P&ID’s

1. P&ID’s PIPING & INSTRUMENTATION DIAGRAMS

2. Format & Layout • Title Block • Sheet Number • Revision Number • Date

3. Format & Layout • Layout Rules of Thumb • No Scale • Flow From Left to Right across page • Important Process Streams Heavy Dark • Less Important (utilities, instrumentation lines lightweight) • Horizontal Lines ‘break’ vertical Lines • Process Lines Break Instrumentation Lines • Pumps along bottom • Tanks above pumps

4. P&ID’s - Symbology • Equipment Symbology • Instrumentation Symbology • See the document “P&ID Symbols and Photos.DOC”

5. P&ID’s - Equipment • Keep in mind the development of the P&ID’s is really developing the process • The way it will start-up / shut-down and normally operate • Procedure • Start with the Simulation and Equipment List • Draw Equipment (including spares) • Draw the major process Lines, then Utilities

6. P&ID’s - Safety - ALWAYS!!!!! • ALWAYS Consider Safety!! • Think, what happens if the control valve doesn’t operate as intended? • What happens if the pump stops working? • How will the operators troubleshoot the problem? • What if the operators ignore an alarm • ... • Consider the need for redundant controls and equipment, but only if deemed necessary. • Redundant things are twice as likely to fail!

7. P&ID’s - Simplicity Rules • The easiest process to operate and understand is the simplest one • K.I.S.S. • Add “indicators” (flow, pressure, temperature) for trouble shooting • Don’t add “controls” unless they are absolutely necessary • Only resort to complicated controls when you have to... Consider the consequences of operators not understanding them.

8. P&ID’s - Rookie Mistakes • Don’t put level control on Storage Tanks • They’re there to take up variations in flow, therefore the level is supposed to ‘float’ • Let Pressures in the process ‘float’ as much as possible, try not to over control operating pressures. • Don’t try to control liquid flow at two points in a pipe - remember conservation of mass • Don’t look at one P&ID only - Look at the big picture then consider the details

9. FIC FT FV FE P&ID’s - Rookie Mistakes • Draw the equipment the way it’s going to be built - don’t oversimplify it’s representation • more equipment/inst detail is better • Show Liquid levels / internals etc. • It helps you design the controls • It helps operators understand how it works Set@ 1200 kg/hr

10. Simplicity • Watch Out For Controls on Different Sheets F L A A

11. P&ID’s - Costs Are Important • Goal: Lowest Capital costs and Lowest Operating Costs. • Only build what’s required • The Cheapest Process that meets the need of all involved is the most profitable. • It’s got to work! After that, make it cheap as possible.

12. P&ID’s - Control • The Flow that occurs in a pipe is a function of the Pressure Drop. • Valves add or subtract from the natural pressure drop of the pipe. • Valves change the pressure drop to give us the flow rate we want

13. P&ID’s • Control (Globe) Valves can have just about any pressure drop and flow combination • On the other hand, pipes have very definite flow/pressure relationship 5 psi 50 gizillion psi 20 m3/hr 2” pipe, 20 m long, 20 m3/hr P = 5 kPa

14. P&ID’s • Piping Pressure Drop “System Curve” for 4” pipe, length 100 ft Resulting Flow Through Pipe Pressure Differential

15. P&ID’s • Piping Pressure Drop “System Curve” for 4” pipe, length 100 ft Pressure Differential Resulting Flow Through Pipe

16. P&ID’s • Piping Pressure Drop “System Curve” for 4” pipe, length 100 ft Pressure Differential With a valve that’s 50% closed Resulting Flow Through Pipe

17. P&ID’s • In a Liquid System (non compressible flow) two valves in series have the same flow rate through them Press 7 bar(g) DP = 3 bar DP = 20 bar Assume each segment of pipe has a DP of 1 bar

18. P&ID’s • Backing Up ? Press 7 bar(g) ?

19. P&ID’s • Pumps (Centrifugal) System Curve Pressure Increase That Pump Is Able To Produce Pump Curve Flow Through Pump

20. P&ID’s - Control Systems • First ask what controls the production rate of the process? • How will we control this production rate Flow control

21. P&ID’s - Control Systems • Mentally take note of other critical things that need to be controlled (flow, temperature, pressure, level) • Feed - do we need flow control ? • Multiple feeds - do we need to ratio one flow rate to another? A Flow of B depends on A B

22. FIC FT FV FE Ratio Control Primary Rate FRIC FT Ratio To Primary FV FE

23. Pressure • To Decrease the Pressure of a Tank • allow material to be removed (at a faster rate) • condense vapour faster PIC PIC PT PT PV PV Control Downstream Pressure Control Upstream Pressure

24. Temperature • Usually you increase the flow or pressure of one stream. The effect of that change is to cause another streams temperature to change.

25. Level • To Decrease the Level of a Tank • allow material to be removed (at a faster rate) • Tanks and Pumps • Always Provide a way of preventing your pumps from running dry • Always Provide a way of preventing your pumps from being “dead headed” • Recirc the pump discharge to the tank with a “minimum flow bypass”

26. Controls • Failure Position of Valves • Most of the time it’s safer to bottle up the process and prevent failure from propagating downstream by making control valves “fail closed” • Occasionally it’s better to fail open • ie. Cooling water