from bfd (block flow diagram) to p&id (piping and
TRANSCRIPT
Communication via Schematics,
from BFD (Block Flow Diagram) to P&ID (Piping and Instrumentation Diagram)
by Larry Coleman
Schematics are necessarycommunication tools for Chem E’s
• Being able to communicate upward to management and laterally to other disciplines is a key skill in any industrial setting
• Your project is more likely to be funded or resourced-prioritized if non-Chem E’s understand its potential
• On a capital project, you WILL work with other technical disciplines and need a common communication tool. In most cases, the process engineer is the project’s “glue”
• Schematics are used at every step of a project, all the way through plant commissioning
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3-prongs of process communication
1. The process schematic ( evolving from BFD to full-blown P&ID)
2. The Heat & Mass Balance
3. The written Process Narrative
• They must be coherent, readable and internally consistent, or your project gets de-emphasized
• As the schematic evolves in detail, so proportionately does the process narrative and H&M Balance
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From Beginning to End
• BFD shows the conceptual process, with no unit operations nor any equipment detail. Preferably on one sheet (A or B size = 8-1/2” x 11” or 11” x 17”)
• Full P&ID schematically shows every piece of equipment, pipe, instrument; coded against specifications of same. Normally printed on “D” or “E” paper and many dozens of pages long. It is the key process document that other technical disciplines reference against.
➢ Rule: If it’s not on the P&ID, it’s not in the project; and vice versa.
• The P&ID will companion with a 3D scaled computer model, showing all equipment & piping. This pair is used through construction & commissioning
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Making a schematic
• Start with a simple pencil sketch showing the overall manufacturing process, as a series of labelled rectangles
• Make a sketch of the overall process, showing inputs & outputs, as well as critical steps
• Use an e-drawing program like Visio® or Dia® to turn your pencil sketch into one that fills the page, but is easy to read. Best software is compatible with *.vsd
• Match it to the process narrative => a rough BFD
• Use ANSI/ISA-5.1 symbology to improve the sketch to a PFD, then a P&ID. Hyatt’s carries process templates
• Drawing software compatible with AutoCad helps
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ANSI/ISA-5.1 Symbology
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Flowsheet Evolution
1. Block Flow Diagram (BFD)
2. Simplified Process Flow Diagram (PFD)
3. Full PFD shows basic controls and “battery limits”
4. Initial P&ID shows all major equipment and piping
5. Developed P&ID shows all equipment, piping and all controls in detail; all out-source packages
6. Final P&ID includes tie-in to specs and call-outs for equipment, piping, instrumentation/controls
➢ Never cram an individual flowsheet with content. Keep it readable by others.
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BFD Essentials
• Shows the overall process, without unit operations or any equipment detail
• Used to illustrate patents or proposals, especially to a non-Chem E audience
• Simple graphic of interconnecting rectangles, sometimes with major stream components.
• Show the process “battery limits”
• If possible, keep it on 1-2 pages and be sure it matches the written Process Narrative
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BFD used in a patent application
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BFD taken from a NASA report
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Simplified PFD Essentials
• Shows major equipment and unit operations using generic icons. Includes recycle streams
• Include stream tags, against a written narrative
• Gives enough detail to explain the process to a technical audience, but without much info on control strategy
• Usually 2-3 pages in length, either “A” or “B” size
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Simplified PFD Example, page 1
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Simplified PFD Example, page 2
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Process Flow Diagram Essentials
• Triggers technology evaluation against safety, market potential, physical property review
• Expands on the Simplified PFD to show generic control strategy and better define battery limits
• Better define plant equipment items, major piping, and outsource packages (example: where a packaged external hydrogen supply ties in with the process)
• Includes stream tags against both a detailed Narrative and a Mass balance, including T & P profile
• Usually less than 10 pages in length, typically “B” size
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PFD of a fluidized bed reactor
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Initial P&ID Essentials
• Triggers preliminary equipment sizing, layout, and a rough cost estimate to gauge the project’s financial merits
• Enhances the level of detail on the PFD• Gives pertinent detail all major equipment and piping;
includes recycle, start-up, and shut-down piping• Has stream tags to reference a detailed Heat & Mass
Balance. Typically uses ISA-5.1 symbology• References a set of equipment functional specifications,
including any math modelling of condensers, distillation columns, thermosiphon reboilers, etc.
• Input to other engineering disciplines• Typically 15-20 “D” size sheets in length, maybe longer
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Initial P&ID of two distillation columns
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Equipment Functional Spec Example
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Developed P&ID Essentials
• Adds to the Initial P&ID to include feedback from other engineering disciples regarding equipment details, including manual valves + vent/drain/purging needs
• Triggers both HAZOP & PSM studies
• Includes feedback from Control Systems regarding details on interlocks, alarms, & safety shutdowns, using ANSI/ISA symbology
• All battery limits are detailed and H&M balance updated accordingly
• References detailed equipment specs, layouts, supports and other project documents (example: electrical one-line diagram)
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Developed P&ID of an FBR quench system
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Developed P&ID of an A/B canned reflux pump
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Final P&ID
• Triggers equipment purchase, land acquisition and final mechanical design
• Becomes final only after many revisions of the Developed P&ID
• Approved for construction by all engineering disciplines, safety, and management
• After Capital Budget approved, project is a “Go”
• Used to get operating permit and insurance underwriting
• Revised after commissioning & start-up to reflect scope changes + any changes found to be needed after initial operation, under Management of Change protocol
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The Final P&ID is perpetual
• Aside from plant construction, the Final P&ID’s use can continue even past eventual plant closure.
• Getting the plant operating permit
• Commissioning & Start-up co-ordination
• Trouble-shooting operational process problems
• De-bottlenecking and plant expansion
• Accident and Environmental Emission resolution
• Documenting the technology for the future
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