ACADs (08-006) Covered Keywords Flow rate, total flow, differential pressure, percent flow, cotameter, Bernouli. Description Supporting Material

Terminal Objective: Given the appropriate equipment and procedures the I&C Technician will calibrate and maintain flow instrumentation. Mastery will be demonstrated by successful completion of a Lab Performance Exercises and written Exam. Measuring Flow

Differentiate between Flow Rate and Total Flow Describe the relationship between differential pressure and flow Given a percent range of DP sensed by an orifice plate, calculate the percent flow Describe the theory of operation of a given flow measurement device Describe the considerations for removing/restoring a rotameter from/to service

Flow Rate vs. Total Flow Flow Rate is the amount of fluid, either in mass or volume that passes a point in a given time. Examples: Pounds mass per hour, gallons per minute  We measure flow rate using ultrasonics, venturi, orifice plates, etc. Total Flow is the flow rate multiplied by an amount of time. It is the accumulated or ‘totalized flow. Result will be in either mass or volume.  Gas pumps and water meters measure total flow

Daniel Bernouli Discovered the square root relationship between DP and flow Bernoulli's Principle states that as the speed of the fluid increases the pressure in the fluid decreases Therefore, across a restriction in flow, as the fluid velocity increases, pressure decreases 9/venturi.html 9/venturi.html

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Flow Instruments

Example 1 Pressure drop range: in H2O Flow: 0 to 100 GPM Currently reading 25 in H2O What is the flow?

Example 2 Pressure drop range: in H2O Flow: 0 to 1000 GPM Currently flow is 80 GPM What is the differential pressure? What devices may be used for the square root function?

Discovered two centuries ago by Italian scientist Giovanni Battista Venturi ( ).

Venturi Tube

Flow Nozzle

Elbow Tap

Henri de Pitot ( )

Annubar

When flow exists, there is a constant differential pressure across the float Rotameter

Replacing a Rotameter Isolate the instrument Drain Verify correct replacement part Install Verify pressure tight Un-isolate slowly to prevent slamming the float In service leak check

Flow Instruments: DP Cell

Ultrasonic Flow Measurement Devices Examples: Controlotron, UFM

Coriolis Offer direct mass flow, volume flow, density, and temperature measurement of liquids, gases, and slurries No moving parts Mass flow rate causes the vibrating tubes to twist The twist of the tubes is proportional to mass flow Watch the Coriolis Flow video-10 min

Electromagnetic Flow Measurement Faraday’s Law

Other methods of measuring flow Rotary Vane Positive Displacement-turbine Nutating Disk or piston Hot wire method, temperature method Pelton Wheel Vortex shedding Calorimetric method Open Channels Weirs Target meter

Read OE18368 at end of ‘Flow’ section in handout. Discuss: What happened? Could it happen here? What can we do to mitigate it? Discuss control of test leads.

On to Measuring Temperature