Nowadays, however, far more UMS ships are in operation. Crews have grown familiar with the systems and training is more prolific. In the immediate future more owners will adopt UMS, not only as a means of cutting crew to a minimum and thus cut operational costs, but also for reasons of safety.
Remote-controf systems. As a number of remote-control stations may be installed, operation must only be possible for one station at a time. There should he no misunderstanding as to which station has control at any time one time, thus there should be continuous indication at all the main control stations showing which one has control. When control is transferred from on'e station to another, a warning must be given. Only one-station which has taken control must acknowledge the fact.
There must be means by which the propulsion machinery can be stopped from the bridge, regardless of whether another station is being operated. Any orders activated from the bridge are to be indicated in the control rooms.
Indicators of the speed and direction or rotation of reversible engines. or the propeller pitch and speed of rotation must be fitted on the bridge. Additionally, an independently-operated stand-by control should be provided in the engine room. It must be able to override the remote-control system.
For diesel plant with fixed-pitch propellers the fuel supply and direction of engine rotation should be effected by a single control lever. The controls must operate the machinery in a time sequence acceptable for the engines, and able to shut-off the fuel supply if the desired and actual direction of rotation of the engine and the cam-shaft position does not match.
In addition to alarm indication for the lubricating oil system, the system must be able to shut down the engine if lubricating (lube) oil is lost. The circuit and sensors for this function must be additional to the alarm circuit required.
On the bridge, both audible and visual alarms are to operate and indication given when the speed of the main engines is to be reduced due to the following fault condition: high scavenge air temperature, oil mist detected in crankcase, low piston coolant outlet flow, low piston coolant pressure, also for low cylinder coolant pressure if on a separate circuit.
Where the lube oil cooling water and oil fuel booster pumps are not driven by the main engine, the standby pump is to start automatically if the discharge pressure from the working pump falls below a predetermined value.
Iiomeiask: Ex. 32. 33.
The fifth class period
Read the text, mind logical units. Translate the text at sight.
The convertors in dc drive systems are designed to control and supply separately-excited dc machines in aimlications that demand rapid response. high accuracy and great reliability.
"The convertors are available with single-convertor arrangement and in double-convertor arrangement.
Operation. The armature simply unit has a closed-loop current control system which ensures that the armature current follows the set current reference. The svstem is based on a current controller, the output signal of which can influence the armature current via the control pulse circuits and the thyristor unit. The current measuring circuits continuallv supplv the current controller with information on the actual value of the armature current, and when this is compared with the reference an error signal is obtained which corrects the output voltage of the controller if necessary.
The controller current includes circuits for adaptive control. This means that the gain of the controller increases if the current is discontinuous. This maintains the response time of the current control system. A tynical response time for the current control is 10—15 min.
The current control system includes a buffer amplifier for the actual current value. This makes it possible to connect a meter to display the armature current, for example. By applying a control signal, the output of the buffer amplifier can be converted, so that the output signal changes sign when the direction of current flow changes in a double convertor.
