Flow Diagrams

CENG 124

The Major Flow Diagrams

Block Flow Diagrams Brainstorming and conceptual design

Process Flow Diagrams (PFDs) Detailed process design and simulation

Piping and Instrumentation Diagrams (P&IDs) Detailed control loops and systems, mechanical specifications

Increasing level of details

Most technical tasks

Block Flow Diagrams

Compressors, pumps, heat exchanges, etc., etc. are not part of the picture yet.

From TBWS

BFDs, continued

The most important system input/output material stream flows Help us to perform material balance calculations. And

rudimentary economic decisions.

Have little processing details, but should have the probable important units or sub-sections

Important stage during conceptual design Help us to explore alternatives and screen for possibilities quickly

and inexpensively

Process Flow Diagrams (PFDs)

Can be S-105

Unit label contains also info on unit type and its location (zone or subsection)

Unless there is a major change in pressure, valves are not part of the preliminary design simulation

Accessory units usually “hidden” in a simulation

From TBWS

Can include the heating duties up here too

PFDs, continued

Contain all the major unit operations and how they are connected (connectivity; TBWS: process topology). Equipment includes pumps and especially compressors, but they

may not be part of a simulation during preliminary design Control loops are usually not part of the PFD. They are only

included if they are crucial in regulation stream flows in ways that the regulation is also part of the simulation.

Complete and rigorous solution thermodynamics, material and energy balance computation Yes, the computation is handled, to the most part, by fancy

flowsheeting Complete flow stream specifications (and operating conditions and

sizing of units) Heating or cooling utilities Basis for costing calculations

PFDs,... (3)

The PFD should display the processing condition of the more important streams

This control loop is not justified at the preliminary design stage.

From TBWS

PDFs,... (4)

The ID signature box

When you have a huge processing plant, divide the PFD into sections.

From TBWS

Process Stream Summary What always accompanies the PFD

Be selective! Include only those streams at crucial locations The complete summary table with every single stream

belongs to the Appendix for auditing

can go on for pages...

P&IDs—the last stage of planning

From TBWS

P&IDs, continued

Have all the process control loops and systems (that's where the instrumentation comes in)

Have all the piping info Have all the detailed utility info From here, the project is transferred to other engineers

(mechanical, instrument, piping, construction, etc.)

Other nice info in TBWS

Figure 1.4—Unit symbols Tables 1.2 to 1.4—Labeling conventions Tables 1.6 to 1.10—How to describe equipment Table 1.11—Recommended equipment spacing (Never

considered in an academic design class! But this table serves to remind you all the other things you need to worry about in real life.)

3-D plant modeling—that comes in during construction phase

From TBWS

PFD Stream Labeling Symbols

Final side comment:— Find out what convention your company follows— Standardized symbols for P&IDs too

From TBWS

PFD Symbols