PFDs and P&IDs

Len ChurchJan, 2011

PFDs• Process Flow Diagram• Prepared early, 85% complete by completion of DBM• Conveys a basic pictorial definition

• Process equipment• Connecting flow paths• Primary control elements.

• Provides an understanding of the process• Pertinent process flow data and• Heat and material balances

• table within the relevant diagram• separate, attached document (preferred).

PFDs• Basis for Piping and Instrumentation Diagrams (P&IDs) development• Responsibility of Process engineers• Used by various members of the project team:

• Customer – review, approve, scope of work, operations• Project Manager - reviews, preliminary HAZOPs• Instrument Engineer - control philosophy, basic control schemes • Mechanical Engineer - major equipment; number, types & sizes, ident. of potential equipment suppliers• Electrical Engineer - Preliminary estimate of major motor loads & identification of Variable Frequency Drives (VFDs)

PFDs• Used by (cont’d)

• Piping Engineer – Equipment Layout, plot plans,•piping specifications selection• Materials Engineer - metallurgy selection• Cost Estimator - preliminary cost estimate

PFDs• PFD Content

• Stream Identification:• Feed• Products• Intermediate• By-products• Waste

• Process piping (mainly)• Major equipment

• Symbolically represented Numbered (tagged)• Named• Sized

PFDs• PFD Content (cont’d)

• Vessel internals• Trays• Baffles• Demisters• Vortex breakers• Etc

• Valves that affect the operation• Control• Block

• Connections with other systems• Steam• Heat medium• Chemical injection required for normal operations

HMS

HMR

PFDs• PFD Content (cont’d)

• Major by-pass and recirculation streams• Stream references to the heat and material balances•

PFDs• PFD Content (cont’d)

•Process stream names (edge of drawing only)• beside the "drawing continuation arrow boxes“• beside feed, product or utility streams thatenter or leave the process unit (but not to another dwg) with origin or destination

PFDs• PFD Content (cont’d)

• Control “bubbles” showing the type of process variable being controlled

• Pressure• Temperature• Level• Etc.

PFDs• PFD Content (cont’d)

• All basic control functions• master/slave arrangements• control functions with calculations• ratio controllers, etc

• Notes for P&ID development• equipment/piping arrangement requirements.

• General notes•assist understanding of the process flow scheme

PFDs• PFDs do not include:

• Pipe classes or piping line numbers or size• Process control instrumentation (sensors and final elements)• Minor by-pass lines• Isolation and shut-off valves• Maintenance vents and drains• Relief and safety devices• Flanges• Minimum flow by-passes on pumps • Nitrogen/inert gas purge lines or steam-out lines

PFDs• PFDs do not include:

• Block valves• except for alternate flow paths, start-up lines etc

• Pressure and temperature indicators and recorders• Pipe and equipment cladding• Other installed features

PFDs• PFD Development Principles:

• Use customer standard symbols (if available)for:

• equipment numbering• equipment title terminology

• Equipment items reflect• physical characteristics• proportion

• Display equipment identification• top of the PFD• vertically above equipment (if possible)

PFDs• PFD Development Principles (cont’d):

• In general, process flows from left to right• Divide the process logically between drawings when more than one PFD is needed• PFD drawing number source or destination

• shown in boxed arrow• source or destination description adjacent

• To show different design options being considered

• include separate PFDs• or separate H&M Balances

PFDs• PFD Development Principles (cont’d):

• Designate stream numbers (names) for all major process flows

• in a logical manner• correspond to the H&M Balance stream numbers

• Start-up, shutdown, and recycle lines may be shown but are generally not numbered unless

• they are key to the process• and have an identified flow in the H&M Balance

• Clearly identify exchanger shell-side and tube-side process streams (otherwise use “blank” symbol)

PFDs• PFD Development Principles (cont’d):

• Show all major process lines• in bold• with stream direction clearly identified

• Other lines essential to understanding process

• lighter weight• Licensed technology package indentified with dashed border• Instrumentation shown in a simplified manner

• no Tags• Reviewed and checked before formal issue

PFDs• Review Tutorial 8 Samples

• PFDs - standard drawing symbols, example PFDs and P&IDs, mass and energy balance tables• PFD controls - Process control depiction on PFDs

P&IDs• Piping & Instrument Diagram• Convey a detailed graphical definition of:

• ALL the process & other equipment• Piping• Control & instrumentation

• Prepared early (in EDS) – other disciplines design from it• Prepared by

• Process engineers - accountable and responsible• Other engineering disciplines - responsible

P&IDs• Prepared from the PFD• Prepared in association with the Line Designation Table (LDT)• Types; Process, Utility & Equipment Auxilliary

P&IDs• P&ID Content

• PFD content• Plus PFD not included items (from above)• Plus miscellaneous other items• Equipment Tagging

• Typically assigned during PFD development• All major equipment must have one

• Equipment Description• All start with equipment name• Pumps & Compressors: rated capacity, head, power• Vessels: diameter ID (or OD), length T/T (or S/S), design press & temp, material, insulation•

P&IDs• Equipment Description (cont’d)

• Tanks: diameter & height, nominal capacity, design press & temp, material, insulation• Shell & Tube Exchangers: duty, shell design press & temp, tube design press & temp, material, insulation• Air Coolers: duty, tube design press & temp, material, insulation• Note: equipment descriptions located along top of drawing, rotating equipment along bottom

• Instrument Tagging• Piping

• Identification: size, specification, commodity, number, insulation, heat tracing• Specification breaks• Slope, no pockets or free draining•

P&IDs• Piping (cont’d)

• spectacle blinds

• reducers

• Valves – required for isolation• block – positive isolation, typically gate or ball valves• ESD – on/off emergency isolation valves• Butterfly - low pressure differential, leakage• globe – throttling• needle – small diameter, throttling, on/off• diaphragm, pinch – slurry service• check – prevent back flow, leakage• CSO or CSC, NO or NC• Vents & drains

P&IDs• P&ID Content (cont’d)

• Relief valves• required to prevent over pressure on equipment & piping

• Control Valves• Generally one size smaller than piping• Fail positions indicated: FO, FC

• consider 1. personnel injury, 2. equipment damage, 3. vessel inventory loss

• Tight shut off (TSO)• Bypasses vs hand jacks• Isolation valves & drains upstream & downstream

P&IDs• P&ID Content (cont’d)

•Insulation• Heat conservation• Personnel protection• Cold insulation• Thickness

• Heat tracing• required for “freeze” protection, maintaining pour point• maintains temperature when flow has stopped

• piping• vessels• its not a heater

• dead legs• electric, steam, glycol

P&IDs• Sparing

• Critical equipment• Rotating equipment - pumps, compressors• Process equipment - filters, adsorbent beds, chemical beds• Philosophy required

• Flow• Meters: orifice plates, vortex, coriolis, ultrasonic

• Size provided by instrumentation engineer• Generally located upstream of system’s control valve

• Transmitters• Pressure, temperature & level

• Gauges• Transmitters

P&IDs• P&IDs do not include

• complete control logic• located in the Control Narrative and/or Shutdown Key

• P&ID Development Principles• Generally the principles for PFDs apply except now all details are added• Reference to H&M Balances are omitted• It’s an art!

P&IDs• Review sample P&IDs

• Location: Tutorial 8, more drawing examples