MSC/Circ. 645 Guidelines for vessels with dynamic positioning systems

1. The Maritime Safety Committee at its sixty-third session (16 to 25 May 1994), approved the Guidelines for Vessels with Dynamic Positioning Systems, set out at annex to the present circular, as prepared by the Sub-Committee on Ship Design and Equipment at its thirty-seventh session.
2. Member Governments are invited to bring the Guidelines to the attention of all bodies concerned, and apply the Guidelines to new vessels with dynamic positioning systems constructed on or after 1 July 1994, in conjunction with implementation of the provisions of paragraph 4.12 of the 1989 MODU Code as amended by resolution MSC.38(63).
3. Member Governments are also invited to use the proposed model form of flag State verification and acceptance document set out in the appendix to the Guidelines.

Preamble

1. These Guidelines for vessels with dynamic positioning systems have been developed to provide an international standard for dynamic positioning systems on all types of new vessel.

2. Taking into account that dynamically positioned vessels are moved and operated internationally and recognizing that the design and operating criteria require special consideration, the Guidelines have been developed to facilitate international operation without having to document the dynamic positioning system in detail for every new area of operation.

1 General

1.1 Purpose and responsibility

1.1.1 The purpose of these Guidelines is to recommend design criteria, necessary

equipment, operating requirements, and a test and documentation system for dynamic

positioning systems to reduce the risk to personnel, the vessel, other vessels or structures,

sub-sea installations and the environment while performing operations under dynamic

positioning control.

 

1.1.2 The responsibility for ensuring that the provisions of the Guidelines are complied

with rests with the owner of the DP-vessel.

1.2 Application

The Guidelines apply to dynamically positioned units or vessels, the keel of which is

laid or which is at a similar stage of construction on or after 1 July 1994.

1.3 Definitions

In addition to the definitions in the MODU Code 1989 the following definitions are

necessary for the guidelines:

 

1.3.1 "Dynamically positioned vessel (DP-vessel)" means a unit or a vessel which

automatically maintains its position (fixed location or predetermined track) exclusively by

means of thruster force.

 

1.3.2 "Dynamic positioning system (DP-system)" means the complete installation necessary

for dynamically positioning a vessel comprising the following sub-systems:

1. power system,
2. thruster system, and
3. DP-control system.

1.3.3 "Position keeping" means maintaining a desired position within the normal excursions

of the control system and the environmental conditions.

 

1.3.4 "Power system" means all components and systems necessary to supply the

DP-system with power. The power system includes:

1. prime movers with necessary auxiliary systems including piping,
2. generators,
3. switchboards, and
4. distributing system (cabling and cable routeing).

1.3.5 "Thruster system" means all components and systems necessary to supply the

DP-system with thrust force and direction. The thruster system includes:

1. thrusters with drive units and necessary auxiliary systems including piping,
2. main propellers and rudders if these are under the control of the DP-system,
3. thruster control electronics,
4. manual thruster controls, and
5. associated cabling and cable routeing.

1.3.6 "DP-control system" means all control components and systems, hardware and

software necessary to dynamically position the vessel. The DP-control system consists of

the following:

1. computer system/joystick system,
2. sensor system,
3. display system (operator panels),
4. position reference system, and
5. associated cabling and cable routeing.

1.3.7 "Computer system" means a system consisting of one or several computers including

software and their interfaces.

 

1.3.8 "Redundancy" means ability of a component or system to maintain or restore its

function, when a single failure has occurred. Redundancy can be achieved for instance by

installation of multiple components, systems or alternative means of performing a function.

 

1.3.9 "Flag State Verification and Acceptance Document (FSVAD)" means the document

issued by the Administration to a DP-vessel complying with these Guidelines. (See

Appendix for model form.)

 

1.4 Exemptions

An Administration may exempt any vessel which embodies features of a novel kind from

any provisions of the guidelines the application of which might impede research into the

development of such features. Any such vessels should, however, comply with safety

requirements which, in the opinion of the Administration, are adequate for the service

intended and are such as to ensure the overall safety of the vessel.

The Administration which allows any such exemptions should list the exemptions on the

Flag State Verification and Acceptance Document (FSVAD) and communicate to the

Organization the particulars, together with the reason therefor, so that the Organization may

circulate the same to other Governments for the information of their officers.

1.5 Equivalents

1.5.1 Where the Guidelines require that a particular fitting, material, appliance, apparatus,

item of equipment or type thereof should be fitted or carried out in a vessel, or that any

particular provision should be made, or any procedure or arrangement should be complied

with, the Administration may allow other fitting, material, appliance, apparatus, item of

equipment or type thereof to be fitted or carried, or any other provision, procedure or

arrangement to be made in that vessel, if it is satisfied by trial thereof or otherwise that

such fitting, material, appliance, apparatus, item of equipment or type thereof or that any

particular provision, procedure or arrangement is at least as effective as that required by

the Guidelines.

 

1.5.2 When an Administration so allows any fitting, material, appliance, apparatus, item of

equipment or type thereof, or provision, procedure, arrangement, novel design or application

to be substituted, it should communicate to the Organization the particulars thereof, together

with a report on the evidence submitted, so that the Organization may circulate the same

to other Governments for information of their officers.

2 Equipment classes

2.1 A DP-system consists of components and systems acting together to achieve

sufficiently reliable position keeping capability. The necessary reliability is determined by

the consequence of a loss of position keeping capability. The larger the consequence, the

more reliable the DP-system should be.

To achieve this philosophy the requirements have been grouped into three equipment

classes. For each equipment class the associated worst case failure should be defined as

in 2.2 below.

The equipment class of the vessel required for a particular operation should be agreed

between the owner of the vessel and the customer based on a risk analysis of the

consequence of a loss of position. Else, the Administration or coastal State may decide

the equipment class for the particular operation.

 

2.2 The equipment classes are defined by their worst case failure modes as follows:

1. For equipment class 1, loss of position may occur in the event of a single fault.
2. For equipment class 2, a loss of position is not to occur in the event of a single

fault in any active component or system. Normally static components will not be

considered to fail where adequate protection from damage is demonstrated, and

reliability is to the satisfaction of the Administration. Single failure criteria

include:

1. Any active component or system (generators, thrusters, switchboards, remote controlled valves, etc.).
2. Any normally static component (cables, pipes, manual valves, etc.) which is not properly documented with respect to protection and reliability.

For equipment class 3, a single failure includes:

 

1. Items listed above for class 2, and any normally static component is assumed to fail.
2. All components in any one watertight compartment, from fire or flooding.
3. All components in any one fire sub-division, from fire or flooding (for cables, see also 3.5.1).

2.3 For equipment classes 2 and 3, a single inadvertent act should be considered as a

single fault if such an act is reasonably probable.

 

2.4 Based on the single failure definitions in 2.2 the worst case failure should be

determined and used as the criterion for the consequence analysis (see 3.4.2.4).

 

2.5 The Administration should assign the relevant equipment class to a DP-vessel based

on the criteria in 2.2 and state it in the Flag State Verification and Acceptance Document

(FSVAD) (see 5.2).

 

2.6 When a DP-vessel is assigned an equipment class this means that the DP-vessel is

suitable for all types of DP-operations within the assigned and lower equipment classes.

 

2.7 It is a provision of the guidelines that the DP-vessel is operated in such a way that

the worst case failure, as determined in 2.2, can occur at any time without causing a

significant loss of position.

3 Functional requirements

3.1 General

3.1.1 In so far as is practicable all components in a DP-system should be designed,

constructed and tested in accordance with international standards recognized by the

Administration.

 

3.1.2 In order to meet the single failure criteria given in 2.2, redundancy of components

will normally be necessary as follows:

.1 for equipment class 2, redundancy of all active components;

.2 for equipment class 3, redundancy of all components and physical separation of

the components.

 

3.1.3 For equipment class 3, full redundancy may not always be possible (e.g., there may

be a need for a single change-over system from the main computer system to the back-up

computer system). Non-redundant connections between otherwise redundant and separated

systems may be accepted provided that it is documented to give clear safety advantages,

and that their reliability can be demonstrated and documented to the satisfaction of the

Administration. Such connections should be kept to the absolute minimum and made to

fail to the safest condition. Failure in one system should in no case be transferred to the

other redundant system.

 

3.1.4 Redundant components and systems should be immediately available and with such

capacity that the DP-operation can be continued for such a period that the work in

progress can be terminated safely. The transfer to redundant component or system should

be automatic as far as possible, and operator intervention should be kept to a minimum.

The transfer should be smooth and within acceptable limitations of the operation.

3.2 Power system

3.2.1 The power system should have an adequate response time to power demand changes.

 

3.2.2 For equipment class 1 the power system need not be redundant.

 

3.2.3 For equipment class 2, the power system should be divisible into two or more

systems such that in the event of failure of one system at least one other system will

remain in operation. The power system may be run as one system during operation, but

should be arranged by bus-tie breakers to separate automatically upon failures which could

be transferred from one system to another, including overloading and short-circuits.

 

3.2.4 For equipment class 3, the power system should be divisible into two or more

systems such that in the event of failure of one system, at least one other system will

remain in operation. The divided power system should be located in different spaces

separated by A.60 class division. Where the power systems are located below the

operational waterline, the separation should also be watertight. Bus-tie breakers should be

open during equipment class 3 operations unless equivalent integrity of power operation

can be accepted according to 3.1.3.

 

3.2.5 For equipment classes 2 and 3, the power available for position keeping should be

sufficient to maintain the vessel in position after worst case failure according to 2.2.

 

3.2.6 If a power management system is installed, adequate redundancy or reliability to the

satisfaction of the Administration should be demonstrated.

 

3.3 Thruster system

3.3.1 The thruster system should provide adequate thrust in longitudinal and lateral

directions, and provide yawing moment for heading control.

 

3.3.2 For equipment classes 2 and 3, the thruster system should be connected to the power

system in such a way that 3.3.1 can be complied with even after failure of one of the

constituent power systems and the thrusters connected to that system.

 

3.3.3 The values of thruster force used in the consequence analysis (see 3.4.2.4) should be

corrected for interference between thrusters and other effects which would reduce the

effective force.

 

3.3.4 Failure of thruster system including pitch, azimuth or speed control, should not make

the thruster rotate or go to uncontrolled full pitch and speed.

3.4 DP-control system

3.4.1 General

1. In general the DP-control system should be arranged in a DP-control station where the operator has a good view of the vessel's exterior limits and the surrounding area.
2. The DP-control station should display information from the power system, thruster system, and DP-control system to ensure that these systems are functioning correctly. Information necessary to operate the DP-system safely should be visible at all times. Other information should be available upon operator request.
3. Display systems and the DP-control station in particular, should be based on sound ergonometric principles. The DP-control system should provide for easy selection of control mode, i.e. manual, joystick, or computer control of thrusters, and the active mode should be clearly displayed.
4. For equipment classes 2 and 3, operator controls should be designed so that no single inadvertent act on the operators' panel can lead to a critical condition.
5. Alarms and warnings for failures in systems interfaced to and/or controlled by the DP-control system are to be audible and visual. A permanent record of their occurrence and of status changes should be provided together with any necessary explanations.
6. The DP-control system should prevent failures being transferred from one system to another. The redundant components should be so arranged that a failure of one component should be isolated, and the other component activated.
7. It should be possible to control the thrusters manually, by individual joysticks and by a common joystick, in the event of failure of the DP-control system.
8. The software should be produced in accordance with an appropriate international quality standard recognized by the Administration.

3.4.2 Computers

1. For equipment class 1, the DP-control system need not be redundant.
2. For equipment class 2, the DP-control system should consist of at least two independent computer systems. Common facilities such as self-checking routines, data transfer arrangements, and plant interfaces should not be capable of causing the failure of both/all systems.
3. For equipment class 3, the DP-control system should consist of at least two independent computer systems with self-checking and alignment facilities. Common facilities such as self-checking routines, data transfer arrangements and plant interfaces should not be capable of causing failure at both/all systems. In addition, one back-up DP-control system should be arranged, see 3.4.2.6. An alarm should be initiated if any computer fails or is not ready to take control.
4. For equipment classes 2 and 3, the DP-control system should include a software function, normally known as 'consequence analysis', which continuously verifies that the vessel will remain in position even if the worst case failure occurs. This analysis should verify that the thrusters remaining in operation after the worst case failure can generate the same resultant thruster force and moment as required before the failure. The consequence analysis should provide an alarm if the occurrence of a worst case failure would lead to a loss of position due to insufficient thrust for the prevailing environmental conditions. For operations which will take a long time to safely terminate, the consequence analysis should include a function which simulates the thrust and power remaining after the worse case failure, based on manual input of weather trend.
5. Redundant computer systems should be arranged with automatic transfer of control after a detected failure in one of the computer systems. The automatic transfer of control from one computer system to another should be smooth, and within the acceptable limitations of the operation.
6. For equipment class 3, the back-up DP-control system should be in a room separated by A.60 class division from the main DP-control station. During DP-operation this back-up control system should be continuously updated by input from the sensors, position reference system, thruster feedback, etc., and be ready to take over control. The switch-over of control to the back-up system should be manual, situated on the back-up computer and should not be affected by failure of the main DP-control system.
7. An uninterruptible power supply (UPS) should be provided for each DP-computer system to ensure that any power failure will not affect more than one computer.UPS battery capacity should provide a minimum of 30 minutes operation following a mains supply failure.

3.4.3 Position reference systems

1. Position reference systems should be selected with due consideration to operational requirements, both with regard to restrictions caused by the manner of deployment and expected performance in working situation.
2. For equipment classes 2 and 3, at least three position reference systems should be installed and simultaneously available to the DP-control system during operation.
3. When two or more position reference systems are required, they should not all be of the same type, but based on different principles and suitable for the operating conditions.
4. The position reference systems should produce data with adequate accuracy for the intended DP-operation.
5. The performance of position reference systems should be monitored and warnings provided when the signals from the position reference systems are either incorrect or substantially degraded.
6. For equipment class 3, at least one of the position reference systems should be connected directly to the back-up control system and separated by A.60 class division from the other position reference systems.

3.4.4 Vessel sensors

1. Vessel sensors should at least measure vessel leading, vessel motions, and wind speed and direction.
2. When an equipment class 2 or 3 DP-control system is fully dependent on correct signals from vessel sensors, then these signals should be based on three systems serving the same purpose (i.e. this will result in at least three gyro compasses being installed).
3. Sensors for the same purpose, connected to redundant systems should be arranged independently so that failure of one will not affect the others.
4. For equipment class 3, one of each type of sensors should be connected directly to the back-up control system and separated by A.60 class division from the other sensors.

 

3.5 Cables and piping systems

3.5.1 For equipment class 3, cables for redundant equipment or systems should not be

routed together through the same compartments. Where this is unavoidable such cables

could run together in cable ducts of A-60 class, the termination of the ducts included,

which are effectively protected from all fire hazards, except that represented by the cables

themselves. Cable connection boxes are not allowed in such ducts.

 

3.5.2 For equipment class 2, piping systems for fuel, lubrication, hydraulic oil, cooling

water and cables should be located with due regard to fire hazards and mechanical

damage.

 

3.5.3 For equipment class 3, redundant piping system (i.e. piping for fuel, cooling water,

lubrication oil, hydraulic oil, etc.) should not be routed together through the same

compartments. Where this in unavoidable, such pipes could run together in ducts of A-60

class, the termination of the ducts included, which are effectively protected from all fire

hazards, except that represented by the pipes themselves.

3.6 Requirements for essential non-DP-systems

For equipment classes 2 and 3, systems not directly part of the DP-system but which in

the event of failure could cause failure of the DP-system, (e.g., common fire suppression

systems, engine ventilation systems, shut-down systems, etc.), should also comply with

relevant requirements of these Guidelines.

4 Operational requirements

4.1 Before every DP-operation, the DP-system should be checked according to a vessel

specific "location" check list to make sure that the DP-system is functioning correctly and

that the system has been set up for the appropriate equipment class.

 

4.2 During DP-operations, the system should be checked at regular intervals according to

a vessel specific watchkeeping checklist.

 

4.3 DP operations necessitating equipment class 2 or 3 should be terminated when the

environmental conditions are such that the DP-vessel will no longer be able to keep

position if the single failure criterion applicable to the equipment class should occur. In

this context deterioration of environmental conditions and the necessary time to safely

terminate the operation should also be taken into consideration. This should be checked

by way of environmental envelopes if operating in equipment class 1 and by way of an

automatic consequence analysis if operating in equipment class 2 or 3. The necessary

operating instructions, etc., should be on board.

 

4.4 The following checklists, test procedures and instructions should be incorporated into

the DP operating manuals for the vessel:

1. Location checklist (see 4.1).
2. Watchkeeping checklist (see 4.2).
3. DP-operation instructions (see 4.3).
4. Annual tests and procedures (see 5.1.1.3).
5. Initial and periodical (5-year) tests and procedures (see 5.1.1.1 and 5.1.1.2).
6. Example of tests and procedures after modifications and non-conformities (see 5.1.1.4).

5 Surveys, testing and the Flag State Verification

5.1 Surveys and testing

5.1.1 Each DP-vessel which is required to comply with the Guidelines is subject to the

surveys and testing specified below:

1. Initial survey which should include a complete survey of the DP-system to ensure full compliance with the applicable parts of the guidelines. Further it includes a complete test of all systems and components and the ability to keep position after single failures associated with the assigned equipment class. The type of test carried out and results should be documented in the Flag State Verification and Acceptance Document (FSVAD), see 5.2.
2. Periodical survey at intervals not exceeding five years to ensure full compliance with the applicable parts of the guidelines. A complete test should be carried out as required in 5.1.1.1. The type of test carried out and the results should be documented in the FSVAD, see 5.2.
3. Annual survey should be carried out within three months before or after each anniversary date of the initial survey. The annual survey should ensure that the DP-system has been maintained in accordance with applicable parts of the guidelines and is in good working order. Further an annual test of all important systems and components should be carried out to document the ability of the DP-vessel to keep position after single failures associated with the assigned equipment class. The type of test carried out and results should be documented in the FSVAD, see 5.2.
4. A survey either general or partial according to circumstances should be made every time a defect is discovered and corrected or an accident occurs which affects the safety of the DP-vessel, or whenever any significant repairs or alterations are made. After such a survey, necessary tests should be carried out to demonstrate full compliance with the applicable provisions of the Guidelines. The type of tests carried out and results should be recorded and kept on board.

5.1.2 These surveys and tests should be witnessed by officers of the Administration. The

Administration may, however, entrust the surveys and testing either to surveyors nominated

for the purpose or to organizations recognized by it. In every case the Administration

concerned should fully guarantee the completeness and efficiency of the surveys and

testing. The Administration may entrust the owner of the vessel to carry out annual and

minor repair surveys according to a test programme accepted by the Administration.

 

5.1.3 After any survey and testing has been completed, no significant change should be

made to the DP-system without the sanction of the Administration, except the direct

replacement of equipment and fittings for the purpose of repair or maintenance.

 

5.2 Flag State Verification and Acceptance Document (FSVAD)

5.2.1 A Flag State Verification and Acceptance Document (FSVAD) should be issued, after

survey and testing in accordance with these Guidelines, either by officers of the

Administration or by an organization duly authorized by it. In every case the

Administration assumes full responsibility for the FSVAD.

 

5.2.2 The FSVAD should be drawn up in the official language of the issuing country and

be that of the model given in the appendix to the Guidelines. If the language used is

neither English nor French, the text should include a translation into one of these

languages.

 

5.2.3 The FSVAD is issued for an unlimited period, or for a period specified by the

Administration.

 

5.2.4 An FSVAD should cease to be valid if significant alterations have been made in the

DP-system equipment, fittings, arrangements, etc., specified in the Guidelines without the

sanction of the Administration, except the direct replacement of such equipment or fittings

for the purpose of repair or maintenance.

 

5.2.5 An FSVAD issued to a DP-vessel should cease to be valid upon transfer of such a

vessel to the flag of another country.

 

5.2.6 The privileges of the FSVAD may not be claimed in favour of any DP-vessel unless

the FSVAD is valid.

 

5.2.7 Control of a DP-vessel holding a valid FSVAD should be carried out according to

the principles of 1.7 in the MODU Code 1989.

 

5.2.8 Results of the FSVAD tests should be readily available on board for reference.

Appendix Model form of FSVAD

Model Form of Flag State Verification and Acceptance Document

FLAG STATE VERIFICATION AND ACCEPTANCE DOCUMENT

(Official seal) (State)

Issued under the provisions of the

GUIDELINES FOR VESSELS WITH

DYNAMIC POSITIONING SYSTEMS

(MSC/Circ...)

under the authority of the Government of

__________________________________________

(full designation of the State)

by _________________________________________________ ____

(full official designation of the competent person or

organization authorized by the Administration)

 

 

Distinctive identification(Name or number)	Type	Port of registry	Official IMO-number

 

Date on which keel was laid or vessel was at similar stage of construction or on which

major conversion was commenced............................................................................

 

THIS IS TO CERTIFY that the above-mentioned vessel has been duly documented,

surveyed, and tested in accordance with the Guidelines for Vessels with Dynamic

Positioning Systems (MSC/Circ...)and found to comply with the Guidelines.

 

The vessel is allowed to operate in DP Equipment Class.............................................................

and in lower equipment classes.

 

This document remains valid until...............................................................................................

unless terminated by the Administration, provided that the vessel is operated, tested, and

surveyed according to the requirements in the guidelines and the results are properly

recorded.

 

Issued at ..................................................................................................................................

                      (Place of issue of document)

 

.......................                          ...............................................................................................

(Date of issue)                           (Signature of authorized official issuing the certificate)

 

................................................................................................................................................

(Seal or stamp of the issuing authority, as appropriate)

 

 

 

 

LIST OF EXEMPTIONS AND EQUIVALENTS

(ref. items 1.4 and 1.5 of the Guidelines)

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LIST OF MAIN SYSTEMS AND COMPONENTS COVERED BY FSVAD*

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* All main systems and components included in the dynamic positioning system are to be listed in a

systematic way. As an alternative reference can be made to drawings, etc. It is important that it is possible

by this list to identify all systems and components covered by FSVAD. Software versions should also be

identified. Equipment installed after date of issuing FSVAD should only be included in the list after control

and testing has been completed and modifications and non-conformities report signed.

 

 

 

 

Record of annual survey reports, and special (5 years) survey reports

 

Date	Test type	Remarks	*Report Reference Date/Number	Sign. of appointed surveyor(IR)	Sign. of Master/Platform Manager

 

* All reports should be filed together with this FSVAD for use during later testing and inspections by

nominated surveyors, flag State surveyors, etc.

IR = if required, ref. item 5.1.2

 

 

 

• Informatietype: Internationaal
• Documentsoort: Circulaire niet in wetten.nl
• Toegangsrechten: Extern
• Identificatie: PUC_1730_14
• Versie: 1
• Datum beschikbaarheid: 06-09-2006
• Geldigheid van: 06-06-1994
• Wijzigingsdatum: 12-04-2017
• Titel: MSC/Circ. 645 Guidelines for vessels with dynamic positioning systems
• Organisatie: International Maritime Organization (IMO)
• Taal: Engels
• Thema: 0600 until 0799