Basics of instrumentation

Basics of instrumentation 

Instrumentation is a detail study of instruments which are used in the process industries to measure the physical changes like flow, temperature, level, pressure, displacement, mass, speed, velocity, direction Etc., and  Instruments include many varied contrivances that can be as simple as valves and transmitters, and as complex as analyzers.

Major conduits in Instrumentation:

Active and Passive instrument (Input feedback control)

Final control instruments (Output device control)

Control platform (PLC, SCADA, DCS, Embedded, Micro controller)

Interfacing platform (Monitoring window)

Network topology (Ethernet , RS 232 ,RS 485, Modbus, Wireless)  

 Control Instrumentation plays a significant role in both gathering information from the field and changing the field parameters, and as such are a key part of control loops.

P&ID Piping and Instrumentation Diagram

P&ID drawing 

A Piping and Instrumentation Diagram - P&ID, is a schematic illustration of functional  relationship of piping, instrumentation and system equipment components.

P&ID shows all of piping including the physical sequence of branches, reducers, valves,  equipment, instrumentation and control interlocks. The P&ID are used to operate the process  system.


P&ID should include:

·        Instrumentation and designations

·        Mechanical equipment with names and numbers

·        All valves and their identifications

·        Process piping, sizes and identification

·        Miscellaneous - vents, drains, special fittings, sampling lines, reducers, increasers and  swagers

·        Permanent start-up and flush lines

·        Flow directions

·        Interconnections references

·        Control inputs and outputs, interlocks

·        Interfaces for class changes

·        Seismic category

·        Quality level

·        Annunciation inputs

·        Computer control system input

·        Vendor and contractor interfaces

·        Identification of components and subsystems delivered by others

·        Intended physical sequence of the equipment

P&ID should not include:

·        Instrument root valves

·        control relays

·        manual switches

·        equipment rating or capacity

·        primary instrument tubing and valves

·        pressure temperature and flow data

·        elbow, tees and similar standard fittings

·        extensive explanatory notes