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Basic Info about Liquefied Petroleum Gas Vessels and Risks while Shipping a Cargo

Demand of the Liquefied Petroleum Gas in XXI century increases. This article contains basic information about LPG vessels, risk assessment and their identification, and the measures to loss prevention.

  • LPG Properties (Physical and chemical properties).
  • LPG Ships.
  • Risks of LPG Ships.
  • Risk Assessment and Loss Preventions of LPG Ships.
  • Example of Risks.

Properties of LPG (Liquefied Petroleum Gas)

Physical and chemical properties:

  • Weight of LPG: Half the weight of Water.
  • Weight of GPG (Gaseous LPG): 1,5 to 2 times the weight of Air.
  • Boiling Temperature of Propane: -43 °C.
  • Boiling Temperature of Butane: -0,5 °C.

Consists mainly of:

  • Propane (C3H8).
  • Butane (C4H10).
  • Non-corrosive, non-toxic, odorless, colorless.
  • Transformed from gas to liquid for transportation.
  • Odorant added to LP gas which gives a distinctive odour.
Chemical reaction
Chemical reaction

USES:

  • Used for refrigeration/air-conditioning/heating, cooking, auto fuel, etc.
  • A “Clear uncontaminated fuel” – An environmental friendly fuel. (Less particles and SOx emissions).
Production of LPG
Production of LPG

Natural Gas Processing and Liquefaction

LNG Processing and Liquefaction
LNG Processing and Liquefaction

LPG Vessels

  • Fully pressurised ships.
  • Semi-pressurised.
  • Fully refrigerated.
LPG Tanker
Photo of LPG Tanker
LPG Tanker in the sea
LPG Tankers

General Arrangement of “GAS XXX”

Front of the ship - click to Zoom inPrincipal Dimensions
Loa230,0 m
Lpp219,0 m
Bmld36,6 m
Dmld20,8 m
dmld (summer)10,756 m
Deadweight49,999 t
Cargo Tank
Right side of the ship - click to Zoom inTypePrismatic independent tank (Type A)
No.4
Capacity78 921 m3
FlagLiberia
ClassNK
Gross Tonnage46 021
Complement27 persons
Service Speed16,7 knots
Right side of the ship - click to Zoom inEnduranceabt. 18 000 sea miles
Main EngineMitsubishi-UE7UEC60LS × 1
M. R.12 360 kW × 100 rpm
N. R.11 120 kW × 96,5 rpm
Aux. Boilercomposite type × 1
Electric GeneratorD/G 880 kW × 3
Cargo Handling Equipment
Scheme of the tanksCargo pump submerged550 m3/h × 8
Emergency cargo pump submerged250 m3/h × 4
Reliquefaction compressor1 360 m3/h × 5
Booster pump/heater300 m3/h × 1
Inert gas generator3 000 Nm3/h × 1
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Scheme of the LPG tanks
Scheme of the LPG tanker
Bird's Eye View of Cargo Tank Insulation Scheme
Bird’s Eye View of Cargo Tank Insulation

Risks to LPG Vessels

  • Because of usual role we normally look at those risks that will affect insurers, such as damage to vessel or cargo.
  • Risks that are particular to the vessel type.
  • Risks that are general to any vessel type.
SPB Tank
Scheme of SPB Tank

Risks Particular to LPG vessels

  • Generally most risks are similar to tankers.
  • Collision or grounding may penetrate insulation and/or cargo tanks.
  • Leakage from cargo tanks into void spaces.
  • Fires/explosions due to cargo leakage.
  • Any damage which involves the tanks and insulation tend to be very costly.

General Risks to LPG Ships

Accidents during sea voyage or during towage:

  • Grounding – Navigation error.
  • Striking a fixed object or a wreck – Navigation error.
  • Collision (with vessel or object) – Navigation error.
  • Unloading/Loading.
    • Sudden pull-away and damage of loading/discharging arms and human injury.
  • Terrorism – Missile attack, boat based explosive and hijacking.
  • Cargo machinery and cargo containment failures.
  • Natural risks – Lightning, typhoon, hurricanes, and tsunami.
  • Other hull/machinery accidents, such as fire in engine room, on bridge and in accommodation, diesel engine damages, and hull structural failures.

Note: Apart from the above LPG risk we must be aware of the high costs and long repair
period arising from damage to cargo containment system on LPG Ships.

Case Reports

Overview of 2007 (by number) Chart - click to Zoom in

Overview of 2007

Comparison of Past Nine Years (by number) Chart - click to Zoom in

Comparison of Past Nine Years (by number)

Casualty Profiles Chart - click to Zoom in

Casualty Profiles

Sample of Risks Identification of LPG Ships

Example of identified Risks
1. Structural failure to hull18. Explosion in cargo handling module34. Loss of emergency powers
2. Structural damage due to incorrect loading19. Explosion in void spaces around tanks35. Loss of Nitrogen
3a. Overfilling of tanks20. Explosion in ballasting tanks36. Loss of hydraulic system – compressed air
3b. Overpressure of tanks21. High wind/waves37. Stowaway
4. Unignited leak in the cargo system22. Earthquake – tsunami38. Unignited leak from tank
5. Release of inert gas23. Lightning39. Ignited leak from tank
6. Release of bunker oil24. Sabotage40. Loss of navigational or manoeuvring capabilities
7. Fire in engine room25. War action41. Grounding
8. Accommodation fire26. Collision42. Hitting the quay
9. Fire on open deck27a. Workplace accident43. Mooring failure/anchor dragging
10. Fire in cargo handling module27b. Crane operations44. Man over board
11. Fire in void spaces around LPG tanks (cargo tank insulation fire)27c. Working in tanks/enclosed spaces45. Fire on bridge
12. Fire in void spaces like ballasting tanks28. Operating error46. Piracy/hijacking
13. Fire in forward storage area29. Failure of mooring system due to tidal effect47. Fire on board neighbouring vessel
14. Explosion and fire in engine room due to fuel and LO in exhaust gas manifold30. Leak from loading arm48. Illness or epidemics
15. Boiler explosion31. Loss of instrumentation during loading operation49. Loss of stability
16. Explosion in accommodation32. ESD not functioning50. Gas freeing
17. Explosion in open area on deck33. Loss of power supplies51. Upstart after repair
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Measures Taken to Reduce Risk (Loss Prevention) on LPG Ships

  • Design e. g. Steel cargo tanks: reduce spill, surge, vacuum, or accidental leak.
  • Gas detection safety and firefighting equipments: Manual and automatic gas detections, foam, powder, water curtain, and sea water fire fighting systems.
  • Safety and Operation Internal Inspection/Audit by crew/shipmanagers: Monthly.
  • Safety and Operation Internal Inspection/Audit yearly by shipmanagers.
  • Safety and Operational and Management Inspection/Audit and Security Screening every 2 or 2 ½ years by External Surveyors.
  • Pre-employment crew training, licensing.
  • Continuous Crew and ship management training.
  • Proper exclusion and buffer zones between public areas, ships, and LPG terminals.
  • Terrorist risk prevention based on ISPS (International Ship and Port Security).
  • Entry and Routine Condition Survey for insurers by BMT Surveys.
  • JH115A general condition survey by BMT M&O Surveys.
  • JH722 Structural survey by BMT M&O Surveys.
  • JH2006/010 A, B, C, Engine room and office management and condition survey by BMT M&O Surveys.
  • JH143 Shipyard Risk Assessment Survey for construction/conversion of LPG Ships by BMT M&O Surveys.

Risk Due To Shortage Of Experienced Gas Tanker Crew

  • 5 experienced senior officers are required for each LPG Ship: Master, Chief Mate, Chief Enginner, 1st Enginner, Cargo Engineer.
  • Experienced Gas Tanker crew receive better pay on LNG Ships than LPG Ships.
  • In addition, due to increase in the construction of LPG & LNG Ships more experienced seafarers are employed as owner’s superintendants during building and operation.
  • There is a great shortage of experienced LPG senior officers in the marine industries.
  • Pre-employment training, licensing, security screening are essential and need to be continuous.
Prevailing risks in the Maritime industry
  • Collision.
  • Grounding.
  • Machinery breakdown.
  • Natural disasters.
  • Fire.
  • Explosions.
  • War risks.
  • Water ingress.
  • Piracy.
  • Terrorism
Common Reported Losses
  • Extensive ship wreckage.
  • Hull damage.
  • Machinery damage.
  • Damage to cargo.
  • Loss of human life.
Machinery Damage (50 %) Photos
Machinery Damage (50 %)
Machinery – aux boiler, photos
Machinery – aux boiler
Ship collision
Collision
LPG Carrier
2007 built LPG Carrier/Grounding
Result of Grounding, Photo
Result of Grounding
Explosion & fire photos
Explosion & fire
Rudder & Propeller failures, Photos
Rudder & Propeller failures
Contact with Quay, Photo
Contact with Quay
Tank leakage, Photos
Tank leakage
Steel replacement, Photo
Part of steel replacement – completed
Detection of welding seam using Helium Gas, Photo
Detection of welding seam using Helium Gas
Corrosion, Photo
Corrosion
Shell plating, Photo
Shell plating

Shipbuilding Risks

  • Worldwide order book.
  • New inexperienced shipyards – quality control.
  • Shortage of trained workers – high demand.
  • Fire safety.
  • Insulation.
  • Typhoon risks in Far East.
  • Subcontractors.
  • General training.
Fire during building, conversion or repair, photo
Fire during building, conversion or repair
Ship-to-Ship Cargo Transfer, Photo
Ship-to-Ship Cargo Transfer
Ship in fire
Terrorism resulting in Oil Spill and Fire
Natural Disasters – Typhoon, Photo
Natural Disasters – Typhoon

Conclusions

  • Generally risks are similar as for a tanker.
  • Specific risks relate to temperature and volatility of cargo, containment etc.
  • Discharge & transhipment risks.
  • Crew expertise and experience – training.
  • High repair costs for containment damage e. g. grounding, contact & collision.
  • Shipbuilding risks increased due to high order book.
Footnotes
Sea-Man

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Сентябрь, 20, 2022 119 0
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