Purpose of this procedure is to define the safe towing operation of the FPSO and FSO from yard to operation field.
This procedure describes all the necessary steps to be taken during wet tow when stern tugs employed for river or channel towing are removed and tow is maintained by lead and assisting tug boats.
Weather Forecast and Stability Check
Site specific marine weather forecast shall be provided to each tug that should include wind,speed,wave height,wave period,current speed,visibility and other related parameters.Limiting criteria of environmental conditions shall be followed from towing guideline and approved by marine warranty surveyor.
Maximum draft during towing shall be based on trim and stability calculation during towing.Intact stability condition shall be checked for 70 not wind and damage stability shall be checked for single compartment damage with 50 knot wind.
Before Towing
Weight changes before towing shall be accesses and impact on stability shall be checked.
Before towing it should be ensured that all watertight hatches are closed properly and related equipment are functioning properly. All towing lines and poly propelyn lines shall be ready.
Towing Vessels
Depending on bollard pull calculation and route weather information,one or two AHTS vessels shall be used. During river towing or channel passage harbour tugs shall be employed. Towing vessels’s towing gerars shall be properly maintained and fuel reserve shall be sufficient for whole towing period.Tugs shall have sufficient bollard pull and all the equipments shall be approved by MWS.Tug boat shall be equipped with towing winch,tow wire and work wire of required length,hydraulic towing pins,open stern with roller,deck tugger winch or capstan and other mechanical and safety equipments.
Normally FPSO-FSO are towed from bow with suitable smith bracket arrangement.Strength and arrangement of all towing equipments shall comply to attending MWS.
Tow lines are connected to vessel by smit brackets.Towing bridle will have two stud chains which are connected at one end to smit bracket and another end is connected to towing wires. Range of angles for bridle chains shall be 45 to 60 degree. Retrieval system shall be provided on vessels to recover towing wire in case of parting.Vessels shall be provide with emergency towing line which shall be of the same property as main towing line.
Towing procedure
All compartments subject to potential flooding should be sounded.Cranes shall be secured and transfer pipe valves shall be closed so that transfer of liquids from one compartment to another can be minimized.All watertight hatches,doors and ventilators shall be closed prior to departure. AHTS will come along FPSO to receive towlines.
During towing draft shall be measured regularly and if any change in draft is measured,all tanks shall be sounded.Safe locations can be used for temporary fixing of the problems.
During towing trim shall be minimized,aft trim shall not increase by 1 degree while forward trim shall be avoided.Roll and pitch shall be monitored and any abrupt change shall be corrected.
Contingencies
In case of lead tug failure,lead tug shall be disconnected and assisting tug shall be employed until another lead tug is secured.If FPSO or FSO towing gear fails,lead tug shall go to recover towing line while assisting tug will hold the vessel.In case of internal flooding in FPSO,assisting tug with salvage pumps shall be berthed along vessel and tow shall be diverted to nearest port of refugee.If power or radio system of tug or FPSO gets fail,tow shall be towards port of shelter to make corrective actions.
Emergency Procedures
Unexpected heel or trim shall be investigated, following might be the reason of this scenario
In case of flooding following measures shall be taken
In case of fire these actions shall be taken
Evacuation shall commence in following order
This procedure describes all the necessary steps to be taken during wet tow when stern tugs employed for river or channel towing are removed and tow is maintained by lead and assisting tug boats.
Weather Forecast and Stability Check
Site specific marine weather forecast shall be provided to each tug that should include wind,speed,wave height,wave period,current speed,visibility and other related parameters.Limiting criteria of environmental conditions shall be followed from towing guideline and approved by marine warranty surveyor.
Maximum draft during towing shall be based on trim and stability calculation during towing.Intact stability condition shall be checked for 70 not wind and damage stability shall be checked for single compartment damage with 50 knot wind.
Before Towing
Weight changes before towing shall be accesses and impact on stability shall be checked.
Before towing it should be ensured that all watertight hatches are closed properly and related equipment are functioning properly. All towing lines and poly propelyn lines shall be ready.
Towing Vessels
Depending on bollard pull calculation and route weather information,one or two AHTS vessels shall be used. During river towing or channel passage harbour tugs shall be employed. Towing vessels’s towing gerars shall be properly maintained and fuel reserve shall be sufficient for whole towing period.Tugs shall have sufficient bollard pull and all the equipments shall be approved by MWS.Tug boat shall be equipped with towing winch,tow wire and work wire of required length,hydraulic towing pins,open stern with roller,deck tugger winch or capstan and other mechanical and safety equipments.
Normally FPSO-FSO are towed from bow with suitable smith bracket arrangement.Strength and arrangement of all towing equipments shall comply to attending MWS.
Tow lines are connected to vessel by smit brackets.Towing bridle will have two stud chains which are connected at one end to smit bracket and another end is connected to towing wires. Range of angles for bridle chains shall be 45 to 60 degree. Retrieval system shall be provided on vessels to recover towing wire in case of parting.Vessels shall be provide with emergency towing line which shall be of the same property as main towing line.
Towing procedure
All compartments subject to potential flooding should be sounded.Cranes shall be secured and transfer pipe valves shall be closed so that transfer of liquids from one compartment to another can be minimized.All watertight hatches,doors and ventilators shall be closed prior to departure. AHTS will come along FPSO to receive towlines.
During towing draft shall be measured regularly and if any change in draft is measured,all tanks shall be sounded.Safe locations can be used for temporary fixing of the problems.
During towing trim shall be minimized,aft trim shall not increase by 1 degree while forward trim shall be avoided.Roll and pitch shall be monitored and any abrupt change shall be corrected.
Contingencies
In case of lead tug failure,lead tug shall be disconnected and assisting tug shall be employed until another lead tug is secured.If FPSO or FSO towing gear fails,lead tug shall go to recover towing line while assisting tug will hold the vessel.In case of internal flooding in FPSO,assisting tug with salvage pumps shall be berthed along vessel and tow shall be diverted to nearest port of refugee.If power or radio system of tug or FPSO gets fail,tow shall be towards port of shelter to make corrective actions.
Emergency Procedures
Unexpected heel or trim shall be investigated, following might be the reason of this scenario
- Hull dmage or failuer of sea chest,valve,pipe fittings
- Transfer of liquids due to lining a pump incorrectly
- Shift of unsecured deck items
In case of flooding following measures shall be taken
- Make sure that all watertight doors,valves and other applications are closed
- Pump out flooded compartment or do cross flooding
In case of fire these actions shall be taken
- Fire general alarm shall be sounded and all the personals shall report to muster station.
- Start all fire pumps
- Confine the fire by closing all the doors and ventilation of fire affected place
Evacuation shall commence in following order
- Close off all compartments and ventilation trunk after full evacuation
- Sound abandon alarm and shut down power
