Interlock is prerequisites need to satisfy & helps in smooth operation. Interlock are basically two kinds.
Process Interlocks:
Interlock which related / dependent on another Instrument / System. Example in line of Operation assume there is an Motor & Valve sequentially.
If we need to close a Valve located after pump, We have to OFF pump too along with valve closing (In order to avoid pressure accumulation in line). So we need to design a logic in PLC that pump should turn OFF when the valve is closed.
System Interlocks:
Interlock relevant to that individual system.
Suppose I made pump ON and didn’t receive the pump ON feedback , Then i need to de-energize with specified time period.
Author - Siva kumar