10/20/2017 1 09/08/2017 Products Solutions Services Level Measurement Transmitters “Applying Level Measurement” Slide 1 Bill Sholette 09/08/2017 Ultrasonic FDU91 FDU93 FDU95 FDU92 FDU90 Installation Guidelines ToF Level Products Slide 2 Bill Sholette 09/08/2017 The Principle – Time of Flight (TOF) Emission of ultrasound pulses Reflection of the pulses from the product surface Receiving of the reflected pulses Measurement of the Time of Flight calculation of the distance between the device and the product surface by 00.40 2 d=c emitting receiving Installation Guidelines ToF Level Products Slide 3 Bill Sholette 09/08/2017 Environmental effects on velocity of sound Temperature 0.17% /°C measured/ compensated Air moisture 0.3% with change in relative moisture from 0 to 100% Pressure change 30bar /435psi change in run time approx 0.3% pmin = 10psia Velocity of sound co = 331.6m/s (1088ft/s) Vapor pressure < 50mbar (20°C)? irrelevant c = M = = 344m /s (1088ft/s) 28.8 cair at 20°C = x Rm (273 + T) 1.4 8314.3 (273+20) c: velocity of sound [m/s] Rm: universal gas constant (8314,3 J/kmol k) T: temperature [°C] x: adiabatic index insignificant no problem M: molecular weight Installation Guidelines ToF Level Products Slide 4 Bill Sholette 09/08/2017 Speed of Propagation for Ultrasound pressure: no influence temperature: approx. 0.17 % / K (air: 0.59 cm / K) C p C T S 0 1 273K p r k T C 0 = = = = = pressure density adiabetic exponent temperature speed of ultrasound at 0°C example: filling of chlorine tank Air: 334 m/s (1095 ft/s) Cl: 206 m/s (676 ft/s) failure: 38% Gas Speed [m/s] Speed [ft/s] CI 206 676 CO2 258 846 Ar 308 1010 O2 32°F 315 1033 O2 ‐300°F 178 584 NO 324 1063 Air 32°F 331 1086 Air +68°F 334 1096 Air +104°F 355 1165 CO 337 1106 N2 377 1237 Coal gas 441 1447 Helium 32°F 971 3186 Installation Guidelines ToF Level Products Slide 5 Bill Sholette 09/08/2017 Ultrasonic Mounting Installation Guidelines ToF Level Products Slide 6 Bill Sholette
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Transcript
10/20/2017
1
09/08/2017
Products Solutions Services
Level Measurement Transmitters
“Applying Level Measurement”
Slide 1 Bill Sholette 09/08/2017
Ultrasonic
FDU91
FDU93
FDU95
FDU92
FDU90
Installation Guidelines ToF Level Products
Slide 2 Bill Sholette
09/08/2017
The Principle – Time of Flight (TOF)
Emission of ultrasound pulses
Reflection of the pulses from the
product surface
Receiving of the reflected pulses
Measurement of the Time of Flightcalculation of the distance between the device
and the product surface by
00.40
2d = c
emitting
receiving
Installation Guidelines ToF Level Products
Slide 3 Bill Sholette 09/08/2017
Environmental effects on velocity of sound
Temperature0.17% /°C
measured/compensated
Air moisture0.3% withchange inrelative moisturefrom 0 to 100%
Pressure change 30bar /435psichange in run timeapprox 0.3%pmin = 10psia
Velocity of sound co = 331.6m/s (1088ft/s)
Vapor pressure< 50mbar (20°C)?
irrelevant
c = M
=
= 344m /s (1088ft/s)
28.8
cair at 20°C =
x Rm (273 + T)
1.4 8314.3 (273+20)
c: velocity of sound [m/s]Rm: universal gas constant
(8314,3 J/kmol k)T: temperature [°C]x: adiabatic index
insignificant
no problem
M: molecular weight
Installation Guidelines ToF Level Products
Slide 4 Bill Sholette
09/08/2017
Speed of Propagation for Ultrasound
pressure: no influencetemperature: approx. 0.17 % / K
(air: 0.59 cm / K)
C p C TS
0 1273K
p
r
k
T
C0
=
=
=
=
=
pressure
density
adiabetic exponent
temperature
speed of ultrasound at 0°C
example: filling of chlorine tankAir: 334 m/s (1095 ft/s)Cl: 206 m/s (676 ft/s) failure: 38%
GasSpeed [m/s]
Speed [ft/s]
CI 206 676
CO2 258 846
Ar 308 1010
O2 32°F 315 1033
O2 ‐300°F 178 584
NO 324 1063
Air 32°F 331 1086
Air +68°F 334 1096
Air +104°F 355 1165
CO 337 1106
N2 377 1237
Coal gas 441 1447
Helium 32°F 971 3186
Installation Guidelines ToF Level Products
Slide 5 Bill Sholette 09/08/2017
Ultrasonic Mounting
Installation Guidelines ToF Level Products
Slide 6 Bill Sholette
10/20/2017
2
09/08/2017
Reflection of Acoustic Energy
• ideal conditions • “light“ foam
• big bubbles
• low density
• condensed foam ,
heavy, small bubbles• high density
“something in‐between“
‐‐> signal absorption
???
Installation Guidelines ToF Level Products
Slide 7 Bill Sholette 09/08/2017
Self Cleaning Transducer Face
FDU91 FDU92
Advantage
Because of an optimized coupling between piezo crystal and membrane much more mechanical force is applied to the membrane strong self cleaning effect (e.g. for condensation conditions)
Installation Guidelines ToF Level Products
Slide 8 Bill Sholette
09/08/2017
Free Space Radar Installations
Installation Guidelines ToF Level Products
Slide 9 Bill Sholette 09/08/2017
Basics Reflection
Water
Air
r=80
r=1
=1.00
=0.001
Radar in comparison to Ultrasonic
r : dielectric constant : specific density
Installation Guidelines ToF Level Products
Slide 10 Bill Sholette
09/08/2017
Basics ReflectionRadar in comparison to Ultrasonic
Air
Oilr=2 =0.85
r=1 =0.001
Shift caused by slower speed of propagation in oil
r : dielectric constant : specific density
Installation Guidelines ToF Level Products
Slide 11 Bill Sholette 09/08/2017
Radar Mounting
• Recommended distance from outer wall
is 1/3 diameter of vessel.• FMR 230/231 minimum distance to wall =
12 inches
• FMR 240/244/245/250 Minimum distance
to wall = 6 inches
Note – It may be desirable to mount the radar closer to a wall to help ignore internal tank obstructions (i.e. agitators). Always observe minimum distance to tank wall requirements.
Installation Guidelines ToF Level Products
Slide 12 Bill Sholette
10/20/2017
3
09/08/2017
Radar ‐ Mounting
A position away from the filling stream will avoid interference echoes. Echoes from fittings are suppressed during calibration
A position above the filling stream will be subject to interference echoes
Installation Guidelines ToF Level Products
Slide 13 Bill Sholette 09/08/2017
Radar ‐ Mounting
A central position strengthens double echoes
A non‐central position avoids double echoes
Min. 12” off wall
Installation Guidelines ToF Level Products
Slide 14 Bill Sholette
09/08/2017
Radar Installed in the Middle of a Dome Vessel
• Radar unit “jumps” between
level signal first harmonic second
harmonic
• Special settings have to be made
to detect the fist echo
(Fist Echo Factor)
• This scenario can be avoided by a
different installation
Installation Guidelines ToF Level Products
Slide 15 Bill Sholette 09/08/2017
Radar Plastic Tanks
When measuring in plastic tanks, Microwave energy can penetrate and reflect off external metal structure.
Installation Guidelines ToF Level Products
Slide 16 Bill Sholette
09/08/2017
Dealing with Condensation
Installation Guidelines ToF Level Products
Slide 17 Bill Sholette 09/08/2017
FMR 245/244 with Condensation
with condensation[water, ~ 113°F (45°C)
w/o condensation
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