FPSO HULL & TOPSIDE INTRODUCTION
1. INTRODUCTION
A Floating Production, Storage and
Offloading (FPSO) unit is a floating vessel by the offshore oil and gas
industry for the processing of hydrocarbons and for storage of oil. A FPSO
vessel is designed to receive hydrocarbons produced from nearby platforms or
sub-sea template, process them, and store oil until it can be offloaded onto a
tanker or, less frequently, transported through a pipeline.
The FPSO, as its name suggests, is a floating contraption
that allows oil rigs the freedom not just to store oil but also to produce or
refine it before finally offloading it to the desired industrial sectors,
either by way of cargo containers or with the help of pipelines built
underwater.
The use of this system ensures that shipping companies do
not have to invest even more money by ferrying the raw and crude oil to an
onshore refinery before transferring it to the required industrial areas. In
simple terms, the FPSO saves time and money effectively.
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Figure 1‑1FPSO Overview
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Understanding FPSO
The following steps will elaborate on the
different functions performed by the FPSO as a system:
Production: The ‘P’ in the FPSO stands for production.
Production means evolving the crude oil obtained from the deeper parts of the
ocean. The FPSO is enabled and fitted with equipment’s that would act as a
refinery of sort to distil the oil obtained from the ocean along with the gases
that are emitted. This is the main feature of a FPSO as only with the help of
this feature can a FPSO attain the reliability that it enjoys in today’s times.
Storage: This is the second most
important feature and the ‘S’ in the acronym FPSO. Second-most important
because just as it is important to filter the excavated oil from its oceanic
reservoirs, it is equally important to store it well. For this purpose, the
FPSO is built in such a way that the tubes and the pipes and the tanks are
perfect for storing the distilled product from the crude raw-material. They are
safe and sturdy so as to resist any chances of unwanted oil spillage and thus
contamination of the marine life-forms.
Offloading: This is ‘O’ in the concept of
FPSO. The offloading aspect is important when the FPSO has to transfer its
contents into ships designed as oil carriers or to pipelines that act as
transfer agents. In simple terms, offloading refers to removing the cargo in a
FPSO and transferring it to another cargo-carrying vessel or equipment. The
offloading part is very tricky as the process is carried out in the middle of
the sea and thus requires a lot of concentration and focus in order to avoid
any sort of spillage.
The FPSO vessel divided into two major
parts, Hull and Topside.
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| FPSO (HULL & TOPSIDE) |
1.1 FPSO INDUSTRIES
The FPSO contains two major parts called
Hull and Topside.
The interfaces between the hull and
topside shall include the power generation heating medium supply, cooling
medium, and shall be flexible in terms of topside supporters.
The FPSO hull is intended for large deep-water
field development, thus leading to
·
A large topside plant,
·
A large production and storage
capacity,
·
A long field life.
Hull control refers to the management and monitoring of the hull of a ship or vessel. The hull is the main body of a ship, typically made of steel or other materials, that provides the structural integrity and buoyancy necessary for the vessel to float and navigate through water.
Hull control involves various activities and systems that ensure the hull's integrity, safety, and efficiency. Some key aspects of hull control include:
1. Hull monitoring systems: These systems use sensors and monitoring devices to track the condition of the hull, including its temperature, pressure, stress, and potential damage from corrosion or impact.
2. Hull maintenance: Regular inspection, cleaning, and maintenance of the hull are essential to prevent corrosion, fouling, and other forms of damage that can compromise the ship's structural integrity.
3. Hull protection: Measures such as anti-corrosion coatings, sacrificial anodes, and cathodic protection systems are used to protect the hull from corrosion caused by exposure to seawater.
4. Hull performance optimization: Monitoring and controlling factors such as hull resistance, drag, and stability can help optimize the vessel's performance in terms of fuel efficiency, speed, and maneuverability.
Overall, effective hull control is crucial for ensuring the safety, seaworthiness, and operational efficiency of a ship or vessel. It requires a combination of proactive maintenance practices, advanced monitoring technologies, and adherence to regulatory standards to keep the hull in optimal condition throughout the vessel's lifespan.
The Hull part is mainly contains,
·
Ballast and Buffer tank systems
·
Bilge system and treatment
package
·
Diesel oil system
·
Fresh water and potable water
system
·
Helifuel system
·
Hull Compressor air system
·
Inert gas distribution system
·
Jockey pump system
·
Methanol storage tank system
·
Nitrogen distribution system
·
Service water distribution
system
·
Slop water treatment system
·
Hydraulic power unit (HPU)
·
Hydraulic power unit for Remote
operated valves (ROV)
·
Emergency Shutdown System
(ESD)/ Fire and Gas System (FGS)
·
Diesel oil purifier
·
Emergency generator
·
Essential generator
·
Fresh water maker package
·
Hull air compressor and dryer
package
·
Heating, Ventilation and
Air-conditioning (HVAC) Package
·
Tandem offloading system
·
Sewage treatment package
·
Tank gauging package
·
Water mist package and
distribution
·
Carbon di-oxide (CO2) package
·
Bow crane package
·
Interface hull with topside
HVAC ventilation system
·
Miscellaneous system (Cold
chamber, Water tight doors, Anode monitoring etc,,)
The topside control systems consists of
·
Inlet manifold
·
Oil separation and
stabilisation
·
Produced water
·
Crude oil storage and
off-loading
·
Sea water treatment
·
Water injection booster pumps
·
Water injection pumps
·
Miscellaneous systems
·
LP Gas compression
·
HP Gas compression
·
Injection gas compression
·
Gas dehydration & TEG
Regeneration
·
Flares system
·
Fuel gas system and diesel oil
·
Closed drain system
·
Inert gas system
·
Air system and Nitrogen
production
·
Hot water system & Main
power generation
·
Cooling water system
·
Chemical Injection system
·
Gas export metering and export
line
·
Crude oil re-circulation
·
MP gas compression
1.1.3 Overall Control and Well Riser (OCWR) CONTROL SYSTEMS
·
Production well – Preservation
control module
·
Production loop – Control
module
·
Methanol distribution and
management control module
·
Preservation overall – Flushing
control module
·
Water injection overall control
module
·
Gas injection control module
·
Production riser – Production
control module
·
Production riser – Slugging
control module
1.2 HULL CONTROL SYSTEMS
1.2.1 BALLAST AND BUFFER TANKING SYSTEMS
A ballast tank is a compartment within a
boat, ship or other floating structure that holds water. The ballast system keeps the offshore
unit in a stable condition and at a suitable draught, heel and trim in all
relevant states of operation. In order to provide adequate stability to
vessels at sea, ballast is used to weight the ship down and lower its center of
gravity.
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Figur 1‑2 BALLAST TANK IN HULL
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Ship board ballast operations
Why ballast is used?
- Maintain seaworthy conditions when lightly loaded
- Draft,trim, stability, bending moment, shear force, slamming propeller immersion, motions
- How the ballast operations are handled?
- Loading conditions is assessed and ballast allocated to remain with in safe operational limits
- Ballast movements co-ordinated with ship (FPSO) operations.
Impact on crew:
- Provides for vessel safety
- Controls vessel motion for better comfort
- Requires daily management of ballast and maintenance of systems and tanks.
Typical Ballast System Components
- Simple liquid storage/handling systemTanks,
- Piping, Valves,
- Pumps, Vents
- Overflows,
- Sounding tubes,
- Level indicators
- Remotely operated Sea chests and
- Overboard discharges
The ballast system
The segregated ballast system is designed
in floating production storage and offloading (FPSO) to comply with
International Convention for the Prevention of Pollution from Ships (MARPOL)
regulations. It has ballasting/ de-ballasting and transfer functions from one
tank to any other ballast tanks. Ballast filling is via ballast main pipes
which run to the ballast seawater from topside seawater lift pumps or topside
utility pumps using gravity filling.
The
Ballast system consists of the following functions:
- Compensation of the heel induced on the FPSO by permanent riser asymmetric hang-off or Topsides CoG eccentricity (permanent ballast).
- Ensure sufficient draft of the FPSO during tow and during on-site operation when little cargo is stored.
- Adjust heel and trim of the FPSO (for lifting of settled water in cargo tank before offloading, tank stripping or during tank inspection and maintenance).
- Minimize stresses in the hull due to still water shear forces and bending moments induced during FPSO towing phase and during on-site operation, especially due to tank inspection/maintenance cases.
- Transfer contaminated ballast water to the slop tanks for settling and treatment.
- Strip ballast tanks, cofferdams and void Spaces (bilge function).
- Emergency pumping of pump room in case of flooding.
The
Ballast system consists of the following:
- · Manifolds
- · Ballast pumps
- · Ballast tanks
- · Void spaces and cofferdam
- · Oil discharge monitoring system
- · Air vent and sounding
- · Ballast system in connection with other systems
Ballast System Overview
1.2.1.1.
Manifolds
The ballast system comprises two completely
segregated manifolds:
- Another secondary manifold serving for aft peak ballast tanks at aft machinery space.
·
Transfer from any buffer tank
to manifold with any pump while the other one is unavailable.
·
De-ballasting with any pump
while the other one is unavailable.
·
Transfer from any buffer tank
to manifold with both pumps simultaneously.
·
De-ballasting with both pumps
simultaneously.
1.2.1.2
Ballast Pumps
Sea inlet and overboard discharge valves are to be secured directly on the shell plating, or on sea chests built on the shell plating, or on extra-reinforced and short distance pieces attached to the shell/wing tank bulkhead. Sea inlet and overboard discharge valves are to be of a flanged type or equivalent.
There
are ballast pumps installed in the engine room or pump rooms. These pumps take
their suction from sea water main line, from the high sea chest being on the
port side or starboard side and from the low sea chest being on opposite side.
And
also, they take their discharge line to the overboard or to the ballast tank
through the ballast main line. When operating ballast, ballast pump takes
suction from sea chest and discharges to ballast main line through the ballast
pump discharge line. When operating de-ballast, ballast pump take suction from
the ballast main line, and discharges to overboard through the overboard valve.
Each ballast tank has butterfly suction valve operated hydraulically and of the
intermediate position controlled type except for the engine room, forward/aft
peak tank fill/suction valves. The engine room, forward/aft peak tank
fill/suction valves are of hydraulic on/off controlled type valves.
Also
ballast tank volume is calculated at the loading computer in accordance with
the measured ballast tank level, which is transferred from the Integrated
Control Safety System (ICSS) to the loading computer by the serial link.
The Integrated Control Safety System (ICSS) monitors each ballast tank level and transfer
to the loading computer by serial link. And the loading computer sends the
calculated ballast volume to the Integrated Control Safety System (ICSS).
Sea inlet and overboard discharge valves are to be secured directly on the shell plating, or on sea chests built on the shell plating, or on extra-reinforced and short distance pieces attached to the shell/wing tank bulkhead. Sea inlet and overboard discharge valves are to be of a flanged type or equivalent.
The ballast ring main is equipped with two
hydraulically driven submerged ballast pumps, (one port and one starboard - 2×50%) and each
having a capacity to deliver 1000 m3 /h
(with turn down capability up to 200 m3/hr) at an operating pressure of 3.8
barg.
The ballast pumps
transfer the water from
buffer tanks to
ballast tanks or
from ballast tanks
to
overboard.
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| Ballast Pump |
The ballast pumps are powered by
the hydraulic power units (HPU). Each ballast pump is located within the
void (V5B P&S) containing the associated buffer tank. The ballast pump arrangement includes
facilities to inspect, maintain and replace one ballast pump keeping the ballast ring main
operational for the other pump.
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| Ballast Pump |
The AFT side ballast manifold is equipped with two electrically driven pumps, 4 GX 8130/ 8140 (one port and one starboard - 2×50%) each having a capacity to deliver 500 m3/h at an operating pressure of 3.8 barG to transfer water from aft buffer tanks, 4 TA 8180A/B, to aft peak ballast tanks 4 TA 8160 A/B, 4 TA 8170, and further from these Aft Peak Ballast tanks to overboard.
The ballast pumps are located in the machinery room pump room, port and starboard, one each side. These pumps also work as emergency bilge transfer from aft machinery space to overboard. In case the AFT Ballast Pumps 4GX8130/ 8140 are used for Machinery space Emergency bilge, the High Oil content trip signal 4ASHH 81901 from Oil Discharge Monitoring Systems ODMS (4UB 8190) is manually overridden (executive action inhibited) in Process Safety Shutdown(PSS).
The total ballasting capacity is sufficient to maintain the FPSO in a stable condition and at a suitable draught while offloading cargo oil at the maximum rate. The fore and aft ballast pumps port/starboard are provided with a priming system to enable tank stripping. The priming system is based on air eductors which has noise level within limits. In addition, AFT ballast pumps are designated as emergency bilge pumps. The emergency suction from starboard machinery room is led to AFT ballast pump port and vice-versa.
Ballast
Tanks (including buffer tanks)
Main
Ballast system
Following buffer tanks, wing ballast tanks
and fore peak tanks are connected with ballast ring main.
- Fore buffer tank (port), 4 TA 8190 A (Capacity: 561 m3)
- Fore buffer tank (starboard), 4 TA 8190 B (Capacity: 561 m3)
- Wing Ballast Tank # 5A (port), 4 TA 8151 A (Capacity: 2992 m3)
- Wing Ballast Tank # 5A (starboard), 4 TA 8151 B (Capacity: 2992 m3)
- Wing Ballast Tank # 4A (port), 4 TA 8150 A (Capacity: 2992 m3)
- Wing Ballast Tank # 4A (starboard), 4 TA 8150 B (Capacity: 2992 m3)
- Mid-ship Ballast Tank # 3 (port), 4 TA 8140 A (Capacity: 21770 m3)
- Mid-ship Ballast Tank # 3 (starboard), 4 TA 8140 B (Capacity: 21770 m3)
- Wing Ballast Tank # 2A (port), 4 TA 8131 A (Capacity: 2992 m3)
- Wing Ballast Tank # 2A (starboard), 4 TA 8131 B (Capacity: 2992 m3)
- Wing Ballast Tank # 1B (port), 4 TA 8130 A (Capacity: 2992 m3)
- Wing Ballast Tank # 1B (starboard), 4 TA 8130 B (Capacity: 2992 m3)
- Fore Peak Ballast Tank (central), 4 TA 8110 (Capacity: 7049 m3)
- Fore Peak Ballast Tank (port), 4 TA 8120 A (Capacity: 8196 m3)
- Fore Peak Ballast Tank (starboard), 4 TA 8120 B (Capacity: 8196 m3)
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| Ballast Tank |
The ballast ring main buffer tanks (i.e.,
fore buffer tanks) are located in the double side void space, V5B (P) and V5B (S)
respectively.
The
seawater drop lines
in buffer tanks
are led to tank
bottom. Above ballast
tanks are connected with ballast ring main by a
ballasting cum de-ballasting line and one stripping line. One is equipped with a bell mouth
designed for large flow (ballasting/de-ballasting, the other is designed for small flow
suction (stripping). The distribution to relevant ballast tanks are achieved from the ballast ring
main through water inlet branches equipped with hydraulic remotely operated fail close type
valves, ROVs, one on each branch connecting lines for ballasting, de-ballasting and
stripping operation. These are fail close type isolation
valves.
Aft
Ballast system (Buffer tanks)
Following buffer tanks and aft peak tanks
are connected with secondary ballast and bilge manifold in the aft machinery space.
- Aft buffer tank (port), 4 TA 8180 A (Capacity: 376 m3)
- Aft buffer tank (starboard), 4 TA 8180 B (Capacity: 376 m3)
- Aft Peak Ballast Tank (central), 4 TA 8170 (Capacity: 6106 m3)
- Aft Peak Ballast Tank (port), 4 TA 8160 A (Capacity: 9120 m3)
- Aft Peak Ballast Tank (starboard), 4 TA 8160 B (Capacity: 9120 m3)
Aft buffer tanks are located in the central
AFT peak ballast tank, on each sides of the pump room.
The
seawater drop lines
in buffer tanks
are led to tank
bottom. Above ballast
tanks are connected with ballast manifold by a
ballasting cum de-ballasting line and one stripping line.
One is equipped with a bell mouth
designed for large flow (ballasting/de-ballasting), the other is designed for small flow
suction (stripping). The distribution to relevant ballast tanks are achieved from the ballast ring
main through water inlet branches equipped with hydraulic remotely operated fail close type
valves, ROVs, one on each branch connecting lines for ballasting, de-ballasting and
stripping operation. These are fail close type isolation valves.
The
Hull seawater distribution
system supply water
to both fore
buffer tanks, 4 TA 8190A/B
(port and starboard) and aft
buffer tanks, 4 TA 8180A/B ( port and starboard).
The
Fore buffer tanks
and AFT buffer
tanks are having
561 m 3 and 376 m
3 capacity
respectively.
1.2.1.4.
Void spaces and Cofferdam
Main Ballast system
Other than ballast tanks following void
spaces and cofferdam around the FPSO vessel are connected with ballast ring main for
emptying any unexpected accumulated water in these areas.
- Aft side Cofferdam, CD2
- Void Tank # 5B (port), V5B(P)
- Void Tank # 5B (starboard), V5B(S)
- Void Tank # 4A (port), V4A(P)
- Void Tank # 4A (starboard), V4A(S)
- Void Tank # 3A (port), V3A(P)
- Void Tank # 3A (starboard), V3A(S)
- Void Tank # 3B (port), V3B(P)
- Void Tank # 3B (starboard), V3B(S)
- Void Tank # 2B (port), V2B(P)
- Void Tank # 2B (starboard), V2B(S)
- Void Tank # 1A(port), V1A(P)
- Void Tank # 1A (starboard), V1A(S)
- Fore side Cofferdam, CD1
The
above spaces are
supposed to be
dry space.
However,
each tank void
space and cofferdam
spaces are provided
with small flow
suction (stripping) line
connection for emptying
out any unexpected
accumulated water in
these areas. These
branches are equipped
with hydraulic remotely
operated fail close
type valves (ROV’s)
for stripping operation.
1.2.1.5.
Oil Discharge Monitoring System
The ballast water overboard lines are
provided with an Oil Discharge Monitoring
System (ODMS) 4 UB 8190, for checking oil content
in the discharge water from ballast system in accordance
with MARPOL 73/78
Annex II requirements.
The system has
centralize sampling points located on all ballast
overboard lines and on the overboard line from cargo transfer header. Discharge from Fore
Ballast pumps, 4 GA 8110 / 8120 and AFT ballast pumps, 4 GX 8130 / 8140 are routed to
overboard for de-ballasting of FPSO vessel. Before the ballast water goes to overboard, the
oil content in the water is tested by this ODMS unit. If oil content is less than 15 ppm,
then the ballast water directly routed to overboard.
In case of high oil content of ODMS,
ballast pumps shall be stopped by high oil content trip (4ASHH-81901). If this occurs, that
means there is pollution in Ballast Tank. In case the AFT Ballast Pumps 4GX 8130/8140 are
used for Machinery space emergency bilge, the High
oil content trip
signal 4ASHH 81901
from ODMS (4UB
8190) is manually Overridden (executive action inhibited) on
PSS.
In case of Instrument Air pressure Low Low
in ODMS, ballast pumps shall be stopped by the signal 4PSLL 81902 and display alarm on
PCS.
- The Polluted water will be diverted to the to cargo oil transfer manifold and the slop tank as follows
- Fitting the spool piece for connecting the ballast pump/s to the cargo oil transfer manifold.
- By closing the manual valve on overboard discharge line and opening the manual valve to the cargo oil transfer manifold.
- The pumps must be re-started after resetting the Trip. The trip will reset by manually flushing the Oil discharge monitoring system (4 UB 8190).
1.2.1.6.
Air Vent and Sounding
The ballast tanks void spaces and
cofferdams are provided with two vent pipes each tank and one sounding pipe.
1.2.1.7.
The ballast System is connected to other systems as follows:
Interface with Bilge system Emergency
bilge suction lines
from machinery space
pump rooms are
connected to the suction
side of Aft
Ballast pumps for
transferring bilge water
to overboard in
case of emergency.
Interface with Seawater System
The
Hull seawater distribution
system supplies water
to both fore
buffer tanks, 4 TA 8190A/B ( port and starboard) and aft
buffer tanks, 4 TA 8180A/B ( port and starboard).
Interface with Cargo Oil System/ Slop Tank System
The ballast water could be delivered to the
cargo oil tanks (through transfer header) during towing. A Spool piece connection has been
arranged for transferring the ballast water. The Cargo Oil Tanks shall be used for loading
and discharging of seawater in case the draft of the FPSO needs to be temporarily increased
during towing. The polluted ballast
water is also transferred through this spool
connection to the slop tanks for settling and treatment.
Interface with Service Air System
The Ballast Pumps priming eductors are
powered by the service Air System.
Interface with Inert Gas Air System
Ballast
tank, void space
and cofferdam (for
tanks adjacent to
cargo tanks only)
are connected to inert gas system through
temporary flexible hose connections for purging and gas freeing in case of oil leak in tank.
Equipment list, Service and location:
- 4 TA 8110 Fore Peak Ballast Tank (central)
- 4 TA 8120A Fore Peak Ballast Tank (port)
- 4 TA 8120B Fore Peak Ballast Tank (starboard)
- 4 TA 8130A Wing Ballast Tank # 1B (port)
- 4 TA 8130B Wing Ballast Tank # 1B (starboard)
- 4 TA 8131A Wing Ballast Tank # 2A (port)
- 4 TA 8131B Wing Ballast Tank # 1B (starboard)
- 4 TA 8140A Midship Ballast Tank # 3 (port)
- 4 TA 8140B Midship Ballast Tank # 3 (starboard)
- 4 TA 8150A Wing Ballast Tank # 4A (port)
- 4 TA 8150B Wing Ballast Tank # 4A (starboard)
- 4 TA 8151A Wing Ballast Tank # 5A (port)
- 4 TA 8151B Wing Ballast Tank # 5A (starboard)
- 4 TA 8160A AFT Peak Ballast Tank (Port)
- 4 TA 8160B AFT Peak Ballast Tank (Starboard)
- 4 TA 8170 AFT Peak Ballast Tank (Central)
- 4 TA 8180A AFT Buffer Tank (Port)
- 4 TA 8180B AFT Buffer Tank (Starboard)
- 4 TA 8190A Fore buffer tank (port)
- 4 TA 8190B Fore buffer tank (starboard)
- V1A(P) Void Tank # 1A(port)
- V1A(S) Void Tank # 1A (starboard)
- V2B(P) Void Tank # 2B (port)
- V2B(S) Void Tank # 2B (starboard)
- V3A(P) Void Tank # 3A (port)
- V3A(S) Void Tank # 3A (starboard)
- V3B(P) Void Tank # 3B (port)
- V3B(S) Void Tank # 3B (starboard)
- V4A(P) Void Tank # 4A (port)
- V4A(S) Void Tank # 4A (starboard)
- V5B(P) Void Tank # 5B (port)
- V5B(S) Void Tank # 5B (starboard)
- VC Void Tank (Fore)
- CD1 Fore side Cofferdam
- CD2 Aft side Cofferdam
- 4 GA 8110 Fore Ballast Pump (Port)
- 4 GA 8120 Fore Ballast Pump (Starboard)
- 4 GX 8130 AFT Ballast Pump (Port)
- 4 GX 8140 AFT Ballast Pump (Starboard)
- 4 UB 8190 Oil Discharge Monitoring System
- 4 UB 8110 A/B/C/D Portable Washing Machine
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