P&ID’s PIPING & INSTRUMENTATION DIAGRAMS

Format & Layout Title Block Sheet Number Revision Number Date

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

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

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

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!

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.

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

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 FV FT FIC FE Set@ 1200 kg/hr

Simplicity Watch Out For Controls on Different Sheets L F A A

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.

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

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

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

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

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

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

P&ID’s Backing Up ? Press 7 bar(g) ?

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

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

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

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

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

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

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”

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