BPZ CX-15 ProjectBallast Control System Overview

Agenda

Ballast Control System (BCS) Methodology

Screens Parameters

Alarms Settings

Ballast Control Sequences Controls

9/4/20122

BCS Overview - Methodology

• Air over water system• Powered by external

hydrostatics and pressurized Tower air

• Tank pressure is equal to external hydrostatic pressure at tank level

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SEA WATER

BALLASTING OPERATIONS

AIR SUPPLY

AIR VENT TOATMOSPHERE

WATER SUPPLY

NO NC NO

NO NC NO

NO O

COMPRESSEDAIR

AIR SUPPLY

WATER SUPPLY

SEA WATER

DECK 4

DECK 3

VENT

NO NC NO

NO NC NO

NO NC

VENT TOATMOSPHERE

WATER SUPPLY

AIR SUPPLY

NORMAL OPERATIONS

NO NC

NO NC NO

NO NC NO

COMPRESSEDAIR

SEAWATER

COLUMN OFSEAWATER

BCS Overview - Methodology

Goals• Maintain acceptable Tilt

to maximize drilling time• Allow for Tilt corrections

by Engineer for any reason

• Minimize load change on bottom

• Minimal involvement from Engineers*

Settings• Drilling

– In the drilling setting, the Tower will automatically ballast once a certain Tilt is reached

• Non-Drilling– In the non-drilling setting,

the Tower will be ballasted only when desired by the Engineer*

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*Engineer refers to any person qualified to operate the Tower BCS

BCS Overview – ConfigurationHeeling towards Tube 1 is Heel positive.

Heeling towards Tube 3 is Heel negative.

Trimmed towards Tube 2 is Trim positive.

Trimmed towards Tube 4 is Trim negative.

Venting a tube releases pressure in the tank and allows

water into the tank thus increasing its weight.

Pressurizing a tube increases the pressure in the tank

which presses water from the ballast tank and

thus decreases the weight in the tank.

Positive Heel is corrected by venting Tube 3 and/or

pressurizing Tube 1; inducing a negative heel.

Negative Heel is corrected by venting Tube 1 and/or

pressurizing Tube 3; inducing a positive heel.

Positive Trim is corrected by venting Tube 4 and/or

pressurizing Tube 2; inducing a negative trim.

Negative Trim is corrected by venting Tube 2 and/or

pressurizing Tube 4; inducing a positive trim.

Tilt is the resultant angle of the Heel and Trim attitudes.

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BCS Overview – System Basics

• Inclination is corrected through 2 methods – In the Drilling mode when Tilt > 0.8o automatically– Any time the Engineer hits the “Back to Zero”

• Ballasting change is always equal and opposite for diagonal tubes

• The Ballast System Steps (“back to zero” or tilt induced)– Greater attitude (Heel or Trim) is corrected first– Venting is performed first to correct half of the major attitude– Pressurization is used to correct for other half of major

attitude• If Tilt > 0.1o then Ballast System Continues

– Greater attitude is corrected until Tilt </=0.1o using the same steps as above

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Screens

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Ballast ControlParameters

Parameters - Inclinometers

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• Two redundant inclinometers will be mounted to the BCS rack in the MCC

• Should be aligned horizontally above the Tower center of gravity

• Sensor output is RS232 but will be converted to 24V 4-20mA before reaching BCS

• Tilt is the Resultant of Heel and Trim

• Deviation tolerance is set by Engineer

• Tilt can be determined by either instrument individually or an average of the inclinometers

Parameters - Inclinometers

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• Two sets of BCS angle alarms– May not be

necessary

• HH in drilling mode is the value at witch BCS automatically starts ballasting

Parameters – Suction Can Foundation

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• Suction can has two pressure indicators– Directly from top deck of

SCF– 1m above deck of SCF– Allowable deviation will

be set to accommodate the difference in level

• Pressure alarms in the SCF are a function of the allowable load on the soil

Parameters – Draft Input

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• The design draft of the Tower is 53.4m may not be the draft after installation.

• The draft of the tower directly affects the pressure–tank level relationship.

• Levels are calculated using the installed draft mark entered by the Engineer.

Parameters – Draft/ Tank Level Relationship

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TL = (Draft‐T1)‐(P*144/γ/3.28)

Where: TL =  Tank Level (m)D = Draft of Tower (m)T1 = Distance from Seafloor to 

bottom of Lower Tank (m)P = Pressure of Tank from 

Transmitter (psi)γ = Specific weight of 

seawater, 64.0 (lb/ft3) 144 = in2 to ft23.28 = ft to m

Parameters – Variable Ballast

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• Each variable ballast tank has 2 pressure indicators– PI9XXA isolated at top of tower– PI9XXB on the ballast manifold

• Parameters screen shows both values and the discrepancy between the two

• The current PIT used for the level calculations shows in blue

• If a PIT is suspected to be faulty, the other can be used

• Tank levels are calculated using the draft mark input

Parameters - Variable Ballast

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• All tanks in a level have the same deck elevations and inlet/outlet levels

• Alarm levels (% Full)– HHH 1%– HH 5%– H 10%– L 90%– LL 95%– LLL 99%

• Mainly used as values of interest, such as when to move to next tank

Parameters – Misc. Alarms

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• Non-Drilling Tilt Change– 0.5o Tilt is greater than

mean Tilt expected by the 95% wave

– Eccentric load or tank leak (void or vb)

• Large Tank Pressure Change – A change of 2.2psi /30min

= level change of 1.5m, (possible tank leak)

• Pressure deviation– Allowable difference

between 2 redundant instruments

• All can be reconfigured

Ballast Control - Actions• Change Mode

– Toggle between drilling and non-drilling

• Go to Zero– Begins ballasting to take

Tower back to a minimal Tilt

• Shutdown– Stops current ballasting

sequence and closes all valves

• Position Reset– Sends platform back to

the original default position; this position is set by the Engineer

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Ballast Control - Sequences

• Shows the operation that the BCS is currently rectifying– Heel Negative– Heel Positive– Trim Negative– Trim Positive

• Shows the current state of BCS– Reset– Shutdown– Hold

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Ballast Control – Leak Detection

• Leak detection is normally closed

• Open circuit means either leak or faulty sensor

• Leak can be confirmed manually using sounding tubes

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Ballast Control – Pressure/Level Indication

• The levels are calculated directly from the pressures with respect to draft

• Percentage full is percentage of available ballast

• Pressure values are blue if the tank is full and green if the tank is in working range

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Ballast Control – Valve• Valves can be operated

manually in the ballast control screen through the valve ballast control panel by clicking on valve

• Closed valves and actuators show in red

• Open valves and actuators show in green

• Valves in transition show in yellow

• Valve control panel allows for the valve to be opened or closed by the engineer

• Current valve state highlights in blue

• Valve can be switched from auto to manual

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Ballast Control – Valve

• Heel, Trim and resultant Tilt are shown on the Ballast Control Screen

• Positive heel and positive trim are towards the respective arrows

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Drawings

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Drawings

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Drawings

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Drawings

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Drawings

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Drawings

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Drawings

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Drawings

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Drawings

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