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Chapter 6: Flow Measurement & Measurement Of Liquid Level - Coggle…
Chapter 6: Flow Measurement & Measurement Of Liquid Level
Flow measurement
A technique used in any process requiring the transport of a material from one point to another.
Primary device
Measure the amount of fluid in term of mass or volume that flows past a given point in a definite period of time.
Advantage: Simple,economic and extremely accurate.
Method
Volumetric method
Flow in the flowmeter, being calibrate is diverted into a tank known as volume
Flowmeter(water)
Flowmeter(gas)
Gravimetric method
Fluid flow in the flowmeter, being calibrated is diverted into a Vessel
Positive-displacement meter
Application: used in flow rate metering application
Advantage: Easy to install/maintained and have moderate cost
Device
Nutating Disc meter
Sliding-vane-type meter
Lobeb-impeller Meter
Secondary or Rate Meters
They not measure the flow directly
Device
Flow rate meters
Principle
Variable head meter
Variable area meters
Variable head and variable area meters
Constant head device
Velocity meter
Principle
VAriable head meter
Turbine/propeler type meter
Pitot tube
Commonly used variable head velocity measuring device
Pitot static tube
P stat/p +v^2 = P stag/ p v= /2 (Pstag/p=Pstat/p)/p
Advantage: simple n low cost, No pressure Loss in the flow system, Easily inserted to a small hole
Drawback: Not suitable for measuring low velocities ,5 m/s , Sensitive to misalignment. 20 -> 2% error, not suitable for highly fluctuationg velocities
Measurement of liquid level
Direct method
actual liquid level is directly indicated by simple mechanical type of device
Dip-stick method
Application: Level of oil in car engine, Level oil in petrol station
Advantage: Economic
Drawbacks: Not accurate, not possible for time observation
Sight Glass method
Advantage: Simple & direct
Drawbacks: Not suitable for dirty,viscous & corrosive liquid, Manually recording needed
Hook gauge method
Advantage: Accurancy up to +-0.1mm
Drawbacks: Manually operate
Float gauge method
Advantage: Capable of giving continuous, direct liquid level measurement
Drawback: proper correction is required
Ultrasonic level sensor
use for non-contact level sensing og highly viscous liquids,as well as bulk solids
use in water treatment application
Hydrostatic Pressure Level Measurement Device
The dial or scale of the pressure gauge is calibrated in the unit of measurement
These gauge function smoothly when the liquids are clean and non-corrosive.
Automatic Level control system
An instrumetn called a sensor is added that is able to measure the value of the level.
When automatic control is applied to system, which are designed to regulate the value of some variable to a set point, it is called process control
