Instrumentation is used to monitor and control the process plant in the oil, gas and petrochemical industries. Instrumentation ensures that the plant operates within defined parameters to produce materials of consistent quality and within the required specifications. It also ensures that the plant is operated safely and acts to correct out of tolerance operation and to automatically shut down the plant to prevent hazardous conditions from occurring. Instrumentation comprises sensor elements, signal transmitters, controllers, indicators and alarms, actuated valves, logic circuits and operator interfaces.
An outline of key instrumentation is shown on Process Flow Diagrams (PFD) which indicate the principal equipment and the flow of fluids in the plant. Piping and Instrumentation Diagrams (P&ID) provide details of all the equipment (vessels, pumps, etc), piping and instrumentation on the plant in a symbolic and diagrammatic form.