10.1 Maintenance and repair of electrical, electronic and control systems of deck machinery.
ANCHOR WINDLASSES
In a typical electrohydraulic mechanism, one constant-speed electric motor drives two variable-stroke pumps through a coupling and reduction gear. Other installations include two motors, one for driving each pump. Each pump normally drives one wildcat. However, if you use a three-way plug cock-type valve, either pump may drive either of the two wildcats. The hydraulic motors drive the wildcat shafts with a multiple-spur gearing and a locking head. The locking head allows you to disconnect the wildcat shaft and permits free operation of the wildcat, as when dropping anchor.
Each windlass pump is controlled either from the weather deck or locally. The controls are hand wheels on shafting that lead to the pump control. The hydraulic system requires your attention. Make sure the hydraulic system is always serviced with the specified type of clean oil.
Normally, you will maintain three types of anchor windlasses-the electric, electro hydraulic, and hand-driven windlasses. Hand-driven windlasses are used only on small ships where the anchor gear can be handled without excessive effort by operating personnel.
The major work on a hand windlass is to properly adjust the link, friction shoes, locking head, and brake and to keep them in satisfactory operating condition at all times. In an electro hydraulic windlass, your principal concern is the hydraulic system.
A windlass is used intermittently and for short periods of time. However, it must handle the required load under severe conditions. This means that you must maintain and adjust the machinery when it is not in use. This practice will prevent deterioration and ensure dependable use.
Windlass brakes must be kept in satisfactory condition if they are to function properly. Wear and compression of brake linings increases the clearance between the brake drum and band after a windlass has been in operation. Inspect brake linings and clearances frequently. Make adjustments according to the manufacturer's instructions.
You should follow the lubrication instructions furnished by the manufacturer. If a windlass has been idle for some time, lubricate it. This protects finished surfaces from corrosion and prevents seizure of moving parts.
The hydraulic transmissions of electrohydraulic windlasses and other auxiliaries are manufactured with close tolerances between moving and stationary parts. Keep dirt and other abrasive material out of the system. When the system is replenished or refilled, use only clean oil. Strain it as it is poured into the tank. If a hydraulic transmission is disassembled, clean it thoroughly before reassembly. Before installing piping or valves, clean their interiors to remove any scale, dirt, preservatives, or other foreign matter.
WINCHES
Winches are used to heave in on mooring lines, to hoist boats, as top lifts on jumbo booms of large auxiliary ships, and to handle cargo. Power for operating shipboard winches is usually furnished by electricity and, on some older ships, by steam. Sometimes delicate control and high acceleration without jerking are required, such as for handling aircraft. Electrohydraulic winches are usually installed for this purpose. Most auxiliary ships are equipped with either electro hydraulic or electric winches.
Some of the most common winches used for general cargo handling are the double-drum, double-gypsy, and the single-drum, single-gypsy units. Four-drum, two-gypsy machines are generally used for mine sweeping.
Electro hydraulic Winches
Electro hydraulic winches (fig 10-39) are always drum type. The drive equipment is like most hydraulic systems. A constant-speed electric motor drives the A-end (variable-speed hydraulic pump), which is connected to the B-end (hydraulic motor) by suitable piping. The drum shaft is driven by the hydraulic motor through reduction gearing.
Normally, winches have one horizontally mounted drum and one or two gypsy heads. If only one gypsy is required, it is easily removed from or assembled on either end of the drum shaft. When a drum is to be used, it is connected to the shaft by a clutch.
Electric Winches
An electrically driven winch is shown in figure 10-40. This winch is a single-drum, single-gypsy type. The electric motor drives the unit through a set of reduction gears. A clutch engages or disengages the drum from the drum shaft. Additional features include an electric brake and a speed control switch.
CAPSTANS
The terms capstan and winch should not be confused. A winch has a horizontal shaft and a capstan has a vertical shaft. The type of capstan installed aboard ship depends on the load requirements and type of power available. In general, a capstan consists of a single head mounted on a vertical shaft, reduction gearing, and a power source.
The types, classified according to power source, are electric and steam. Electric capstans are usually of the reversible type. They develop the same speed and power in either direction. Capstans driven by ac motors run at either full, one-half, or one-third speed. Capstans driven by do motors usually have from three to five speeds in either direction of rotation.
Maintenance of Winches and Capstans
You will maintain the winch or capstan similarly. Where band brakes are used on the drums, inspect the friction linings regularly and replace them when necessary. Take steps to prevent oil or grease from accumulating on the brake drums. Check the operation of brake-actuating mechanisms, latches, and pawls periodically.
Inspect winch drums driven by friction clutches frequently for deterioration in the friction material. Check also to see if oil and grease are preventing proper operation. Lubricate the sliding parts of positive clutches properly. Check the locking device on the shifting gear to see if it will hold under load.
MOORING
- Mooring winch is a mechanical device used for securing a ship to the berth.
- An equipment with various barrels used for pulling ropes or cables, mooring winches play an important role in berthing the ship ashore.
- The barrels, also known as winch drums, are used for hauling in or letting out the wires or ropes, which will help in fastening the ship to the berth.
- Mooring winches assembly comes in various arrangements with different number of barrels, depending on the requirement of the ship.
- The main parts of a mooring winch include a winch barrel or a drum, a warp end and a driving motor. Modern mooring winches comprises of elaborate designs with various gear assemblies, which can be electric, pneumatic or hydraulic driven
CONSTRUCTION & WORKING PRINCIPLE
A mooring winch assembly consists of a winch drum which has cable or rope wound around it.
The winch drum and warp end is driven with the help of a motor drive.
All these parts are supported with the help of a substantial frame, which also support a band brake, clutch and geared drives.
The motor drive is connected to the barrel and warp end using a spur gear transmission system.
The transmission system is also provided with a clutch and a band brake. Thus, the spur gear transmission system controls both the barrel and the warp end.
The warp end acts like a locking device, which prevents the rope from sliding off the barrel when pulled excessively.
Warp end is extremely important for moving the ship along the berth for alignment purposes. This is done by fastening one end of the ropes or wires to the bollards on the shore and the other end around the warp end of the winch.
Most of the modern mooring winches help in avoiding the stress related to constant monitoring of the mooring winches when the ship is berthing at a port.
It is essential to tension or slacken the mooring wires according to the flow of the tides and the change in the draught that takes place due to cargo operations.
The modern mooring assemblies act as an automatic self-tensioning unit, which provides for paying out or recovering wires when a pre-set tension is not present.
Appropriate control of the drum movement is an important aspect of the mooring operation. For this reason, band brakes are provided to stop the drum whenever required.
Also, it is important that the drum rotates smoothly in both reverse and forward direction.
A controller arrangement of the drive motor facilitates forward and reverse direction as and when required, including selection of speeds as per the requirement.
Hydraulic power pack
Electro hydraulic
In a typical electro hydraulic mechanism, one constant-speed electric motor drives two variable-stroke pumps through a coupling and reduction gear.
Other installations include two motors, one for driving each pump. Each pump normally drives one wildcat.
However, if you use a three-way plug cock-type valve, either pump may drive either of the two wildcats.
The hydraulic motors drive the wildcat shafts with a multiple-spur gearing and a locking head.
The locking head allows you to disconnect the wildcat shaft and permits free operation of the wildcat, as when dropping anchor
Each windlass pump is controlled either from the weather deck or locally.The controls are hand wheels on shafting that lead to the pump control.
The hydraulic system requires your attention.Make sure the hydraulic system is always serviced with the specified type of clean oil.
Types of windlass
Normally, you will maintain three types of anchor windlasses-the electric,electro hydraulic, andhand-driven windlasses.
Hand-driven windlasses are used only on small ships where the anchor gear can be handled without excessive effort by operating personnel
Windlass
The major work on a hand windlass is to properly adjust the link, friction shoes, locking head, and brake and to keep them in satisfactory operating condition at all times.
In an electro hydraulic windlass, your principal concern is the hydraulic system.
A windlass is used intermittently and for short periods of time. However, it must handle the required load under severe conditions.
This means that you must maintain and adjust the machinery when it is not in use.
This practice will prevent deterioration and ensure dependable use.
Windlass brake
Windlass brakes must be kept in satisfactory condition if they are to function properly.
Wear and compression of brake linings increases the clearance between the brake drum and band after a windlass has been in operation.
Inspect brake linings and clearances frequently. Make adjustments according to the manufacturer's instructions.
Maintenance
You should follow the lubrication instructions furnished by the manufacturer.
If a windlass has been idle for some time, lubricate it.
This protects finished surfaces from corrosion and prevents seizure of moving parts
The hydraulic transmissions of electro hydraulic windlasses and other auxiliaries are manufactured with close tolerances between moving and stationary parts.
