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?