DECK MACHINERY & STEERING GEAR
(Ranger Hope © 2008, contains edits of material courtesy of A.N.T.A. publications.)
Common items of deck machinery found on small vessels are the anchor windlass, winches and the crane or derrick.
The anchor windlass is used for handling anchor chain. It is usually located in an exposed position on the fore-part of the vessel, hence most of its moving parts are enclosed. Routine maintenance is usually carried out through the provision of grease nipples. Inspection of the equipment frequently involves the opening of plates or panels in the cover.
Figure 2.1 shows a typical anchor windlass. The cable lifter (or gypsy) can be clutched to the drive shaft by means of a simple dog clutch arrangement. The braking arrangement is usually a band brake. Warping drums may be provided at the ends of the drive shaft. These are used for heaving mooring ropes.
Maintenance of Anchor Windlass
Maintenance should be strictly carried out as per the equipment manufacturer’s instructions. However, general guidelines for maintenance are suggested as follows :
Charge all grease points.
Operate clutch through full travel.
Inspect clutch plates and inspect for wear and corrosion
Examine mechanical brake for wear.
Examine base and mountings for corrosion.
2.1 Anchor Windlass 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. 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.
Fig. 2.1 Anchor Windlass
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.
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):
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.
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.
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.
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)
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.
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.
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.
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
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
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
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
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
The electro-hydraulic system, shown in figure 2.9, has the advantage that the signal from the wheelhouse to steering flat is transmitted by electrical wires. Further, the system uses a uni-directional pump which is less complicated and cheaper than a bi-directional.
The pump supplies oil at a constant rate to a directional control valve, which is usually positioned in the steering flat.
The valve consists of three positions, and depending on the position, will supply oil to either side of the double acting ram. When in the neutral position, oil is locked in the ram, thus maintaining the given rudder angle, whilst the pump flow is circulated back to the tank. The valve is operated by solenoids controlled from the wheelhouse via the control box.
As with the previous system there is a by-pass and relief valve fitted between the left and right sides of the ram. Emergency steering can be carried out by operating the emergency steering lever located in the steering flat.
Figure 2.9 Electro-hydraulic System
Steering Gears are surveyed during a vessel’s annual and periodic surveys. The requirements for steering gears are laid down in the National Standards.
. These are summarised below.
All vessels except twin screw vessels and vessels where the normal means of steering is a hand tiller shall be fitted with two independent means of steering.
The steering gear shall be of adequate strength to steer the vessel at maximum speed both ahead and astern.
Rudder movement should be 35 degrees port and starboard.
In vessels 12.5m and over the steering gear shall be capable of putting the rudder from 35 degrees on one side to 30 degrees on the other in 30 seconds at maximum speed.
The steering gear shall be so designed and constructed to prevent violent recoil of the steering wheel.
In hydraulic systems, changing over from primary to secondary systems should be able to be carried out easily and quickly.
Power driven hydraulic systems shall be fitted with a relief valve to prevent mechanical damage.
The rudder indicator shall move in the same direction and give a true indication of the rudder angle.
If the emergency steering is remote from the steering/navigation position an adequate form of communication between these two positions shall be installed.
Where necessary the steering gear will be fenced and have adequate guards to avoid injury to personnel.
As stated above if the tiller and hence the rudder is rotated by hand as in small vessels it is not required to have a back up or emergency system. However, in most modern vessels a mechanical means is employed to move the tiller, thus requiring an emergency back up. This may take the form of a hand tiller, which can be quickly and easily fitted to the top of the rudder stock. This emergency tiller must be kept in a place close to the steering flat and stock.
Survey RequirementsThe National Standards specify the survey schedule is as follows:
Annual Survey: Operational test of main and emergency means of steering.
2 Yearly Survey: Inspection of Rudders.
8 Yearly Survey: Steering gear.
If the vessel is fitted with an automatic pilot the manual steering shall be tested after prolonged use and before entering areas where navigation requires special caution.
Within 12 hours before departure the vessel’s steering systems shall be checked and tested, where applicable by the operation of the following:
1. the main steering gear
2. the auxiliary system
3. the remote steering gear control system
4. the wheelhouse steering position
5. the emergency power supply
6. the rudder angle indicators
7. the system power failure alarms.
Tests and checks shall include :
1. the full and accurate movement of the rudder
2. visual inspection of all parts and linkages
3. the operation of the means of communication between the wheelhouse and steering gear compartment
Simple operating instructions and a block diagram should be permanently displayed in the wheelhouse and steering gear compartment.
Emergency steering drills shall take place at least once every three months.
Details of all tests, checks and emergency steering drills shall be recorded in the log book or the vessel record book.