Ship diagrams are used to accurately portray the electrical system.
Over the years, many techniques have been used to simplify the diagram for the reader. These attempts often produced more questions than they answered.
Symbols were not standardized, and pictorial schematics showed the electrical system in various degrees of accuracy. Often the illustrator took for granted that his codes could be understood.
In effect, there were no industry standards. Although each diagram might be electrically accurate, it was not developed for uniform individual interpretation.
Today, as electrical systems become more complex, the electrical community has adopted specific standards to allow a more universal comprehension of the electrical circuits they describe.
However, you will still find many variations due to physical constraints, cost, and the broad time span encompassing the mammoth shipping industry e.g., you may not find modem flow charts and computer-aided diagrams onboard a vessel that is at the end of long spell at sea and about to enter the ship-breaker’s yard!
There are various types of diagrams, which attempt to show how an electrical circuit operates and some types are explained in this chapter. Symbols are used to represent components / items of equipment.
A diagram always illustrates contacts, switches, and devices in their de-energized position.
A picture is portrayed of the position they are in when the device is unaffected by an outside force. The force that changes the position of contacts can come from any number of places. For example, the force can be the electromagnetic force from a relay coil (solenoid) becoming energized and physically moving an armature thus changing the position of its contacts. The force can also be exerted manually as in the case of a simple switch.
A normally open or N/O contact means that the contact’s magnetic coil, for instance, has not yet been energized.
Therefore, when the coil is energized, the normally open contact closes, and a normally closed or N/C contact would open.
The shipbuilder provides a complete set of ships’ electrical diagrams. It is important that you study these diagrams to be able to read and understand them completely, and to use them as an aid in locating electrical faults.
-Do not write over existing prints or permanently mark the schematics in controllers or other electrical components. Instead, use a pencil or make a copy from a technical manual.
-Maintain existing diagrams in their original conditions and ensure they are always legible.
-Note any modifications to a system in a dedicated logbook and procure updated diagrams.
These will serve to help you and others onboard a ship especially in an emergency when a legible diagram is extremely important to help one to react sensibly!