Flow Meter Ultrasonic : Type, Working Principle and Applications.

Definitions of Flow Meter Ultrasonic

Ultrasonic flow meter is a type of flow meter to measure the flow of a fluid using ultrasound to get the flow velocity. The ultrasonic flow meter works based on speed, where ultrasonic waves are transmitted by the transducer which is passed by the flowing medium so that the flow velocity is obtained by the ultrasonic transmitter.

Ultrasonic flow transmitter will capture and process the signal from the sensor or transducer by providing the average flow velocity of the medium being measured. Ultrasonic flowmeters take advantage of the ultra sound vibrations generated by the transducer to measure the flow rate of liquids. There are two types of ultrasonic flowmeters, namely Doppler and Transit Time. Ultrasonic flow meters are ideal for measuring all types of fluids or fluids that are homogeneous and independent of the conductivity of the liquid.

Type of Flow Meter Ultrasonic

There are 2 types of ultrasonic flow meters based on theory and how they work, namely ultrasonic Doppler flow meters and ultrasonic transit time flow meters.

– Flow Meter Doppler Ultrasonic

Ultrasonic Doppler Flow Meter works on the principle of the Doppler Effect, which was documented by physicist Christian J Doppler in 1842. He discovered the fact and explained that the frequency of sound waves received by an observer depends on the motion of the source or observer with respect to the sound source.

Doppler ultrasonic flowmeters use a transducer to emit ultrasonic beams into a stream flowing through a pipe. Ultrasonic Doppler Flow Meter locates the frequency shift as a result of particle motion received by the ultrasonic transducer. For the flow meter to operate, there must be solid particles or air bubbles in the flow to reflect ultrasonic waves.

Ultrasonic Doppler Flow Meters measure the frequency shift, which is directly proportional to the flow rate. This value is multiplied by the internal cross-sectional area of the pipe to obtain the volumetric flow as shown below:

• Δf= 2fT sinθ • VF/VS
• VF = f/fT • VT/sinθT = KΔf

the explanation :

• VT = Sound Velocity of flowing material
• T = Angle of transmitter beam
• K = Calibration factor
• VF = Flow velocity
• f = Doppler frequency shift
• VS = Sonic velocity of fluid
• fT = Transmitter frequency = Angle of ft entry into liquid Volumetric flow rate = K• VF • D²
• K = Constant
• D = Inner diameter of the pipe

Ultrasonic Doppler Flow Meters operate depending on the particles flowing in the liquid, therefore it is necessary to pay attention to the minimum concentration and size of solids or bubbles contained in the liquid. Likewise, to maintain the continuity of the suspended solid the liquid must flow at a sufficiently high rate.

– Flow Meter Ultrasonic Transit time

Ultrasonic Transit Time Flow Meters operate by measuring the time difference between signals sent and received by a transducer passing through the fluid in the pipe. Comparisons are made of upstream and downstream. If there is no flow in the pipe, the travel time will be the same in both directions. When there is a flow, the ultrasound travels faster if it moves in the same direction and slower if it moves the other way around.

Because the ultrasonic signal sent and received by the transducer or ultrasonic sensor must pass through the pipe, the liquid must be homogeneous or cannot consist of various types of material or contain a lot of solids or bubbles, or the high frequency sound will be reduced and too weak to pass through the pipe.

The difference in upstream and downstream measurements taken through the same path is used to calculate flow through the pipe:

• V = K • D/sin2θ • 1/(T0 – t)2 

the explanation

• V = the average velocity of the flowing fluid
• K = Constant
• D = Inner diameter of the pipe = Angle of incidence of ultrasonic wave T0 = Zero flow transit time
• T = T1 – T2
• T1 = Wave transit time from upstream transmitter to downstream receiver
• T2 = Wave transit time from downstream transmitter to upstream transmitter
• t = Time of transit of waves through walls and pipe layers

The above equation shows that the fluid flow velocity is directly proportional to the difference between upstream and downstream measurements.

The transit time ultrasonic flow meter has three possible transducer configurations: Z, V, and W. All are recognized as a single measurement path, whereas the ultrasonic beam follows a single path. In all three configurations, the output produced by the transducer is converted into a current, frequency or voltage signal.

The quality and measurement results are determined by the strength of the ultrasonic signal which is determined by the following factors:

• Pipe sizes such as pipe diameter and thickness
• Pipe type material and media type being measured
• Transducer mounting distance and type
• Condition of the inner wall of the pipe
• Guaranteed flow in laminar pipe

Ultrasonic Flow Meter Components

Types of Ultrasonic Flow Meters by Installation

In Line Ultrasonic Flow Meter

In accordance with its development, ultrasonic flow meters are also produced with an In line flow meter installation system. For this type of in-line ultrasonic flow meter, the ultrasonic sensor or transducer is permanently connected to the flow tube which is then transferred to the ultrasonic transmitter or flow computer using a cable.

For this type of ultrasonic flow meter, the connection type or installation method is by cutting the pipe which is then installed with a flange or made of thread.

Insertion Ultrasonic Flow Meter

Clamp On Ultrasonic Flow Meter

Clamp on Ultrasonic Flow Meter is the most widely known type of ultrasonic flow meter because this flow meter installation method does not need to stop the flow in the pipe. Clamp on ultrasonic flow meters are widely assumed to be a type of portable ultrasonic flow meter that is widely used by engineers for checking and testing flow capacity in pipes. However, nowadays, clamp-on flow meters are starting to be widely used to monitor the total flow in the pipe as the purpose of installing the flow meter

Flow Meter Ultrasonic Clamp On fix ( Wall Mount )

The type of ultrasonic clamp-on flow meter that is fixed is often associated with accuracy which is used as a reference for the quality. Ultrasonic clamp-on flow meter has a fairly good accuracy.

The ultrasonic clamp-on flow meter is a type of flow meter whose installation does not cut or perforate the pipe where the ultrasonic sensor or transducer is simply affixed to the outer surface of the pipe, then bracketed and clamped.

The clamp-on ultrasonic flow meter has excellent accuracy between 0.5% to 0.1% and can be installed on all types of pipe materials such as carbon steel, stainless steel, PVC, HDPE and others. In addition, it can be used on various pipe diameter sizes from DN25 to DN6000

Portable Ultrasonic Flow Meter

• Portable flow meter is an ultrasonic type flow meter that is very effective for measuring the quality of the flow of a liquid in a pipe. This portable

flow meter is very easy to operate because there is no need to damage either by cutting or perforating the pipe. Portable flow meters are very suitable for inspection work, control, audit of equipment related to the quality of the flow of a liquid in a pipe, this is because this type of portable flowmeter is quite light and easy to carry anywhere.

Also Read : Water flow sensor jenis clamp on ultrasonic flow meter

How to install a portable flow meter for liquid using a clamp on installation type, where the ultrasonic transducer is simply clamped on the surface of the pipe. Because the installation process does not cut or perforate the pipe, the installation of a portable flow meter is very cheap and fast.

Portable ultrasonic flow meters are usually used by engineers to:

• Checking a system that wants to know the amount or flow rate of a production process.

• Knowing the performance of the engine cooling system (cooling system)

• Reading the amount of energy in a liquid such as in HVAC or chillers

• Check the performance of the lubrication system

• Checking the performance of the pump

• Read fire fighting system capability by reading flow rate

• Testing the performance of the flow meter measuring instrument as a confirmation of the quality of the flow meter accuracy

Jenis flow meter portable biasanya dilengkapi dengan data logger secara internal maupun external dan menggunakan battery. Battery yang digunakan adalah battry yang bisa dicharge serta mampu bekerja pada waktu cukup lama diatas 5 jam.

Open Channel Flow Meter

Open Channel Flow Meter is a flow meter that is applied to measure medium or large flow capacity in channels or ditches. In practice, it is also widely used for rivers and culverts with super large sizes. The use of an Open Channel Flow Meter in a flow with an open system and usually the flow is due to the force of gravity. The way the open channel flowmeter works is to calculate the flow velocity and surface height which is calculated against the channel cross-sectional area.

For flow velocity measurement is used flow sensor as well as calculating flow capacity based on delta pressure due to differences in water level.

Product Specification Ultrasonic Flow Meter

Ultrasonic flow meters have various specifications depending on the type, model and brand as presented by the manufacturer. However, in general, the specifications for ultrasonic flow meters can be informed as follows:

• Flow range : 0 ft/s ~ ± 40 ft/s ( 0 m/s ~ ± 12 m/s ).
• Accuracy : ± 0.5% of measured value.
• Repeatability :  ±0,1% of measured value
• Pipe size :  1″ ~ 200″ ( DN25 mm ~ DN5000 mm ).
• Outputs :
  • Analog output: 0/4 ~ 20 mA, ( max load 750 Ω );
  • Pulse output: 0 ~ 9999 Hz, OCT ( min. and max. frequency is adjustable );
  • Relay output: max. frequency 1Hz ( 1A@125VAC or 2A@30VDC ).OCT, Relay, RS485, 4-20mA
• Communication Interface : RS232 & RS485 Modbus
• Power supply :  90 ~ 245 VAC, 48 ~ 63 Hz Or 10 ~ 36 VDC.
• Keypad : 16 light tactile keys.
• Display :   256*128 lattice, backlit LCD.
• Temperature :
  • Transmitter: -40°F ~ 140 °F (- 40℃ ~ 60℃ ).
  • Transducer: -40℉~176℉(-40℃~80℃, TT01)
  • Transducer: -40℉~356℉(-40℃~180℃, TT03)
• Humidity : Up to 99% RH, non-condensing
• Transmitter : PC+ABS,IP65
• Transducer :
  • Encapsulated design, IP68,
  • Double-shielded transducer cable,
  • Standard/maximum cable length:30ft/1000ft(9m/300m)
• Memory : TF card (Max 8G)

How to Install Ultrasonic Flow Meter Clamp on

The installation method that is the most popular and sought after by users of instrumentation equipment is the type of clamp-on installation. There are 2 types of clamp-on flow meters, namely the portable ultrasonic flow meter and the wall-mounting ultrasonic flow meter. For this type of clamp on flow meter, it can be used on pipe sizes from DN15 to DN6000, with several transducer sizes that are adjusted to the pipe diameter. Another advantage of this clamp-on flow meter is that it can be operated on all types of pipe materials and all types of homogeneous fluids.

Also read : Pengertian dan Fungsi Flow Meter

Cara instalasi flowmeter utrasonic clamp on is very easy and fast, with the first step is to collect pipe and liquid data as variables that must be entered into the ultrasonic flow transmitter. When the data entered corresponds to the actual one, a good ultrasound power will be obtained.

In addition to the pipe diameter, what is usually rather difficult is the pipe thickness data, because the average user does not have a thickness gauge. However, we can enter the thickness of the pipe based on the pipe dimension table which is downloaded via Google. When we need an output from an ultrasonic transmitter that can be input to a PLC or other, don’t forget to set the output parameters, and this is usually based on the flow rate or pulse.

Before doing the installation, there are several important things that must be considered when choosing and buying the type of ultrasonic clamp-on flow meter, namely:

• What is the diameter of the pipe to be measured?
• What is the minimum and maximum temperature of the application
• The type of power supply available or must use a battery or solar cell
• The desired output must be clear, is it analog, digital, pulse?
• What is the maximum and minimum flow rate
• What is the maximum and minimum flow velocity
• Upstream and Downstream distance available
• Is there sound wave interference in the pipeline or not that can interfere with the work performance of the ultrasonic sensor?
• What are the minimum and maximum flow rates
• Make sure the liquid in the pipe is full or modify the pipe installation
• Make sure the accessories to protect the performance of the ultrasonic transducer for outdoor installation

Advantages and Disadvantages of Clamp On Ultrasonic Flow Meter

Here are the advantages and disadvantages of clamp on Ultrasonic Flow Meter :

Advantages

• It does not block the path of fluid flow.
• These O/P meters differ for the density, viscosity & temperature of the liquid.
• Liquid flow is bidirectional
• The dynamic response of this meter is good.
• The output of this meter is in analog form
• Energy conservation
• It is suitable for large quality flow measurement
• Very useful for customizing and maintaining
• Flexibility is good
• No contact with liquid
• No risk of leakage
• No moving parts, pressure loss
• Pretty good accuracy around 1%
• Enough investment for large pipe diameters above 6″
• Operational, maintenance and installation costs are quite cheap

Disadvantages

• Quite expensive compared to other mechanical flow meters for small pipe diameters
• Too complicated design
• The sensor part of this meter is expensive.
• This meter is complicated compared to other meters, so it requires a specialist to maintain and repair this meter
• Cannot measure cement pipes or corroded concrete.
• Doesn’t work after the pipe contains holes or bubbles in it
• Cannot measure cement/concrete pipes or pipes with such material layers

How to Operate Portable Ultrasonic Flow Meter

Portable ultrasonic flow meters generally consist of 3 parts, namely portable flow transmitter, transducer and cable transducer to transmitter. While the accessories that must be available are clamp, bracket, battery charger, meter, acoustic gel. To make it easier to carry anywhere, it should be equipped with a compact and lightweight casing, bag or suitcase.

How to operate an ultrasonic portable flow meter is very simple and usually begins by determining the position or point where the flow must be laminar. While the variables that must be known before using this tool are the type of pipe material, the diameter of the pipe being measured, the thickness of the pipe and the type of fluid in the pipe.

Also read : Flow Meter Ultrasonic Portable untuk Mengecek Sistem Pendingin Mesin

When there is an error in entering the above variables, the readings from the portable flow meter are usually inaccurate and can lead to errors. On the other hand, if the input variables are correct, including the distance of the transducer and the magnitude of the sound velocity, then the ultrasonic signal is good. So that the ultrasonic signal is in accordance with the requirements so that the flow transmitter readings will be accurate, which is in the range of 0.5% – 1%.

The main parameters needed to operate it are pipe diameter, pipe thickness, pipe material type, liquid type, ultrasonic transducer distance, desired measurement unit and the quality of the signal generated when the flow in the pipe is measured.

Important Things In Installing Ultrasonic Clamp On Flow Meters

• The clamp-on ultrasonic flowmeter has two modes, diagonal and reflection.
• When the reflection mode cannot be measured, the diagonal mode may be able to measure.
• The clamp on ultrasonic flowmeter has high requirements on the pipe, and the insulation layer must be clean. Make sure the liquid in the pipe is full.
• The authenticity of the flowmeter readings depends on the strength of the ultrasonic signal
• Since readings can vary, the approach is to let the flowmeter take continuous readings and take the average.
• Pay attention to the temperature of the liquid being measured because this must match the type of transducer and the type of ultrasonic gel
• For transit time ultrasonic flow meters, ensure that the liquid can conduct ultrasonic waves adequately.
• Ultrasonic waves must be able to penetrate liquids for flowmeters to operate accurately.
• For Doppler ultrasonic flow meters, ensure that the liquid reflects the ultrasonic waves adequately. Because the flowmeter will not operate without the reflected ultrasonic signal.
• Be careful applying ultrasonic technology when solid particles can be concentrated in one part of the flowing stream. As in a horizontal pipe that flows at a relatively low speed.
• Avoid liquids that can coat the wetted transducer or coat the tube wall in front of the unwetted transducer.
• Use a Clamp on Transducer and bracket that fits the pipe diameter, because the flowmeter will not measure when ultrasonic waves cannot reach the fluid.

Also Read : Flow Meter Ultrasonic untuk Aliran Kecil Tanpa Menggunakan Pompa

Thus the article about “Ultrasonic Flow Meter” Hopefully it can help the readers and hopefully can add insight, hopefully useful.