Process Variables and Sensors

Process Variables and Sensors

Parts and materials needed for today (instructor will provide):DP transmittersThermocouplesFilled-bulb temperature sensorRTDsHeat source (e.g. cigarette lighter)Vortex flowmeterThermal flowmeterMagnetic flowtubeTurbine flowmeterOrifice platesCoriolis flowmeterMultimeters

Process Variables and Sensors

Documents you will need for today:“Realistic Instrumentation Diagrams” worksheet (from the Socratic Instrumentation project website)

Fundamental Principles

Brainstorm all the fundamental principles of physics you can recall that are relevant to the sensing of process variables such as pressure,level, temperature, and flow!

Pressure Measurement

Pressure Measurement

Pressure Measurement

Pressure Measurement

Level Measurement

Level Measurement

Level Measurement

Level Measurement

Level Measurement

Temperature Measurement

Temperature Measurement: filled-bulb sensor

Temperature Measurement: RTD

Temperature Measurement: thermocouple

Flow Measurement: orifice

Flow Measurement: orifice

Flow Measurement: orifice

Flow Measurement: vortex

Flow Measurement: magnetic

Magnetic Flow MetersMagnetic Flow Meters

Process must be a liquid

Minimum conductivity Meter must be full

Magnetic FlowmetersMagnetic Flowmeters

MAGNETICADVANTAGES

• No Moving Parts

• Very Wide Rangeability

• Ideal For Slurries

• Unobstructed Flow Path

DISADVANTAGES

• Liquid Must Be Conductive

• Physical Pressure and Temperature Limits

Magnetic FlowmetersMagnetic Flowmeters

No moving parts No pressure drop Flowrate independent of viscosity, temperature, and density Minimum upstream piping requirements Electronics interchangeable without regard to size Measure dirty liquids with solids Measure highly corrosive fluids Very large turndown Linear output

Advantages Over Other Technologies

Vortex Meter Vortex Meter

Vortex MeterVortex Meter

Principle of Operation

Q = V x A

VortexVortex

ADVANTAGES

• No Moving Parts

• For Liquid, Gas, or Steam

• Uneffected by Pressure, Temperature, or Density Changes.

• Wide Rangeability

DISADVANTAGES

• Span Limitations Due to Viscosity

• Flow Profile Sensitive (Vortex)

VORTEX / SWIRLMETER

Turbine MeterTurbine Meter

Principle of Operation

Rotor velocity is proportional to fluid velocity

Turbine MeterTurbine Meter

High accuracy (.5% of rate) High rangeability (up to 50:1) Compact design Fast response time Broad range of sizes Clean water applications onlyClean water applications only NIST Traceable Factory CalibrationNIST Traceable Factory Calibration Low cost, Easy to installLow cost, Easy to install In and out of line, under pressureIn and out of line, under pressure

Turbine MeterTurbine Meter

Straight pipe run requirements Process fluid lubricity Reynolds number constraints

ViscosityDensity

Maintenance & recalibration

Performance Considerations

Turbine FlowmetersTurbine Flowmeters

TURBINEADVANTAGES

• High Accuracy

• Suitable for Extreme Temperatures and Pressures

• Can Be Used On Gas or Liquid

DISADVANTAGES

• Only For Low Viscosities

• Moving Parts

• Sensitive to Flow Profile

Flow Measurement: turbine

Flow Measurement: ultrasonic

Ultrasonic FlowmetersUltrasonic Flowmeters

Doppler Time of

flight

Types

DopplerFlowmeter

Ultrasonic FlowmetersUltrasonic FlowmetersPrinciple of OperationPrinciple of Operation

Ultrasonic FlowmetersUltrasonic FlowmetersPrinciple of OperationPrinciple of Operation

Transit-TimeFlowmeter

Ultrasonic FlowmetersUltrasonic Flowmeters

Reynolds number constraints Entrained gas or particles for

doppler Clean liquids for time of flight Installed without process shut

down Straight upstream piping

requirements

Performance Considerations

Flow Measurement: true mass

Application: distillation process

Extra: hydrostatic level sensor calculation

Extra: hydrostatic level sensor calculation