HOW TO READ COMPLEX ELECTRICAL DIAGRAM?
Most Frequently asked question in everybody s mind, How to read a complex electrical diagram in plants Like Boiler, N2 generator, Fuel Conditioning modules, Ballast water treatment systems, etc. Sometimes Engineers call ETO for assistance if there is any malfunctioning of the plant so you start tracing for the circuit for fault. Tracing circuits complex circuits can be easier if you practice it well. Nothing comes without effort reading complex diagrams can never be easier but you can if you follow these 5 tips.
PRACTICE SYMBOLS & ANSI/IEEE NUMBERING
The fundamental block of the circuit diagram is components and their symbols. You must know the working and function of all components. Some symbols may have multiple ways to represent. The below figure shows an example of how timer can be represented.
WHY & WHAT FOR?
It is the most important attitude to learn electrical and electronics. As an ETO you must know the working and functioning of electrical components. The tracing diagram has meaning only if you know why and what for the components is used. In below figure shows the circuit diagram of the AC dimmer circuit for Lamp. In this circuit, you must think about why DIAC is used with TRIAC?
DIAC conducts heavily after breakdown voltage also it is seen that after breakdown current increases voltage decreases. TRIAC needs very less Gate voltage to conduct hence DIAC is used as trigger voltage to TRIAC. R1 is used as a Current limiting resistor because when VR1 is a minimum large current can flow causing Capacitor C to charge and discharge continuously. When Charging voltage reaches breakdown voltage DIAC conducts capacitor discharges this process continues. VR1 controls the charging rate of the Capacitor.
Also, be familiar with the safety devices employed in the plant because a safety device has interlock with plant working plant will not operate if a safety device like Emergency stops are activated.
READ FLOW CHART PROCESS DIAGRAM
Every plant will have a flow chart start from scratch until the plant stops. In every step, you can easily make out which relay starts and whats stops.
In above flow chart shows the firing sequence of Boiler. Starting sequence we can see that 1st AIR FAN must run. To start 1st air fan corresponding relay must be started. Similarly for 2nd AIR FAN. This sequence continues till flame monitor and corresponding relays are activated. This is how we can trace circuit for boiler. Not only Boiler similar technique can be applied to other plants also.
SPLIT DIAGRAM INTO PARTS
There are two parts in the electrical diagram Power and Control circuit. Power circuits are easy to read because this mainly contains Motors, Heaters, etc. Controls circuit are quite complex because it contains so many components like relays, solenoid valves, switches, sensors, PLC.
If very difficult to analyze what is going inside control circuits where PLC is involved but looking at the flow chart can make out what output it gives to where. The below figure shows how the circuit can be split same can be applied for complex circuits also.
Control circuits have two-part Auto and Manual operation some have the only manual operation, It can also be split if it is having two operations.
TAKE ADVICE
In the worst case, you can ask a concerned engineer. Sometimes you may not have more time to read diagrams so to understand how control goes from the start you can ask concerned engineers like what problem he/she faced with the plant because he/she will be more familiar with the plant,
Engineers may or may not help in some cases but this does not mean you can completely rely on them. Taking his/her ideas can make your troubleshooting easier because you may or may not be familiar with the plant.
CONCLUSION
In the manual and circuit diagram onboard, detailed function of whole plant control is mentioned clearly It is good to have a glance at manuals when you are onboard. During the breakdown, you will have an idea about the plant. I hope this post is helpful.
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