Piping and Instrument Diagram(P&ID)

• P&ID – Construction Guide/Manual
• P&ID is also known as mechanical flow diagram (MFD)
• Contains: plant construction information (piping, process, instrumentation, and other diagrams)
• Provides information needed by engineers to begin planning for the construction of the plant

• Look at V-102 on P&ID
  • V-102 contains an LE (Level Element)
    • LE senses liquid level in separator and adjusts flow rate leaving
    • LE opens and closes a valve depending on liquid level
    • LE and valve represent a feedback control loop

// P&ID Summary

• The final control element in nearly all chemical process control loops is a valve.
• Key to understanding the control logic is to identify which flowrate is being manipulated to control which variable.
• Based on the P&ID diagram:
  • Mech and Civil Engrs will design and install pieces of equipment.
  • Instrument Engrs will specify, install and check control systems.
  • Piping Engrs will develop plant layout and elevation drawings.
  • Project Engrs will develop plant and construction schedules. v
• Before final acceptance, P&IDs serve as a checklist against which  each item in the plant is checked.
• Design Case Vs Base Case

// How to Read P&ID