|
|
|
|
Copyright © 2009
by Chetas Control Systems Private Limited.
All Rights Reserved.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
The non-contact ultrasonic flow
meter is a non-invasive flow meter available in
two types: transit time and doppler. Both technologies
feature clamp on designs with transducer arrangements
that can detect in-situ flowrates from outside
the pipeline, without any interruption to flow
or process. Transit time flow meters, or also
known as 'time of flight' meters are mainly designed
to the measurement of clean liquids, although
many flow measurement devices have a maximum tolerance
of 15% solids. The principle behind this type
of non-intrusive clamp-on (strap on) flow meter
is that acoustic waves with a frequency of >20kHz
are emitted from one transducer to the other side
of the pipe back to the opposite transducer requires
less time than when traveling in the opposite
direction. The differential transit time of the
synchronized signals is proportional to the flow
rate of the fluid. Transit time flow meter are
widely accepted in all types of industries due
to its accuracy, repeatability & application
acceptability.
|
|
|
|
|
|
Ultrasonic flow
measurement is possible with 2 methods
|
|
Doppler
Type |
|
Transit
Time |
Doppler type flow measurement
technique is useful only for liquids containing
dirt particles, air bubbles which can provide
reflection hence Doppler type technique
is not very accurate on clear portable liquids
like pure water.
|
|
|
|
|
Click on the image to play
movie.
|
|
|
|
|
|
Transit type technique is an
universal technique of flow measurement and with
the help of advance sensor design technology like
micro structure ceramic it can handle most of
the applications.
Principle of Operation :
A flow meters along with pair of probes and interconnections
cable is the basis hardware required for flow
measurement.
|
|
|
|
|
|
|
|
|
|
|
|
Both probes A & B acts as
'Trans-Receiver'.
At first cycle, electronic unit sends a pulse
to probe A and event gets memorized. The acoustic
beam gets returned towards velocity, gets acknowledged
by probe B generating signal called as 'ECHO'.
On the reception of ECHO time gets memorized by
electronic device. Electronic device calculates
the time of flight TAB (Time Taken
to travel from Probe A to Probe B).
At second cycle electronic unit sends pulse to
Probe B and event gets memorized. Probe A acknowledges
the acoustic beam that penetrates against velocity.
Electronic device calculates the time of flight
TBA (Time taken to travel from Probe
B to Probe A)
Electronic device calculates the flow as follows.
|
|
|
|
|
|
|
|
|
|
|
|
Q = A × V × KH
Where,
|
|
|
A
|
=
|
Area of Pipe
|
V
|
=
|
Velocity
|
KH
|
=
|
Hydraulic Coefficient
|
|
|
|
|
|
|
Advantage
of transit time Flow Meter |
|
|
1.
|
Universality : The
most important advantage of Transit Time
Ultrasonic Flow meter is 'Universality'.
|
|
a) Suitable
for all types of pipe diameters : Transit
Time Ultrasonic Flow meter are practically
independent of pipe diameter i.e. the same
flow meter can be used from 10 mm to 10000
mm pipe diameter. |
|
b) Suitable for
practically all kinds of liquids including
petrochemicals, hydrocarbon, raw water,
pure water, light slurries. Measurement
is independent of electrical conductivity
which is not possible with any type of magnetic
flow meter pipe line for 5 to 6 mm.
|
|
c) Suitable for
all types of pipe materials like Steel,
Stainless Steel, Glass, Copper, Aluminum,
PTFE, Nylon, Rubber, PVC, Polyethylene and
many more.
In case of concrete pipelines,
intrusive type probe assembly is used which
penetrates inside the pipe line for 5 to
6 mm.
|
2.
|
Bi-Directional Measurement
: Flow measurement is possible in both
directions for realistic measurement.
|
3.
|
Easy Installation &
Commissioning : Clamp-on flowmeters
are very easy to install being a non-contact
flow measurement. For insertion / wetted
type sensors also installation is very simple
and can be installed without taking shutdown
(Online). This is the most important feature
against other type of flowmeter like Full
bore Magnetic / Vortex / Turbine / Woltman
wherein you have to cut the pipe for installation
which is practically impossible in many
applications. In fact in existing distribution
network during installation of full bore
magnetic flow meter the line water wastage
is more than the cost of flowmeter Hence
Ultrasonic flow meters are the best choice
in water industry.
|
4.
|
Easy Maintenance :
The complete Flow metering constitutes Probes,
Converter and Interconnecting cables hence
fault finding is very simple and hence maintenance
is very easy. Secondly due to Universal
Electronics, inventory cost for spares is
practically zero.
|
5.
|
Easy Shifting of flowmeter
: Shifting of flow meter from one location
to another is also possible without additional
hardware which is not possible with other
type of flowmeters.
|
6.
|
Accuracy : The
most important feature of transit time method
is consistent accuracy over a period of
time.
Accuracy of measurement is possible better
than ± 1% of reading. Ultrasonic
flowmeter does not require any flow laboratory
for calibration. Since accuracy is dependent
on measurement of time, which is sampled
by most standard techniques, having resolutions
of 40 Pico seconds.
By increasing the number of path we can
achieve the accuracy up to ± 0.25%.
Accuracy can be verified at laboratories
on request. It offers great benefit of compensating
the effect of disturbed flow conditions
by using multi path systems specially when
straight runs are limited.
|
|
|
|
|
|
|
|
|
Ultrasonic
Flow Meters, Ultrasonic
Inline Flow Meters, Ultrasonic
Water Meters, Water
Meters, Level
Transmitters, Water
Measurement, Water
Metering,
GSM Flow Meters, GPRS
Flow Meters, Multipath
Ultrasonic Flow Meters, Metering
Solutions, SCADA,
Portable
Ultrasonic Flow Meters, AMR
Water Meters, Bulk
Water Metering, Ultrasonic
Metering, Domestic
Water Metering, Water
Audits, Doppler
Type Ultrasonic Flow Meters, Inline
Flow Meters, Water
Transmitters
|
|
|
|
|
|