Common Mistakes

TYPE	Description
Presentation	Inconsistencies & errors Too much detail (See Note 1) Batch processes not clearly presented Stream labels not oriented upright; font size too small Stream data/flowrate/compositions - too many significant figures
Process Engineering-related	Use of fired heater for column reboiler (See Note 2) Unrealistic design parameters (See Note 3) In reactors, heating and cooling requirements not considered Source of energy for heating and cooling not shown No KO Drums after compressor discharge cooler - stream likely to be 2-phase gas/liq
Controls	No control loops shown (with controlled process parameter & final control elements) Impractical control schemes Two control valves in series along short length of pipe

Use block diagrams within PFDs if overall process is too complicated
High skin temperature in fired tubes can cause coking of HC components - use ony if there are no other practical means to achieve required temperatures
e.g. differential pressure for pump is only 1 bar - unusual spec for pump

Review and understand intent of production process
Make flow scheme simple and elegant
Add main isolation valves - some may be normally closed (NC)
Show flow direction arrows where they add clarity. Some lines are intentionally bi-directional
Conduct Team Review to solicit comments and identify errors/omissions