flow advantages Flashcards
PD Meters
Nutating Disc
Advantage
Ideal for viscous fluid
High accuracy & repeatability Minimal straight piping runs May be constructed from a variety of materials
Disadvantage
Mechanical parts on flow indication wear
Accuracy is adversely affected by viscosities below the meter’s designated threshold.
PD Meters
Oval & Gear
Advantage
Measurement independent of viscosity(high)
Ease of installation(tight areas, no straight pipe runs required )
Disadvantage
Not recommended for water or water like fluids (slippage) Mechanical parts wear
PD Meters
Sliding Vane
Advantage
Sweeping action of vanes prevents buildup of sediment and keeps compartment clean.
Wide choice of construction materials.
High accuracy and repeatability.
Low pressure drop over entire range of flow measuring capabilities
Disadvantage
Mechanical parts wear
PD Meters
Piston
Advantage
High accuracy and repeatability.
Only one moving part to cause wear.
Can be made of materials to ensure sanitary needs of food and beverage processing.
Disadvantage
Can only be used with relatively clean liquids.
DP Meters
Orifice
Advantage
Use on liquid, gas, and steam Suitable for extreme temperatures and pressures No moving parts
Low material cost Changeable without de- pressuring process
Low cost
Disadvantage
Limited range ability Affected by changes in density, pressure, and viscosity
Maintenance intensive High pressure loss Non-linear output, square root extraction required
DP Meters
Nozzle
Advantage
Use on liquid, gas, and steam Nozzle used in Steam applications
Low system pressure loss
Do not require upstream flow profiling
Disadvantage
Limited range ability 6:1 & accuracy ±2%
Expensive to install Requires high Reynolds numbers (>10,000)
Less permanent pressure loss than orifice, more than Venturi
Non-linear output, square root extraction required
DP Meters
Venturi
Advantage
Venturi principally used in Water & Wastewater apps Lower non-recoverable pressure loss than orifice
Disadvantage
Initial cost more expensive than orifice plate Non-linear output, square root extraction required
DP Meters
V-Cone
Advantage
Less straight-run upstream piping required than orifice plate
Disadvantage
Non-linear output, square root extraction required
DP Meters

Pitot Tube
Advantage
Very small pressure loss
Disadvantage
Non-linear output, square root extraction required Used with clean fluids
Variable Area
Rotameters
Advantage
No external power required for local reading
Simple design able to be mass produced, low cost
Scale is linear due to variable area design
Disadvantage
Mounted in vertical position only, flow moving upwards Floats designed for specific gravity, correction required when used in other medium
Turbine
Advantage
Easy to install and operate Easy to service in the field High Accuracy &Repeatability Self-clearing design Instantaneous flow rate Indicator & totalizer on every model
Flow range of up to 10:1 No Power Needed
Used with Gas or liquid
Disadvantage
Requires clean low viscosity fluid Upstream conditioning (straightening vanes) Vibration sensitive Numerous moving parts that could clog, bearings wear out Frequent calibration required Loss of linearity at low flow rate
Paddle Wheel
Advantage
Low cost for certain degree of accuracy
Measure flow in either direction
Axles and paddles easily replaced
Disadvantage
Use with clean fluid Solids in fluid can damage paddles
Avoid low flow
Linear
Magnetic
Advantage
No obstructions to the flow No moving parts to wear or break
Maintenance free
Debris or solids will not clog the meter, ideal for slurries No head loss
Bi-directional flow Unaffected by changes in density and viscosity
Linear output Large turndown
Disadvantage
Mag meters require a conductive process fluid
No gases or steam Entrapped air, foam, or two- phase flow cause errors
Liner pressure/temperature limits
Power consumption of 4-wire device
Special installation requirements Grounding/Valve liner requirements
Meter must be full
Linear
Ultrasonic
Advantage
No moving parts Unobstructed flow path Wide range ability
Disadvantage
Reynolds number constraints Entrained gas or particles for Doppler
Clean liquids for time of flight Straight run piping requirements
Linear
Vortex
Advantage
No moving parts Regular calibration not required
Liquid, gas or steam Wide range ability
Disadvantage
Span limitations due to viscosity
Flow profile sensitive(high Reynolds number)
