1.13 Steering Gear

readily accessible and, as far as practicable, separated from machinery spaces; and

provided with suitable arrangements to ensure working access to steering gear machinery and controls. These arrangements shall include handrails and gratings or other nonslip surfaces to ensure suitable working conditions in the event of hydraulic fluid leakage.

• the steering-wheel transmitter-located in the bridge space

• the rudder-control receiver unit -located aft in the steering compartment

• the systems conveying the transmitter signal to the receiver

• the power system which moves the rudder

• the rudder-control feedback to the system

The Electro-Hydraulic Steering Gear consists mainly of tiller, ram and ram pin, hydraulic cylinder, pump, valves and piping.

The hydraulic pump is of fixed displacement type and delivers the rated volume of oil in the rated direction.

This direction of oil is controlled by the solenoid valve or sol-hyd. valve according to the order angle from the steering stand on the bridge and the oil acts on the ram.

The ram thrust produced by the pressure oil is transmitted to the tiller arm through the ram pin and the roller bearings and converted to the torque of the tiller keyed to the rudder stock and then the rudder is moved.

The actual angle is feed-backed to the steering stand through the repeal back unit and the ram stops since the valve is shifted to neutral position when order and actual angles are completely coincident

The rams acting in hydraulic cylinders operate the tiller by means of a swivel crosshead carried in a fork of the rams. A variable delivery pump is mounted on each cylinder and piped to each cylinder to enable suction or discharge from either. A replenishing tank is mounted nearby and arranged with non-return suction valves which automatically provide make-up fluid to the pumps.

A bypass valve is combined with spring-loaded shock valves which open in the event of a very heavy sea forcing the rudder over. A spring-loaded return linkage on the tiller will prevent damage to the control gear during a shock movement

During normal operation one pump will be running. If a faster response is required, for instance in confined waters, both pumps may be in use. The pumps will be in the no-delivery state until a rudder movement is required by a signal from the bridge telemotor transmitter.

A ship consists of electromechanical steering gear unit which steers the vessel from one port to other. Normally steering gear unit is 2 or 4 ram electro-hydraulically operated unit with two or more hydraulic motor for the ram movement.

A situation can occur in which the remote control operation may fail to work and their can be a sudden loss of steering control from the bridge. This can be due to sudden power failure, any electrical fault in the system or the control system which includes faulty tele-motor or servo motor which is used for transferring the signal from bridge to the steering unit.

To have control the steering of the ship at such emergency situation with manual measure from within the steering gear room, an emergency steering system is used.

The following points should be followed for emergency steering operation.

The procedure and diagram for operating emergency steering should be displayed in steering gear room and bridge.

Even in emergency situation we cannot turn the massive rudder by hand or any other means, and that’s why a hydraulic motor is given a supply from the emergency generator directly through emergency switch board (SOLAS regulation). It should also be displayed in the steering room.

Ensure a clear communication for emergency operation via VHF or ships telephone system.

Normally a switch is given in the power supply panel of steering gear for tele motor; switch off the supply from the panel.

Change the mode of operation by selecting the switch for the motor which is supplied emergency power.

There is a safety pin at the manual operation helms wheel so that during normal operation the manual operation always remains in cut-off mode. Remove that pin.

A helms wheel is provided which controls the flow of oil to the rams with a rudder angle indicator. Wheel can be turned clockwise or anti clockwise for going port or starboard or vice versa.

If there is a power failure, through sound power telephone receive orders from the bridge for the rudder angle. As soon as you get the orders, turn the wheel and check the rudder angle indicator.

A routine check should always be done for proper working of manual emergency system and steering gear system. An emergency steering drill should be carried out every month (prescribed duration – 3 months) in the steering gear room with proper communication with bridge to train all the ship’s staff for proper operation of the system so that in emergency situation ships control can be regained as soon as possible, avoiding collision or grounding.

With this type of steering gear a vaned rotor is securely fastened onto the rudder stock. The rotor is able to move in a housing which is solidly attached to the ship's structure. Chambers are formed between the vanes on the rotor and the vanes in the housing. These chambers will vary in size as the rotor moves and can be pressurised since sealing strips are fitted on the moving faces. The chambers either side of the moving vane are connected to separate pipe systems or manifolds. Thus by supplying hydraulic fluid to all the chambers to the left of the moving vane and drawing fluid from all the chambers on the right, the rudder stock can be made to turn anti-clockwise. Clockwise movement will occur if pressure and suction supplies are reversed.

Three vanes are usual and permit an angular movement of 70°: the vanes also act as stops limiting rudder movement. The hydraulic fluid is supplied by a variable delivery pump and control will be electrical, as described earlier. A relief valve is fitted in the system to prevent overpressure and allow for shock loading of the rudder.

A bow thruster is simply a propulsion device located at the bow that provides lateral (port and starboard) thrust, making the vessel more maneuverable.

The addition of bow thrusters allows a boat to move to the side (port or starboard) without forward or backward thrust from the engine or rudder. Thrusters use suction to draw in water from one side of the boat and push it out the other side to move the boat in the opposite direction.

Our thrusters are not designed to be run continuously(for example holding against a dock for long periods), and we recommend a maximum run time of 30 seconds with at least a 10 second cool down.