
- Nine questions to ask a vessel operator about DP
Comparison of Different ABS Classification for DPS
Click here to download this chart in PDF format.
| 1. Vessel Machinery Requirements | DPS-0 | DPS-1 | DPS-2 |
|
Thrusters/Thruster
Prime Movers Rated for Continuous Duty | Required | Required | Required |
|
Number of Bow
Thrusters Needed | 1 | 1 | 2 |
|
II.
Dynamic Positioning Equipment Requirements | |||
|
A.
Basic ABS Guidelines | |||
|
Central Control
Station w/Automatic Heading Control | Required | Required | Required |
|
Independent Control
Station w/Automatic Heading Control | Required | Required | |
|
Maintain DP Qualified
Position with Loss of any Single Point Failure | Required | ||
| Transfer of Control | Not required | Manually | Automatically |
|
B.
Environmental Sensors | |||
|
Positions referencing
Systems Needed | 1 | 2 | 3 |
| Wind Sensors | 1 | 2 | 2 |
|
Gyro Compass | 1 | 2 | 2 |
|
Vertical Reference
Unit | 0 | 1 | 2 |
|
Signal Processing | Not required | Not required | Required |
| C. Miscellaneous | |||
| Consequence Analysis and DP Alert System | Not required | Not required | Required |
| Communications between Bridge and Engine Room Control Station | 1 Means required | 1 Means required | 2 Means required |
| Power Management | Not required | Not required | Required |
| Uninterruptible Power Supply | Not required | Required | Required |
| Failure Modes and Effects Analysis (FEMA) | Not required | Not required | Required |
| Uninterruptible Power Supply | Not required | Required | Required |
Typical Dynamic Positioning System - Class 0
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Typical Dynamic Positioning System - Class 1
Click here to download schematic in PDF format.
Typical Dynamic Positioning System - Class 2
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Illustrations reproduced courtesy of Nautronix, Ltd.
Nine Questions to Ask a Vessel Operator about DP
- Ask the Operator to provide a short "break down" of the DP configuration for the vessel he proposes.
- Require the Operator to provide DP capability plots for the vessels being proposed. Plot requirements should be standard for the industry. The recommended standard should be as follows. The 1st plot should should 80% thrust, 0-50 knots wind, and 0-2 knots current. The second will show 100% thrust, 0-50 knots wind and 0-2 knots current. Both plots should be at a continuous duty rating. (If an Operator cannot provide these plots, serious consideration should be given as to the Operator's knowledge of his DP equipment and its function aboard his vessel).
- Is the DP system "classed" by a recognized classification society? If so, what is the classification and which society?
- If a DP vessel is "non-classed" as the Operator if the thrusters are continuous duty rated for the DP plots.
- Does the Operator have a written standard DP operating procedure?
- Does the Operator have a DP performance resumé for his fleet?
- Does the Operator have a minimum DP training requirement for his Marine Officers? If so, what is that requirement?
- Can he provide resumés or "CVs" for his Marine Officers?
- Are there any costs not carried in the day rate for reference systems or differential signal fees? Contractors of vessels with DP functionality need to ask about hidden costs.
Many of our vessels can be completely customized and configured to meet your needs.
If you have additional questions or more specific requirements, please contact the us at (985)727-6945 or send us an email.