We are going to discuss the types of deck machinery onboard and the operations for various functions. Such as mooring equipment, Anchor handling equipment, Cargo handling equipment and the Hatches. Also, there are some other facilities such as Lifeboats, life crafts, watertight doors and weathertight doors. These types of equipment all need to control by the pull and lift with chain cable or ropes. For these heavy pulls and lifts generally 3 way of the source are using Steam, Hydraulic and electric.
Source From Steam for types of deck machinery onboard:
For the operation of types of deck machinery onboard mentioned above need steam for the operation. So we can see that various pipes help to supply steam onboard the ship. First, the steam allows them to go to the direction valve and after allow to pass through the admission valve. To drive these machineries, generally double-acting steam engines with two-cylinder are using.
Also, there is a back pressure valve. This will help to control the tension in the winches in the case of a sudden stop of the machinery by the load. And these steam equipment widely used in the tanker vessels since the steam machinery reduce the risk of the fire and explosion. But the drawback is the length of the supply pipe on the deck will gradually increase according to the size of the ship.
Source from Hydraulic System for types of deck machinery onboard:
here for the operation of the types of deck machinery onboard need the hydraulic system. The hydraulic motor will get the oil from the tank by the help of the pumps and the open-loop circuit. Also, a control valve is there parallel to the motor. The motor will operate according to the control valve signal. When the control valve is open, then the motor will be at the stationary position. And if the valve is closed, then the motor will start working. Also, there is a re-circulation of the oil to the tank itself.
Also, the live line circuit helps to maintain the high pressure when the control valve supply oil to the hydraulic motor. And in the closed-loop system, the exhaust oil will be recirculated to the pump suction itself. The system is considered as the closed system because the oil will not enter the open tank. The low-pressure system will use the open-loop system with a simple design. But it is inefficient and may overheat will occur. And the medium pressure system will use either an open circuit or closed circuit.
Source from Electrical Operation for types of deck machinery onboard:
In earlier days the electric operation is used for the operation of various types of deck machinery onboard. By using the DC supply and with some resistance in series for controlling the speed. But the main thing about DC is the inefficient power wasting. The better solution is the Ward Leonard control. But the disadvantage of this method is the expensive rate of the equipment.
The machines that are working with AC system need a speed control with a slip ring motor or the pole charging. The slip ring needs an only small amount of current but the other side is that it needs regular maintenance. In the case of the pole charging system, the construction is squirrel cage and will provide a different rate of speed. Also, it needs a large current for starting but the maintenance is less. But if we see the disadvantage, all the electric system will experience difficulty if it runs with a heavy load.
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a) Mooring Equipment:
The axial mooring equipment on board the ship is the windlass with some arrangements of barrels. There will be an arrangement of winch barrel or drum. It will help to heave up and letting out the ropes that will help to tie the ships to ports. The warp end will use to tie the moving ships to the Ballards in the shore by the ropes or wires.
The construction of the mooring winches is, there will be a motor with a spur gear. Also, the clutch connects the drum and then to the warp end. And there will be a bank brake that helps to hold the drum when we required. We can control the motor to either forward or to reverse direction also can adjust the speed. The modern winches nowadays have an automatic self-tensioning unit. Also, the changes in ship draught due to cargo loading and the emerging of the waves will change the tension of the mooring ropes. In these cases, the automatic tensioning unit will help to release or remove the wire.
b) Anchor Handling Equipment:
The main equipment for this we usually use is the windlass to handle the anchor. And one windlass is usually used to operate both anchors. Also, the most recent development in this is that there will be a split windlass. This means, one machine will use to operate for each anchor. This will only be used in large vessels.
There will be a rotating unit with a cable lifter that has snugs for getting grip while holding the anchor cable. Also, a mooring drum is present that will help to heave up and letting out the rope. We can control each of the units separately by the use of a dog clutch. Another equipment is the spur gear assembly which helps to transmit the motor to the shaft. At that point, the dog clutch will enable power. Also, auxiliary bank brakes are there. That will help to hold the cable lifter if the power is switched off.
Also, the cable lifter is using to heave up and lower the chain cable of the anchor through the Spurling pipe. The Spurling pipe is located at the centre part of the chain locker. We can only see the cable lifter on the main deck and all the other equipment that driving this will be below the deck.
c) Cargo Handling Equipment:
There will be various types of derrick system for handling the cargo onboard the ship. Also, the equipment should work under the safe working load. And if it is working with half load, then it can run with double speed. The spur reduction gear will transmit the motor to the shaft as we said earlier. Also, there will be a warp end to operate the topping lift of derrick. There is an arrangement of bank brakes. And also another brake arrangement in the motor. That will help to hold the load if any power loss occurs.
There will be two units of derricks. The one will be at the quayside and the next one will be in the hold. There will be the topping wires that will determine the height of the derricks and sometimes it will prevent the movements to forward and aft. There will be two winches and the wire for handling the cargo will come through the windlass followed by a hook. This will help to lift, transfer and lower the cargo.
But in modern ships, they are using cranes instead of the derricks. The crane will be there between the hold and can rotate a full round to carry out the work. Also, it can operate immediately and only one man need to operate. It has double gearing arrangement that helps to get double speed when loading small loads. There are many types of crane such as general duty cranes and grabbing cranes. The grabbing type cranes are using for bulk carriers.
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d) Hatch Covers:
As we know, the hatch covers are using to cover the hatches on board the ship. That will help to cover the hatch as watertight. In the earlier days, wooden hatch covers are used. That have beams and boards. And the steel hatch covers are using now which have some steel cover. There are various designs for opening and closing the hatches. But generally, we using quick open and closing system. This general quick open and closing system promotes the ease of cargo handling operation.
Some hatch cover has rollers to move the cover. There will be a number of covers and will attach with chains. To operate the big hatch cover, we need a power source. The power source can be used from the control box located at the end of the hatch cover. We can operate the hatch cover by pulling the wire from the crane with ease. The hatch cover has a compressible join strip. This will help to cover the hatches as watertight.
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Conclusion: Hope you got the idea of the machinery on the deck of the ship. Comment your queries and opinion below.