DP Systems Flashcards
How many DP references or position sensor need to be online to conduct diving ops
3 independent systems of 2 different types
Describe Neap and Spring tides
Neap: sun and moon at 90 of each other
Spring: sun and moon in line
Spring tides will cause the biggest change in tides.
Describe Veering and Backing winds
Veering: Clockwise
Backing: Anti-clockwise
Max deflection of Taut wire before having to reset
15 degrees
State DP alert levels and their meaning
Green
Normal operational status
Clear to dive
Yellow/Amber flashing
Degraded operational status
Loss of 1 DP system
Red Flashing/Audible
EMERGENCY STATUS
No negotiations, divers up and out ASAP
Therapeutic deco if required.
Max thruster output allowed on DP
80% only for brief periods
State maximum vessel movements with divers in the water
Maximum 10m in steps of 5m
5 degrees
Cannot change both heading and distance at the same time.
What is the most common cause of DP incidents?
Operator Error
Max thruster output allowed on DP
80% only for brief periods
State the 5 systems of DP
Power Propulsion Control Reference Sensors
Before diving operations commence the vessel should be on DP for how long?
At least 30mins
State and explain the 3 classes of DP vessels
Class 1; Loss of position may occur from a single fault
Class 2; Loss of position should not occur from a single fault of an active component.
One redundant engine will come online automatically
Class 3; loss of position should not occur from a single point failure, including a flooded or burnt out compartment.
Two independent control rooms
Examples of DP propulsion systems are;
Thrusters
Azimuth
Tunnel thruster
Main engines
Minimum number of DP control systems online for diving operations
2 automatic, fully redundant control systems.
In the case one fails, the other will seamlessly come online and be unnoticed.
Since 3 position sensor need to be online. Is it a violation of this to re-plumb the taut wire?
It is acceptable and required to re plumb the taut wire.
This should be done as quickly and safely as possible.
Examples of position sensors are;
- Taut wire
- HPR Hydroacoustic Position Ref
- DGPS Differential Global Positioning System
- Laser Radar; ex Fan Beam or CyScan
- Artemis
- FM Radar System; ex RadScan RADius
Some possible sources of interference to HPR Transponders are;
Water Jetting
Divers Bubbles
A vessel transponder should not be placed with what distance of subsea structures?
10m
Maximum range of a fan beam laser
2,000m
It relies on line of sight. Fog and rain will reduce effectiveness
Fan beam laser head oscillates how many degrees through its arc?
20 degrees
For an artemis system there is a fixed antenna and a mobile antenna, where are each of these located?
Fixed antenna is positioned on the platform or installation.
Mobile antenna is mounted on the vessel
Which zone is more likely to contain an explosive atmosphere on the platform?
Zone 0 or Zone 2
Zone 0.
Zone0; high risk area, gas mixture present most of the time
Zone1; air and gas mixture likely to be present
Zone2; unlikely to have air or gas mixture present.
Wind speed and direction are measure by what devices?
Anemometers
2 independent anemometers in different locations are required to be online during diving ops
Vessel heading is controlled by what device?
Gyro
How many methods of communication are required from Dive Control to the DP Control Room?
2
A dedicated, hard wired system with a backup such as VHF
Joystick is an acceptable means of vessel control during dive ops?
True or False
False
In shallow water the scope of taut wires are increased?
True or False
FALSE.
The scope of a taut wire is reduced in shallow water.
The bell or basket must be at least how many meters from any mooring lines or anchors?
50m
How many meters above any subsea structure or wellhead must the bell or basket be kept?
5m above
Shallow water does not effect the use of DP systems for dive ops?
True or False
False.
Shallow water will reduce the efficiency of the DP system.
How close can a vessel approach a platform before permission from the OIM is required to come closer?
500m
What vessel classes are required for DP diving ops?
DP2 or DP3
What is the purpose of a DP system?
To maintain vessel position and heading
Minimum number of personnel required in the DP control room during diving ops?
2.
One must be fully competent in all aspects of DP without supervison
What lights are displayed at night, indicating diving operations are taking place?
Red White Red
What symbols are displayed in daylight to indicate the vessel is carrying out dive ops?
Ball Diamond Ball
Vessel heading changes will usually rotate around what location during diving ops?
The Bell or the work station
-be sure to notify divers on deck, ROV
What are the 6 main vessel movements and specify them?
Heave: up and down Sway: straight port and starboard Surge: forward and stern Roll: Rolling port and starboard Pitch: Rolling bow and stern Yaw: circular movement
Dive ops should not be conducted within what distance of seismic surveying WITHOUT contact with the survey vessel?
30km
Signage; circular, blue background with symbols in white
A) prohibition
B) warning
C) safe condition
D) mandatory
D) Mandatory
Signage; circular, red boarder and crossbar over black symbol on white background
A) warning
B) prohibition
C) mandatory
D) safe condition
B) prohibition
In conditions of reduced visibility, decisions about the suitability for diving from DP vessels should rest with who?
Diving supervisor and Captain/OIM
Single most important concern for divers exposed to LOW frequency sonar?
disorientation due to vestibular stimulation
Signage; triangle, black boarder and symbol on yellow background
A) prohibition
B) warning
C) safe condition
D) mandatory
B
Warning
