Understanding Process Diagrams

1. Understanding Process Diagrams Dr. AA PiCS, UTM

2. Introduction to Flowsheeting Now that I are an Inguneer, all I do is right! Roughly speaking, communication is paramount ~ As an Engineer, transfer the most amount of information with the least amount of effort on the part of the reader.

3. Flowsheeting Flowsheets are the pictorial representation of the process. Goal: Transmit the most amount of information with the least amount of effort on the part of the reader!

4. Flowsheet • Is a diagrammatic model of the process • Shows the arrangement of equipment selected to carry our the process • Includes • stream connections, names of streams, stream flow rates • compositions and operating conditions (temp., Pressure) • instruments • optional details of streams molar compositions • physical data (, ),code no. of streams,Enthalpies of streams • Brief description of stream

5. Type of Diagrams Block Diagram Material Flow Sheet Energy Flow Sheet Process Flow Diagram Information Flow Diagram Piping & Instrumentation Diagram

6. Type of Flowsheets Block Process Piping and Instrumentation Increasing Detail

7. Block Diagram • Conveys what is achieved in a given step, not how it is achieved • Particularly useful in initial studies • Useful for conveying information to management • Useful to show inter-relation of streams • Useful in conveying global, not detailed, material balance Feed 1 Product 1 Process Feed 2 Product 2 Feed 3 Product 3 This particular block flow could be used to obtain (assist) in the development of an initial material balance for streams crossing the battery limits. You might use it in your input/output structure development during synthesis.

8. Block Flow Diagram Example: Byproduct to Refinery Refinery Gas Product Low Temp Clean-up Compression Reaction & Cooling Purge Air Separation Recycle Compression Oxygen Major steps are conveyed but no equipment details. Sometimes the blocks may be process flow diagram symbols. Sometimes steps may include equipment if it is particularly important to the communication.

9. Block Flow Diagram I find block flows to be particularly useful for setting up (identifying) the key streams to solve the material balance around the major blocks. I subsequently solve the material balance inside each block. 113 128 T-102 T-103 114 104 T-101 134 101 F-105 153 F-101 147 103 106 140 150 T-104 T-105 151 109 108 111 159 146 160 105

10. Material Flow Sheet Is drawn with standard symbols and labeled and include all data obtained If no space available to label equipment, a equipment key can be drawn at the bottom of the flow sheet Following data should be shown on the flow sheet in deferent ways flow rate of each component total stream flow rate percentage composition

11. N Component Flow rate T P N Component Flow rate T P C1 R2 Equipment key C1 Column R2 Reactor Simplest method suitable for simple processes with few equipments: tabulate the data in blocks alongside the process stream

12. Better method applicable for all complex processes: stream line is numbered and the data tabulated at the top or bottom of the sheet

13. Energy Flowsheet Energy balance is to determine the energy requirement of the process In energy flow sheet Inlet and outlet energy flow rates should be shown separately for each piece of equipment. Include: energy of each component in all (inlet and outlet) streams process conditions of all (inlet and outlet) streams process conditions of the specific equipment

14. Energy Balance Sheet

15. Information Flow Diagram (IFD) Is used in simulation programs Is presented by blocks Each block represents a calculation module in the simulation program, usually a process unit or part of a unit units in which no change of composition or temperature or pressure occurs are omitted from IFD But other operations not shown on the process flow diagram as actual pieces of equipment, but which can cause changes in the stream composition must be shown. Flow of information should be shown with lines and arrow

16. Process Flow Diagrams Dr. AA PiCS, UTM

17. Process Flow Diagram • Conveys the major processing steps represented by the equipment • Useful for conveying the heat and material balances • Useful for conveying major pieces of equipment • Useful for conveying processing conditions • Useful for conveying utilities • There are no hard and fast rules but Howat Standards include • essentially every major piece of equipment • every flow • every temperature • every pressure • auxiliary services (utility flows) • equipment sizes • process control

18. Heat exchange Sealed tank Reactor Fluid contacting column Tray column Standard symbols BS 8888 ; BS 1553

22. Material Flow Sheet • Is drawn with standard symbols and labeled and include all data obtained • If no space available to label equipment, a equipment key can be drawn at the bottom of the flow sheet • Following data should be shown on the flow sheet in deferent ways • flow rate of each component • total stream flow rate • percentage composition • Simplest method suitable for simple processes with few equipments, • tabulate the data in blocks alongside the process stream Slide 14 • Better method applicable for all complex processes, • stream line is numbered and the data tabulated at the top or bottom of the sheet (above and below the equipment layout) Slide 15

23. Process Flow Diagram • The following diagrams are examples of class and commercial process flow diagrams (PFD’s). The content depends on the goals for the communication. • Unless there are reasons to the contrary, the standard is: • All major equipment • All major process lines • All major utility lines involving material flow • All stream numbers, temperatures, pressures, flows • All major process controls and valves • All equipment sizes with relevant MEB information as required • All equipment names and numbers

24. Process Flow Diagram • The goal is to present the most amount of information with the least amount of effort on the part of the reader. • The flowsheet should generally flow from left to right. • The flowsheet should not be cluttered - use multiple sheets. • The flowsheet should be in landscape with the bound edge at top. • The equipment should be drawn in approximately relative size, e.g. towers larger than drums, exchangers larger than pumps etc. • The major towers and reactors are generally on one, or nearly one, level. • The reader should be able to follow it with his or her eye. • The streams should have the minimum of direction changes. • The streams that enter across the battery limits should be on the left. • The streams that leave across the battery limits should be on the right. • The streams that move to the next sheet should leave on the right. • The streams that recycle to earlier sheets should leave on the left.

25. 153 Flowsheeting The process flowsheet shown below is one possible expansion of the block flow for T-104. When this PFD was drawn, the process was not complete as is evident by the missing equipment sizes, pump discharge pressures etc. In this case, the process control scheme was not included. It generally is, however. 140 T-104 109 146 160 105

26. Process Flow Diagram The following process flow is an approximate rendition of a refinery alkylation unit. This is however not as complete as it is required in industry practice Note that equipment sizing is not included. The material balance grid is included. Many companies require the material balance to be imposed on the diagram. In those cases, the stream numbering may not be as extensive as we typically use in design. Or, only a limited number of streams are included in the material balance grid.

27. Process Flow Diagram

28. Another example from design. This includes the equipment sizing and material balance block. Note the symbol key is included. This is frequently necessary when client standards differ.

29. Process Flow Diagram The following two sheets are examples of a commercial PFD developed prior to construction. Note that the content is, yet again, different. In this case, the control scheme is included as is the legend key. There are some differences. Note that there are three different feed points shown on the diagram. It is typical to have multiple feed points for a column but unusual to show them on the PFD. They were shown here because it was critical for discussing different feedstocks in the process design report. The process description which accompanied the PFD described the reason for the multiple feeds. On the second diagram, you will note the pressure control. This is a split range controller with the primary control being a flooded condenser and the secondary control being a vent. Note that the pumps show operating and design conditions.

30. The process description will sometimes dictate the content of the process flow diagram. For most purposes, the process control scheme will be included in our work. Multiple feed points or side stream points will not be shown unless it is critical to the process. We will typically not be showing the future equipment such as the reboiler shown on the left of the column. When you examine the flowsheet, you should be able to deduce the type of equipment. Tower type? Repoiler type? Pump type?

31. This is the other part of the previous flowsheet. Because of scan limitations, I’ve broken the flowsheet into two parts. However, the original is all one flowsheet drawn in landscape. In this flowsheet, you will not the original reboiler is on flow control reset by temperature. The primary measured variable is steam flow, the manipulated variable is steam flow and the controlled variable is steam flow. The secondary measured variable is temperature. What is the temperature indicative of? Why above the bottom?

32. Process Flow Diagram This process flow diagram is another commercial example. This client standard had two PFD’s per page, each shown in landscape, one on top of the other on the same page. I have taken the top PFD and split in two. (This is the basis for the following EFD’s.) This was a revamp. Shaded equipment is new, unshaded equipment is existing. Note that the control scheme is included. There are additional symbols which indicate that the controls are connected to a digital distributed control system. The tags at the edge of the page indicate connections to other PFD’s.

33. This is an extractive distillation tower. There are additional reboilers here (type?) that are in place for heat recovery. The shaded equipment is new. The unshaded equipment was existing. The equipment might be in a new service, however. We will generally not show instrument connections to the DCS (distributed control system). The instruments will be shown but the connection will be implied.

34. This is the overhead system for the extractive distillation column. Note that there is a vent condenser from F-204. Why might we add a vent condenser? What is the purpose? Note that the F-204 Reflux Drum has a ‘boot’. What might that be for? The circle symbol in the center bottom is a professional stamp of a licensed engineer. He/she is signifying that the engineering integrity of the process.

35. Process Flow Diagram Unless stated otherwise, the target content for PFD’s is: All major process equipment All major process and utility streams – all numbered All major process controls necessary to operate the process All operating temperatures All operating pressures All operating flows All equipment sizes

36. Piping and Instrumentation Diagram Dr. AA PiCS, UTM

37. Piping and Instrumentation Diagram Similarly to electrical schemas, the control industry (especially the chemical and process industry) describes its plants and their instrumentation by a P&ID (pronounce P.N.I.D.) (Piping and Instrumentation Diagram),sometimes called P&WD (Piping and wiring diagrams) The P&ID shows the flows in a plant (in the chemical or process industry) and the corresponding sensors or actors. At the same time, the P&ID gives a name ("tag") to each sensor and actor, along with additional parameters. This tag identifies a "point" not only on the screens and controllers, but also on theobjects in the field.

38. Piping & Instrumentation Diagram (P & I) P & I should be included with All process equipment identified by equipment number All pipes identified by a line number. Pipe size and material of construction should be shown (material may include as a part of the identification number) All valves with an identification no. along with their type & size should be shown Ancillary fittings that are part of piping system such as inline sight glasses, strainers and stream traps with an identification no. Pumps identified by a suitable code no. All control loops and instruments with identification

40. Instrument Identification

41. P&ID The P&ID mixes pneumatic / hydraulic elements, electrical elements and instruments on the same diagram It uses a set of symbols defined in the ISA S5.1 standard. Examples of pneumatic / hydraulic symbols: pipe heater 350 kW valve one-way valve (diode) vessel / reactor binary (or solenoid) valve (on/off) analog valve (continuous) heat exchanger pump, also

42. Instrumentation identification The first letter defines the measured or initiating variables such as Analysis (A), Flow (F), Temperature (T), etc. with succeeding letters defining readout, passive, or output functions such as Indicator (I), Record (R), Transmit (T), and so forth FIC V1528 tag name of the correspondingvariable mover (here: solenoid) S function (here: valve)

43. ISA S5.1 General instrument or function symbols Primary location accessible to operator Field mounted Auxiliary location accessible to operator Discrete instruments Shared display, shared control Computer function Programmable logic control 1. Symbol size may vary according to the user's needs and the type of document.2. Abbreviations of the user's choice may be used when necessary to specify location.3. Inaccessible (behind the panel) devices may be depicted using the same symbol but with a dashed horizontal bar. Source: Control Engineering with data from ISA S5.1 standard

44. Example of P&ID The output of FIC 101 is an electrical signal to TY 101located in an inaccessible or behind-the-panel-board location. TIC 101’s output is connected via an internal software or data link (line with bubbles) to the setpoint (SP) of FIC 101 to form a cascade control strategy Square root extraction of the input signal is part of FIC 101’s functionality. FT101 is a field-mounted flow transmitter connected via electrical signals (dotted line) to flow indicating controller FIC 101 located in a shared control/display device TT 101 and TIC 101 are similar to FT 101 and FIC 101 but are measuring, indicating, and controlling temperature The output signal from TY 101 is a pneumatic signal (line with double forward slash marks) making TY 101 an I/P (current to pneumatic transducer)

45. First letter Measured or initiating variable Modifier A Analysis B Burner, combustion C User's choice D User's choice Differential E Voltage F Flow rate Ration (fraction) G User's choice H Hand I Current (electrical) J Power Scan K Time, time schedule Time rate of change L Level M User's choice Momentary N User's choice O User's choice P Pressure, vacuum Q Quantity Integrate, totalizer R Radiation S Speed, frequency Safety T Temperature U Multivariable V Vibration, mechanical analysis W Weight, force X Unclassified X axis Y Event, state, or presence Y axis Z Position, dimension Z axis The ISA code for instrument type

46. Common connecting lines Connection to process, or instrument supply Pneumatic signal Electric signal Capillary tubing (filled system) Hydraulic signal Electromagnetic or sonic signal (guided) Internal system link (software or data link) Source: Control Engineering with data from ISA S5.1 standard

47. DIN ISA etc Many Standards