Flow measurement Cảm biến lưu lượng

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Flow Measurement

Slide 1 / 76

13 October 2015

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10/13/2015

Learning Objectives
The participant knows…
• … coriolis, electromagnetic, vortex and thermal flow measurement
principle
• …application and installation limits

The participant understands…
• …each measurement technology has different limitation
• … application
li ti and
d process conditions
diti
and
d iinstallations

t ll ti
are very
important

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10/13/2015

The first step to find the solution
• The first step in finding a solution for a flow metering point is finding the best suitable measuring
technology
• The selection is based on the requirements of the measuring point e.g.:

Expecte
d
accurac
y
Require
d tturndown

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Accepta

ble
pressur
e loss

Mass
flow,
di
direct
t or
calculate
d

Installati
on
situation

E
Etc.

GBO


10/13/2015

Influences on the selection of the measuring system
Liquid /
Gas

Mass
or

Volume

Viscosit
y

Conduc
C
d
tivity

Abrasion

Pressur
e

Corrosio
n

Density

Price

Best fit
measuring
system

Accepte
d
pressure
loss

Temp.

Pipe
inlet

Pipe
Homog
eneity

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Disturb
ances

GBO

Flow
profile

Turn
down


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Rough classification of applications
• Conductive liquids

>80% of all liquids are conductive (Drinking- and waste water,
beverages acids
beverages,
acids, alkalines
alkalines, etc
etc.))
• Non conductive liquids
Oils, hydro carbons, liquefied gases, demineralized water
• Gas
Air, nitrogen, natural gas, biogas, etc.
• Steam
Saturated and superheated steam
• Special applications
Abrasive slurries, custody transfer, measurement from
outside, bidirectional, etc.

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Flow technologies overview

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LU/MSA


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Application Range

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Application Range
1000

Temp.
[°C]
Differential Pressure

400
350

Vortex

Coriolis

200
Magnetic Inductive

pressure
[bar]

Ultrasonic
Thermal

40

0
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160

250

400

420


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Solutions

Flow Measurement – Coriolis Measurement

Slide 9 / 76

13 October 2015

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Services


10/13/2015

The Coriolis Measuring Principle

Inventor of the measuring principle
of the same name.
Caspard Gustave de Coriolis

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Basics of Mass Measurement - Why Measure Mass?
•Temperature
•Volume 1 ≠ Volume 2
•Mass
M
1 = Mass
M
2

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Mass 1

Mass 2

V l
Volume
1

Volume 2

13 October 2015

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10/13/2015

Basics of Mass Measurement

•ω
•Fc

= Angular velocity
= Coriolis force

•Δ
Δϕ = Phase shift
•A,B = Sensors
•y
= Amplitude
•t
= Time

Δϕ ~ Fc ~ m

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Basics of Mass Measurement - Density Measurement
mt

c

1
⋅
2π mfl + mt
mfl = V ⋅ ρfl
fR =

fR = Resonant frequency
mt = Tube
T b mass
mfl = Fluid mass

ρfl = Fluid density
c = Constant

fR

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mfl

13 October 2015

GBO

fR = ƒ(ρfl)


10/13/2015

Basics of Mass Measurement- Measuring System

• Δϕ = Phase shift
•m

= Mass flow

•Ω

= RTD resistance

• fR

= Resonant frequency

•ρ

= Density

•T

= Temperature
T
t

Δϕ ~ m

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13 October 2015

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fR

~ ρ

Ω

~ T


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Coriolis flow meter advantages
• Universal measuring principle for liquids and gases
• Simultaneous and direct measurement of mass
flow density
flow,
density, temperature and viscosity
(multivariable sensors)
• Measuring principle is independent of the physical
fluid properties
p p
• Very high measuring accuracy
– typically ±0.1% o.r.
– optionally ±0.05% o.r.
• Not affected by flow profile
• No inlet/outlet runs necessary

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Coriolis flow meter disadvantages:
• Relatively high initial investment.
• Outlay for installation can be considerable, depending on the design
and manufacturer
manufacturer.
• Limited temperature range: typically –50 to +350 °C (–60 to +660 °F).
• Restricted usability if the gas content of the fluid is high and in the
case of multi-phase fluids.
• Larger
L
sizes
i
are h
heavy iin some d
designs.
i

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Products

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Flow Measurement – Electromagnetic Measurement

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The Electromagnetic Measuring Principle
Michael Faraday

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Flow

Basics of Electromagnetic Measurement
A voltage is induced in an
electric conductor is moved
through a magnetic field.

L

B

B

-

+

v

Faraday‘s
Faraday
s Law
0

+

Ue

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13 October 2015

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Ue = B × L× v
B = Strength of Magnetic Field
L = Length of Conductor
v = Velocity of Conductor


OHNE DETAILS

Flow

Basics of Electromagnetic Measurement

Ue = B × L× v
B = Strength of Magnetic Field
L = Length of Conductor
v = Velocity of Conductor

U~v
U = Induced voltage
v = Flow velocity

Q=vxA
U=Approx. 300 μV per m/s

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Q = Volume flow
v = Flow velocity
A = Pipe area


Flow

Basics of Electromagnetic -Various EMF Design

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Flow

Basics of Electromagnetic - Ranges of Conductivity in Liqui
Oil,
Hydrocarbons
Ultra pure water

0.05 µS/cm
Water:
1 µS/cm

Min. Conductivity

for EMF’s
10 µS/cm
Mi Conductivity
Min.
C d ti it
for EMF’s in water

Pure water

Industrial water

100 µS/cm
Potable water
1 mS/cm
Food:

Beer
Milk
Orange juice
Apple juice
Tomato juice

Process:

Phosphoric acid
Sulphuric acid
Hydrochloric acid
Caustic soda

10 mS/cm

100 mS/cm
1000 mS/cm

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Flow

Basics of Electromagnetic - Empty Pipe Detection (EPD)

EPD electrode

Measuring
electrode
l t d

Measuring
electrode
l t d

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Flow

Basics of Electromagnetic - Reference Electrode
EPD electrode

Measuring
electrode

Measuring
electrode
Reference
electrode

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Basics of Electromagnetic - Electrode Cleaning Circuit
Function settings:
• Cleaning time
• Relaxation time
• Cycle time

Measuring

electrode

Measuring
electrode

U
Reference
electrode
l t d
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13 October 2015

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ECC inhibits the build-up
build up
of (conductive) coating