level measurement (radar trasnmitter )
TRANSCRIPT
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Level Measurements
Prepared by : Instrument Technical Training Yemen LNG- Sana’a
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Level Measurements
Level Gauges Level Float & Displacers Level Differential Pressure Bubble Tube Radar Level Gauge Level Switches
What are the methods oflevel measuring devices
What is level measurement
Level measurement is defined as the measurement of the height of the interface between two different media relative to datum level or bottom of the vessel
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Level Measurements
Level Gauges
Local visual indication No output signal
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Tape Level Gauges Float Operated GaugeLever Gauge Torque Tube
Continuous Level Float
Level Measurements
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High accuracy Reliable in liquid at constant density Can be mounted internally or externally Most popular because they do not
require motion
Require stilling chamber for internal unit
Continuous Level Displacers
Level Measurements
What are the advantages and disadvantages
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Types of Level Displacers
Side-external (standard API RP-550) possible to recalibrate without process shutdown
Side-internal (difficult to maintain)
Level Measurements
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Differential Pressure Level
Level Measurements
P = ρ g h
P: Hydrostatic Pressure
ρ : Density
g: Gravitation Constant (9.81 m/sec2 )
h: Distance between the surface of the liquid and the centre of the process diaphragm
Hydrostatic Pressure Measurement
Pressure measurement for LEVEL calculation
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D.P. Cell Connected to an Open Tank
Wide measurement range Can be used for open/closed vessel Good for high temperatures Simple and easy to install
Density variation causes errors The mounting location affects
calibration
Differential Pressure Level
D.P. Cell Connection to a Closed Tank
Level Measurements
What are the advantages and disadvantages
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D.P. Cell with “Wet Leg” connection
Differential Pressure Level
Level Measurements
When is a “dry leg” system used
The dry leg system is used providing:
Fluid is not corrosive There will be no plugging There are no condensates at normal operating temperature
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Bubbles Tube
Corrosive liquid / slurry Simple and inexpensive Measurement of underground levels
Level Measurements
Less accurate (1~2 %)
(Constant flow)
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Radar Level
Non-contact method High pressures up to 160 bar High temperatures up to + 400 °C Measuring range up to 35 m
The time-of-flight principle is the basis of a pulse radar
A very short radar impulse is emitted towards the media
The pulse is reflected on the surface, received by the combined sending-and- receiving system and converted into the level
Level Measurements
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Spectrum of electromagnetic waves
110
100
HzHzHz
110
100
kHzkHzkHz
5,8 / 6,3 GHz
10 GHz
24 GHz
110
100
MHzMHzMHz
- (10 Hz)15
- (10 Hz)12
- (10 Hz)18
- (10 Hz)21
- (10 Hz)24
110
1001
10100
110
1001
10100
TV- (10 Hz)8
110
100
GHzGHzGHz
110
100
THzTHzTHz
TelephoneAC current
Radio
Television
Microwaves
Heat
visibleLight
ultra violet
X-rays
Gammawavescosmic radiation
kilometre
metre
decimetrecentimetremillimetre
micrometre
nanometre
picometre
femtometre
Frequency Wave length
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Basic prinicple of radar transmitter
AntennaTransmitterTransmission
path
AntennaReceiver TransmissionPath
Ref
lect
ing
ob
ject
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The measurement principle - Time of Flight
Transmission of microwave impulses
Reflection on the surface of the medium
Receipt of the reflected impulses
Calculation of the distance between unit andmeasured surface via:
Measurement of the Time of Flight
00.3300.33--.----.--00.0000.0000.0200.0200.0400.0400.0600.0600.0800.0800.1000.1000.1200.1200.1400.1400.1600.1600.1800.1800.2000.2000.2200.2200.2400.2400.2600.2600.2800.2800.3000.3000.3200.3200.3400.3400.3600.3600.3800.3800.4000.40
00.4000.40
2d = c
Tra
nsm
itti
ng
Rec
eivi
ng
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No moving parts High accuracy Less maintenance
Radar Level
Relatively high cost
Level Measurements
What are the advantages and disadvantages
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Level Switches
Float typeFloat level switch configuration
Level Measurements
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Displacer typeInstallation of level switch
Level Switches
Level Measurements