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Drawing Piping andInstrumentation
Diagrams
Presented by James Yeary
• Piping is process and utility plumbing, connections and ductwork; depicts all flow paths
• Instrumentation is control elements, transmitters and more; depicts all functionality
• Diagram because it is not to scale or intended to be a mechanical drawing
P&ID
• Inner diameter or nominal size• Schedule (wall thickness)• Basic design criteria– Phase– Flow rate @ Pressure– Temperature
• Example: 2” Schedule 80
Piping Geometry
• Common ASTM/ANSI standards• Basic design criteria– Pressure– Chemical resistance– Environment, corrosion– Surface roughness
• Examples: Seamless 316L SS, 304 SS, Carbon Steel, Galvanized, PVC, Silicone Flex Tube, HDPE, Glass Lined Steel, Clean Copper
Piping Material
• Flange, screwed, tri-clamp, weld• Examples:– ASME/ANSI B16.5 150# F.F. flange– 1/2” NPT– 2” ASME BPE, Tri-Clover– Butt weld
Piping Connections
Flanged
Picture from Autodesk P&ID
Welded
Picture from Autodesk P&ID
• Describes intended process fluid• Utility supply or return• Examples:– Acid– Feed or product transfer– Dry process air– Process wastes– Clean-In-Place (CIP) Supply– Steam condensate
Service
• Slope requirement• Insulation for protection, heat, chilled
Piping Extras
• Plant-wide typical piping specifications
• Uniquely identify each line or service• Fictional Examples:– 2-160-SST4-BPE-CIPS-XXX-PP– 4-80-BGS-BW-PW-XXX– 1/2-FLEX-FEED-XXX– 2-80-CC-NPT-HWFI-XXX-HC
Line Specs
• Measurement or Control• Input or Output– Analog or Discrete
• ANSI/ISA S5.1 standard symbols and tag nomenclature
Instrumentation
• Control system’s perspective of the process and operators
• Inputs bring measurements or status• Outputs can manipulate the process• Examples:– Thermometer = input–Magnetic stir bar speed = output
Input or Output?
• Analog values vary along a scale• Discrete values are on or off• Thermostat example:– Temperature sensor = analog input– Toggle switch = discrete input– Fan speed = analog output– Gas valve = discrete output
Analog or Discrete?
• Valves• Motors• Elements and transmitters• Heat exchangers
Common Instruments
• Diaphragm• Butterfly• Ball and V-Ball• Globe, Gate, Plug, Needle• Check• Safety and Relief• Regulator• Solenoid
Types of Valves
Types of Valves
Pictures from Fisher Valve
• Manifolds• Block and bleed• 3-way, 4-way
Specialty Valves
• Hand wheel• Instrument air pressure• Analog throttling– Electro-pneumatic positioner
• Discrete open or closed– Electro-pneumatic solenoid pilot valve
• Electrical motor actuators
Valve Actuation
Pilot Solenoid Valves
Picture from Festo
Picture from eBay of SMC Manifold
Valve Positioner
Pictures from Fisher Valve
• Fail Closed valve– Instrument air actuates open– Springs force closed
• Fail Open valve– Springs force open– Instrument air actuates closed
Valve Fail Position
• Limit switches• Absolute registers• Depicted as sharing common housing
with valve
Valve Feedback
• Positive displacement pump– Diaphragm– Gear
• Peristaltic pump• Centrifugal pump• Agitator
Motors
• Variable Frequency Drive (VFD) can control RPM of an AC motor
• Voltage can control RPM of a DC motor
• Tachometer is used to provide feedback RPM
Rate of Rotation
• Vibration sensors can be used to detect cavitation or other conditions
• Current sensing relays can be used to confirm a motor is running
• Hand-Off-Auto (HOA) switch is typically for pumps
• Emergency stop switch typically interlocks motors
Motor Extras
• Elements sense process conditions• Transmitters convert element’s
response into signal for control system
• Switches are discrete transmitters, flip at preset point(s) on scale
Elements, Transmitters, and Switches
• Differential producers: pitot, orifice, Venturi
• Inertial: Coriolis• Positive displacement: rotary,
bellows• Velocity: magnetic, vortex, turbine,
ultrasonic
Flow
• Capacitance, conductivity, resistance• Radar, optical, laser• Differential pressure, bubbler• Vibration, ultrasonic
• Strapping table accounts for vessel geometry
Level
• Gage• Differential• Absolute• Switches• Diaphragm connection
Pressure
• RTD• Thermocouple
Temperature
• Load Cells• Flush with floor plates
Weight
• Hydrogen ion concentration (pH)• Dissolved oxygen (DO)• Turbidity/Optical density• Viscosity• Conductivity• Offline sampling to GC, MS and more
Analyzers
• Provide nearby operator quick overriding pump contol
• Acknowledge and reset alarm push buttons
• Emergency stop mushroom push button
Hand Switches
E-Stop• Typically cuts off instrument air
supply, stroked valves return to fail state
• Stops and interlocks all moving parts
• Hard-wired Interlocks• DCS or PLC Software Interlocks• Use notes to detail cause and effect
Interlock Conditions
Autodesk P&ID
http://students.autodesk.com/
Questions?
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