Life Boats/life saving appliances Flashcards
what is the function of the release hook/ release gear mechanism?
A release hook is a device usedto secure and release a life raft orrescue boatfrom a ship in case of an emergency. They are equipped release gear mechanisms which ensure that lifeboats and rescue boats are securely held in place while the ship is at sea.
These mechanisms release the boat from the davit, which is attached to a wire or fall by means of a release hook. By detaching the release hook, the lifeboat can be set free to propel away from the ship.
what is the function of Hydrostatic Release Unit and how does it work?
Function of the ‘hydrostatic release unit’ is to ensure that the life raft is automatically released when ship is under water, they operate between 1.5 to 4m of water depth.
how it works?
There is a main strap that runs over the top of the life raft container, on the end is is a sent house slip (hook), used for quick manual release of life raft for self launching. The end of the of sent house slip is attached to a yellow part of the HRU called the low friction attaching point. This is specifically designed with less friction for when the HRU operates, the other end of the HRU is attached to the deck with a shackle. The other part of a HRU is the weak link, which is attached to the painter. The weak link is designed to pull the painter tight enough to break the weak link when vessel is underwater. Inside the HRU Is a sealed chamber with a flexible diaphragm and spring, when the HRU unit is submerged water pressure acts on the diaphragm and compresses it which then brings the securing pin up and clear of the blade. the spring which is attached to a knife is then activated forcing the knife to cut the line. With the line completely free the low friction attaching point is separated from the sent house slip. The entire securing strap is now completely free so life raft container floats upwards, as it continues upwards the painter is pulled tight enough to trigger the life raft inflation. As the life raft inflates increased buoyancy applies even more force to the painter until eventually the weak link breaks and the life raft floats up to the surface.
What are the safety devices on life boat?
1.Mechanical brake (to prevent accidental release of lifeboat, holds it stationary)
2.Centrifugal brake (controls life boat falling speed, to 36 m/min)
3.Limit switch ( used to cut power to the winch, when the boat is hoisted to correct stowage height)
- safety pin (secure release hooks to release gear mechanism to prevent accidental release)
State four features which assist in the starting of lifeboat engines in cold
climate conditions
- Jacket water heater system to maintain engine temperatures.
- Regular weekly maintenance of lifeboat, running for a minimum of 30 Mins, keeping the engine enclosed so that it isn’t exposed to the elements
- The use of Pre lubricating oil plungers, By pre-lubricating an engine the wear and damage that can occur during the starting of the engine, after it has been off or after an extended idling period, can be prevented or at least minimized.
- Electric starter motors rather than hand crank only.
Describe TWO devices that control the rate of fall of a lifeboat when
launched from standard davits.
Lifeboat davits have two distinct braking systems:a holding brake (mechanical brake)anda centrifugal brake. Both of these control the rate of fall of a lifeboat
1.Holding brake
The holding brake is designed to stop and hold the lifeboat stationary at any point between its fully housed position in the davit or when it is near the water’s edge. The holding brake is disengaged by lifting the weighted brake handle thus allowing the lifeboat to descend downward toward the water. The holding brake arrangement consist of a weighted lever, a brake drum with break shoes and break lining. Its function is to control the speed of descent. Lifting the lever using a remote line from the lifeboat or the boat deck. The winch can then lower the lifeboat using gravity. Releasing the hand brake, on the other hand, will halt the lowering procedure. The lifeboat can be stopped and held in place by the manual brake at any time between its fully housed position in the davit and when it is close to the water’s edge. By pulling up on the handle attached to the weighted brake, the holding brake can be withdrawn, allowing the lifeboat to move closer and closer to the sea.
2.Centrifugal break
A centrifugal brake is located on the winch. The brake controls the speed of descent for the lifeboat. The centrifugal brake has a brake lining on top of the breaking shoe and restraining springs. When the boat is lowered, the centrifugal effect pushes brake shoes outwards against the restraining springs. Thus, the centrifugal break restricts the lowering speed of the boat to not more than 36 m/min. The brake is enclosed, and provides reliable operation in all climate conditions. Normally, the winch is fitted with a one-way clutch, so in the event of power loss during hoisting, the brake will automatically activate and davit motion will stop. Holding brake is frequently used to control the rate at which the lifeboat is lowered into the water. When lowering the lifeboat into the sea, it is imperative that the holding brake be entirely released so that it does not accidentally engage. When the weighted handle is raised and the holding brake is released, the centrifugal brake will engage automatically when the winch drum reaches a pre-set rotational speed in the downward direction. This will ensure that the boat is lowered in a controlled and smooth manner. If you lower the boat while the holding brake disc is partially engaged, the brake lining will wear down. The centrifugal brake never reaches the fixed rotational speed necessary for engagement when the motion of the lifeboat is controlled solely by the holding brake. As a result, the brake pads spin, but they do not make contact with the drum, which prevents the brake from functioning properly. The brake is enclosed, and provides reliable operation in all climate conditions. When the centrifugal brakes are employed as they were intended to be, the shoes rotate outward and make contact with the drum.
describe the construction of a lifeboat?
The lifeboat is constructed of fire-resistant polyester resins and fiberglass. The hull, inner hull, canopy, and roof are all individually moulded in one piece. The area between the hull and inner hull will be filled with synthetic foam for buoyancy, which will keep the lifeboat floating and upright even if it is holed below the waterline. When filled with its full complement of people and equipment, the lifeboat has ample stability in a seaway and sufficient freeboard, and in the event of capsizing, it can automatically acquire a position that will allow the occupants to escape.
what are the two ways of launching a lifeboat in an emergency?
Free fall
Using a davit
What are some of the requirements for a lifeboat?
They must carry rations for several days, together with survival and signalling equipment such as fishing lines, first-aid equipment, compass, lights, distress rockets and smoke flares.
The boat can be raised and lowered by means of an electrically driven winch. The winch is manually controlled by a weighted lever known as a dead man’s handle, which releases the main brake. Should the operator lose control of the brake the lever causes the winch to stop.
The speed of descent is also controlled by a centrifugal brake which limits the speed to a maximum of 36 m/min.
Both the centrifugal brake and the main brake drum remain stationary during the hoisting operation. If the power fails while raising the boat, the main brake will hold the boat.
Other than lifeboats what are some of the other lifesaving appliances provided on a ship?
Ships also carry life rafts having sufficient capacity for half of the ship’s crew. The life rafts are inflatable and carry survival equipment similar to the lifeboats.
Each member of the crew is supplied with a life jacket which is capable of supporting an unconscious person safely.
Lifebuoys are provided in case a man falls overboard. Some are fitted with self-igniting lights for use at night and others fitted with smoke signals for pin-pointing the position during the day.
All ships carry line throwing apparatus which consists of a light line to which a rocket is attached. essentially an explosive line that can be fired capable of reaching about 230 m. This enables contact to be made between the ship and the shore or another ship. the line is hawser so its weighted so that ships can be pulled alongside for towing.
what is a davit?
a small crane on board a ship, used for suspending or lowering a lifeboat.
how is the release hook detached?
The hook is released when ‘release lever arm’ is turned in anti clockwise direction while ‘operating cable’ is pulled down. the safety pin must be removed before operating the release hook. safety pin must be always in position when the life boat is secured to the ship.‘safety pin’ is a fall prevention device (FPD)
function of a FPD
A ‘Fall Prevention Device’ (FPD) is used to minimise risk of injury or death in the event of the failure of the release hook or release gear mechanism, or by accidental release of the release hook.
what is an EPIRB?
An emergency position indicating radio beacon (EPIRB) is a small electronic device that can help search and rescue authorities find people in distress.
They can be activated either manually (by pressing a button) or automatically (when they float free of a sinking vessel). They should only be set off in a distress situation. Once set off they transmit a coded message (not voice) to satellites which identify that you are in distress.
If EPIRB includes a built-in GPS it will also transmit your position, if not the satellites can triangulate your position to within a matter of miles within a few hours.
what is a SART?
SARTs or Search and Rescue Transponders are used in distress situations. When activated they send out a signal when they detect a radar pulse (9GHz), this signal is visible on a radar screen.
It will not identify the vessel but simply display the position of the SART with 12 dots trailing behind on radar screen, as the vessel gets closer the dots turn into dashes and finally as the vessel comes very close to the SART the dashes become concentric circles around its location.
SARTs are made of waterproof components, which protects them against damage by water.
SARTs are battery-operated and, hence, can be operative for a long time.
SARTs are used in ships, lifeboats and life rafts. they remain afloat on the water for a long time if the vessel finds itself submerged in water.
The bright colour of SARTs enables quick detection, whereas the combination of transmitter and receiver enables it to transmit and receive radio signals.
Describe the different types of lifeboat release gear mechanisms:
There are three types of lifeboat releasing mechanisms- on load and offload release and free fall lifeboat release mechanism
The onload and offload mechanisms release the boat from the davit, which is attached to a wire or fall by means of a hook. By releasing the hook the lifeboat can be set free to propel away from the ship.
Offload release mechanism:
The offload mechanism releases the boat after the load of the boat is transferred to water or the boat has been lowered fully into the sea. There is a hydrostatic piston unit provided at the bottom. the piston is connected to the operating lever via a link.As the ship becomes waterborne, the water pressure will move the hydrostatic piston up. The piston will continue to move up, pushing the lever and as a result, it will operate the hook arrangement releasing the fall wire. There is a safety pin arrangement provided near the clutch box, which disables the offload release (in case of rough weather or hydrostatic piston malfunction) allowing the operator to perform onload release of the lifeboat.
On load release mechanism:
On load mechanism can release the lifeboat from the wire, with the ship above the water level and with all the crew members inside the boat. The load will be still in the fall as the boat would not have touched the water. Normally the on-load release is operated when the boat is about to touch the surface of the water so that the fall is smooth without damaging the boat and harming the crew inside. A lever is provided inside the boat to operate this mechanism. As the lever is operated from inside, it is safe to free the boat without goingout of thelifeboat, when there is a fire on the ship.
Free Fall lifeboat release mechanism:
In Free fall lifeboat, the launching mechanism is similar to on load release. the only difference is that the freefall lifeboat is not lowered till 1m above water level, it is launched from the stowed position by operating a lever located inside the boat which releases the boat from rest of the davit and boat slides through the tilted ramp into the water.
