Interposing Relay Panel (IRP)

Check the locations of the components like relay’s and Terminal blocks in the IRP panel shall be as per the approved IRP GA/IA drawing. Refer to the above photograph for easy understanding.

Also Read: What Is Interposing Relay in a PLC?

Termination of Digital Input (DI) signals

Identify the terminal block for the DI signal as per Instrument wiring interconnection drawing and Electrical schematic wiring drawing.
Check the cross-wiring between the Electrical side MCC terminal and the System side Instrument terminal.
Check the proper ferrule for the input signal i.e. Status, L/R, and Fault from and to assigned terminals.

Testing of the Digital input (DI) Signals

Identify the terminal block for the DI signal as per Instrument wiring interconnection drawing and Electrical schematic wiring drawing.
Short the terminal blocks of the DI signal at the MCC end in the IRP cabinet.
Check and ensure the continuity in the multimeter at the terminal end in the IRP cabinet for the same.
Repeat the above steps for each DI signal and highlight each signal in the I/O list to ensure all the DI signals are covered under the test.

Termination of Digital Output (DO) Signals

Identify the terminal block and relay numbering for the DO signal as per Instrument wiring interconnection drawing and Electrical schematic wiring drawing.
Check the cross-wiring between the Electrical side MCC terminal, Relay, and the System side Instrument terminal.
Check the proper ferrule for the output signal i.e. Start, Stop, and Trip from and to assigned terminals.

Testing of Digital Output (DO) Signals

Identify the terminal block and relay numbering for the DO signal as per Instrument wiring interconnection drawing and Electrical schematic wiring drawing.
Inject 24V DC with current ranging from (50-100mA) to the Coil side of the DO signal.
Confirm that the intended relay is energized / de-energized as per the Electrical schematic wiring drawing.
Check and ensure the continuity at the MCC end for the same signal using a multimeter.
Repeat the above steps for each DO signal and highlight each signal in the I/O list to ensure all the DO signals are covered under the test.

Note: Hope the above explanation for the wiring and testing of the Interposing relay panel is understood.

Have a nice day!!

Stay Safe!!

Author: Mohammed Khaleel

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Interposing Relay Panel (IRP) – Wiring and Testing Requirements