DP Operator Manual
Based on IMO circular 645
Equipment Classes
1) A single fault can result in position loss
2) Failure of a single active component should not cause
position loss.Also static components where protection or reliability not
documented.
3) Failure of no component, static or active should cause
position loss.Loss of any single watertight or fire subdivision considered failure.
An act of mal operation is a single failure if it is reasonably probable.
Operational Classes (not IMO)
1) Where loss of position may cause damage or pollution of small consequence.
2) Where loss of position may cause personal injury with large economic
consequence.
3) Where loss of position may cause fatal accidents, pollution, or damage with
major economic consequences.
Power
Have adequate response time
Class 2 and 3 have redundancy
Class 3 redundant by space
Power management system should also be redundant
DP Control
Set up with good view of vessel and surrounds
Display power, thrusters, and DP control so function can be checked
Based on an ergonomic design for ease of operation, selection of mode, and mode to be
displayed
No single act of mal operation to cause a critical condition in 2 or 3.
Thrusters
To prove adequate thrust for surge, sway, yaw
To be set up so that after failure still have control in class 2, and 3
Forces used in consequence analysis allow for interaction
Thruster system failure in pitch azimuth speed should not fail to uncontrolled full pitch
and speed
Computers
Class one need not be redundant
Class 2
At least 2 independent computer systems common facilities should not cause a failure of both
Class 3
2 independent systems with self checking and alignment common facilities should not cause
failure of both
A back up computer that is Updated, with manual change over, failure of main should not
affect backup separated by A60 bulkhead.
Redundant computers have an automatic transfer that is as smooth as possible
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Computers (contd)
Have a Ups for each computer system
Class 2 and 3 to have consequence analysis continuously verifies remaining thrusters can
provide same resultant after worst case
Give an alarm if this is not the case
Operations that take a long time to safely terminate should simulate thrust power remaining
after worst case, based on weather input
(not in existence to our knowledge)
PRS
Class 2 and 3 to have at least 3 PRS, simultaneously available
Where 2 or more PRS required, they should not all work on the same principle, and
They should be suitable for and accurate enough for intended ops, bearing mind deployment
and expected performance
Provide warning, if PRS incorrect, or substantially degraded
Class 3, one PRS connected directly to backup and behind A60 bulkhead
Vessel Sensors
Measure at least heading, motions, wind direction and speed
When class 2 and 3 is fully dependent on correct sensor readings, then 3 systems should be
installed
(many class 2 systems have only 2)
Sensors should be set up independently so that failure of one does not affect others
One of each type of sensor should be connected to the class 3 back up, and be behind an A60
bulkhead.
DP Control
Alarms should audible and visual, also a permanent record kept
Failure in one system should not be transferred to another
A failed redundant item should be isolated, and the other component started
Manual thruster control by joystick, and levers should be possible
Software should be approved by Administration.
Cables and Piping
Class 2, should be located with due regard to fire hazards, and mechanical damage
Class 3, cables or pipes for redundant systems should not be routed together.
If unavoidable they could routed through A60 ducts cable connection boxes not allowed
The only fire hazard would be from the cables or the pipes themselves.
Operations
Systems should be checked
Prior to use
At regular intervals during use
Have checklists and procedures for new location
Regular checks (watch keeping)
Annual tests and procedures
Initial and periodical (5 year) test and procedures
Examples of tests and procedures after mods and non conformities
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Operations (contd)
Should be stopped if Environmental conditions such that vessel would not survive worst case
Consequence analysis should warn in 2 and 3
Allowance should be made for time to stop ops and the rate of deterioration of weather (IMO
not specific if auto or operator)
Class 1 should assess operational limits using Environmental envelopes (capability plots)
Systems
Designed to meet IMO guidelines
Do not necessarily follow exactly
Button pushes
Consequence analysis
3 gyros
Not covered FMEA
Systems
Kongsberg Alstom
SDP 11 and 12 ADP 11 and 12
SDP 21 and 22 ADP 21 and 22
SDP 31 and 32 ADP 31 and 32
Diagram
3 ANEMOMETERS 3 VRUS 3 GYROS 3 PRINTERS PME 1 PME 2 PME 3
* * * * *
printer printer printer
DP C - OPTIONAL SLAVE
DP A DP B DP C
A60
Bulkhead
* 3 UPS
PLC PLC PLC PLC
DP NETWORK
DUAL FIBRE FIELDBUS NETWORK
* Dependent on classifiation society required.
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DET NORSKE VERITAS
EXTRACT FROM RULES FOR CLASSIFICATION OF MOBILE OFFSHORE
UNITS PART 6 CHAPTER 7 DYNAMIC POSITIONING SYSTEMSJULY 1989
101 Systems for dynamic positioning of vessels are divided into five (5) groups
dependent on DP-system layout:
Group T A semi-automatic position keeping system without redundancy.
Group AUTS An automatic position keeping system without redundancy.
Group AUT An automatic position keeping system, with a remote thrust
control back-up and a position reference back-up.
Group AUTR An automatic position keeping system with redundancy in
technical design.
Group AUTRO An automatic position keeping system with redundancy in
technical design and physical arrangement.
Note: The Norwegian Maritime Directorate has adopted an equivalent structure in
NMD Guidelines on Positioning Systems for Mobile Offshore Units with the
following correlation to these Rules:
DYNPOS T not applicable
DYNPOS AUTS NMD Class 0
DYNPOS AUT NMD Class 1
DYNPOS AUTR NMD Class 2
DYNPOS AUTRO NMD Class 3
100 General
101 The requirements for system arrangement for the different notations T,
AUTS, AUT, AUTR, and AUTRO are summarized in Table E1.
Subsystem or component Minimum requirements for group designations
T AUTS AUT AUTR AUTRO
Power Generators and prime Non- Non- Non- Redundant Redundant separate
system movers redundant redundant redundant compartments
Main switchboard 1 1 1 1 with bus- 2 with normally open
tie bus-ties in separate
compartments
Bus-tie breaker 0 0 0 1 2
Distribution system Non- Non- Non- Redundant Redundant, through
redundant redundant redundant separate
compartments
Power management No No No Yes Yes
Thrusters Arrangement of Non- Non- Non- Redundant Redundant, in
thrusters redundant redundant redundant separate
compartments
Control Auto control; no. of 0 1 1 2 2 + 1 in alternate con-
computer systems trol station
Manual control; Yes No Yes Yes Yes
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joystick with auto
heading
Single levers for each Yes Yes Yes Yes Yes
thrusters
Sensors Pos. ref. systems 0 1 2 3 3 whereof 1 in
alternate control
station
External Wind 0 1 1 2 2 Whereof 1
sensors VRS 0 1 1 2 2 in alternate
Gyro com- 1 1 1 2 3 control
pass station
Other nec- n.a. 1 1 2 2
essary
sensors
UPS 0 0 1 1 1+1 in separate
compartment
Alternate control station for back- No No No No Yes
up unit.
Table E1 System arrangement
SECTION 3 CONTROLLER AND MEASURING SYSTEM
A. System arrangement.
B. Measuring system.
B 100 Position reference systems.
103 Position reference systems are to provide measurements with
adequate repetition rate. See 104.
104 Systems that only produce new position data with long intervals
relative to the response time of DP-vessels, will be accepted as auxiliary
systems but will not count as a position reference as required in Sec. 2,
Table E1.
105 Position reference systems are to provide position data with adequate
accuracy with respect to the intended DP-operations.
Note: The accuracy of the position reference data is generally to be within
a radius of 2% of water depth for bottom based systems, and within a
radius of 3m for surface-based systems.
SECTION 4 THRUSTERS
SECTION 5 POWER SYSTEMS
SECTION 6 ENVIRONMENTAL REGULARITY NUMBERS, ERN
A. Concept description (Excerpt)
A 100 General
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101 Each Class Notation DYNPOS is to be associated with a rating
according to the concept of the Environmental Regularity Numbers,
hereafter called ERN, which is to indicate the position keeping ability of the
vessel.
The ERN represents the static balance of environmental forces and
thruster output.
ERN is quantified with basis in the weather statistics of a chosen location in
the North Sea, the location of the weathership M.
102 The environmental forces caused by wind, waves, and current are to
be calculated by recognized methods. Ref. MOU Rules Pt.3 Ch.1.
Alternatively, environmental forces established by model testing will be
considered.
A capability plot
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Example of the D.P. classes under various bodies.
IMO Equipment Class 1 2 3
DNV AUT AUTR AUTRO
Class notations LR DP (AM) DP (AA) DP (AAA)
ABS DPS-1 DPS-2 DPS-30
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