BILGE SYSTEM

BILGE SYSTEM

1.1.1     BILGE SYSTEM

The Bilge is the lowest compartment on a ship, below the water line, where the two sides meet at the keel.

Introduction:

The bilge system enables water and oily water to be removed from machinery spaces, pump rooms, void spaces and other compartments. There are two suction lines for emptying each bilge well. The first line is connected to the bilge through bilge main pumps (or daily bilge pumps) which have 5-10 m3/hr capacity. The second line is the direct bilge suction (or emergency bilge suction) and must be connected directly t emergency bilge pumps suction. This is used in emergency and at least two direct bilge suctions (or emergency bilge suction) must be provided at machinery space in each pontoon area in semi-submerisbile project and pump room and aft & forward machinery spaces in FPSO project. It is a classification requirement that the bilge system has an emergency connection that is connected to the largest seawater pump. This is provided so that the maximum possible pump capacity can be used in case of flooding of the pump room or machinery space. The bilge water separator is capable of producing an effluent containing no more than 15 ppm (1 ppm = 10-6) of oil in compliance with MARPOL and classification requirements.

The word is sometimes also used to describe the water collects in this area. Water does not drain off the side of the deck drains down through the ship into the bilge. The water may be from rough seas, rain, leaks in the hull or stuffing box, or other interior spillage. The collected water must be pumped out to prevent the bilge from becoming too full and threatening to sink the ship.

Bilge water:

Bilge water is the collective term for a cocktail of wastewater, oil and fluids from operational sources such as technical rooms, propulsion systems and on board machinery. An international regulation requires ships to treat this waste to a level where it can be pumped overboard without impacting upon the ocean's ecological balance.




Figur 1‑4 Bilge Water tanks

The Bilge system contains:

  • ·         Bilge collection system
  • ·         Sludge collection system
  • ·         Bilge wells
  • ·         Bilge pumps
  • ·         Bilge transfer pump
  • ·         Sludge transfer pump
  • ·         Bilge collection pump
  • ·         Bilge treatment skids
  • ·         Bilge interface with other system (Ballast, Air and Fresh water system)

 The main purpose of the Bilge System is to collect, treat and dispose liquid drains from various origins on the FPSO machinery space. The Bilge System handles all waste liquids such as drains, waste oil and sludge and separates them into oil and water.

The Bilge System comprises Bilge Tank (4TA 8610), Sludge Tank (4TA 8620), Bilge Pumps, Large and Small (4GX 8630/40/50), Sludge Transfer Pump (4GX 8620) which transfer sludge to Bunker Station, Bilge Transfer Pump (4GX 8610)  which  transfer  bilge  to  Bunker  Station  and  bilge  collection  pumps  (4GX  8670A/B).  If disposal via bunker station are not available, the content of these tanks may also be pump to slop tank, after fitting of a temporary spool piece.  

Bilge collection System:

The  bilge  collection  system  consists  of  pipes  and  2  pumps  (M/S  level-3)  directing  drains  from machinery  room,  Flushing  water  from  sewage  treatment  plant,  diesel  oil  purifiers,  all  water leakages in machinery room, etc. to the bilge tank(4TA 8610).The Bilge Tank (4TA 8610) level will be measured by radar type level transmitter(4LT 86101).

Sludge Collection system: 

The sludge collection consists of pipes directing drains from sewage discharge pump, emergency

DG drip pan, essential DG drip pan, DO service tank and all oily leakages in the machinery room

etc. to the Sludge Tank (4TA 8620). The Sludge Tank (4TA 8620) level will be measured by radar type level transmitter (4LT 86201).

Bilge Wells:

Four Bilge Wells at four corner of the double bottom level in the AFT machinery space. All these

well  are  connected  with  bilge  pumps.  Level  transmitters  (4LT  86015/16/17/18)  are  installed  in these wells with high and low alarm in the PCS.

 

Additional 12 bilge wells (7 bilge wells are at port side and 5 at starboard side) are at level -3, fitted   with  branch  bilge  suction.  Level  transmitters  (4LT 86801, 46801/02/03/04/05/06/07/08/09/10/11/12)  are installed with high and low alarm in PCS.

Two Level transmitters (4LT 86039/40) are installed for high level alarm in PCS in case of flooding in machinery space double bottom pump room at 4.1 mm level at both portside and starboard side respectively.

 Bilge Pumps: 

Large Bilge (4GX 8630/40) and Small Bilge Pump (4GX 8650)

There are two Large Bilge Pumps (4GX 8630/40) and one Small Bilge Pump (4GX 8650).These

pumps shall send effluents contained in Bilge Wells in the double bottom level to the Bilge Tank

(4TA 8610). Bilge water from other sources shall discharge via gravity or by pumping with the

bilge collection pumps (4GX 8670A/B) to the Bilge Tank. Two separate headers are provided for

pumped effluents and gravity effluents. 

Priming System: Large Bilge (4GX 8630/40) and Small Bilge Pump (4GX 8650)

Each Large Bilge Pumps (4GX 8630/40) is provided with air eductors for automatic priming and

stripping operation. The purpose of this system is to prime the pump suction to avoid dry running of the pump. Service air is connected to air eductors with solenoid operated valve (4XSOV 86306, 4XSOV 86405). The suction line of the bilge pump (4GX 8630/40) is also connected to air eductor with solenoid operated valve (4XSOV 86305, 4XSOV 86406). A pressure transmitter is installed on the discharge line of each pump for controlling the priming system (4PT 86304 and 4PT 86404) The small Bilge Pump (4GX 8650) inlet is provided with fresh water supply as priming medium with 4ROV 86501 for controlling the fresh water from PCS.

 Bilge Transfer Pump (4GX 8610):

The  bilge  transfer  pump  is  designed  to  allow  the  safe  and  secure,  Transfer  of bilge  to  a  supply vessel via the bilge bunker station. If disposal via the bilge bunker station are not available, the contents of these tanks may also be pumped to the slop tank, after fitting the temporary spool piece. The bilge transfer pump start/stop is manually operated by operator based on the availability of the bilge bunker station. This pump is equipped with overpressure, low, low pressure (4PT 86206 with PSHH/PSLL) to trip the pump to prevent potential leak or any clogging on the outlet line. The  bilge  transfer  pump  (4GX8610)  inlet  is  provided  with  fresh  water  as  priming  medium  and 4ROV 86101 for controlling the fresh water.

Sludge Transfer Pump (4GX 8620):

The  sludge  transfer  pump  is  designed  to  allow  the  safe  and  secure  transferring  of  sludge  from sludge tank    (4TA 8620) to bilge bunker station (Bilge bunker station not to be combine with sewage bunker station).After fitting the dedicated spool piece, the sludge can also be transferred to the slop tank system instead the bunker station.  The  local  control  station  is  provided  to  start/stop  pump  locally  based  on  the  availability  of  the bunker station. Sludge pump is equipped with overpressure, low, low pressure (4PT 86207 with PSHH/PSLL) to trip the pump to prevent pump cavitations or blockage in case of the outlet line clogging. The sludge transfer pump (4GX8620) inlet is provided with fresh water as priming medium and 4ROV 86201 for controlling the fresh water.

Bilge Collection Pump (4GX 8670A/B):

The bilge collection pump is designed to allow the safe and secure, transfer of oily effluent to bilge tank from 12 bilge wells at machinery space level -3. Diaphragm type pneumatic operated vacuum pump is used discharge bilge from bilge wells to bilge tank (4TA 8610). Service compressed air is used to operate these pumps. Level transmitters (4LT 86801/02/03/04/05/06/07/08/09/10/11/12) are installed with high and low alarm in PCS. To operate the pump, respective pneumatic valves shall be open/Close locally by operator, when high and low level alarm in PCS.

Bilge Treatment 1st Skid/ 2nd   Skid (4UB 8660/70):

The bilge treatment package has been segregated into two package, One is bilge treatment 1st   skid (4UB 8660) which can lift the bilge from the bilge tank (4TA 8610) and other is bilge treatment 2nd skid (4UB 8670) which will purify bilge in order to overboard directly. 

The bilge treatment 1 st  & 2 nd  skid is provided with local control panel (4-PR-UCP-8670) for bilge treatment operation. The bilge treatment start/stop is controlled by bilge tank level 4LXHL 86101 and also depends on high level alarm (4LAH 86201) in sludge tank (4 TA 8620) from HCS.  Bilge  treatment  2nd  skid  outlet  is  equipped  with  oil-in-water  monitoring  system  (4AIR  86603) which measures oil-in-water content in the system. An oily water separator which is able to reduce the  oil-in-water  content  down  to  15  ppm  in  accordance  with  MARPOL  requirements.  The recovered water from bilge treatment package shall be sent overboard. In case oil content is found higher than 15 ppm then oily water will be automatically diverted back to Bilge Tank (4TA 8610) by 3 –way valve inside the package(this logic is included in the package). Oily residues from Bilge Treatment 2nd skid packages shall be sent to a Sludge Tank (4 TA 8620). General  alarm  (4XA  86601)  and  oil-in-water  content  monitoring  (4AIR  86603)  signals  will  be displayed in HCS.

Interface with other system : (Ballast, Air and fresh water system)

Machinery emergency bilge suctions (port and starboard) will be routed to the opposite AFT ballast pump in pump well (respectively starboard and port).The Oily residues from various sources shall discharge via gravity or by pumping to the sludge tank (4TA 8620). Three separate headers shall be provided for pumped effluent and gravity effluent.

 Figure 1 General Process sketch- Bilge System

Equipment list of Bilge system:-

Equipment

Service/ Function

4GX 8630

Large Bilge Pump (Port side)

4GX 8640

Large Bilge Pump (Starboard side)

4GX 8650

Small Bilge Pump (Port side)

4GX 8650

Small Bilge Pump (Starboard side)

4GX 8610

Bilge Transfer Pump

4GX 8620

Sludge Transfer Pump

4GX 8670A

Bilge Collection Pump (Port side)

4GX 8670B

Bilge Collection Pump (Starboard side)

4TA 8610

Bilge Tank

4TA8620

Sludge Tank

4UB8660 / 70

Bilge Treatment 1st & 2nd Skid

Bilge Water Management Including Ship Specific OWS (video)



Bilge treatment package:

The bilge treatment package has been segregated in to two packages.

-          Bilge treatment skid (4-UB-8660) which can lift the bilge from tank

-          Bilge treatment skid (4-UB-8670) which will purify the bilge water in order to overboard directly.

 Local Control Panel (UCP) shall be installed on the 2nd skid. The bilge treatment unit start/stop is controlled by level transmitter from control system.

Bilge treatment 2nd skid shall be equipped with oil-in-water monitoring system which measures oil-in-water content in the system. An oily water separator which is able to reduce the oil-in-water content down to 15ppm in accordance with MARPOL requirement. The recovered water from bilge treatment package shall be sent overboard. In case oil content is found higher than 15ppm then oily water will be automatically diverted back to bilge tank (4-TA-8610) by 3 way valve. Oily residues from bilge treatment 2nd skid packages shall be sent to a sludge tank (4-TA-8620).

General alarm and oil-in-water content monitoring signals shall be connected to HMI system.

 

 


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