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.

                                      Figure 11FPSO Overview


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.

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.

Figur 12 BALLAST TANK IN HULL


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.



In previous FPSO projects, the ballast pumps were located in pump room, but recently projects have installed the hydraulic operated, submersible centrifugal type pumps in the central wing ballast tanks. In semi-submersible type projects, ballast pumps had functions of ballasting/ de-ballasting and located at the machinery space in pontoon areas. However, in the recent projects, the ballasting is operated by topside seawater lift pumps and electric motor driven, centrifugal type, de-ballasting to overboard above the deepest waterline. To size ballast pumps, cargo loading/ offloading capacity is to be considered in ships shape projects and restoring units from damage conditions in semi-submersible projects.





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: 
  • One ballast ring  main,  routed  through  double  side  tanks  (ballast  and  void),  fore ballast tanks and cofferdams that segregates the machinery spaces from cargo area.
  • Another secondary manifold  serving  for  aft  peak  ballast  tanks  at  aft  machinery space.
The ballast ring main performs the following:

·         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

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. 

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.

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)

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:
  1. 4 TA 8110 Fore Peak Ballast Tank (central)
  2. 4 TA 8120A Fore Peak Ballast Tank (port)
  3. 4 TA 8120B Fore Peak Ballast Tank (starboard)
  4.  4 TA 8130A Wing Ballast Tank # 1B (port)
  5.  4 TA 8130B Wing Ballast Tank # 1B (starboard)
  6.  4 TA 8131A Wing Ballast Tank # 2A (port)
  7.  4 TA 8131B Wing Ballast Tank # 1B (starboard)
  8.  4 TA 8140A Midship Ballast Tank # 3 (port)
  9.  4 TA 8140B Midship Ballast Tank # 3 (starboard)
  10.  4 TA 8150A Wing Ballast Tank # 4A (port)
  11.  4 TA 8150B Wing Ballast Tank # 4A (starboard)
  12.  4 TA 8151A Wing Ballast Tank # 5A (port)
  13.  4 TA 8151B Wing Ballast Tank # 5A (starboard)
  14.  4 TA 8160A AFT Peak Ballast Tank (Port)
  15.  4 TA 8160B AFT Peak Ballast Tank (Starboard)
  16.  4 TA 8170 AFT Peak Ballast Tank (Central)
  17.  4 TA 8180A AFT Buffer Tank (Port)
  18.  4 TA 8180B AFT Buffer Tank (Starboard)
  19.  4 TA 8190A Fore buffer tank (port)
  20.  4 TA 8190B Fore buffer tank (starboard)
  21.  V1A(P) Void Tank # 1A(port)
  22.  V1A(S) Void Tank # 1A (starboard)
  23. V2B(P) Void Tank # 2B (port)
  24.  V2B(S) Void Tank # 2B (starboard)
  25.  V3A(P) Void Tank # 3A (port)
  26.  V3A(S) Void Tank # 3A (starboard)
  27. V3B(P) Void Tank # 3B (port)
  28. V3B(S) Void Tank # 3B (starboard)
  29. V4A(P) Void Tank # 4A (port)
  30. V4A(S) Void Tank # 4A (starboard)
  31. V5B(P) Void Tank # 5B (port)
  32. V5B(S) Void Tank # 5B (starboard)
  33. VC Void Tank (Fore)
  34. CD1 Fore side Cofferdam
  35. CD2 Aft side Cofferdam
  36. 4 GA 8110 Fore Ballast Pump (Port)
  37. 4 GA 8120 Fore Ballast Pump (Starboard)
  38. 4 GX 8130 AFT Ballast Pump (Port)
  39. 4 GX 8140 AFT Ballast Pump (Starboard)
  40. 4 UB 8190 Oil Discharge Monitoring System
  41. 4 UB 8110 A/B/C/D Portable Washing Machine





Comments

Popular posts from this blog

BILGE SYSTEM

BALLAST CONTROL SYSTEM (FPSO)