ROLLS-ROYCE ATC-3-A7033172 AQUAMASTER TURNING CONTROLLER

ROLLS-ROYCE ATC-3-A7033172 AQUAMASTER TURNING CONTROLLER

Pitch Indication

The Pitch Indication system is independent of the Normal Pitch Control system by

means of separate transmitters and electronic circuits. The pitch indicators are connected

in series and are driven from the Backup Control system.

Pitch Order Scaling

The system may need to reduce the pitch order for different reasons. The pitch reduction

can either be activated from a digital or anlogue input signal.

To reserve engine power to heavy consumers as alternators, fire pumps, etc., it may be

necessary to reduce the available propeller output power. This is normally done by

means of a fixed propeller pitch reduction.

If the drive motor is a diesel engine the system is prepared to handle a fuel limiter

contact, from the RPM governor (i.e. high scavange air pressure). If the contact is closed

the pitch order will stop increasing to a higher value, only decrease of pitch order against

zero is possible.

For azimuth thrusters, a pitch reduction will be activated if the azimuth order is changed

faster then the thruster azimuth servo can follow.

Thruster Azimuth Control

The azimuth control function is to obtain the correct thruster azimuth position in

accordance to the control lever order. Valve controlled hydraulic motors or frequency

controlled electro motors perform the positioning of the thruster azimuth.

Detailed information regarding the hydraulic system or motor data is available in the

Thruster Instruction manual

Normal Control

The azimuth controller computes the thruster position and order on the basis of signals

from the thruster feedback and control levers. A two-wiper linear potentiometer

provides two outputs with 90 degrees of phase shift named cosine and sine phase

respectively.

The lever order signals and feedback signals are monitored and verified against alarm

limits. If the signals exceed the limits this will release an alarm to the alarm plant with

a visual and audible system failure alarm on the manoeuvre stations.

Backup Control

The Backup Control system consists of closed loop control identical to the normal

control system. The Backup Control is a separate system, and is independent of the

Normal Control system. A system failure in the Normal Control system will

automatically switch to and engage the Backup Control.

Lever order signals and feedback are monitored and verified against adjustable alarm

limits. If the signals exceed the limits this will release an alarm to the alarm plant with

a visual and audible system failure alarm on the manoeuvre stations

Backup Control Operation

If a failure occurs on important parts of the Normal control for the Pitch/Azimuth/RPM

control function, the control will automatically be switched over to the backup control

system. A system failure audible and visible alarm will be activated on each of the

control panels.

The thruster control will continue to follow the lever in command, and command

transfer is done by using the common in command buttons. The command can be

transferred between all bridge position and the bridge control levers will continue to

work as in Normal Control.

A failure that occurs on important parts of the Backup control for the Pitch/Azimuth/

RPM control function, will not affect the Normal control system. If a system failure

occurs on the Backup Control an audible and visible alarm will be activated on each of

the control panels.