ICD (Instrumentation control and design)

Download the pdf of Ziegler-Nichols Tuning procedure
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Loop Wiring Diagram

             This is the picture of loop wiring diagram, in which we can understand how wiring cable routed from field area to system cabinet and from system cabinet to field again. This is the basic idea how signal goes from field to cabinet and vice versa.

Loop wiring basic

Marshalling cabinet (Cable spreading room)

             This is the room where all field wiring gets sorted or arranged in proper manner so that during any maintenance it will be easy for operator or person to resolve specific problem.  

Marshalling cabinet rooms

Junction Boxes

             This junction boxes includes bunch of terminal block (terminal strip) in which our field signal come first. These are located on field itself. These are having so many types according to hazardous area classification means for fireproof or blast proof design we can installed fireproof JB's but we have to compromise with cost only since they are providing safety to your other devices.
             During recognition of JB's some basic terminology used which is shown in picture below.

Junction box

Cable routing

           
             On basis of signal cables or power cables, cables are routed from field to cabinets as shown in picture below. Signal and power cables are never goes together because it results into an interference of external magnetic field on signal cables which results in wrong readings. As shown in right picture we can sort the cables i.e. signal cables will goes from one side while power cables from other side.

Cables routing

System Cabinet

             This is the place where our controllers are situated. These are actually situated in cold and dust proof environment. Since total plant activity depends on controller status and working that's why it should be at safe and good place. Mostly there is restriction to enter in controller rooms. In some industries controller room where all input and output is coming is at one place (In highly cold and dust proof environment) and control rooms from which we can change the controller program or excess any information from controller is at another place. 

Control rooms

Hookup wiring Diagram

This term specifies how our instrument or device installed in field. Maintenance/commissioning engineer need to see this document before installation of instrument in field. Following picture shows how it look like.

Hookup Drawing

P&ID's

Line designation are written like below example,

Line Designation

P&ID Line and Tag Number can be written as follow,

P&ID Line and Tag Number

Refer below link for more information
click here

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How to make control panels for PLCs?

Refer below link

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What is Sinking and Sourcing?

“Sinking” and “Sourcing” terms are very important in connecting a PLC correctly with external environment. These terms are applied only for DC modules.

Sinking

                The sinking name itself tells that it absorbs the power it means it provides the common GND path (-) for supply. Sinking IO's in PLC or DCS circuits receive (sink) current from external sourcing devices. The sinking term related with NPN transistor it means sinking IOs accepts the current from field and complete the loop. Following Picture clears all idea about sinking

Sinking

 Sourcing

                The sourcing name itself tells that it provides the power it means it provides the + 24V supply. Sourcing IO's in PLC or DCS circuits provides (source) current to external devices. The sinking term related with NPN transistor it means sinking IOs accepts the current from field and complete the loop. Following picture gives you overall idea about sourcing

Sourcing

                  The most brief definition of these two concepts would be:

SINKING = Common GND line (-) normally termed as NPN
SOURCING = Common VCC line (+) normally termed as PNP

Most commonly used DC module options in PLCs are:
*Sinking input and
*Sourcing output module

Positioner working

Control valve positioner
  

P and ID (Process and Instrumentation diagrams)

                This is the way how we can indicate actual devices in field in process sheet by using P and ID.

Click here (For P and ID pdf file)

Click here (For drawing P and ID sheets online / You can also use Microsoft visio for drawing P and ID sheets)  

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Troubleshooting of process loops

Click here Link1

Click here Link2 (Split range control inspection)

Click here Link3

Click here Link4