Flow Measurement

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• Flow Measurement
• In
• Wastewater Applications

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FLOWMETER SELECTION

• Everything you forget to ask yourself before
  applying a flowmeter, that comes back to bite you
  in the rear later on.

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FLOWMETER SELECTION

• NOT A NO BRAINER
• LESSER OF ALL EVILS
• MANY DIFFERENT TECHNOLOGIES TO CHOOSE FROM
• TIERED OFFERINGS WITHIN TECHNOLOGIES
• CONTROL SYSTEMS

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WHY MEASURE THE FLOW?

• PERMIT REPORTING REQUIREMENTS
• HOW MUCH IS PRODUCED
• HOW MUCH IS CONSUMED
• BLENDING CONTINUOUS OR BATCH
• CUSTODY TRANSFER BETWEEN UTILITIES
• MONITOR / INDICATE

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VARIOUS FLOWMETER TYPES

• HEAD PRODUCING (DP)
• - ORIFICE
• - NOZZLE
• - VENTURI
• - WEDGE
• - ANNUBAR / PITOT TUBE
• - ELBOW TAP
• - TARGET
• - VARIABLE AREA / ROTAMETER
• - VENTURI CONE
• POSITIVE DISPLACEMENT
• - DIAPHRAGM SEAL
• - MECHANICAL SEAL

VELOCITY - TURBINE -
ELECTROMAGNETIC - VORTEX - ULTRASONIC -
SONAR DIRECT MASS - CORIOLIS -
THERMAL INFERED MASS -
MULTI-VARIABLE DP
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FLOWMETER SELECTION FACTORS
FLUID PROPERTIES LIQUID OR
GAS TEMPERATURE AND PRESSURE DENSITY OR
S.G. VISCOSITY LUBRICITY CHEMICAL
MAKEUP ABRASIVENESS MULTIPLE PHASES SOLIDS
CONTENT
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FLOWMETER SELECTION FACTORS
INSTALLATION CONSIDERATIONS ORIENTATION FL
OW DIRECTION UPSTREAM AND DOWNSTREAM
ELEMENTS SERVICE ACCESS VIBRATION ELECTRICAL
CLASSIFICATION RFI AND EMI CAVITATION INTER
MITTENT / PULSATING FLOW SIZE / WEIGHT
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FLOWMETER SELECTION FACTORS
PERFORMANCE CONSIDERATIONS ACCURACY REPEAT
ABILITY LINEARITY HYSTERESIS RANGEABILITY /
TURNDOWN UPDATE RATE DEAD TIME RESPONSE
TIME STABILITY / FILTER CAPABILITY TOTAL
PROBABLE ERROR
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FLOWMETER SELECTION FACTORS
ENVIRONMENTAL CONSIDERATIONS AMBIENT
TEMPERATURE EFFECTS BAROMETRIC PRESSURE
EFFECTS FUGITIVE EMISSIONS POTENTIAL HUMIDITY
EFFECTS SAFETY FACTORS SUBMERGENCE
POTENTIAL LIGHTNING PROTECTION AREA
CLASSIFICATION
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FLOWMETER SELECTION FACTORS
ECONOMIC CONSIDERATIONS PURCHASE
PRICE INSTALLATION COSTS OPERATING
COSTS CALIBRATION COSTS MAINTENANCE
COSTS INSTRUMENT LIFE RELIABILITY SPARES
COST AND AVAILABILITY PUMPING COST FROM
HEADLOSS PROCESS / PLANT OPTIMIZATION
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FLOWMETER SELECTION PROCESS

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Theory of Operation
MAG METER BASICS
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MAGNETIC FLOWMETER
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MAGNETIC FLOWMETER BASICS
PROS AND CONS PROS CONS TRUE
VOLUME INITIAL COST (AC) ACCURACY CONDUCTIVI
TY WIDE RANGEABILITY MATERIAL
COMPATIBILITY LOW FLOW CAPABILITY NUMBER OF
DESIGNS ZERO HEAD LOSS VELOCITY
LIMITS BI-DIRECTIONAL/OBSTRUCTIONLESS INSENSITIV
ITY TO UPSTREAM PIPING
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MAGNETIC FLOWMETER BASICS
ACCURACY /- 0.2 TO 1 RANGEABILITY 101
TO 501 REYNOLDS NUMBER NO LIMIT PIPING
EFFECTS MINIMAL COST OF OWNERSHIP INITIAL L/
H INSTALLATION L/M OPERATION M MAIN
TENANCE L/M
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• Less Than Ideal Straight
• Run Installation Testing

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Introduction

• Standard specification for straight run piping to
  maintain specified accuracy
• 5 pipe diameters upstream
• 2 pipe diameters downstream
• Distance measured from electrodes (center of the
  flowtube)
• What if this requirement is not met?

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Test Results Summary

• Readings were offset by 0 to 3
• Offset could be positive or negative
• Flow readings were repeatable to within 0.1
• Reading offset was dependent on the type of
  disturbance, length of upstream straight run,
  line size, and position of electrodes
• Reading offset was independent of flow rate
  (velocity) within lab accuracy

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Short Run Test Setup
Weigh Tank
TestMagmeter
ReferenceMagmeter
Upstream Dimensions
Upstream Disturbance

• Summary of Tests
• ½, 4, 10 and 24-inch meters
• 4 inch test had extended scope, other line sizes
  had limited scope

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Rosemount Magmeter4-inch Test Scope
Test Magmeter
Weigh Tank
ReferenceMagmeter

• Upstream Dimensions
• 0D
• 1D
• 2D
• 3D

• Upstream Disturbance
• Single Short-radius Elbow
• Double Short Radius Elbow Out of plane
• Double Short Radius Elbow In plane
• 6 x 4 inch Reducer
• Gate Valve in 3 positions
• Butterfly valve in 3 positions

• Summary of Tests
• 6 points per run (average is recorded)
• 6 velocities from about ½ to 25 ft/s

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4-inch Single Elbow Setup

• Piping schematic for the 4-inch single elbow test
• Reference meter installed with more than 5D up
  and 2D down
• Adjustable pipe sections used to test various
  lengths of upstream straight run

Adjusted for different upstream lengths
Similar piping schematics were used for the other
disturbances and line sizes tested
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Overall Summary

• Best practice for magmeter installations is to
  have straight run of 5 pipe diameters upstream
  and 2 pipe diameters downstream
• Less than ideal straight run will cause an offset
  or shift in the reading
• Reading will still be repeatable
• Reading offset is dependent on type of upstream
  disturbance, length of upstream straight run,
  line size, and position of electrodes, but
  independent of velocity
• Correction factor could be entered electronically
  to accommodate the shift in reading