Chapter10 - DP Operations

8/17/2019 Chapter10 - DP Operations

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© Marine Institute Centre for Marine Simulation 10-1

School of Maritime Studies 2014 Rev. June/2014

Chapter 10

PLANNING and CONDUCTING DP OPERATIONS


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10-2 Centre for Marine Simulation © Marine Institute

Rev. June/2014 School of Maritime Studies 2014

Notes


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Planning and Conducting DP Operations

Planning

Figure 10.1 on the next page shows a DSV next to a platform with divers and ROV deployed. The operation is taking

place in 142m of water and the drawing is to scale. A crane hook is being lowered and the diver will connect it to the end

of a pipeline which has to be repositioned. Thorough planning was required before the commencement of this operation

and is a requirement for any DP operation. All aspects of the operation must be reviewed and discussed by all parties

involved. Planning should cover approaching the worksite, setting up at the worksite, conducting of the DP operation and

departure from the worksite. The planning process should also include contingency planning in the event that failures or

emergencies occur. This section will give a general overall review of the various aspects of planning and conducting DP

operations. Details will vary depending on the type of vessel and operation being conducted.

Before planning the operation we need to know worksite information, environmental conditions, vessel capability, vessel

system information and particulars of the job that is to be completed by the vessel.

Worksite Information

The position or positions that the vessel will be asked to maintain during the DP operation will have to be determined. The

operation could involve holding station at one location for the entire operation (working close to one side of a platform

as an example). The operation could require that the vessel work on all four sides of the same platform during the course

of the operation with moves around the platform being conducted while on DP. No platforms may be involved at all and

the operation may take place in open water. The vessel might be in transit during the entire operation (cable laying for

example). A review of the physical layout of the worksite has to be completed with respect to required vessel positions

during the DP operation.

The vessel might have to be positioned in a drift-on or blow-on location. Meaning that, should there be a loss of power or

thrust, to the extent that the vessel is unable to hold position, the environmental conditions will push the vessel towards an

obstruction (such as a platform). Ideally a drift-off or blow-off location is preferred as the vessel would be pushed awayfrom the obstruction. Unfortunately, the required operational location may prevent such a setup.

The heading or headings that the vessel will be asked to maintain during the DP operation will have to be determined.

Heading change might not be possible at all during the operation. The operation may take place close to the side of a

platform where limited or no heading changes are possible. The operation being undertaken might limit the ability to

change heading (laying a rigid pipeline, for example).

Worksite information can be determined from diagrams provided by the client, from surveyors onboard the vessel for this

particular job or by researching vessel records of past operations at the site (assuming the vessel has previously operated a

this location). Every effort should be made to ensure that the worksite information is as recent and as accurate as possible.

A review of the worksite noting all hazards and obstructions located on the surface or subsea has to be completed. Thiswould include the approach to the worksite, the worksite itself and any other areas the vessel may transit during the course


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ROV

Diver

TMS

Bell

Figure 10.1


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» Location of any buoys or oating lines on the surface.

» Location of any platforms in the area.

» Water depths, bottom contours and type of bottom, wrecks, etc.

» Surface dimensions of platforms including distance between lowest decks and sea level.

» Information and dimensions regarding attachments to platforms such as are towers, catwalks, etc.

» Subsea dimensions, layout and shape of platforms. This would include location of any attachments such as

umbilicals, pipelines, etc. » Location on the seabed of pipelines, umbilicals, wellheads, manifolds, communications cables and any

» other manmade objects that have been placed or dropped on the seabed.

» In operations involving vessels or installations with anchor lines the location and characteristics of the

moorings have to be determined.

» In operations involving mobile platforms such as FPSOs or TLPs the motion characteristics and maximum

position movements of the platforms have to be determined.

Any required guidance, rules or regulations for this particular work location have to be obtained and reviewed. Guidance,

rules or regulations may be provided by the client, eld operator, industry or government..

Master’s standing orders have to be considered. The company DP Operation Manual will also provide guidance regardingthe conduct of DP operations.

Environmental Conditions

Latest short and long term weather forecasts for the operations area will have to be obtained. Forecast should include

information about the expected wind, sea conditions and visibility at the worksite. The latest forecast should be available

at all times during the DP operation.

Information regarding current/tidal rate and direction for the operations area has to be obtained. The information can come

from relevant publications, client supplied information or from past vessel experience in the particular area.

Weather trends and environmental conditions for the area pertaining to the season of operation have to be reviewed. The

vessel may, for example, have to conduct operations at a time of year when hurricanes occur frequently in the area of the

worksite.

The worksite may be in an area where ice is present at different times of the year. If there is a possibility of ice being

present, ice forecasts would have to be obtained. Large numbers of icebergs may mean that the vessel will be frequently

forced to move away from location. Isolated oes may cause no problems for the vessel but may prevent HPR beacons

deployed on wires or Taut Wires from being used.

Environmental information obtained will be used to determine vessel capability to carry out the job at hand.

Thrusters and Power Supplies

The status of the components of the vessels propulsion system used for DP has to be determined. Status of vessel power

supply components (generators, UPS, etc.) relating to the DP system must be determined as well. Between DP operations

the engineers or ships electrician may be taking advantage of downtime to perform required maintenance or repairs on

equipment. Ample notice will have to be given of the intention to commence DP operations. A determination will have to

be made as to whether equipment undergoing repairs or maintenance is required for the DP operation and if so, the time


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at which the work is expected to be completed. The effect on the DP operation of any faulty equipment will have to be

determined as it may affect vessels DP capability.

Depending on the required level of redundancy (see next section) and power supply requirements for the job, a decision

has to be made as to the number of generators to be run. To operate with the switchboard bus-tie (if tted) closed or open

will also have to be determined. Guidance on this matter may be provided by regulation, client requirements or company

policy. The open or closed bus-tie decision has to be made taking into account vessel equipment conguration and risksinvolved with the job at hand.

Capability / Redundancy

Having determined worksite layout, expected environmental conditions and vessel equipment status, a determination can

be made as to whether the vessel is capable of carrying out the required DP operation.

When considering vessel capability the required level of redundancy has to be considered. Redundancy implies that

critical components of the DP system are duplicated or backed up. The required level of redundancy will depend on the

operation to be conducted and will be determined by regulatory, industry or company requirements. On a Class 1 DP

vessel some or all of the components of the DP system may have no backups and a single fault may cause loss of position.Class 2 & 3 vessels have different levels of redundancy (see class requirements in Appendixes 1 and 2 of this manual) that

are aimed at preventing loss of position in the event of a single point failures.

A Class 2 or 3 vessel does not automatically ensure that the vessel always has redundancy. This must be checked and

veried before the DP operation begins and at all times throughout the operation. A vessel has 3 main generators that

supply power for the thrusters but only one is running to meet current power requirements. The vessel does not have

redundancy in the event the running generator fails. There are backup generators but they require time to start and during

this time, no power is available for the thrusters. Redundancy would be achieved when 2 generators are running, 1 shuts

down and the remaining generator can supply sufcient power to meet current thrust requirements. Another example

might be a Class 2 vessel having 2 fully operational bow thrusters which produce 15 tonnes of thrust each, at full power. If

the total thrust requirement on the bow is only 3 tonnes and one thruster fails, there would be redundancy as the remaining

thruster has enough power to meet requirements. However, if there is an increase in environmental forces causing totalthrust requirements to increase to 17 tonnes, there would not be redundancy. The remaining thruster would not have

sufcient thrust and the vessel is likely to drift off position. Problems affecting redundancy, such as faulty backup

systems, might be detected during checks prior to setting up on DP. Others, such as the above requirement for too much

thrust, may not be observed until the vessel is actually set up on DP. In any event, corrective action must be taken before

the operation can proceed.

The ability to change vessel heading can sometimes solve problems relating to vessel capability. A monohull vessel

typically will have more capability when the overall environmental force is on the bow or stern, rather than on the beam.

The thrust problem above might be solved by choosing a more appropriate vessel heading where the vessel has more

capability and consequently requires less thrust. This assumes that from the worksite information obtained, the vessel can

change heading and that work being done permits the required heading change.

A single fault on a Class 1 DP vessel, such as problems with a single DP bridge console, could cause loss of position. This

does not imply that all faults will cause loss of position on a Class1 vessel. Some components on the vessel may have

backups and these backups need to be considered. The bow thruster arrangement described above might be tted and

redundancy provided by the dual thrusters should be given consideration when planning the operation.

Along with redundancy, operational planning must ensure that the vessel has enough thrust capability to hold both

position and heading while conducting the operation.


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To determine vessel capability in different environmental conditions, capability plots for the vessel can be consulted.

These may be in paper format or as available, on some DP systems, in electronic format . Electronic capability plots which

are incorporated into some DP systems allow for the input of a greater number of variables regarding actual conditions

and thus may be more accurate. Vessel capability indicated on the plots should be used as guidance only. Conditions

used for compiling the plot such as draft, list, sea state, trim & windage area may be different than those currently

being experienced by the vessel. Records of past vessel performance while on DP can also provide guidance on vessel

performance.

On a Class 2 or 3 vessel, position and heading must be maintained after a worse case failure. Vessel capability must be

determined taking into consideration the worst case failure. Capability plots often will indicate vessel capability in the

event of such failures. On a vessel with all thrusters driven electrically of a switch board the worst case failure might be

a blackout on half the switchboard which would result in half of the vessels power supply being lost. On a vessel where

each thruster has its own power supply and runs independently of other ships systems, the worst case failure might be the

loss of the single most important thruster for a given situation. A vessel may have sufcient capability to hold position

with all systems operational but may not be able to hold position in the event of a worse case failure.

Some DP systems have a built in function known as online consequence analysis. When the vessel is on DP an analysis

of the vessels ability to maintain position in the event of failures is regularly performed. If the system determines that a

failure will result in loss of position, an alarm alerts the DP operator. This feature has to be activated by the DP operatorand its setup varies depending on DP system manufacturer.

Further checks which can be completed after the vessel is set up on DP to ensure capability will be discussed later in this

chapter.

Sensors

Sensors tted will include gyros, wind sensors and motion sensors in the form of Motion Reference Units (MRUs),

Vertical Reference Sensors (VRSs) or Vertical Reference Units (VRUs). Some vessels may be tted with draft sensors.

Shuttle tankers using hawsers at loading terminals may have sensors feeding hawser tension into the DP system. Cable

laying vessels that tow plows may feed towline tension into the DP system via sensors. Pipe tension on a rigid pipe layvessel and drag head tension on a dredge are two more examples.

The operational status of all sensors required for the DP operation has to be determined. If more than one sensor of a

particular type is tted, readings have to be compared to ensure that differences (if any) are within acceptable limits. The

reason for any unacceptable differences must be determined. The number of properly functioning sensors required to

provide the level of redundancy necessary for the job at hand must also be considered.

Gyros tted have to be checked to ensure proper operation and gyro errors determined. Wind sensors must be checked

to ensure that the readings provided reect actual wind conditions being experienced by the vessel. Actual vessel motion

should be compared with readings from motion sensors. Actual vessel draft has to be compared with draft sensor readings.

Tension sensors should be checked for faults and readings checked before values are input to the DP system.

Position References

The number of position references required will depend on the nature of the operation and the required level of

redundancy needed for that job. References tted will vary from vessel to vessel. This section will highlight some items to

be taken into account when planning the use of the six principle types of references for a DP operation.


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Artemis:

» Determine a location at a suitable range from the worksite for the Artemis x station (either on a xed

platform or onshore).

» Obtain permission to locate Artemis at the chosen location.

» Determine coordinates of the x station and determine the location of a visual reference object for calibrating

the x station for azimuth. Calculate the bearing of the reference object. » If a suitable x station is already set up at the worksite and available for the operation, it may be possible to

obtain permission to use it. This will save the time required to up your own reference station.

» Determine how transfer of Artemis equipment and setup personnel to the xed station location will take

place.

» Decide on the frequency pair and selective address code used to avoid interference with other Artemis users

in the area.

» Review work locations to determine if the mobile station on the vessel will have line of sight with the x

station at all times during the operation. Consider objects that might block signals such as platforms, other

vessels, crane operations, etc.

» Consider x and mobile antenna heights with regard to limitations of vertical beam width.

» Consider any possible dip zones where direct and reected signals may interfere with each other.

» Determine availability of a suitable power supply for the x station. Platform supply may be used or Artemis

x station batteries might be only power source.

» Ensure x station is located to avoid possible interference caused by platform operations or personnel.

Consider possibility of station being tampered with if positioned ashore.

» There may be a requirement for the Artemis to be intrinsically safe when used in some areas.

» To avoid possible interference, the vessels 3cm radar should not be used when using Artemis as a DP

reference. A request might also be made of any vessels operating in the immediate area that they also not use

3cm radars.

» Consider the effects that any forecast heavy precipitation will have on system performance.

Cyscan/Fanbeam (Laser Systems):

» Determine a suitable location for the Cyscan/Fanbeam reector (normally on a nearby platform).

» Obtain permission to locate the reector/reectors at the chosen location. Having more than 1 reector will

provide backup in the event that one reector becomes unusable.

» If a reector or reectors of suitable quality are already set up at the worksite, they may be used instead.

» Determine how reector is to be transferred to deployment location and determine who will set it up.

» Review work locations to determine if the sending unit on the vessel will have line of sight with the reector

at all times during the operation. Consider objects that might block signals such as platforms, other vessels,

crane operations, etc. It might be determined that more than one reector has to be installed to ensure that

there is at least one target available at all times.

» Ensure reector is located to avoid possible interference caused by platform operations or personnel.

» Consider objects in the vicinity of the vessel deployed reector that may also return false target signals to the

sending unit or cause loss of target. This might include bright lights or reective tape on life rings, lifeboatsor workers clothing.

» Consider sending unit and reector heights with regard to limitations of vertical beam width of laser signal.

» Sun low on the horizon behind the reector might cause interference.

» Ensure that the lens of the sending unit is clean.

» Dirt on the reector may cause reduced signal strength or loss of signal.

» Forecast rain or snow may cause disruption or loss of signal.


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Differential Global Navigation Satellite Systems (DGNSS):

» Determine location of the source of differential correction signals and frequencies used. These might come

from a satellite, from a coast station via HF radio or from a nearby platform via UHF radio.

» Review the location of receiving antennae on the vessel for possible sources of signal interference or blockage

of signals. It might be determined that on some vessel headings differential signals might be interfered with

because a mast or crane is between the antenna and the signal source. » Review work locations to determine if the receiving antenna on the vessel will have line of sight with

differential signal transmission station at all times during the operation. Consider objects that might interfere

with or block signals such as platforms, other vessels, crane operations, etc.

» If possible, determine when atmospheric conditions might cause interference with or total blockage of signals

from navigational satellites and/or differential correction signals. Vessel or company records on signal outages

in the area or data from differential signal provider are possible sources of information.

» Corrections received via HF radio may be subject to atmospheric interference. Especially when the vessel is

operating close to the limits of radio coverage from the reference station.

» Ensure that all times the differential correction station is able to track and provide corrections for the same

satellites that are being tracked by the receiver on the vessel (sufcient satellites to obtain a position x). This

may not be possible if the range to the correction station is too great.

» Compare datum used by DP system with the received GPS datum. Charts and surveys to be used for the

operation may be in a different datum.

Hydroacoustic Positioning Reference (HPR):

» Determine how many beacons are required for the job and ensure that the number required are available and

have sufcient battery capacity. Depending on job length, plans may have to be made to replace beacons

during the course of the operation so that batteries can be recharged or replaced.

» Review subsea worksite layout so as not to position beacons in areas where the beacons or attached weights

might cause damage to subsea equipment.

» Note subsea obstructions/seabed features that may cause blockage or interference with HPR signals.

» Determine how HPR beacons used for the operation are to be deployed (on a wire, on acoustic release, byROV, etc.).

» If beacons to be used by the vessel have been prelaid, their positions and channel numbers must be obtained.

» Prelaid beacons that can be utilized, might be available at a eld. These can be accessed after obtaining eld

operator permission and position/channel information.

» Other vessels in the area might be using HPR. They should be contacted to determine if their operations

require the use of HPR and if so, what channels are being/going to be used. This will avoid interference

caused by two operators using the same frequencies at the same time.

» Users of HPR on own vessel, such as ROV or drilling department, must be consulted as to beacon use. If they

are using the same frequencies as used for DP reference purposes, interference may result.

» Sources of acoustic noise that may interfere with HPR performance have to be considered. These might

include noise caused by the operation being conducted i.e. drilling, rock dumping, ROV. In shallow water

noise from vessels own thrusters may have an adverse effect on HPR performance. » HPR can have slow update rates in deep water.

» Consider any interference that deployed beacons may cause for subsea operations such as diving or ROV.

» Consider any maximum speed limitations for the vessel when HPR poles are deployed and ensure sufcient

water depth before extending poles.

» If vessel has capability, obtain water density and temperature information for input into HPR system. This wil

allow the system to apply corrections for these variables when performing calculations.


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Taut Wire:

» Review subsea worksite layout so as not to position clump weight in areas where it might cause damage to

subsea equipment.

» Ensure adequate wire length on the winch for the water depth at the worksite.

» Water depth may be such that the weight of the wire causes it to bend, creating angle measurement errors.

» Current may be too strong (i.e. bending of the wire) to use the taut wire at the worksite. » Water depth may be too shallow to use the taut wire. Example: Small vessel movements (1 - 3m) while on DP

will cause wire to move outside maximum allowed angle limits or touch the vessels hull if taut wire is used at

worksite.

» Determine maximum vessel movements that will be possible before having to replumb taut wire.

» Consider vessel movement in forecast sea conditions with regard to launch and recovery of clump weight as

well as taut wire ability to operate properly in forecast conditions (i.e. ability of the winch to respond quickly

enough to vessel motion).

» Determine the type of bottom at the worksite. A rocky bottom might mean that the clump weight may drag as

smaller than normal angles. A soft muddy bottom might mean that the clump weight will sink into the bottom

and be difcult to recover if left in location for long periods without being replumb.

» Consider any interference that deployed clump weight may cause for subsea operations such as diving or

ROV.

RadaScan/RADius (Microwave Systems):

» Determine a suitable location for the responder/responders or transponder/transponders on the platform.

» Obtain permission to locate the responder/responders or transponder/transponders at the chosen location.

Having more than 1 responder or transponder will provide backup in the event that one becomes unusable.

» If responders or transponders are already set up at the worksite, they may be used instead. If permission for

the use of these transponders is granted, obtain the identication codes.

» Determine how responder/transponder is to be transferred to deployment location and determine who will set

it up.

» Review work location to determine if the scanner/interrogator on the vessel will have line of sight with theresponder/responders or transponder/transponders at all times during the operation. Consider objects that

might block signals such as platforms, other vessels, crane operations, etc. It might be determined that more

than one reector has to be installed to ensure that there is at least one available at all times.

» Ensure that responder/transponder is located to avoid possible interference caused by platform operations or

personnel.

» Consider scanner/interrogator and responder/transponder heights and positions with regard to limitations of

vertical and horizontal signal beam widths.

» Check remaining battery life if responders/transponders are battery powered.

» If responders/transponders require platform power, determine availability of suitable power supply.

» There may be a requirement for the responders/transponders to be intrinsically safe when used in some areas.

As far as possible, operational status of reference systems should be checked before the job commences. As mentioned

above, there will be a minimum number of references required for each job. If a vessel is equipped with references in

addition to that minimum requirement, it may be prudent to use these addition references or at the very least have them on

standby and ready to go. This will provide backup in case of a reference system failure and possibly prevent suspending

DP operations because insufcient references are available.


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Operational Considerations

From Chapter 4 we can see that a wide variety of operations are conducted by DP vessels. The operation being conducted

requires consideration when planning operations. Aspects of the operation may require consideration with respect to the

DP system.

Example:

A vessel is to conduct DP operations where air divers are to be deployed. When conducting such operations there are safetyrequirements regarding how close the divers can get to oper ational thrusters. Figure 10.2 shows a diagram which shows maximumallowable umbilical lengths when divers are working at various depths. Consulting this document during operational planning mightindicate that the proposed vessel position would have the divers working at an unsafe distance from the thrusters. Vessel position orheading may have to be adjusted to provide a safe distance. It may be determined that a particular thruster could not be used duringthe operation. This might impact on vessel capability or required redundancy.

MSV CHALLENGER SAT AND AIR DIVE

SAFE UMBILICAL LENGTHS

40m Diver Depth

30m Diver Depth

20m Diver Depth

10m Diver Depth

Air DiveBell Dive (Moonpool)

18m

20m

25m

32m

40m

27m

29m

34m

41m

48m

Thruster5m No Go Areas

Thruster5m No Go Areas

Depths

Below Sea Level

50m Diver Depth

49m

60m Diver Depth

56m

Maximum Umbilical Lengths Maximum Umbilical Lengths

Figure 10.2

Contingency Planning

Failures or emergency situations can occur at any time during a DP operation. The planning process should include

contingency planning to cover procedures to be followed if the operation does not go as expected.

An essential component of any DP operation is an escape route. It is an identied and dened route away from any

hazards or nearby structures. It can also be known as an emergency exit strategy which is a pre-planned route away from

hazards within any working area or worksite. There should always be a planned escape route that positions the vessel at

a safe location in the event of a DP system failure. This should include the approach to the worksite, conducting the DP

operation and the departure from the worksite. By having an escape route planned in advance, there is no delay while the

DPO decides where to move the vessel and the safest route to get there. An escape route that is planned in advance can be

thoroughly reviewed for problems. A plan that is formulated in haste after the DP failure occurs may cause more problems

than it solves.


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Example:

A vessel is conducting DP operations close to a platform and is in a blow on situation. The deployed ROV has connected a load tothe crane wire and the load has just been lifted off the bottom when a partial blackout occurs. Half of the vessels power supply is lostalong with half of the thrusters. Redundancy had been conrmed before commencing the operation and sufcient power and thrustersremain online to hold the vessel on station. Power has however failed to the crane and the load is suspended and cannot be raised orlowered. Due to the fact that the vessel now has no redundancy and is in a blow on situation, a decision is made to move the vessel

to a location where it will drift clear if remaining power fails. The fastest way to move the vessel to safety (the escape route) is tomove astern. While making the move the suspended weight on the crane hooks something on the seabed causing loss of heading andnear contact with the platform. Before the vessel can be stopped the crane wire parts and the load falls to the seabed where it causesdamage to a pipeline.

A subsequent investigation determines that a new pipeline had recently been laid from the platform. A hold back line usedto commence the lay was run from the platform leg to the pipe and had not been removed. This information was included indocumentation sent to the vessel prior to commencement of the job. The supplied information was not adequately reviewed during

planning for the operation and in this case, the escape route was decided in haste after the problem occurred, without considering allavailable information, resulting in vessel and eld equipment damage.

At the point that the planned escape route is utilized, the vessel may be experiencing reduced power or thrust capability.

The prospect of such reduced capability should be taken into account as the vessel might not be capable of utilizing the

planned escape route.

Contingency plans should be altered as required to take into account changes in conditions that occur while the DP

operation is being conducted. For example, weather conditions may change or a vessel may arrive on location and be

positioned so as to block the planned escape route.

Contingency planning should also take the form of deciding what action to take should a problem occur. The DPO at the

control desk should, as far as possible, preplan for things that may go wrong. “Given the job at hand, what action will I

take if this particular fault or problem occurs?” would be the sort of planning the DPO should undertake. Knowing what

you are going to do when a fault occurs saves valuable time and may prevent incorrect decisions.

Example:

A thruster fails to full pitch. The DPO reviews available information and determines that the thruster has failed to full pitch. Having previously reviewed procedures for such a problem, the DPO quickly shuts down the correct thruster minimizing heading/positionexcursions.

The same problem occurs but this time the DPO has not preplanned. After determining the fault the DPO must now decide what actionto take. On making the decision to shut down the thruster the DPO rushes to the thruster control panel and pushes the emergency stop

All the buttons are close together on one panel and not having reviewed the procedure, the DPO accidentally stops the wrong thruster.The time taken to decide a course of action may have been short, but it does allow for a greater heading/position excursions. Stopping

the wrong thruster, while leaving the faulty one running, will certainly compound the problem.

While on DP it is a good practice to note thrust and power settings applied by the DP control system on an ongoing basis.

If a failure occurs which requires the DPO to resort to manual control to hold the vessel on location, using either joystick

or individual thruster controls, the settings that were previously being used are known. Thus, the DPO has a starting point

regarding the amount of thrust to apply manually. Orientation of the joystick is also important as a joystick or thrustercontrol accidentally pushed the wrong way can move the vessel towards an obstruction as opposed to being held in

position away from that obstruction.

It must be noted, that the reaction to a particular problem will depend on the circumstances of the case and may not

always be the same. The DPO can never plan for all eventualities but can plan for faults that occur with DP systems in

general and faults that could occur/have occurred on his/her particular vessel.


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Checklists

A checklist is a pre-prepared list of tasks and checks to be completed prior to commencing an operation or an individual

phase of an operation. Checklists ensure that the DP system is working properly and it also ensures that there is a standard

set of checks carried out by all DP operators on board the vessel.

Checklists should be completed at various stages of the DP operation. The type, frequency and content of the checklistswill vary depending on the vessel and the type of operation. The “name” of the checklist can vary from company to

company but the content and purpose of a checklist may be the same.

A “Pre-DP” checklist is a checklist intended to be completed immediately prior to transferring the vessel from

conventional navigation to DP control. There may be separate Pre-DP checklists for bridge, and Machinery Control Room

A “Pre-operational” checklist is a checklist intended to be completed once the vessel is established under DP control,

before commencing her operational tasks.

The following are some checklist types that might be performed:

» When arriving at a new location and setting up on DP a comprehensive “Field Arrival”, “New Location” or

“Pre- DP” checklist is completed. This may be completed even if the new location is close to the old location. » Before starting operations under DP control a “Pre-operational” checklist is completed. Vessels involved in

different operations may have requirements for checklists at certain times during the operation. On a dive

support vessel there would be a requirement to complete a “Pre–operational” (perhaps called Pre-Dive”) DP

checklist before the diving bell or air divers are permitted to enter the water.

» When DPOs change watch a “Change of Watch” DP checklist is completed.

» At intervals (i.e. every 4 or 6 hours) during the watch a “Watchkeeping” DP checklist is completed.

The following is an example of what a “Pre-Operational” checklist for a dive support vessel might contain.

MSV Challenger Pre-Operational Checklist

Note: Add comments where required.

Date ____________________ Time ____________________ Location ____________________

Position N ____________________ E ____________________

Water Depth ____________________

Lights / Shapes (On/Up) Y / N

Read Latest Forecast Y / N

Lamp/Alarm Test Completed & O.K. Y / N


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System Setup

Computer Online A B

Operator Station in Use 1 2

Centre of Rotation Selected ____________________

Speed Setting ____________________

Turn Rate Setting ____________________

Acceleration/Retardation Settings:

Low Speed Acceleration Factor Surge _____ % Sway _____ % Yaw _____ %

Retardation Factor Surge _____ % Sway _____ % Yaw _____ %

High Speed Acceleration Factor Yaw _____ %

Retardation Factor Yaw _____ %

Gain (Select 1 of the 4 Below)

___ High Precision Gain Setting: Low Medium High

___ Customized High Precision Gain Setting: Surge _____ Sway ______ Yaw ______

___ Relaxed Outer Radius ____________

___ Green DP Outer Radius ____________ Inner Radius ____________

Joystick Thrust Reduced _____ Full _____

Joystick Precision High Speed _____ General _____ Low Speed _____

Joystick Environmental Comp. Surge _____ Sway _____ Yaw _____

DP Mode Standby _____ Joystick _____ Auto Position _____

Auto Yaw _____ Auto Surge _____ Auto Sway _____

*Auto Pilot _____ *Auto Track _____

*Follow Target _____ *Trackline _____

* Before using, review specic settings for these modes and complete checklists as required.


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Alarms

Alarms Page Checked Y / N

Position Alarm Settings Warning _____ Alarm _____ Enabled Y / N

Heading Alarm Setting Warning _____ Alarm _____ Enabled Y / N

Cross-Track Alarm Settings Warning _____ Alarm _____ Enabled Y / N

Propulsion

Joystick Operational Y / N

Thrusters Available for DP Control #1 __ #2 __ #3 __ #4 __ #5 __ #6 __ #7 __

Thrusters Selected #1 __ #2 __ #3 __ #4 __ #5 __ #6 __ #7 __

Thruster #3 on Bus 1 __ Bus 2 __

Thruster Setpoint/Feedback O.K. Y / N

Rudders Available for DP Control Port __ Stbd. __

Rudders Selected Port __ Stbd. __

Rudder Setpoint/Feedback O.K. Y / N

Thruster Mode Selected _____________________________________

Power Status

Generators Available #1 __ #2 __ #3 __ #4 __ #5 __ #6 __

Generators Online #1 __ #2 __ #3 __ #4 __ #5 __ #6 __

Main Switchboard Split Y / N

Power (if Bus is Common) Used ____________ Available ____________

Power (if Bus is Split) Bus 1: Used ____________ Available ____________

Bus 2: Used ____________ Available ____________

UPS Checked & O.K. Y / N

Sensors

Gyros Available #1 __ #2 __ #3 __

Gyro in Use #1 __ #2 __ #3 __


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Differences Checked & Acceptable Y / N

Vessel Heading in Use ____________ °

Wind Sensors Available #1 __ #2 __ #3 __

Wind Sensor in Use #1 __ #2 __ #3 __


Wind Speed & Direction in Use _____________________________________

VRS Available #1 __ #2 __ #3 __

VRS in Use #1 __ #2 __ #3 __


Values Used Heave _____ Pitch _____ Roll _____

Draught Sensor Available Y / N

Draught Input Sensor __ Manua __ Operational __ Transit __

Draught Input Checked & Acceptable Y / N

Draught in Use _____________________________________

Reference Systems

Available Selected

Artemis Y / N Y / N

DGPS 1 Y / N Y / N

DGPS 2 Y / N Y / N

Fanbeam Y / N Y / N Targets ____________ ____________

HPR 1 Y / N Y / N Transponders _____ _____ _____ _____

HPR 2 Y / N Y / N Transponders _____ _____ _____ _____

Radius Y / N Y / N Transponders _____ _____ _____ _____

Taut Wire Port Y / N Y / N

Taut Wire Stbd. Y / N Y / N

Gate Valves Port: Open / Closed Stbd.: Open / Closed

HPR Poles Port: Down / Up Stbd.: Down / Up


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ROV Transponder _____

Bell Transponder _____ Diver Transponder _____

Datum Settings Checked & O.K. Y / N

Communications Tested & O.K. (as applicable)

Crane Cab/Cabs Y / N

Dive Control Y / N DP Status Lights Y / N

Engine Control Room Y / N

ROV Control Y / N DP Status Lights Y / N

Checklists

Engineroom Checklist Complete Y / N

Dive Checklist Complete Y / N

ROV Checklist Complete Y / N

Vessel Capability

Trends Page Checked Y / N

Capability Plot Setup & Checked Y / N

Consequence Analysis Enabled Y / N

Deselect Thrusters #1, (#3), #5 & #7 (Only if thruster #3 is connected to BUS 1)

Position Maintained Y / N Reselect Thrusters

Deselect Thrusters #2, (#3), #4 & #6 (Only if thruster #3 is connected to BUS 2)

Position Maintained Y / N Reselect Thrusters

Vessel on Auto DP for 30 Minutes Y / N

DP Current _____________________________________

All Page Settings Checked Y / N

Printer Online Y / N Print Status Y / N

Signed _________________________________ Date _________________________

Signed _________________________________ Date _________________________


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Initial DP Setup

On arrival at the work location, the vessel will have to switch from transit to DP mode. The main propellers and rudders

or the azimuth thrusters used for propulsion during transit may also be used for DP. The engine room will be informed

of the intention to commence DP operations and any extra thrusters required for DP will have to be started as per vessel

procedures. The thrusters should be tested manually to ensure proper operation.

Any required load or reload of DP computers should be completed before entering DP mode. The position reference

system or systems to be used for the operation (taking into account factors discussed previously) should be checked

for readiness. Sensors (gyro, wind, motion and others as required) would also be checked for readiness. Any gyro and

magnetic compass errors present to be determined.

The mathematical model requires time to build up, when rst entering DP mode. Vessel position is likely to oscillate for a

period of time during this process. When entering DP mode, there is no guarantee that all components of the DP system

are going to work properly. For these reasons the vessel should be set up on DP at a location well away from anything

that the vessel might collide with because of position oscillations or DP system failures. If the worksite is in open water

with no obstructions in the area then the setup location can be at or near the worksite. If there are obstructions near the

worksite (i.e. work location 15m from the side of a platform) the setup should be completed at a distance well clear of

the obstruction. Depending on vessel and eld procedures this may mean setting up outside the platform 500m exclusionzone. This a dened area around an offshore structure or complex within which vessel and other operations are within the

jurisdiction of the Offshore Installation Manager (OIM). Commonly this exclusion zone is set at 500m but may vary.

When ready to enter DP mode the vessel is normally stopped and control of the thrusters is switched from manual to DP

control and the thrusters are selected on the DP desk. Reference systems, sensors and thrusters are enabled at the DP desk

as per system operating procedures. The DP joystick can now be tested as part of the appropriate DP checklist required

when the vessel starts operations at a new location (see items to be reviewed on sample checklist above).

It is important to remember that the vessel speed should ideally be as close to zero as possible when entering Auto DP

mode. The same would apply for rate of turn. The possibility exists to place surge, sway and yaw under DP control all

at once. If this is done and the vessel is moving the DP system will attempt to stop the vessel at the current position and

heading. This can result in large amounts of thrust being used and can, in some circumstances, result in partial or fullvessel blackout depending on power consumed. A smoother transition can usually be accomplished by entering DP one

step at a time. The vessel can be steadied on heading using the joystick and the auto yaw selected. Next the speed in the

surge axis can be reduced to as close to zero as possible and auto surge selected. Finally the same is accomplished with the

sway axis and when auto sway is selected full DP control is enabled. On some DP systems surge and sway are switched

into DP together and cannot be manipulated independently. Some DP systems have functionality that prevents entering

Auto DP mode when speed or turn rate is excessive. When commanded to enter Auto DP mode, these systems will rst

slow the vessel to an appropriate speed and only then will the mode be activated.

After the vessel is on full Auto DP, time is taken for the vessel to settle down on position. The mathematical model will

build giving an indication of the DP current in the area. As the current strength and direction becomes apparent, changes

may have to be made in the operational plan to reect the newly obtained information. When making any changes it

should be noted that although the worksite is nearby, there is a possibility that environmental conditions may not bethe same at that location. The DP current in open water might be different than at the platform due to environmental

interaction with the platform structure or subsea features. Previously mentioned procedures can be utilized to determine

vessel capability and redundancy. Vessel redundancy can be observed by putting the vessel on the desired working

heading and then simulating the worst case failure by deselecting the appropriate thrusters. The observed vessel

performance may dictate that the heading previously chosen for the worksite will put the vessel beyond its limits with

regard to the required level of redundancy. A new heading and/or position for the worksite may have to be chosen or the

DP operation at hand may have to be postponed to await more favorable conditions.


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Communications

Good communications between DP and all parties involved in the DP operation are essential at all times. The means of

communication should, as a minimum, be duplicated to provide backup in the event of system failure. Communications

systems used can consist of telephones, sound powered telephones, talk back systems, UHF radios, VHF radios and DP

status lights (see below). With reliable communications all parties involved in the operation can inform each other about

existing or planned changes in operational status. Modes of communication should be checked for correct operation, before commencing DP operations (often an item on DP checklists). Some examples of two way lines of communication

to be established are as follows:

» DP and dive control (dive support)

» DP and ROV control (any vessel using ROV)

» DP and engine control (all vessels)

» DP and installation (all vessels in close proximity or within 500 zone of platform)

» DP and drill oor (drilling vessels)

» DP and production control (oating production)

» DP and gangway control position (oating accommodation platforms)

» DP and crane cab(s) (any vessel conducting lifting operations)

» DP and ballast control ( heavy lift vessels)

» DP and lift control personnel (heavy lift vessels)

» DP and cargo/platform loading control (shuttle tankers)

» DP and cable/pipe lay personnel (cable/ pipe lay vessels)

» DP and tension control (cable/pipe lay vessels)

» DP and trencher/plow control (cable/pipe lay vessels)

DP Alert Levels

On a DP vessel, there may be a system of alert levels to indicate the status of the DP system. An example of alert levels

might be as follows:

Green - normal operational status, adequate equipment is on line to meet the required

performance within the declared safe working limits.

Yellow - degraded operational status; with the equipment on line, safe working limits are

being exceeded but a loss of position is not taking place and should not take place

unless there is another fault, failure or mistake.

Red - emergency status; there is a loss of position, or position loss is inevitable.

Some vessels have an additional Blue or White advisory level between Green and Yellow.

Alarms indicating status are visual (lights) and depending on status level (Red) audible. The exact meaning of each alert

level and the procedures to be followed in the event of a particular level will vary depending on the type of operation being conducted.


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Worksite Approach

After the vessel position has settled the approach to the worksite can begin. We will assume for this example that the

worksite is located 15m from the side of a platform and that up to this point the vessel is within required capability

limits. Having obtained permission to enter the 500m zone, the vessel has been set up on DP at a distance of 300m from

the platform (see Figure 10.3). Vessel heading has been set to that required at the nal work location. The approach is to

be made on Auto DP from this distance. The vessel will approach using a series of short position moves as opposed tomaking one move which places the vessel directly at the worksite. A few minutes settling time between moves will allow

the mathematical model to update for the new location. Initially a series of 50m moves are used. When getting close to

nal position (about 50m) the moves are reduced to 10m at a time with the nal few moves at 5m each. During the nal

moves, close to the platform, vessel speed should be kept slow at 0.2-0.3 knots. The low speed will minimize overshoots

when arriving at a new position, reduce thrust used to stop the vessel at the position and make it easier to stop the vessel

should problems occur. As the vessel moves towards the platform, fore/aft position is adjusted to align the vessel with

desired work location.

Entering 500m Zone

Transfer Control to DP Desk

Joystick Control

Auto DP

Moving Towards Worksite

Moving Astern to

Align with Worksite

Reduce Speed and

Length of Moves

Auto DP at Worksite

Wait 30 Minutes

to Build the ModelA

B

Figure 10.3


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Additional position references will be deployed as required during the approach to the platform. Client/company/eld/

vessel requirements as well as industry practice will dictate the number of position reference systems required for a

particular job. The vessel might be set up on DP using a minimum number or references (perhaps only DGPS) due

to system availability. HPR beacons deployed at the setup location might be out of range at the worksite. Taut wires

will have to be deployed closer to the worksite because of wire angle limitations. If HPR and/or taut wire are required

references during approach they may be walked along using a series of replumbs when beacon distance (HPR) or angle

(taut wire) limits are reached. The Artemis x station, Fanbeam reector or RADius transponder may not be visible fromthe setup location or perhaps they have to be transferred from the vessel to the platform when closer in. The minimum

number of required references for a given stage of the operation should always be deployed. Standby references, if

available, should be ready if one fails. Using more than the minimum required references is good practice. The greater

number of good quality references online, the less chance that the failure of one will have a serious inuence on vessel

positioning capability. Deploying references with possible common mode failures should be avoided. Two DGPS systems

using the same receiving antenna or using a common software package are subject to single point failures. Three HPR

beacons used in SSBL mode are subject to single point failure from a single subsea noise source.

During the approach a visual lookout should be kept both as a check of vessel progress and to alert the DP operator to

unforeseen problems which might develop. This might be due to supplied worksite information being insufcient (i.e. a

helideck or are tower which is not on the plans). It could be crane operations which have the crane swinging loads over

the worksite. There may be unreported vessel trafc in the area or reported vessels that are not where they are supposed

to be. Vessel progress may also be monitored on an electronic chart/survey spread (if tted). Care should be taken that the

information displayed is accurate and up to date.

Worksite Setup

The mathematical model is constantly updated from the point that the vessel is under manual control at the DP console.

The optimum mathematical model is achieved when the vessel is stopped at one location. After arriving at the worksite the

vessel should be allowed to settle for at least 30 minutes to allow the mathematical model to update fully. Before a green

light is given to commence operations (diving, ROV, pipelay, etc.) the following have to be considered:

» Has the vessel model had sufcient time to build at this location? » Note position/heading deviations and determine if there are within acceptable limits for the operation to be

conducted.

» Ensure that gain settings are appropriate for the conditions.

» Ensure that sufcient reference systems are online and that their performance has been checked and found to

be acceptable.

» Vessel capability and redundancy must be reconrmed.

» Check wind sensors to ensure proper selection and that readings reect actual wind. Readings that were

correct away from the platform may now have induced errors caused by wind interaction with the platform

structure.

» Recheck gyro and magnetic compass readings.

» Review and analyze any DP system alarms. » Complete applicable checklist.

When all checks have been completed and all is in readiness (with regard to DP) a “green light” can be given for

operations to commence.


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Conducting Operations

While the DP operation is underway the vessel may be stopped at one location or moving as per the requirements of the

job. The DPO is to monitor the DP system and ensure that operations are conducted in a safe and efcient manner.

Any required heading or position moves while on DP, are to be conducted at a speed that is safe for the operation at hand

(moving at 3 knots with an ROV in the water that has a maximum speed of 2 knots is not acceptable). A 5m move to portwith the same 1 knot speed that was used a short time ago for a 500m move straight ahead might result in a 5m overshoot

past the setpoint, in addition to large amounts of thrust required to start and stop the vessel as well as settle it down on the

new position. A rate of turn which is beyond the turning capability of the vessel in the present conditions may result in the

system putting so much effort into the heading change that the vessel drifts off position (system priority on heading).

The required levels of redundancy must be maintained at all times. Without redundancy the vessel is subject to loss of

position if a fault in a critical component fails. When lack of redundancy is detected the DPO should take immediate

action to correct the problem. This might involve starting extra generators or thrusters. It could involve changing the

position or heading of the vessel. Stopping the operation at hand and moving the vessel to a safe location may be the

appropriate action, if redundancy cannot be regained.

Example:

A Class 2 dive support vessel with divers deployed has a partial blackout. The bus is split and half the vessels power supply is stillavailable. Adequate redundancy was available prior to the failure and the vessel maintains station. Divers should be immediatelyrecalled to the bell and recovered until such time as the problem can be xed. The job is almost nished and the divers only require a“few” minutes to collect their tools. The vessel will then be free to proceed to the next job location. A decision (incorrect) is made toallow the divers to collect their tools and during those “few” minutes more problems develop which result in a further loss of power.Unable to hold station, the vessel drifts, dragging the divers with it. Successful recovery of the divers is now largely based on goodluck. Hopefully they can get safely back to the bell and recover to deck before they or the bell become entangled in subsea obstructionslocated in the area. Obstructions that were at a safe distance when the vessel was on station with full redundancy now become a

hazard to the divers.

Vessel performance (heading & position) must be constantly monitored to ensure that deviations stay within acceptable

limits. Gain settings may have to be altered to take into account changes in environmental conditions.

Monitoring and controlling vessel’s motion (i.e. changing heading to reduce rolling) may be required for some jobs. This

might include reducing rolling when heavy loads are moved on deck using the vessel’s crane, launching an ROV over the

side or limiting motion to the point where a helicopter is able to land.

All alarms are to be investigated and action taken as appropriate to correct any problems indicated by the alarms.

Position references are to be monitored on an ongoing basis to ensure correct operation and action taken to ensure that the

minimum number of required references, are always online.

Power consumption is monitored and generators not required may be shut down to save on fuel. Thrusters not required

may also be shut down to save on equipment wear. Any shutdowns should be made taking into consideration the required

level of capability and redundancy.

Worksite Departure

When the job is completed the vessel will switch from DP to manual control and steam to the next jobsite or port as

required. If the vessel is working in open water with no obstructions nearby the switching procedure can be followed and

the vessel can steam away. If the vessel is located close to an obstacle (such as a platform) it should be moved to a safe


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distance under DP control before going to manual mode. Safe distance will depend on weather conditions and on the skill

of the DPO to control the vessel in manual mode.

Example:

A vessel is 20m from the side of a platform. Subsea operations are complete and the vessel is clear in all respects to depart. Thevessel is switched to joystick mode by the DPO with the intention of moving away under manual control. Shortly afterwards the vessel

strikes the platform, maybe due to the DPO not having adequate knowledge of the operating characteristics of the vessel in joystickmode (lack of practice). Perhaps he initially pushed the joystick the wrong way (lack of system knowledge) and could not correct forthe mistake in time. Possibly environmental conditions were such that switching from computer to manual at such close proximity(irrespective of operator skill) was simply not advisable.

Before departing from the work location checks must be completed to ensure that all is in readiness for the departure. The

subsea work might be completed but the diving bell might not yet be back onboard. Lines used to transfer tools to the

divers on the bottom may not be completely out of the water. The ROV might not be back on deck and secured. Crane

operations might be ongoing that would be adversely affected by a change in vessel heading as it steams away from

location.

Vessel position references will have to be recovered depending on type in use (Artemis x station, Fanbeam reector/s,

HPR beacons or Taut Wire, etc.). However, sufcient references must remain online until the vessel is ready to switch outof DP mode. HPR poles must be retracted before vessel speed rises to the point where they could be damaged.

Manning

The DP desk should be manned at all times while the vessel is under DP control. The majority of DP operations are

conducted with at least two DP operators on the bridge or manning the DP control room. For some operations that require

no redundancy (i.e. vessel using DP to follow an ROV doing a pipeline inspection in open water) there may be only one

DPO on watch at a time. When two DPOs are present, one should be totally dedicated to the DP console and the DP

operation. The other would carry out other bridge duties (i.e. radar/visual lookout, non DP communications, issue of work

permits, etc.). The two DPOs should normally alternate an hour on the desk and an hour off.

Long periods of calm with little activity can occur during some DP operations. When DP operators are not required

to make vessel moves and are not actively involved in the vessel’s operations, there is the possibility of lapses in

concentration where the DPO is not fully aware of the status of the ongoing operation and of the current operation of the

DP system. Alternating DPOs at the DP desk every hour will help to avoid this problem. It is equally important to change

hourly when operations are more hectic as fatigue could become a problem over the course of a 12 hour watch.

The DP control area should be free from distractions and inuences which take the DPO’s attention away from the DP

system (i.e. conversations carried out by personnel having nothing to do with the ongoing operation).

Watch Handover

Before taking over a DP watch, the DPO must be fully aware of all aspects of the operation. If there are 2 DPOs on awatch it would be good practice not to have both change watch at the same time. If the 4 DPOs on the vessel are doing

12 hour watches, watches could be changed at 0600, 1200, 1800 and 2400. This would mean that at least 1 DPO would

always be on the bridge who has current knowledge of the situation (having come on watch 6 hours previous).

Information to be passed over by the departing DPO and obtained by the one coming on watch would vary depending on

the operation but would include the following:


24/26



» What is the status of the operation (i.e. Diving Operations: Are the divers down? What is the current position

of the divers? What are they doing? What their future plans? etc. Pipe Lay: What is the planned route? What

vessel speed is being used? Is the vessel currently moving or stopped? etc.)?

» How has the DP system been performing and have there been any problems?

» How is the DP console set up (DP mode selected, gain settings, screen options, etc.).

» What position references are in use and how have they been performing?

» Are all thrusters/propellers/ rudders available and how are they performing? » What is the situation regarding power supply?

» Is the vessel meeting redundancy requirements (if applicable)?

» What are the current weather conditions and what is the latest forecast?

» What is the DP current and how has it changed over the course of the watch?

» What has been the position keeping performance of the vessel?

» Are there any new orders, notices to mariners, etc., of which the DPO coming on watch is unaware?

The DPO coming on watch should complete a checklist to gain situational awareness regarding DP system settings and

current system performance.

Logs

A log must be kept of all aspects of the DP operation. All required information may not be recorded on the printer/s

connected to the DP system. Information manually logged would include but not be limited to the following:

» Times of starting and stopping DP operations as well as signicant events during the operation. (i.e. time

ROV was off deck, time diving bell left the surface, time shuttle tanker disconnects from loading buoy, times

for temporary stop of loading crude due to weather, etc.)

» Any operator input changes of heading or position while on DP.

» Deploying or recovering of position references.

» Starting or stopping of thrusters or generators.

» Any problems encountered with the DP system. » Changes in system status with regard to redundancy/vessel capability.

» Movements of other vessels in the area.

Logs can provide a record of evens to be referred to during the investigation of an accident. Times of starting and stopping

DP operations may be used to settle nancial disputes with charterers. Records of encountered problems may help

technicians when repairing the DP system. These are some of the uses of the information recorded in the DP log.

Some DP systems provide the ability to save trend graphs to disk for future reference. A DP system with a data logger

function may save system operation and status information to an external computer for future reference.


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DP Printers

An aid to accurate log keeping are print outs from the DP system. An example of a DP system print out is shown

following. This is a print out from a shuttle tanker equipped with two bow thrusters, two main props, and two rudders.

A 12:42:33 17 SEP 2012 Current CP position E 671114.3 N 5179077.2

A 12:42:33 17 SEP 2012 SIMRAD (10) PME selectedA 12:42:37 17 SEP 2012 Set Heading = 50.0 degrees

A 12:42:52 17 SEP 2012 Set Heading = 49.9 degrees

A 12:43:10 17 SEP 2012 Current CP osition E 669114.5 N 5179007.1

A 12:43:10 17 SEP 2012 SIMRAD (11) PME selected

A Alarm 12:43:32 17 SEP 2012 Thruster 1 high thrust warning


A Alarm 12:43:32 17 SEP 2012 Stbd Main Prop high thrust warning

A Alarm 12:43:32 17 SEP 2012 Port Main Prop high thrust warning

A 12:43:45 17 SEP 2012 Stbd Main Prop high thrust warning OK

A 12:43:45 17 SEP 2012 Port Main Prop high thrust warning OK

A Alarm 12:44:00 17 SEP 2012 Con. analysis: Thruster failure critical

A Alarm 12:44:02 17 SEP 2012 Con. analysis: Bus section failure criticalA Alarm 12:44:27 17 SEP 2012 SIMRAD (10) PME failed

A Alarm 12:44:27 17 SEP 2012 Current CP position E 671113.1 N 5179077.6

A 12:44:27 17 SEP 2012 SIMRAD (10) PME deselected

A Alarm 12:44:30 17 SEP 2012 Mismatch between PME/sensor selections

A 12:44:35 17 SEP 2012 Mismatch between PME/sensor selections OK

A 12:44:38 17 SEP 2012 Thruster 1 high thrust warning OK


A 12:44:49 17 SEP 2012 Current CP position E 671114.6 N 5179077.4

A 12:44:49 17 SEP 2012 ARTEMIS PME selected


A Alarm 12:45:10 17 SEP 2012 Thruster 2 high thrust warningA 12:45:33 17 SEP 2012 Set Heading = -4.2 degrees

A 12:46:31 17 SEP 2012 Con. analysis: Bus section failure not critical

A 12:46:33 17 SEP 2012 Con. analysis: Thruster failure not critical

A Alarm 12:46:40 17 SEP 2012 Ofoading position warning



A Alarm 12:47:08 17 SEP 2012 Stbd Main Prop high thrust warning

A Alarm 12:47:08 17 SEP 2012 Port Main Prop high thrust warning

A Alarm 12:47:35 17 SEP 2012 Con. analysis: Thruster failure critical

A Alarm 12:47:45 17 SEP 2012 Con. analysis: Bus section failure critical

A Alarm 12:48:10 17 SEP 2012 Thruster 1 pitch feedback fault

A Alarm 12:48:10 17 SEP 2012 Thruster 2 pitch feedback faultA 12:48:16 17 SEP 2012 Thruster 1 pitch feedback OK

A 12:48:16 17 SEP 2012 Thruster 2 pitch feedback OK

A 12:48:56 17 SEP 2012 No Push-Pull mode selected

A Alarm 12:49:47 17 SEP 2012 Anemometer 1 failed

A 12:49:47 17 SEP 2012 Anemometer 1 deselected

A 12:50:00 17 SEP 2012 Console B selected

Documents

Chapter10 - DP Operations