Showing posts with label bridge. Show all posts
Showing posts with label bridge. Show all posts


Preventive Maintenance


The bridge manoeuvring system does not require maintenance due to its design, yet it would be an advantage if the below mentioned items were checked occasionally.

Safety Panel.

Activate the "Test shut-down" and "Test slow-down" one at a time, and check that the appropriate white lamps immediately light up strongly. The test buttons should be activated (pushed) for at least 20 s in order to initiate the appropriate functions.

Bridge Emergency Button.

Open the cover which protects the three emergency buttons, and activate the STOP button.

Check that the emergency stop valve (ESV) is activated and draws the fuel pumps to "0" index. Set the button back in the neutral position after checking is completed.

Check the emergency "Full" button whilst an upward regulation through the load program is ordered, i. e. when max. r.p.m. are ordered on the bridge telegraph. As soon as the load program lamp lights up to indicate that further upward regulation is blocked for a short period, activate the "Full" button. Observe that the load program lamp extinguishes and that the main engine r.p.m. immediately begin to rise. Immediately this is checked, the button must be placed in the neutral position, since the function is then working.

The third emergency button "cancelling" is best checked by activating the test slow-down or test shut-down on the safety panel in the engine manoeuvring console. Press the test button in until a slow-down takes place respectively. As soon as the main engine begins to regulate downwards, the function is cancelled by activating the cancelling button on the bridge. The main engine should now regulate upwards again in a normal manner.

The cancelling button can now be set back in the neutral position, and the cover closed over the three emergency buttons, as all functions have now been controlled.

Voltage Supply.

A knob is.mounted on the Voltmeter Unit to enable all voltage groups in the control panel to be measured. Turn the knob through all 13 measuring positions and check that the voltmeter reading is always within one of the two green areas.

A reading up to 60 V is permitted in position 2, since in this case measurement takes place across the unloaded emergency supply. If the system is furnished with an emergency battery supply, its capacity should be regularly checked by placing the "Normal-battery" contact in the "Battery" position.

Now check whether the pointer of the emergency supply voltmeter in the control room manoeuvring stand remains within the green area.

Precautions at Slow- and Shut-Downs

In the event of a slow- or shut-down occurring, the appropriate lamps light up on the bridge telegraph and in the signal panel for emergency in the control room. If, with regard to the safety of the vessel, it proves necessary to start the engine again, the "cancel" button on the bridge telegraph can be activated. Since this is an emergency function, it will immediately release an alarm in the engine room.

Precautions at Slow- and Shut-Downs

If it is not imperative for the engine to run, the fault should be rectified before the engine is stated again. When the fault has been rectified, the reset button is pressed on the control room.

When this button is activated, the slow down circuit will be reset, and the engine will be automatically regulated up to the position of the handle. In the case of a shut-down, the engine will be automatically restarted after reset and the engine will regulate up to the value at which the bridge telegraph is set to.

Reset of a slow- or shut-down can also take place from the bridge by placing the telegraph on the bridge in stop position. An automatic reset order is thereby transmitted to the control panel, and if the slow- or shut-down condition has vanished automatic restart can be done by placing the telegraph in an arbitrary position.

However, it should be noted that it is only a reset arrangement. If the slow- or shut-down condition is still present, an automatic start can only be done by cancelling with the emergency buttons.

If an overspeed shut-down occurs, such a condition cannot be cancelled from the bridge by means of the cancelling button, but only by means of the regulating handle in the control room which has to be in the stop position.

When an overspeed shut-down has occurred, it should be noted that the fault could be due to a fault in the governor, or a fault in the remaining part of the manoeuvring system. In the case of an overspeed shut-down, the manual regulating system should be examined before the engine is allowed to start again and run to load.

A slow-down or shut-down can be due to a fault in the pressure switches or thermostates alone, without the measured value indicating a fault.

The contact for the appropriate channel can therefore be pressed in on the safety panel, thereby placing the channel out of action. This should, however, be carried out only whilst the pressure switch or thermostat is being replaced or repaired. A fixed light will appear in the safety panel whilst the channel is coupled out. It must be noted that such switching off a channel cannot cancel a slow- or shut-down. The reset button on the signal panel for emergency must always be pressed in afterwards.

Daily Use of the Bridge Manoeuvring System

Preparation and change over. Preparation and change over of the engine for the bridge control should be made in accordance with the instructions issued by the engine builder. The following points should be noted: The pump station for the hydraulic amplifier is started to provide oil pressure in the amplifier.

The automatic stop piston valve must be turned to the "Service" position.

Control Panel.

Check that the test telegraph switches on the mimic diagram are in the "Normal" position.

Check also that the switch in the engine speed test unit is in the "Tacho" position. If this switch is left in the "Test" position, the unit lamp will light up. If a start attempt is made, registration of the engine's turning will not take place and the tacho and repeated start supervision unit (TRS) will register the missing tacho signal, and after 6 sastart blocking and a tacho failure alarm will be initiated. If the control system is not furnished with a TRS Unit, starting air will be admitted until the pressure switch is activated.

The overspeed, slow turning, load program and reversing level switches on the mimic diagram are to be placed in the "On" normal position in order to incorporate these functions.

Check with the aid of incorporated voltmeter that all necessary voltages are present.

Check that the power supply switch is in the "Normal" position. If it is in the "Battery" position, the system will still be able to work, but normal running calls for the switch in the "Normal" position. Remember to press button if a change over from "Battery" to "Normal" becomes necessary.

Examine whether any of the lamps in the signal panel for emergency are lit up. If some are lit, the indicated fault should be remedied.

Check whether the safety panel shows any alarms or any shut- or slow-down channels. The lamps in the panel are extinguished under normal conditions. If an alarm occurs, the lamps will light up strongly. If a channel has been "pushed" out of working order, the lamp will continue to light up weakly provided there is no alarm on the channel. If an alarm occurs on a channel, the lamp will .also light up strongly in this condition.

When these preparations have been carried out the system is ready for automatic control.