ABS_Dynamic_Positioning_System

PART

4

CHAPTER SECTION

3 Propulsion and Maneuvering Machinery 5 Thrusters and Dynamic Positioning Systems

1

1.1

General

Application

The provisions of this section apply to maneuvering thrusters not intended to assist in propulsion, and to azimuthal and non-azimuthal thrusters intended for propulsion, maneuvering or dynamic positioning, or a combination of these duties.

Maneuvering thrusters intended to assist maneuvering and dynamic positioning thrusters, where fitted, may, at the request of the owners, be certified in accordance with the provisions of this section. In such cases, appropriate class notations, as indicated in 4-3-5/1.3, will be assigned upon verification of compliance with corresponding provisions of this section.

Thrusters intended for propulsion with or without combined duties for assisting in maneuvering or dynamic positioning are to comply with appropriate provisions of this section in association with other relevant provisions of Part 4, Chapter 3.

Thruster types not provided for in this section, such as cycloidal propellers, pump or water-jet type thrusters, will be considered, based on the manufacturer’s submittal on design and engineering analyses.

1.3 Class Notations

1.3.1 APS Notation

Self-propelled vessels, where fitted with thrusters capable of producing thrusts primarily in the athwartship direction and intended to assist in maneuvering the vessel, at the discretion of the owners, may comply with the provisions of 4-3-5/1 through 4-3-5/13 of this section. And upon verification of compliance, the class notation APS (athwartship thruster) may be assigned. 1.3.2 PAS Notation

Non-self-propelled vessels, where fitted with thrusters to assist in the maneuvering or propelling while under tow, at the discretion of the owners, may comply with the provisions of 4-3-5/1 through 4-3-5/13 of this section; and upon verification of compliance, the class notation PAS (propulsion assist) may be assigned. 1.3.3 DPS-0, -1, -2 & -3 Notations

Self-propelled or non-self-propelled vessels, where fitted with a system of thrusters, positioning instruments and control systems to enable the vessel to maintain position at sea without external aid, at the discretion of the owners, may comply with 4-3-5/1 through 4-3-5/15 of this section. Upon request by the owner and upon verification of compliance with the applicable requirements, the class notation DPS (dynamic positioning system) followed by a numeral of 0, 1, 2 or 3, to indicate the degree of redundancy of the system, will be assigned.

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1.5

Definitions

For the purpose of this section, the following definitions apply:

1.5.1 Thruster

1.5.1(a) General. Thrusters are devices capable of delivering side thrust or thrusts through 360q to improve the vessel’s maneuverability, particularly in confined waters. There are three generic types of thrust-producing devices: the lateral or tunnel thruster, commonly known as ‘bow-thruster’, which consists of a propeller installed in a athwartship tunnel; jet type thruster, which consists of a pump taking suction from the keel and discharge to either side; and azimuthal thruster, which can be rotated through 360° so that thrust can be developed in any direction. Cycloidal propellers can be considered a type of azimuthal thruster.

1.5.1(b) Propeller-type thruster. Regardless of whether they are normally used for propulsion, propellers intended to be operated for an extended period of time during service in a condition where the vessel is not free running approximately along the direction of the thrust are to be considered thrusters for the purposes of this section.

1.5.2 Continuous Duty Thruster

A continuous duty thruster is a thruster designed for continuous operation, such as dynamic positioning thrusters, propulsion assist, or main propulsion units. 1.5.3 Intermittent Duty Thruster

An intermittent duty thruster is a thruster which is designed for operation at peak power or rpm levels, or both, for periods not exceeding one (1) hour followed by periods at the continuous rating or less, with total running time not exceeding eight (8) hours in twenty (20) hours. Generally, such thrusters are not meant to operate more than 1000 hours per year.

1.7

Plans and Particulars to be Submitted

The general arrangements of the thruster installation, its location of installation, along with its supporting auxiliary machinery and systems, fuel oil tanks, foundations, watertight boundary fittings, etc., are to be submitted. The rated power/rpm and the rated thrust are to be indicated. For azimuthal thrusters, the mechanical and control systems for rotating the thruster assembly or for positioning the direction of thrust are to be submitted. In addition, plans of each component and of the systems associated with the thruster are to be submitted as detailed in the applicable sections of these Rules. Typically, the following are applicable:

Supporting structures: Diesel engine prime mover: Electric motor and controller: Gearing: Shafting: Propellers: Piping system:

Control and instrumentation:

Section 3-1-2 4-2-1/1.9

4-8-1/5.5.1 and 4-8-1/5.5.4 4-3-1/1.5 4-3-2/1.5 4-3-3/1.5 4-6-1/9 4-9-1/7

3

3.1

Materials

General (2008)

Materials entered into the construction of the torque-transmitting components of the thruster are to be in accordance with the applicable requirements of Part 4 of the Rules. For instance, material requirements for propellers are to be in accordance with 4-3-3/3; materials for gears, 4-3-1/3; materials for shafting, 4-3-2/3; materials for steering systems, 4-3-4/3.1, etc. All material specifications are contained in Part 2, Chapter 3.

Where alternative material specifications are proposed, complete chemical composition and mechanical properties similar to the material required by these Rules are to be submitted for approval.

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3.3 Material Testing

3.3.1 Testing by a Surveyor

The materials of the following components are to be tested in the presence of a Surveyor for verification of their compliance with the applicable requirements of Part 2, Chapter 3, or such other appropriate material specifications as may be approved in connection with a particular design.

x Shafts, shaft flanges, keys x Gears (propulsion and steering) x Propellers x Impellers x Couplings x Coupling bolts

Bolts manufactured to a recognized standard and used as coupling bolts need not to be tested in the presence of a Surveyor.

3.3.2 Thruster Rated 375 kW (500 hp) or Less

Materials for thrusters of 375 kW (500 hp) or less, including shafting, gears, pinions, couplings and coupling bolts may be accepted on the basis of the manufacturer’s certified mill test reports and a satisfactory surface inspection and hardness check witnessed by a Surveyor.

5

5.1

Design

Prime Movers

5.1.1 Internal Combustion Engines

Internal combustion engines used for driving thrusters are to comply with the design, construction, testing and certification requirements of Part 4, Chapter 2. Engine support systems are to be in accordance with Section 4-6-5; except that standby pumps and similar redundancy specified for propulsion engines are not required for thruster engines. 5.1.2 Electric Motors

Electric motors driving thrusters are to comply with the design, construction, testing and certification requirements of Section 4-8-3. Power for thruster motors may be derived from ship service generators; except that precautions, such as interlock arrangements, are to be fitted to prevent starting except when there are enough generators on-line to support the starting and running of the thruster motor. All ship service generators may be put on line for this purpose, see 4-8-2/3.1.2.

5.3 Propellers

5.3.1 General

In general, the thruster propellers are to comply with the requirements of Section 4-3-3, except as modified below. 5.3.2 Propeller Blades of Conventional Design

Where the propeller blades are of conventional design with skew angle not exceeding 25q, the thickness of the propeller blade is not to be less than determined by the following equations. Fillets at the root of the blades are not to be considered in the determination of the blade thickness.

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5.3.2(a) Fixed pitch propellers. The minimum required blade thickness at 0.25 radius, t0.25, is to be determined by the following equations:

t0.25 K1A 1.0 A 7.2

§Cs·§BK·AH

¸¨ mm (in.) r¨¸©4C¸CnCRN¨C¹©n¹6.0

4.3P0.25 P0.70

2.0

4.3P0.25 P0.70

2

3

for free running propellers

For propellers performing bollard pull, athwartship thrusting, dynamic positioning and similar duties;

4300wa§R·§D·B ¸¨¸ ¨

N©100¹©20¹C 1.0 1.5P0.25 Wf B

Other symbols are defined in 4-3-5/5.3.2(d).

5.3.2(b) Controllable pitch propellers. The minimum required blade thickness at 0.35 radius,

t0.35, is to be determined by the following equations:

t0.35 K2A 1.0 A 7.2

§Cs·§BK·AH

¸¨r¨¸ mm (in.) ¨CnCRN©Cn¸.C63©¹¹6.0

3P0.35 P0.70

2.0

3P0.35 P0.70

2

3

for free running propellers

for non-free running propellers [see 4-3-5/5.3.2(a)]

4900wa§R·§D·B ¨¸¨¸

N100©¹©20¹

C 1.0 0.6P0.35 Wf B

Other symbols are defined in 4-3-5/5.3.2(d).

5.3.2(c) Nozzle propellers (wide-tip blades). The minimum required blade thickness at 0.35

radius, t0.35, is to be determined by the following equations:

t0.35 K3A 1.0 A 7.2

§Cs·§BK·AH

¸¨r¨ mm (in.) ¸©5.6C¸CnCRN¨C¹©n¹6.0

2.8P0.35 P0.70

2.0

2.8P0.35 P0.70

3

for free running propellers

for non-free running propellers [see 4-3-5/5.3.2(a)]

4625wa§R·2§D·B ¸¨¸ ¨

N100¹©20¹©C 1.0 0.6P0.35 Wf B

Other symbols are defined in 4-3-5/5.3.2(d).

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5.3.2(d) Symbols. The symbols used in the above formulas are defined, in alphabetical order, as follows (the units of measure are in SI (MKS and US) systems, respectively):

a as Cn

= = =

expanded blade area divided by the disc area

area of expanded cylindrical section at 0.25 or 0.35 radius, as applicable; mm2 (in2)

section modulus coefficient at 0.25 or 0.35 radius, as applicable; to be determined by the following equation: Cn

I0UfWT2

If the value of Cn exceeds 0.1, the required thickness is to be computed with Cn = 0.1.

Cs

=

section area coefficient at 0.25 or 0.35 radius, as applicable, to be determined by the following equation: Cs

as

WT

The values of Cs and Cn computed as stipulated above are to be indicated on the propeller drawing.

D

=

propeller diameter; m (ft) material constants, see table below:

SI & MKS units f w 2.10 8.3 2.13 8.0 2.62 7.5 2.37 7.5 2.10 7.75

US units

f w 68 0.30 69 0.29 85 0.27 77 0.27 68 0.28

f, w = Material

type 2 3 4 5 CF-3 H I0

= =

power at rated speed; kW (PS, hp)

moment of inertia of the expanded cylindrical section at 0.25 or 0.35 radius about a straight line through the center of gravity parallel to the pitch line or to the nose-tail line; mm4 (in4)

rake of propeller blade, in mm (in.) (positive for aft rake and negative for forward rake)

K =

K1, K2, and K3 are constants and are to be of values as specified below:

K1 K2 K3 N

=

SI unit 337 271 288

MKS unit 289 232 247

US unit 13 10.4 11.1

number of blades

pitch at 0.25 radius divided by propeller diameter

pitch at 0.35 radius divided by propeller diameter, corresponding to the design ahead condition

pitch at 0.7 radius divided by propeller diameter, corresponding to the design ahead condition

251

P0.25 = P0.35 = P0.7 =

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R T

= =

rpm at rated speed

maximum design thickness at 0.25 or 0.35 radius from propeller drawing mm (in.)

required thickness of blade section at 0.25 of propeller radius; mm (in.) required thickness of blade section at 0.35 of propeller radius; mm (in.) maximum normal distance from the moment of inertia axis to points in the face boundary (tension side) of the section; mm (in.)

expanded width of a cylindrical section at the 0.25 or 0.35 radius

t0.25 = t0.35 = Uf W

= =

5.3.3 Blades of Unusual Design

Propellers of unusual design for thruster duties, such as:

x Propellers with the skew angle T ! 25q

x Controllable pitch propellers with skew angle T ! 25q x Propellers with wide-tip blades and skew angle T ! 25q x Cycloidal propellers, etc.

are subject to special consideration based on submittal of propeller load and stress analyses. See 4-3-3/5.7.

5.3.4 Propeller Blade Studs and Bolts

5.3.4(a) Area. Studs used to secure propeller blades are to have a cross-sectional area at the minor diameter of the thread of not less than that determined by the equations in 4-3-3/5.13.2.

5.3.4(b) Fit of studs and nuts. Studs are to be fitted tightly into the hub and provided with an effective means for locking. The nuts are also to have a tight-fitting thread and be secured by stop screws or other effective locking devices.

5.3.5 Blade Flange and Mechanism

The strength of the propeller blade flange and internal mechanisms of controllable-pitch propellers subjected to the forces from propulsion torque is to be determined as follows:

x For intermittent duty thrusters, be at least equal to that of the blade design pitch condition. x For continuous duty thrusters, be at least 1.5 times that of the blade at design pitch condition.

5.5 Gears

5.5.1 Continuous Duty Gears

Gears for continuous duty thrusters are to meet the provisions of Section 4-3-1.

5.5.2 Intermittent Duty Gears

Gears for intermittent duty thrusters, as defined in 4-3-5/1.5.3, are to be in accordance with a recognized standard and are to be submitted for consideration. See e.g., Appendix 4-3-1A1.

5.7 Shafts

5.7.1 Gear Shafts

Gear and pinion shaft diameters are to be determined by the equations in 4-3-1/5.9.

5.7.2 Propeller and Line Shafts

Shafting is to be in accordance with the provisions of 4-3-2/5.1 through 4-3-2/5.17, and cardan shafts, 4-3-2/5.21. 5.7.3 Couplings and Clutches

Shaft couplings, clutches, etc. are to be in accordance with the provisions of 4-3-2/5.19.

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5.9

Anti-friction Bearings

Full bearing identification and life calculations are to be submitted. Calculations are to include all gear forces, thrust vibratory loads at maximum continuous rating, etc. The minimum L10 life is not to be less than the following:

i) ii)

Continuous duty thrusters (propulsion and DPS-0, 1, 2, and 3): Intermittent duty thrusters:

20,000 hours 5,000 hours

Shorter life may be considered in conjunction with an approved bearing inspection/replacement program reflecting calculated life.

5.11

Steering Systems (2007)

Steering systems for azimuthal thrusters are to meet the requirements of Section 4-3-4, as applicable, and the following requirements.

5.11.1 Vessels with Only One Azimuthal Thruster

For vessels that are arranged with only one azimuthal thruster as the only means of propulsion and steering, the thruster is to be provided with steering systems of a redundant design such that a single failure in one system does not effect the other system. 5.11.2 Cargo Vessels with Two Azimuthal Thrusters

For cargo vessels that are arranged with two azimuthal thrusters as the only means of propulsion and steering, each thruster is to be provided with at least one steering system. The steering system for each thruster is to be independent of the steering system for the other thruster. 5.11.3 Passenger Vessels with Two Azimuthal Thrusters

For passenger vessels that are arranged with two azimuthal thrusters as the only means of propulsion and steering, each thruster is to be provided with steering systems of a redundant design such that a single failure in one system does not effect any other system. 5.11.4 Performance

Each azimuthal thruster is to be capable of rotating at a speed of not less than 0.4 rpm (from 35 degrees on either side to 30 degrees on the other side in not more than 28 seconds) while steering the vessel with the vessel running ahead at the maximum continuous rated shaft rpm and at the summer load waterline. Where the azimuthal thruster is arranged to rotate for the crash stop or astern maneuver, the azimuthal thruster is to be capable of rotating at the speed of not less than 2.0 rpm (180 degrees in not more than 15 seconds) to account for the crash stop or astern maneuver.

5.13

Access for Inspection (2007)

Adequate access covers are to be provided to permit inspection of gear train without disassembling thruster units.

7

7.1

Controls and Instrumentation

Control System

An effective means of controlling the thruster from the navigation bridge is to be provided. Control power is to be from the thruster motor controller or directly from the main switchboard. Propulsion thrusters are also to be fitted with local means of control.

For specific requirements related to class notation DPS-0, 1, 2 or 3, see 4-3-5/15.9.

7.3

Instrumentation (2008)

Alarms and instrumentation are to be provided in accordance with 4-3-5/Table 1, as applicable.

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TABLE 1

Instrumentation for Thrusters

Monitored Parameter

Engine low lubricating oil pressure alarm Engine coolant high temperature alarm Motor overload alarm Thruster RPM

Thrust direction (azimuthing type) Thruster power supply failure alarm

Controllable pitch propellers hydraulic oil low pressure alarm Controllable pitch propellers hydraulic oil high pressure alarm Controllable pitch propellers hydraulic oil high temperature alarm Fire detection Notes:

1 2

Either an individual indication or a common trouble alarm may be fitted at this location, provided individual indication is installed at the equipment (or main control station)

For vessels not fitted with a main control station, the indication is to be installed at the equipment or other suitable location

Navigation Bridge x (1) x (1) x (1) x x x x (1) x (1) x x

(1)

Main Control Station (1, 2)

x x x x x x x x x x

9 Communications

A means of voice communication is to be provided between the navigation bridge, main propulsion control station and the thruster room.

For specific requirements related to class notation DPS-0, 1, 2 or 3, see 4-3-5/15.11.

11 Miscellaneous Requirements for Thruster Rooms

11.1 Ventilation

Thruster rooms are to be provided with suitable ventilation so as to allow simultaneously for crew attendance and for thruster machinery to operate at rated power in all weather conditions. 11.3 Bilge System for Thruster Compartments

Thrusters installed in normally unattended spaces are to be arranged such that bilge pumping can be effected from outside the space. Alternatively, where bilge pumping can only be effected from within the space, a bilge alarm to warn of high bilge water level is to be fitted in a centralized control station, the navigation bridge or other normally manned control station. For bilge systems in general, see 4-6-4/5.5.11.

Thrusters in enclosed modules (capsules) are to be provided with a high water level alarm. At least one pump capable of bilging the module is to be operable from outside the module.

11.5 Fire Fighting Systems

In general, spaces where thrusters are located, including enclosed modules, are to be protected with fire fighting system in accordance with 4-7-2/1.

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13 Certification and Trial

Thrusters and associated equipment are to be inspected, tested and certified by the Bureau in accordance with the following requirements, as applicable:

Diesel engines: Gas turbines: Electric motors: Gears: Shafting: Propellers:

Section 4-2-1 Section 4-2-3 Section 4-8-3 Section 4-3-1 Section 4-3-2 Section 4-3-3

Upon completion of the installation, performance tests are to be carried out in the presence of a Surveyor in a sea trial. This is to include but not limited to running tests at intermittent or continuous rating, variation through design range of the magnitude and/or direction of thrust, vessel turning tests and vessel maneuvering tests.

15 Dynamic Positioning Systems

15.1 General

15.1.1 Class Notations and Degree of Redundancy

Dynamic positioning systems may be assigned with different class notations depending on the degree of redundancy built into the system, as defined below. These notations are not a requirement for class and are to be assigned only at specific request.

DPS-0 For vessels which are fitted with a dynamic positioning system with centralized manual position control and automatic heading control to maintain the position and heading under the specified maximum environmental conditions.

DPS-1 For vessels which are fitted with a dynamic positioning system which is capable of automatically maintaining the position and heading of the vessel under specified maximum environmental conditions having an independent centralized manual position control with automatic heading control.

DPS-2 For vessels which are fitted with a dynamic positioning system which is capable of automatically maintaining the position and heading of the vessel within a specified operating envelope under specified maximum environmental conditions during and following any single fault, excluding a loss of compartment or compartments.

DPS-3 For vessels which are fitted with a dynamic positioning system which is capable of automatically maintaining the position and heading of the vessel within a specified operating envelope under specified maximum environmental conditions during and following any single fault, including complete loss of a compartment due to fire or flood.

15.1.2 Definitions

15.1.2(a) Dynamic positioning (DP) system. The dynamic positioning system is a hydro-dynamic system which controls or maintains the position and heading of the vessel by centralized manual control or by automatic response to the variations of the environmental conditions within the specified limits.

15.1.2(b) Specified maximum environmental conditions. The specified maximum environmental conditions are the specified wind speed, current and wave height under which the vessel is designed to carry out intended operations.

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15.1.2(c) Specified operating envelope. The specified operating envelope is the area within which the vessel is required to stay in order to satisfactorily perform the intended operations under the specified maximum environmental conditions.

15.1.2(d) Single fault. The single fault is an occurrence of the termination of the ability to perform a required function of a component or a subsystem in any part of the DP system. For vessels with DPS-3 notation, the loss of any single compartment is also to be considered a single fault.

15.1.3 Plans and Data to be Submitted (2008)

Where one of the class notations described in 4-3-5/15.1.1 is requested, the following plans and data are to be submitted for review as applicable.

x System description including a block diagram showing how the various components are

functionally related x Details of the position reference system and environmental monitoring systems x Location of thrusters and control system components

x Details of the DP alarm system and any interconnection with the main alarm system

x Electrical power generation and distribution system and its interconnections with the control

system x Details of the consequence analyzer (see 4-3-5/15.9.6) x Thruster remote control system

x Automatic DP control and monitoring system

x Certification of suitability of control equipment for the marine atmosphere x Environmental force calculations and design safe operating envelope x Thruster design

x Thruster force calculations and predicted polar plots

x Failure modes and effects analysis (FMEA) (see 4-3-5/15.1.4) (DPS-2 and DPS-3) x DP operations manual (see 4-3-5/15.1.5) x Test schedule

15.1.4 Failure Modes and Effect Analysis (2008)

A failure modes and effect analysis (FMEA) is to be carried out and is to be sufficiently detailed to cover all the systems associated with the dynamic positioning of the vessel and is to include but not be limited to the following information:

x A description of all the systems associated with the dynamic positioning of the vessel and a

functional block diagram showing their interaction with each other. Such systems would include the DP electrical or computer control systems, electrical power distribution system, power generation, fuel systems, lubricating oil systems, cooling systems, backup control systems, etc. x All significant failure modes

x The most predictable cause associated with each failure mode x The transient effect of each failure on the vessels position x The method of detecting that the failure has occurred

x The effect of the failure upon the rest of the system’s ability to maintain station x An analysis of possible common failure mode

Where parts of the system are identified as non-redundant and where redundancy is not possible, these parts are to be further studied with consideration given to their reliability and mechanical protection. The results of this further study are to be submitted for review.

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15.1.5 DP Operations Manual (2008)

For each vessel, a dynamic positioning operations manual is to be prepared and submitted solely for verification that the information in the manual, relative to the dynamic positioning system, is consistent with the design and information considered in the review of the system. One copy of the operations manual is to be kept onboard.

The DP operations manual is intended to provide guidance for the DP operator about the specific dynamic positioning installations and arrangements of the specific vessel. The DP operations manual is to include but not be limited to the following information.

x A description of all the systems associated with the dynamic positioning of the vessel, including

backup systems and communication systems x The block diagram showing how the components are functional related, as described in

4-3-5/15.1.3 x A description of the different operational modes and transition between modes. x Definitions of the terms, symbols and abbreviations

x A functional description of each system, including backup systems and communication systems x Operating instructions for the normal operational mode (and the operational modes after a

failure) of the DP electrical or computer control systems, manual position control system, manual thruster control system, DP equipment (thrusters, electric motors, electric drives or converters, electric generators, etc.) x Operating instructions for the systems and equipment, indicated in the above paragraph,

during failure conditions x References to where more specific information can be found onboard the vessel, such as the

detailed specific operation instructions provided by the manufacturer of the DP electrical or computer control systems, manufacturer’s troubleshooting procedures for vendor-supplied equipment, etc.

15.3 Thruster System

15.3.1 General

In general, the thrusters are to comply with the requirements of 4-3-5/3 through 4-3-5/13, as applicable. 15.3.2 Thruster Capacity

15.3.2(a) Vessels with DPS-0 or DPS-1 notation. These vessels are to have thrusters in number and of capacity sufficient to maintain position and heading under the specified maximum environmental conditions.

15.3.2(b) Vessels with DPS-2 or DPS-3 notation. These vessels are to have thrusters in number and of capacity sufficient to maintain position and heading, in the event of any single fault, under the specified maximum environmental conditions. This includes the failure of any one thruster.

15.3.3 Thruster Configuration

When determining the location of thrusters, the effects due to the interference with other thrusters, hull or other surfaces are to be considered.

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15.5 Power Generation and Distribution System

15.5.1 General

The following requirements are in addition to the applicable requirements in Part 4, Chapter 8. 15.5.2 Power Generation System

15.5.2(a) Vessels with DPS-2 notation. Generators and their distribution systems are to be sized and arranged such that, in the event of any section of bus bar being lost for any reason, sufficient power is to remain available to supply the essential ship service loads, the critical operational loads and to maintain the vessel position within the specified operating envelope under the specified maximum environmental conditions.

Essential services for generators and their prime movers, such as cooling water and fuel oil systems, are to be arranged such that, with any single fault, sufficient power remains available to supply the essential loads and to maintain position within the specified operating envelope under the specified maximum environmental conditions.

15.5.2(b) Vessels with DPS-3 notation. Generators and their distribution systems are to be sized and arranged in at least two compartments so that, if any compartment is lost due to fire or flood, sufficient power is available to maintain position within the specified operating envelope, and to start any non running load without the associated voltage dip causing any running motor to stall or control equipment to drop out.

Essential services for generators and their prime movers, such as cooling water and fuel oil systems, are to be arranged so that, with any single fault in the systems or the loss of any single compartment, sufficient power remains available to supply the essential loads, the critical operational loads and to maintain position within the specified operating envelope under the specified maximum environmental conditions.

15.5.3 Power Management System (2008)

For DPS-2 and DPS-3 notations, power management systems are is to be provided to ensure that sufficient power is available for essential operations, and to prevent loads from starting while there is insufficient generator capacity. At least two power management systems are to be provided, to account for the possible failure of either power management system. Consideration will be given to techniques such as shedding of non essential loads or interfacing with control system to provide temporary thrust reduction to ensure availability of power.

Each power management system is to be supplied with power from an uninterruptible power system (UPS) and arranged such that a loss of power to one power management system will not result in the loss of power to the other power management systems.

For DPS-3 notation, the power management systems are to be located and arranged such that no single fault, including fire or flood in one compartment, will render all the power management systems inoperable.

15.5.4 Uninterruptible Power Systems (UPS) (2008)

For DPS-1, DPS-2 and DPS-3 notations, an independent uninterruptible power system is to be provided for each independent control system and its associated monitoring and reference system. Each uninterruptible power system is to be capable of supplying power for a minimum of 30 minutes after failure of the main power supply.

For DPS-3 notation, the back-up control system required by 4-3-5/15.9.3(c) and its associated reference system is to be provided with a dedicated independent UPS. The uninterruptible power systems are to be located and arranged such that no single fault, including fire or flood in one compartment, will interrupt the power supplied to back up control system required by 4-3-5/15.9.3(c) and its associated reference system.

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15.7 Environment Sensor and Position Reference System

15.7.1 Vessels with DPS-0 or DPS-1 Notation

For DPS-0 notation, a position reference system, a wind sensor and a gyro-compass are to be fitted. For DPS-1 notation, they are to be provided in duplicate. 15.7.2 Vessels with DPS-2 Notation (2008)

In addition to the systems in 4-3-5/15.7.1 for DPS-1 notation, a third independent position reference system, a third wind sensor and a third gyro-compass are to be provided. Two of the position reference systems may operate on the same principle. A single failure is not to affect simultaneously more than one position reference system (i.e., no common mode failures).

15.7.3 Vessels with DPS-3 Notation (2008)

In addition to the requirements in 4-3-5/15.7.2 for DPS-2 notation, the third wind sensor, third gyro-compass and the third independent position reference system are to be directly connected to the back-up control station with their signals repeated to the main control station. 15.7.4 Signal Processing

Where three position reference systems are required, the control computers are to use signal processing techniques to validate the data received. When out of range data occurs, an alarm is to be given.

15.9 Control System

15.9.1 Control and Monitoring System Components

In general, control and monitoring (alarms and instrumentation) system components for dynamic positioning systems of vessels intended to be assigned with DPS notations are to comply with the provisions of Section 4-9-7. 15.9.2 Control Stations

15.9.2(a) Control station arrangement. The main dynamic positioning control station is to be so arranged that the operator is aware of the external environmental conditions and any activities relevant to the DP operation.

15.9.2(b) Emergency shut-down (2008). An emergency shut-down facility for each thruster is to be provided at the main dynamic positioning control station. The emergency shut-down facility is to be independent of the automatic control systems (4-3-5/15.9.3), manual position control system (4-3-5/15.9.4) and manual thruster control system (4-3-5/15.9.5). The emergency shut-down facility is to be arranged to shut-down each thruster individually.

15.9.2(c) Vessels with DPS-3 notation. For DPS-3 notation, an emergency back-up control station is to be provided in a separate compartment located and arranged such that no single fault, including a fire or flood in one compartment, will render both the main and back-up control system inoperable.

15.9.3 Position Keeping Control System Redundancy (2008)

15.9.3(a) Vessels with DPS-1 notation. An automatic control system and a manual position control system with automatic heading control are to be fitted. Transfer of control between the two systems is to be initiated manually.

15.9.3(b) Vessels with DPS-2 notation. Two automatic control systems and a manual position control system with automatic heading control are to be fitted. The two automatic control systems are to be independent, self-monitoring and arranged such that, should one fail, control is automatically transferred to the other. The cabling for the control systems and the thrusters is to be arranged such that under single fault conditions it will remain possible to control sufficient thrusters to stay within the specified operating envelope.

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15.9.3(c) Vessels with DPS-3 notation. Three automatic control systems and a manual position control system with automatic heading control are to be fitted. The two automatic control systems located at the dynamic positioning control station are to be independent, self-monitoring and arranged such that, should one fail, control is automatically transferred to the other. The third automatic control system is to be located in the emergency back-up control station and transfer of control to it is to be initiated manually. The cabling for the control systems and the thrusters is to be arranged such that under single fault conditions, including loss of a compartment due to fire or flood, it will remain possible to control sufficient thrusters to stay within the specified operating envelope.

15.9.4 Manual Position Control System (2008)

The manual position control system described in 4-3-5/15.9.3 is to be independent of the automatic control systems so that it will be operational if the automatic control systems fail. The system is to provide one joystick for manual control of the vessel position and is to be provided with the arrangements for automatic heading control. 15.9.5 Manual Thruster Control System (2008)

In addition to 4-3-5/15.9.3 and 4-3-5/15.9.4, a manual thruster control system is required as per 4-3-5/7.1. The manual thruster control system is to be independent of the automatic control systems so that it will be operational if the automatic control systems fail. The system is to provide an effective means of individually controlling each thruster from the navigation bridge. The system is to provide an individual joystick for each thruster.

Any failure in the manual position control system is not to affect the capabilities of the manual thruster control system to individually control each thruster.

15.9.6 Consequence Analysis and DP Alert System – Vessels with DPS-2 or DPS-3 Only

For vessels with DPS-2 or DPS-3 notation, the DP control system is to incorporate a consequence analyzer that monitors the vectorial thrust necessary to maintain position under the prevailing environmental conditions and perform calculations to verify that in the event of a single failure there will be sufficient thrust available to maintain position in steady state and during transients. 15.9.7 Alarms and Instrumentation

The displays, alarms and indicators as specified in 4-3-5/Table 2 are to be provided at each control station, as applicable.

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TABLE 2

Instrumentation at DPS Control Station (2008)

System

Monitored Parameters

Engine lubricating oil pressure – low Engine coolant temperature – high CPP hydraulic oil pressure – low and high CPP hydraulic oil temperature – high CPP pitch Thruster RPM

Thruster

Power System

Thrust direction

Thruster motor/semiconductor converter coolant leakage Thruster motor semiconductor converter temperature Thruster motor short circuit

Thruster motor exciter power available Thruster motor supply power available Thruster motor overload Thruster motor high temperature

Power

Distribution System

Status of automatically controlled circuit breakers Bus bar current and power levels High power consumers – current levels Excursion outside operating envelope Control system fault

System

Performance

Position sensor fault

Vessels target and present position and heading Wind speed and direction Selected reference system Thruster location (pictorial)

Specific

Requirements for DPS-2 & DPS-3

Percentage thrust

Available thrusters on stand-by DP alert through consequence analyzer

Position information of individual position reference systems connected

Alarm x x x x x x x x x x x

Display

x x x x x x x x x x x x x x x x x

15.11 Communications for Vessels with Dynamic Positioning (2008)

One means of voice communication is to be provided between each DP control position and the navigation bridge, the engine control position, any other relevant operation control centers associated with DP and any location required by 4-3-5/9. 15.13 Certification and Trials

15.13.1 Control and Monitoring System Equipment

Control and monitoring (alarms and instrumentation) system equipment used in a dynamic positioning system to be assigned with a DPS notation are to be certified for suitability for marine atmospheres.

Hydraulic and pneumatic piping systems associated with the dynamic positioning system are to be subjected to pressure tests at 1.5 times the relief-device setting using the service fluid in the hydraulic system and dry air or dry inert gas for pneumatic systems as testing media. The tests are to be carried out in the presence of a Surveyor.

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15.13.2 Trials (2010)

Upon completion and installation of the dynamic positioning system, complete performance tests are to be carried out to the Surveyor’s satisfaction at the sea trials. The schedule of these tests is to be designed to demonstrate the level of redundancy established in the FMEA (Failure Modes and Effects Analysis, see 4-3-5/15.1.4). Where practicable, the test environment is to reflect the limiting design operating conditions.

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