Winches

Winches are used to haul wires or ropes. They may be hand operated or driven by an electric or hydraulic motor or a steam engine. Basically they consist of one or more rotating drums on which a rope or wire may be wound and in some cases stored. A winch with a drum rotating on a vertical axis is known as a capstan. Winches are widely used with cranes, derricks and for mooring purposes.

1.2.1 Maintenance of Winches

A winch requires the same care and maintenance as a windlass. In addition you must check the condition of the associated wires and ropes prior to use to ensure that they are free from breaks or frays. Wires should be regularly coated with a lubricant to protect them from corrosion.

Cranes

Modern cranes rely on a vessel’s power to electrically or hydraulically operate winch drums and slewing gear. On many cranes three motions are possible - lifting, slewing and luffing (raising or lowering the jib boom). Figure 2.2 shows a crane where lifting and slewing motions are possible.

Cranes should always be marked with their Safe Working Load.

Figure 2.2  Slewing Davit Crane

Maintenance of Cranes

Suggested maintenance schedule for cranes (similar to the one shown in fig 2.2):

Weekly

Turn davit boom through normal arc by hand slewing gear.

Check winch brake for freedom of action.

Inspect brake lining for wear and grease deposits.

Conduct running test with dummy load. Failure of this test will probably require the replacement of brake linings.

Monthly

Lubricate and grease all points on the crane.

Check oil levels.

Check brake linings for wear.

Clean and examine all wire ropes and lubricate running gear.

Six Monthly

Examine all parts for corrosion, distortion, cracks or any other defects.

Check slewing gear for backlash.

Check hand raising clutch, brake assembly and gear box clutch for damage, wear, and oil contamination.

Survey Requirements

The survey requirements for deck machinery are laid down in section 14 of the USL Code. After the initial commissioning survey, deck machinery is surveyed during annual and periodic surveys or as required by the appropriate authority. The surveys include the inspection of windlass mounting and surrounding deck to insure that these are adequate for their task and have not deteriorated with use or due to corrosion. It is a requirement that the machinery should operate as specified and within safe limits.

Any gear (including cranes) used for handling cargo must comply with Commonwealth regulations contained within Marine Orders Part 32 (Cargo and Cargo Handling - Equipment Safety Measures)

Precautions in Deck Machinery Operations

Ensure that operating and control handles are clearly marked to show ‘heave in’ and ‘pay out’ directions.

Never exceed the safe working load of the equipment.

Never operate the machinery if there is a fault in the clutch or brake.

Ensure that gear wheels and other moving parts are always protectively covered.

Keep the working area free from oil and grease.

Do not operate the machinery if you cannot sight the load.

Ensure that you know how to stop the running machinery in an emergency.

Always use the machinery in the manner specified, and within the limits suggested by the manufacturer.

Steering Gear

Most vessels are steered with the aid of a rudder, which is rotated to the required angle by a steering mechanism. The type and size of steering mechanism depends on the size and design of vessel.

Rudders

The National Standards specify the sizes and materials used for the construction of rudders. Two methods of mounting the rudder are shown in figure 2.3.

Figure 2.3 Rudders

Drawing (a) shows a mounting arrangement where the forces on, and the weight of the rudder are carried by the rudder stock. This means that the stock and bearings should be of adequate size and strength to withstand stresses under any weather condition.

Drawing (b) shows a pintle type rudder arrangement. The rudder is hung on pintles and has a further pintle in the extension to the keel.

The rudders are secured to the stock by flanged couplings and these need to carefully checked whenever the vessel is out of the water.

Wire and Pulley

A wire and pulley arrangement is shown in figure 2.4. which consists of a wire wound around a drum fitted to the wheel. The wire passes through a series of pulleys on the two sides which connect to the tiller or quadrant of the rudder mechanism.To avoid excessive strain and bending of the wire the pulley blocks should be as big as possible and positioned to avoid an excessive angle or be easily fouled. Buffer springs are provided on both port and starboard to prevent violent recoil of the steering wheel. All components should be inspected and greased or oiled as appropriate.

Figure 2.4  Wire and Pulley

Chain and Box

A wide variety of chain and box installations make use of automotive parts such as shafts, universal joints and truck steering boxes. These systems require periodic inspection and lubrication. The chain is liable to stretch and should be checked regularly. For this reason the chain length is usually adjustable.

Figure 2.5  Chain and Box Gear

Push-Pull Cable

A push-pull cable type steering arrangement is shown in figure 2.6. This arrangement is similar to that used on outboard motors. The length of the cable should not be too long or short as this can affect the tiller response. If the push-pull cable or rod seizes, there must be provision for releasing the push-pull rod from the tiller to operate the emergency steering.

Figure 2.6 Push-Pull Cable Gear

Basic Hydraulic Systems

Hydraulic systems are common in vessels of 20 metres or more in length. These systems range from simple manual systems to electro-hydraulic oned. Figure 2.7 shows a simple manual system with a single steering station.

The system operates utilising the flow of hydraulic fluid under pressure to control the movement and position of the rudder.  The system consists of a two way hydraulic pump, usually an internal gear pump, connected to the wheel. Two pipes lead from the pump to the hydraulic cylinder and ram, which in turn is connected to the tiller. The rotation of the wheel will force oil from the pump to one side of the ram thus rotating the rudder.

A major problem associated with any hydraulic system is air in the system therefore, most systems are built to be self purging of air.

The emergency steering will require the oil to be by-passed and a valve is placed between the two sides of the system for this purpose. To prevent hydraulic locking, this valve will need to be opened when the emergency system is to be operational. In addition, there should be a relief valve which spills the oil from one side to the other in the event of shock loading to the system.

Specific maintenance requirement for this system is to ensure that the oil level is adequate and that there are no leaks.

Figure 2.7 Simple Hydraulic System

Simple Telemotor

In most larger systems the signal from the steering wheel is transmitted to the steering gear by means of a telemotor. This not only ensures that the steering system is isolated to the steering flat, it also means that the steering system can be used even if the wheel and connections are damaged or become inoperative.

Figure 2.8 shows a steering system incorporating a telemotor.  The latter consists of a transmitter in the wheelhouse and a receiver in the steering flat.  The movement of the wheel activates an hydraulic piston in the transmitter. The fluid displaced by this piston is used to displace a similar piston in the receiver. This movement is used to control the main steering gear’s hydraulic pump, which in turn operates the steering gear and rudder. The receiver is usually spring loaded so that the steering wheel will easily return to the midships position.

Figure 2.8  Steering Gear and Telemotor