Life Raft on Ships: A General Overview

Posted 2021-04-27 吴汉军航海资讯

 新朋友请 点上方蓝字“吴汉军航海资讯”关注

 

Life rafts are provided as a life saving appliances on every sea going merchant or passenger vessel in addition to the lifeboats. Life rafts are much easier to launch as compared to life boats and in case of emergency situation, evacuation from the ship can be done without manually launching any of them as the life rafts are designed with auto inflatable system. SOLAS chapter III gives all the details for types and number of life raft to be carried as per the size and type of the ship.

Life rafts

Life rafts are normally located on muster station, on port and starboard side near the life boat, and fwd and aft of the ship. The location generally depends on size of the ship. Life rafts are stored in a fiberglass container, incorporated with a high pressure gas used for inflating life raft at the time of emergency. A Hydrostatic Release Unit (HRU) is connected to raft container and ship, which release the raft even after the ship sinks in water.

The particulars of the raft is stenciled on the container which includes the capacity, manufacturing date, servicing date, company name etc. along with the launching procedure with a photogenic display for easy understanding. The basic survival items are already stored in the raft which includes rations, pyrotechnics, life jackets etc.

Some ships carries a davit launching system which allows the crew to inflate and  board the raft on deck, avoiding the risk of going into the sea water.

General requirements for Life Rafts

• Capable of withstanding exposure for 30 days afloat in all sea conditions

• When dropped into the water from a height of 18 metres, the life raft and all equipments in it will operate satisfactorily

• The floating life raft should be capable of withstanding repeated jumps on it from a height of at least 4.5 metres above its floor both with and without the canopy erected

• Can be towed at 3 knots with its full equipment, compliment of persons and one anchor streaming

• Canopy to provide insulation and protection against heat and cold by two layers of material separated by air gap

• Interior to be of a non discomforting colour

• It shall admit sufficient air for the occupants at all times, even when the entrance is closed

• It shall be provided with at least one viewing port

• It shall be provided with a means of collecting rainwater

• It shall be provided with a means to mount a survival craft radar transponder (SART) at a height of at least 1 meter above the sea level

• It shall have sufficient headroom for the sitting occupants under all parts of the canopy

• Minimum carrying capacity must be at least 6 persons

• Maximum weight of its container as well as the equipment should not exceed 185 kilos

• The life raft shall be fitted with an efficient painter of length equal to miniumum 10 metres plus the distance from the stowed position to the waterline in the lightest seagoing condition or 15 metres, whichever is greater

• A manually controlled lamp shall be fitted on the top of the canopy and the light shall be white and it must operate for at least 12 hours with a luminous intensity of not less than 4.3 candela

• If the flash light is fitted, it shall flash at a rate of not less than 50 flashes and not more than 70 flashes per minute for the 12 hours that it burns

• A manually controlled lamp shall be fitted inside the life raft capable of continuous operation for a period of at least 12 hours

• When the liferaft is loaded with full complement of persons and equipment, it should be capable of withstanding a lateral impact against the ship side at an impact velocity of not less than 3.5m/s and also drop into the water from a height of not less than 3 metres without damage

• Inflation is done by CO2 with a small quantity of N2 which acts as an anti freezing element. Also, CO2 is non flammable and also weighs more than air hence adds buoyancy to the raft. Freezing point of CO2 is -78 degrees so it can inflate life raft at really low temperatures

• Location on ship:
  – Forward
  – At embarkation stations on both port and starboard sides

• The painter breaking strength should be:
  – 15kN for 25 people and more
  – 10 kN for 9 to 24 people
  – 7.5 kN Rest (6-9)

Safety on life raft

• Pressure relief valve

• Stabilizing pocket

• Insulated canopy with two layers for protection against heat and cold

Life raft equipments

• Rescue quoits with minimum 30 metre lines

• Non folding knife with a buoyant handle. If the life raft holds more than 13 persons, then a second knife

• For 12 persons or less, 1 bailer. For more than 13 persons, 2 bailers should be kept

• 2 sponges

• 2 buoyant paddles

• 3 tin openers

• 2 sea anchors

• 1 pair of scissors

• 1 first aid waterproof kit

• 1 whistle

• 1 waterproof torch for communicating morse code with 1 spare set of batteries and bulb

• 1 signalling mirror/heliograph

• 1 radar reflector

• 1 life saving signals waterproof card

• 1 fishing tackle

• Food ration totaling not less than 10000 kJ for each person

• Water ration- 1.5 litres of fresh water for each person

• One rust proof graduated drinking vessel

• Anti sea sickness medicine sufficient for at least 48 hours and one seasickness bag for each person

• Instructions on how to survive (Survival booklet)

• Instructions on immediate action

• TPA sufficient for 10% of the number of persons or two, whichever is greater

• Marking shall be SOLAS ‘A’ Pack

• 6 Hand Flares

• 4 Rocket Parachute Flares

• 2 Buoyant Smoke Signals

Markings on a Life Raft container

• Maker’s name and trademark

• Serial number

• Name of authority

• Number of persons carried

• SOLAS emergency pack enclosed

• Date of last service

• Length of painter

• Maximum height of stowage

• Launching instructions

Markings on an inflatable Life Raft

• Maker’s name and trademark

• Serial Number

• Date of manufacture

• Name of approving authority

• Name and place of last service

• Number of persons permitted

Launching of life raft when the ship sinks and HRU activates (Auto)

• When the ship sinks upto 4 metres, the water pressure will activate a sharp knife in the HRU

• It will cut the securing rope around the container/canister of the raft and the raft will float free

• As the ship sinks further, the painter line will stretch and it will inflate the life raft

• Due to the increase in buoyant pressure, the weak link will break at around 2.2 kN +/- 0.4 and the raft will be on the surface

Launching the life raft manually

• Take out the painter of the raft

• Fasten it to the ship side at a strong point

• Remove the railing and check overboard for any obstructions

• Unfasten the hook from the cradle

• Two people can lift the life raft and throw it overboard

• After its thrown, pull the painter sharp until the life raft inflates

• With the painter, pull it towards the ship side

• Lower the embarkation ladder or jump directly onto the life raft depending on the situation and the time at hand

• Sit order wide face to face to prevent any imbalance

• Ensure SART and EPIRB have been carried

• Take a head count

• Cut the painter using the knife given and using the paddle or the anchor, clear away from the ship

If the life raft inflates and  it is upside down, the raft has a righting strap which is capable of stabilize it. Climb onto the CO2 cylinder and pull it in the same direction as the wind to do so.

Launching the life raft by the davit

• Remove ship’s hand rail

• Remove lashings from the container

• Lower the davit and lock it with the lifting shackle

• Secure canister lines outboard

• Secure bowsing line

• Pull the painter out approximately 5-6 metres

• Secure the painter line

• Pull the full length of the painter

• Now lift the life raft canister upto some height

• Pull the painter sharply and let it inflate

• After it inflates, secure the liferaft

• One person should go in and make some checks

• Collect the SART and EPIRB

• Go inside and sit evenly

• Release the bowsing line and pass to the raft

• Check if the launching area is clear

• Lower the raft using the brake release

• Operate hook release 1m above the water or allow the raft to ride a crest of the wave to put the load on the water and it will automatically release

• Cut the painter and clear away