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JACOBS Engineering SA
INITEC Energia

I
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1
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Flow measurement is vital to many different industries such as oil, power, water and waste
treatment
...
Flowmeters help to determine how much fluid is passing through to determine how
much money should be billed or how much product is being produced
...


1
...
Choosing the right flowmeter:
1
...
1
...
,

It is also recommended that the cost of the installation be computed only after taking these steps
...
2
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Tangible factors:
 Fluid and flow characteristics
The fluid and its given and its pressure, temperature, allowable pressure drop, density (or specific
gravity), conductivity, viscosity (Newtonian or not?) and vapor pressure at maximum operating
temperature are listed, together with an indication of how these properties might vary or interact
...

 Pressure & temperature ranges:
Expected minimum and maximum pressure and temperature values should be given in addition to the
normal operating values when selecting flow meters
...


 Piping and Installation Area
Concerning the piping and the area where the flow meters are to be located, consider: For the piping, its
direction (avoid downward flow in liquid applications), size, material, schedule, flange-pressure rating,
accessibility, up or downstream turns, valves, regulators, and available straight-pipe run lengths
...

 Flow rates and Accuracy
The next step is to determine the required meter range by identifying minimum and maximum flows
(mass or volumetric) that will be measured
...
Typically accuracy is specified in percentage of actual reading (AR), in percentage of
calibrated span (CS), or in percentage of full scale (FS) units
...

Unless you know these requirements, your flow meter's performance may not be acceptable over its full
range
...
When measuring the flow of compressible
materials, volumetric flow is not very meaningful unless density (and sometimes also viscosity) is
constant
...
In
other velocity sensors, pipe lines can cause problems (ultrasonic), or the meter may stop functioning if
the Reynolds number is too low (in vortex shedding meters, RD > 20,000 is required)
...

 Mass or Volumetric Flow Rate
With fluid flow defined as the amount of fluid that travels past a given location, this would seem to be
straightforward — any flow meter would suffice
...

Q=Axv
Q is flow rate, A is the cross-sectional area of the pipe, and v is the average fluid velocity in the pipe
...
Note that
Q is a volume per unit time, so Q is commonly denoted as the “volumetric” flow rate
...

Putting this equation into action, the flow rate will be 1 kilogram per second when 1 cubic meter per
second of a fluid with a density of 1 kilogram per cubic meter is flowing
...
In most applications, measuring the
volumetric flow is the thing to do
...
Volumetric flow may be of interest to avoid overflowing a tank where liquids of
differing densities can be added
...
) Consider controlling fluid flow into a process that can only accept a
limited volume per unit time
...

In other processes, mass flow is important
...
Of interest is the number of molecules present (its mass), not its volume
...
The
major factor, of course, is matching the right instrument to the particular application
...
Flow meters with no moving parts usually will
require less attention than units with moving parts
...

1
...
Key questions to ask when choosing a flow meter:
1
...
Do you require rate measurement and/or totalization?
3
...
Do you require a local display on the flow meter or do you need an electronic signal output?
5
...
What is the minimum and maximum process pressure?
7
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Is the fluid chemically compatible with the flow meter wetted parts?
9
...
Velocity flow meters (measuring volumetric flow):

a
...


Working principle:



Ultrasonic flowmeters use sound waves to determine the velocity of a fluid flowing in
a pipe
...


Characteristics (depending on the model, better refer to datasheets):








Fluid particulates: 100 PPM of 100 microns in size particulates or gas bubbles in the
liquid
...
01-20m/sec (Bi-Directional)
Accuracy: ±0
...

Repeatability: Typically ±0
...
7-7600mm
Temperature: -40°C to 200°C
Pressure: generally can handle high pressures
...

High turndown (can read low as a percentage of the full scale or top reading),
handles high pressures, is repeatable (consistent), handles extreme temperatures
...




Disadvantages can include high cost, sensitivity to stray process vibrations, problems
with pipe diameter change due to buildup and clamp-on units have lower accuracy
...


Key questions which need to be answered before selecting a magnetic flow meter:









Does the liquid have particulates of 100 ppm of 100 microns in size?
Do you require a handheld or continuous process monitor?
Do you require an analog output?
What is the minimum and maximum flow rate for the flow meter?
What is the minimum and maximum process temperature?
What is the minimum and maximum process pressure?
What is the size of the pipe?
Is the pipe always full?

Key applications:
Ultrasonic flowmeters are commonly applied to measure the velocity of liquids that allow
ultrasonic waves to pass, such as water, molten sulfur, cryogenic liquids, and chemicals
...
rshydro
...
uk/flow-meters/ultrasonic-flow-meters/,
https://www
...
com/prodinfo/ultrasonicflowmeters
...
flowmeters
...
Turbine & pistons flow meters:
Definition:
The turbine flowmeters are a technology of flowmeters that are characterized by the use of
a turbine to determine the flow of liquid in a pipe
...
The rate of spin is measured to calculate the flow
...

Temperature: max 105°F
...

Accuracy: 0
...
5 %

Advantages and drawbacks:






The turbine meter can have an accuracy of 0
...

Very accurate meter and can be used for clean liquids and viscous liquids up to 100
centistokes
...

Turbine flowmeters do not work well when the water flow is low
...
g
...
azom
...
aspx?ArticleID=15058,
https://enggcyclopedia
...
instrumentationtoolbox
...
html,

c
...


Working principle:





An electromagnetic flowmeter operate on Faraday's law of electromagnetic induction
that states that a voltage will be induced when a conductor moves through a
magnetic field
...

The voltage produced is directly proportional to the flow rate
...


Characteristics (depending on the model, better refer to datasheets):







Temperature range: -27 C to 200 C
...
05 to 10 m/sec
...
5 % to 1%
No Pressure drop
...

They are mechanically obstruction less and can be equipped with abrasion-resistant
liners, making them effective for measuring slurries and other erosive fluids
...

Relatively small amounts of electrode metals are needed for magnetic flowmeters
...
125 inches and a maximum volume of up to 10 cubic
feet
...


Despite these advantages, magnetic flowmeters also present certain difficulties for flow rate
measurement:
 These flowmeters are only effective on conductive fluids, and materials such as
unmixed hydrocarbons and gases cannot be measured
...

Depending on their size and capacity, magnetic flowmeters can be relatively heavy,
and those with higher corrosion and abrasion resistance can be expensive
...

More at: https://www
...
com/prodinfo/magnetic-flow-meters
...
thomasnet
...
Vortex-shedding flow meters:
Definition:
A vortex flow meter is a flow measurement device best suited for flow measurements
where the introduction of moving parts presents problems
...

The frequency that the vortexes are shed depends on the size and shape of the
body
...

Suitable for measuring fluid; gas, liquid and steam
...

The vortex flowmeter can measure also measure wet and/or dirty gases
...

Their initial and maintenance costs are low
...


Downsides:


Vortex meters do require sizing for specific applications
...

Pressure: 230 psi (1
...
8MPa)
...
5 fps (3
...

Accuracy: 1
...
5% for gas or steam
...

They are widely used for steam flow measurement is that they can tolerate the high
temperatures of steam
...
flowcontrolnetwork
...
smartmeasurement
...
omega
...
uk/prodinfo/vortex-flow-meter
...
Mass flow meters (measuring mass flow):
Introduction:
When precise measurement of mass rate of a liquid is your requirement, then mass flow
meters are the ideal solution
...
These flow meters are largely
used for measuring liquids whose viscosities vary with velocity
...
Coriolis flow meters:
Definition:
The Coriolis flowmeters are a technology of flowmeters that are characterized by the
measurement of mass flow (instead of volumetric flow) of both liquids and gases
...
Due to the Coriolis forces, the tubes will deform and
an additional vibration component will be added to the oscillation
...

The Coriolis flow meters require force acting on a tube carrying flowing fluid
...
The amount of deformation
depends directly on the mass flow rate through the tubes
...


Advantages and drawbacks:
Advantages:





Used for direct, in-line and accurate mass flow measurement for both liquids and
gases
...
1% for liquids and 0
...

Multi-variable capability as mass flow, density and temperature can be addressed
from the one sensor
...


Downsides:







They are very expensive
...

In gas/vapor applications, large pressure drops across the flowmeter and its
associated piping can occur
...

Current technologies limit the pipeline diameter to 150 mm
...


Key applications:




They can handle sanitary applications, chemical processes
...

Coriolis mass flowmeters measure the mass flow of liquids, such as water, acids,
caustic, chemicals, and gases/vapors
...
engineeringtoolbox
...
html,
https://www
...
com/2017/02/how-coriolis-mass-flow-meterworks
...
flowmeters
...
Thermal flow meters:
Definition:
Thermal flow meters, also known as thermal dispersion or immiscible mass flow meters
comprise a family of instruments for the measurement of the total mass flow rate of a fluid,
primarily gases, flowing through closed conduits
...

The conducted heat is directly proportional to the mass flow rate and the
temperature difference is calculated to mass flow
...

They feature no moving parts
...

Insertion models are a very good choice for large pipe sizes if used as insertion
meters
...

Its dependence upon thermal properties those are almost independent of gas
density
...

Potential problems include the condensation of moisture (in saturated gases) on the
temperature detector
...

Unable to measure the flow of gases with unknown and/or varying composition, such
as hydrogen-bearing off-gases
Not good for steam flow
...

Thermal flow meters can measure combustion air measurement in large boilers,
semiconductor process gas measurement, air sampling in nuclear power plants,
process gas measurements in the chemical and petrochemical industries, research
and development applications, gas chromatography, and filter and leak testing
...




They can also be used in chemical and petrochemical plants when the thermal
properties of the gas are known
...


More at: https://www
...
com/technical-learning/thermal-mass-flow-working-principletheory-and-design
...
omega
...
html,
https://www
...
com/flow-meters-d_493
...
Open channel flow meters:
Definition:
Open channel flowmeters perform flow measurement of liquids that are open to the
atmosphere at some point in the flow measurement path
...




The liquid may be entirely open to the atmosphere, or may be contained within a
closed pipe that is not full of liquid and only open to the atmosphere at the
installation point of the flowmeter itself
...





Weir Flow Measurement Standards - Important and common used standards within
weir flow measurement
Measuring Flow Rate with Weirs - Weirs are often used for measuring flow rates in
open channels and rivers in connection to water supply and sewage plants
Weir Flow Measurement Standards - Important and common used standards within
weir flow measurement

Advantages and downsides:
Advantages:





Easy to construct
...

Parshall flumes produce one-fourth the head loss of a weir designed to handle the
same flow range
...


Downsides:




Devices must be installed in the stream in a location where there is no disruption of
steady flow by upstream or downstream blockages
...

Specific constraints on pipe/channel sizes and grades
...
Flumes, with their inherently self-cleaning
design, meter flows that contain sand, grit and other heavy solids
...
che
...
umich
...
ht
ml,
https://www
...
com/literature/transactions/transactions_vol_iv
...
smartmeasurement
...
Differential Pressure Flowmeters:
Definition:
The differential pressure flowmeters are a technology of flowmeters that are characterized
by the use of use of Bernoulli’s equation to measure the flow of fluid in a pipe
...




The relation between flow rate and pressure is given by:



The purpose of the primary element is to introduce a constriction in the pipe that
contains liquid
...
The secondary element in the unit measures this pressure differential, and
accordingly determines the fluid flow
...
The plate obstructing the flow offers a precisely measured obstruction that
narrows the pipe and forces the flowing fluid to constrict
...

Venturi Tubes flow meters: Due to simplicity and dependability, the Venturi tube
flowmeter is often used in applications where it's necessary with higher Turn Down
Ratios, or lower pressure drops, than the orifice plate can provide
...
After the constricted area, the
fluid is passes through a pressure recovery exit section, where up to 80% of the differential
pressure generated at the constricted area, is recovered
...


The flow nozzle is relative simple and cheap, and available for many applications in many
materials
...


The pitot tube measures the fluid flow velocity by converting the kinetic energy of
the flow into potential energy
...
With the "annubar", or
multi-orifice pitot probe, the dynamic pressure can be measured across the velocity profile,
and the annubar obtains an averaging effect
...


The pressure difference results from the centrifugal force
...
However, the accuracy is very poor;
there are only applied when reproducibility is sufficient and other flow measurements
would be very costly
...
Elements
are designed for either clean or dirty service and are offered in various materials,
pipe sizes, and pressure ratings
...


Advantages of target flow meters:
 Can be used for any type of liquid, gas, or steam cryogenics
...

 High reliability where life tests have been made to 20,000,000 cycles
...
5 inches and up with any type of mounting
...

 variable-area flow meters or rotameter: The rotameter consists of a vertically oriented
glass (or plastic) tube with a larger end at the top, and a metering float which is free to
move within the tube
...


Design variation:
There are three major types of rotameter:
 Glass Tube Rotameters (with metal float): Safety-shielded glass tube
rotameters are in general use throughout industry for measuring both liquids
and gases
...
These meters are
used for services where high operating pressure or temperature, water

hammer, or other forces would damage glass metering tubes
...

 Plastic-tube rotameters: re ideal for applications involving corrosive fluids
or deionized water
...


Variable- area flow meter’s characteristics:








For glass Tube Rotameter: flow capacities to about 60 GPM, temperature limit is
204°C (400°F), pressure 100 psig- 500 psig (depending on the model), accuracy of
1-2 % FS
...

For plastic tube rotameter: Gas： 40 sccm - 1000 slpm, Liquid: 100 gr/m - 375
kg/m, accuracy of 2-10% FS, Pressure of max 100 psig, max temperature of 72C
(160F)
...
25% of the actual flow rate
...
omega
...
uk/prodinfo/rotameters
...
omega
...
uk/literature/transactions/volume4/variable-area-flow
...
brooksinstrument
...
setra
...

They can measure both liquids and gases
...

Their construction is robust and simple with no moving parts
...

They are configurable in bidirectional measures
...

they can be used to meter a wide variety of fluids and gases ;

Drawbacks:










They cause pressure drop (The pressure drop generated is proportional to the square
of the flow in some cases)
...

the calibration of the differential pressure transmitter can be affected by the
accumulation of liquid or gas in the impulse tubing
...

They are very obsolete when measuring slurries, fluids with high viscosity, such as
some hydrocarbons and foods, because their accuracy can be degraded when
Reynolds number is low
...

This technology is slowly receding
...
160 psi / 2320
...

Flange: DN50…600 / 2…24
External connection: 2-wire 4…20 mA/
Communication protocols: HART®, FF, Profibus-PA

Key applications:











generally applicable to many flows in most industries, such as mining, mineral
processing, pulp and paper, petroleum, chemical, petrochemical, water, and
wastewater industries
...

Measuring waste waters only if diaphragm seals are used
...

High-pressure flow on offshore oil platforms
Chemical injection
Purge liquid or gas metering

More at: https://krohne
...
smartmeasurement
...
mecholic
...
html,

https://www
...
co
...
flowmeters
...
Positive displacement flowmeters:
Definition:
Positive Displacement Flowmeters, which employ one of the oldest-known flow measurement
techniques, are widely used in industry and have one of the largest install bases of any flow
meter technology
...
Known and fixed volumes are displaced between the rotors
...


Different types of PD flow meters:
There are several models of flow meters that fall within the same category
...

Oval gear: have two rotating, oval-shaped gears with synchronized, close fitting
teeth
...
Shaft
rotation can be monitored to obtain specific flow rates
...
The pressure of the liquid passing through the
measuring chamber causes the disk to rock in a circulating path without rotating
about its own axis
...

Rotary vane meters: consists of equally divided, rotating impellers, two or more
compartments, inside the meter's housings
...
A fixed volume of liquid is swept to the meter's outlet from each
compartment as the impeller rotates
...


Working principle:


PD Flow meter measures flow rate by trapping pockets of fluid between rotating
components housed within a high precision chamber
...

Rotor rotational velocity is directly proportional to flow rate, since the flow of fluid is
causing the rotation
...

high accuracy (up to 0
...

high temperature operation,
high viscosity operation,
no upstream or downstream straight pipe requirement,
The ability to be used with mechanical registers which require no electrical power, and
readings which are immune to changes in viscosity
...

They cause a considerable pressure drop
...

They are also not suitable for applications where large pockets of air are present
within the fluid
...

PD meters represent only 8% of global sales for flowmeters
...

Some designs can measure gas flow although liquid flow applications are much more
prevalent
...

The positive displacement flowmeter may be used for all relatively nonabrasive fluids
such as heating oils, lubrication oils, polymer additives, animal and vegetable fat,
printing ink, Dichlorodifluoromethane R-12, and many more
...
smartmeasurement
...
omega
...
html,
http://www
...
com/positive-displacement-technology,
http://www
...
com/blog/types-of-the-flow-meters/,

II
...

A thermometer has two important elements: a temperature sensor (e
...
the bulb of
a mercury-in-glass thermometer or the digital sensor in an infrared thermometer) in which
some change occurs with a change in temperature; and some means of converting this
change into a numerical value (e
...
the visible scale that is marked on a mercury-in-glass
thermometer or the digital readout on an infrared model)
...

Some of the principles of the thermometer were known to Greek philosophers of two
thousand years ago
...


Technologies of Temperature Sensors:
There are different types of temperature sensors that have sensing capacity depending upon
their range of application
...
Thermocouples:
Definition:
A thermocouple is a sensor used to measure temperature
...
The junction is placed
on the surface or in the environment that's being measured
...

Naturally, a thermocouple outputs a millivolt signal, therefore, as the resistance changes, the
change in voltage can be measured
...


Working principle:


There is two wires composed of dissimilar metals are joined at both ends and one of
the ends is heated, there is a continuous current which flows in the thermoelectric
circuit
...


Types of thermocouples:






Chromel – gold/iron alloy thermocouple
...

Platinum/molybdenum alloy thermocouple
...

Pure noble metal thermocouple
...

They are self-powered, no need for external power supply
...


Downsides:






Their linearity is very poor, and they need reference
...

*their sensitivity is low
...
Any type
of light corrosion can result in a misreading by the thermocouple
They are vulnerable to corrosion, which can sometimes be difficult to detect
...




Their package can be large
...

Process plants
...

Thermopile radiation sensors
...
engineeringtoolbox
...
html,
https://www
...
in/6-different-types-of-temperature-sensors-with-their-specifications/,
https://www
...
com/types-and-applications-of-thermocouples
...
Resistor temperature detectors RTD:
Definition:
Resistance Temperature Detector (RTD) is a temperature sensor that contains a resistor
whose resistance value varies as its temperature changes
...


Working principle:



An RTD sensor consists of a sensing element, usually made of highly pure metal
(copper, platinum or nickel), housed within a protective probe and connected to
monitor or control equipment by insulated lead wires
...


Advantages and drawbacks:
Advantages:





Their linearity is good
...

High sensitivity
...


Downsides:





All RTD needs external power supply to monitor the temperature
...

Small resistance change
...


Key applications:








They are suitable for use whenever accuracy and stability of measurement are needed
across a wide temperature range
...

Measuring temperatures of materials and equipment in industrial manufacturing
facilities
Measuring air temperature in laboratories, clean rooms, and other locations
Measuring temperature inside air ducts
...

Measuring temperatures inside ovens, stoves and food processing equipment

More
at:
https://www
...
com/prodinfo/rtd
...
ws/io/io_3
...
electronics-

3
...
The word is a portmanteau of thermal and resistor
...
An NTC is commonly used
as a temperature sensor, or in series with a circuit as an inrush current limiter
...
PTC thermistors are
commonly
installed
in
series
with
a
circuit,
and
used
to
protect
against overcurrent conditions, as resettable fuses
...

In contrast to RTDs that change resistance in a nearly linear way, NTC thermistors
have a highly nonlinear change in resistance and actually reduce their resistance with
increases in temperature
...

High level of repeatability and stability
...

A small size means fast response to temperature changes
...

Thermistors need external power supply to monitor the temperature
...

They are used as current limiters, current protectors, and heating elements
...


More at:
https://www
...
com/articles/electronic_components/resistors/thermistortechnology-types
...
omega
...
html,
https://forum
...
com/t/common-temperature-sensing-technologies/1560,
Comparison between the three main thermometers used in industry:

4
...
It does this by either emitting or detecting infrared radiation
...


Types of infrared sensors:
Infrared sensors can be active or passive and they can be split into two main types:



Thermal infrared sensors – use infrared energy as heat
...
Thermal detectors do not require
cooling but do have slow response times and low detection capabilities
...
Their photo sensitivity is dependent on wavelength
...


Working principle and theory of their operation:
The physics behind infrared sensors is governed by three laws:



Planck’s radiation law: Every object at a temperature T not equal to 0 K emits
radiation



Stephan Boltzmann Law: The total energy emitted at all wavelengths by a black body
is related to the absolute temperature
...

The battery used in infrared devices last for long duration due to lower power
consumption
...

The sensor does not require any contact with the product to be sensed
...




They are physically smaller in size and are more affordable
...

It provides good stability over time
...

➨It delivers high repeatability
...
g
...
Hence it does not work through walls or doors
...

In monitor & control application, it can control only one device at one time
...
It requires line of sight
between transmitter and receiver to communicate
...

It supports lower data rate transmission compare to wired transmission
...




Primary and Secondary Glass Manufacturing



Petroleum exploration



Gas detectors
...




Textiles…

More at: http://www
...
com/_Uploads/dbsAttachedFiles/MM_ENG_F_W
...
rfwireless-world
...
html,
https://www
...
com/article
...
Semiconductor temperature sensors:
Definition:
Semiconductor temperature sensors are the devices which come in the form of integrated
circuits i
...
ICs hence, popularly known as IC temperature sensors
...
They give an effective linear output in the form of voltage
signals
...




Current Output Temperature Sensors: As opposed to voltage output temperature
sensors, the output impedance of these sensors is very high
...
They also need an input voltage which can vary between 4 and 30 V
...
These sensors
don’t provide standard digital interfaces
...
Some of them are specially fabricated
to enable their use with microprocessors for thermal management
...

The usual temperature resistance characteristics of semiconductor materials make
their use simpler
...
However, extra care must be exercised while employing these sensors owing
to their other characteristics
...
These are the most inexpensive type of temperature sensors which are
competent enough to provide very adequate results if constant and steady excitation
current is supplied to them
...
An ordinary semiconductor diode provides a sensibly linear forward biased
voltage whose temperature coefficient is around 2
...
A typical diode
temperature sensor is shown in the figure below
...
Pressure meters technologies:
General Introduction:
Pressure measurement is the analysis of an applied force by a fluid (liquid or gas) on a
surface
...
Many
techniques have been developed for the measurement of pressure and vacuum
...

A manometer (not to be confused with nanometer) is a good example, as it uses a column of
liquid to both measure and indicate pressure
...

Other methods of pressure measurement involve sensors that can transmit the pressure
reading to a remote indicator or control system (telemetry)
...
The
different types of pressure are differentiated only by the reference pressure:



Absolute pressure: The clearest reference pressure is the pressure zero, which exists
in the air-free space of the universe
...
For the required differentiation from other
types of pressure, it is denoted with the index “abs”, which is derived from the Latin
“absolutus”, meaning detached, independent
...




Atmospheric pressure: The probably most important pressure for life on earth is the
atmospheric pressure, Pamb (amb = ambiens = ambient)
...
500 km
...
At sea level, pamb averages
1,013
...
25 mill bar (mbar)
...




Differential pressure: The difference between two pressures, p1 and p2, is known as
the pressure differential, Δp = p1 - p2
...

Accordingly, in order to measure differential pressure, at first two different pressures is
captured in a measuring instrument
...
Instances where it is required to
measure differential pressure are, for example, level measurement and monitoring
applications
...

Overpressure (gauge pressure): The most frequently measured pressure in the
technological field is the atmospheric pressure differential, Pe (e =exceeding)
...

A positive overpressure is referred to when the absolute pressure is greater than the
atmospheric pressure
...

Gauge is used to measure pressure relative to ambient conditions, such as with car
tyre pressure
...
Care must be taken that units are installed in dry areas (otherwise internal
circuitry can fail)
...

Sealed pressure: Measures the input pressure (of your media) with reference to a
sealed chamber closed with atmospheric pressure (approximately 1bar)
...
This range is normally restricted to
minimum 7bar and above
...
Our industrial pressure sensors are ideal
...
Different types of temperature sensors are as follows:







Manometers: manometers instruments can be split into two major types:
 Simple manometers:
 Piezometers
...

 Micro manometers
...

 Inverted U-tube
Elastic pressure gauges: also can be split into four major types:
 Boudon tube
...

 Diaphragm gauge
...

Pressure transducers (used with different pressure gauges):








Strain Gauge Pressure transducer
Capacitance Pressure transducer
...

Optical type transducer
Fiber optic type transducer
Electromagnetic type transducer

From: http://www
...
com/electrical-pressure-transducers/2011/09/,
https://www
...
com/articles/pressure-sensors-types-working

1
...
Five different types of manometers are detailed below
...
Manometers can be categorized into two types, namely simple manometer and
differential manometer
...

Readability; Scales must be clear, sharp, accurate and easy to read
...


Limitations of manometer:



Being fragile, get broken easily
...




A capillary effect is created due to surface tension of manometric fluid, and



For better accuracy meniscus has to be measured by accurate means
...


Accuracy of manometers:
Accuracy in Liquid Manometers




U-tube type: +/- ½ of minor scale graduation
Well type: +/- ½ of minor scale graduation
Inclined type: +/- ½ of minor scale graduation

Key Applications:


specific pressure monitoring applications



Visual monitoring of air and gas pressure for compressors
...




In power plants,mercury absolute manometer have been used to check condenser
efficiency by monitoring vacuum at several points of the condenser



Used for the research of atmosphere of other planets
...




Some types of liquids used in manometers are toxic and can be damaging to the
environment
...
This could cause the liquid to be forced out of the tube
...




Never operate damage equipment
...




Electronic manometers do not measure water pressures; under these conditions they will
fail
...


Safety regarding the use of manometers:


Some types of liquids used in manometers are toxic and can be damaging to the
environment
...
This could cause the liquid to be forced out of the tube
...




Never operate damage equipment
...




Electronic manometers do not measure water pressures; under these conditions they will
fail
...


More at: http://www
...
com/blog/manometer/,
https://sciencestruck
...
org/manometer-types/2/
1
...
Simple manometers:
 Simple manometric devices measure pressure at a single point in a fluid
...


1
...
1
...
It can be used for measuring moderate
pressures of liquids
...

The tube extends vertically upward to such a height that liquid can freely rise in it
without overflowing
...




Pressure at point A is given by :

A=ρxgxh
Where,
ρ = Density of liquid
g = Acceleration due to gravity
h = Rise of liquid in Piezometer glass tube
Absolute pressure at Point A = Pa + ρ x g x h

Advantages and drawbacks:
Advantages:




Technique of using Piezometer is very simple
...

Piezometer tube will provide the accurate pressure reading
...

Piezometer tube will not be used to measure the pressure of gas
...

Piezometer tube will not be used to measure the negative pressure, i
...

iquid will be exposed to atmosphere in Piezometer tube and therefore liquid must be
clean and non-toxic
...




Used for any applications where liquids’ pressure are greater than atmospheric one
...
html,

https://mechanicsoffluids
...
com/2009/01/simple-manometers-

http://www
...
com/2017/12/simple-manometer-piezometer-advantages
...
pdf,

1
...
2
...

Working principle:


The unknown pressure is applied in the one arm of the tube and the mercury in the
tube or manometeric liquid filled in the tube moves in the tube or rises to the constant
region
...
The pressure is calculated by using the formula

P1-P2 = Pmhg


Where: P1 = applied pressure, P2 = 0,
P1 – P2 is approximately equal to Pmhg

Advantages and downsides:
Advantages:





simple in construction
Low cost
Very accurate and sensitive
It can be used to measure other process variables
...

Very sensitive to temperature changes
...


Characteristics:





Liquid’s viscosity should be low
...

The liquid should stick on the walls
...


Key applications:






It is used for low range pressure measurements
...

Is used in Orifice meter and Venturi meter for flow measurements
...

It is used for measuring pressure drop in different joints and valves
...
acmasindia
...
blogspot
...
html,
https://engineeringinsider
...
1
...
Micro manometer (single column manometer):
Characteristics




Micro-manometers are modified forms of simple U-tube manometer
...

Simple U-tube manometer has a problem: any change in pressure causes a rise of the
liquid in one limb of the manometer and a drop in the other
...


Working principle:


A single column manometer is a modified form of a U-tube manometer in which a
shallow reservoir having a large cross-sectional area (about 100 times) as compared
to the area of the tube is connected to one limb of the manometer
...


More at: http://ecoursesonline
...
res
...
php?id=147013,

1
...


Differential manometers:

An instrument in which the difference in pressure between two sources is determined from th
e vertical distance betweenthe surfaces of a liquid in two legs of an erect or inverted Ushaped
tube when each of the legs is connected to one of the sources
...

 Inverted U-tube manometer
...
2
...
Differential U-tube manometer:
Definition:
Differential U-tube manometer is very handy to measure the pressure difference directly and
is basically similar to the U-tube manometer discussed in simple U-tube manometer
...
By measuring the difference between the heights of liquid, it is
possible to calculate the difference in pressure
...


Downsides:




Fragile in construction
...

Error can happen while measuring the h
...

Low surface tension is required
...

The liquid should not get vaporized
...

Extensively used in laboratories
...

It is used for calibration of gauges and other instruments
...


More at: https://sciencing
...
html,

https://engineeringinsider
...
2
...
Inverted U-tube manometer:
Definition:
Inverted U-tube manometer is used for measuring pressure differences in liquids; it is
principally used for the measurement of the difference in small pressure differences in liquids
when the difference between liquids’ densities is low
...




Air is present at the center of the two limbs
...

Air or mercury is used as the manometric fluid
...




Advantages and drawbacks:


Easy to fabricate and relatively inexpensive;



Good accuracy;



High sensitivity;



Require little maintenance;



Not affected by vibrations;



Specially suitable for low pressure and low differential pressures; and



It is easy to change the sensitivity by affecting a change in the quantity of manometric
liquid in the manometer
...




Readings of the manometers are affected by changes in temperature, altitude and gravity
...




Usually bulky and large in size
...

Extensively used in laboratories
...

It is used for calibration of gauges and other instruments
...


Morea at: https://sciencestruck
...
org/manometer-types/,
https://me-mechanicalengineering
...
Elastic pressure meters:
Elastic pressure elements or mechanical type of transducers are used for measurement of
very high pressures up to about 700MN/m^2
...
They incorporate measuring
elements which deform elastically under the influence of pressure
...
These are:





Bourdon Tube
Bellows
Diaphragm
Dead weight

2
...


Bourdon tube pressure gauge:

Definition:
Bourdon tube pressure gauges are classified as mechanical pressure measuring instruments,
and thus operate without any electrical power
...


Working principle:

The pressure of the measuring medium acts on the inside of the tube and produces a motion
in the non-clamped end of the tube
...


Advantages and limitations:
Advantages:






They give accurate results
...

Bourdon tube cost low
...

They can be modified to give electrical outputs
...


Limitations:






They respond slowly to changes in pressure
They are subjected to hysteresis
...

Amplification is a must as the displacement of the free end of the bourdon tube is low
...


Characteristics:




Pressure measurement range covers 0
...
1,000 bar
...

Accuracy : up to ±0
...


Key applications:
Bourdon tube pressure gauges are suitable for liquid or gaseous media, which are not highly
viscous or crystallising, as long as they do not attack copper alloy parts
...
blogspot
...
html,

https://en
...
com/landingpage_bourdon_tube_pressure_gauge_en_co
...
ametekusg
...
wikapolska
...
pdf,
https://www
...
com/MoreAboutCategory?CategoryID=5151,

2
...


Bellows pressure gauge:

Definition:
The bellow type gauges are used for the measurement of absolute pressure
...
It may be used for measuring pressures up to 40 mm Hg
...
Pressure is applied to
one side of the bellows and the resulting deflection is counter balanced by a spring
...

By suitable linkage and calibration of the scale, the pressure difference is indicated by a
pointer on the scale
...




Reliable with low hysteresis and creep
...

It is good to low-to moderate range
...

Sensitive to vibration and shock
...

The availability of construction metals is limited
...
0 à 0
...

Accuracy : up to ±0
...


Key applications:




Their primary application is in the measurement of low pressures or small pressure
differentials
...


More at: https://www
...
com/MoreAboutCategory?CategoryID=5151,
http://firecontrolman
...
com/14104/css/Bellows-Gauge-234
...
prisma-instruments
...
co/bellow-type-pressure-gauge/,
2
...


Diaphragm pressure gauge:

Definition:
Diaphragm pressure gauges pressure measurement units that are used to measure gases and
liquids
...

The positive or negative pressure acting on these diaphragms causes deformation of the
measuring element
...


Advantages and limitations:
Advantages:





They have a relatively high actuating force, so insensitive to vibration
...


Limitations:




Seismic, impact resistance is not good
Difficulty in maintenance
Lower measurement pressure
...

standard accuracy of ± 2% FSD
...

Mostly used in commercial heating, filtration system level measurement, Gas
distribution
...
sika
...
html,
http://www
...
com/english/NewsShow_95
...
prisma-instruments
...


2
...


Capsule element pressure gauge:

Definition:
Capsule element pressure gauges are used to measure air and dry gases at low pressures
...
5 mbar to 600 mbar
...
This capsule element expands when the pressure inside the
element is higher than the external pressure, and it contracts when the internal pressure is
lower
...


Advantages and limitations:
Advantages:


Good at the measurement of low pressures, as low as 16 mbar
...


Characteristics:





Pressure range: 0
...
600 mbar (filled), 0
...
5 mbar to 0
...

Nominal size: 63, 100 and 160 mm
Accuracy: (+/-) 1
...
6)
...

All stainless steel design for gaseous, aggressive media in corrosive environments

More at:
https://www
...
us/upload/DS_PM632_51_en_us_15882
...
sika
...
html#documents,
https://www
...
pl/upload/DS_IN0001_GB_1366
...


Level measurements’ devices and technologies:
Introduction:

Integral to process control in many industries, level measurement sensors fall into two main
types:

 Point level measurement sensors are used to mark a single discrete liquid height–a
preset level condition
...

 Continuous level sensors are more sophisticated and can provide level monitoring of
an entire system
...
To
create a level management system, the output signal is linked to a process control
loop and to a visual indicator
...
Different types of level sensors are as follows:






Point level indicators of liquids:
 Magnetic and mechanical float
 Magnetostrictive detector
 Ultrasonic detector
 Radar detector
 Optical detector
Continuous level indicator:
 Capacitance type
 Float level detector (magnetic, mechanic and magntoresistive types)
 Magnetostrictive detector
 Air bubbler system
 Radar type
 Hall based detector
 Ultrasonic type
 Hydrostatic level sensor
both point level detection or continuous monitoring:
 Ultrasonic level sensors
 Capacitance level sensors
 Radar type
 Optical detector
 Hall based detector

1
...
They are used for surface demarcation and level measurement
...


Working principle:
The principle behind magnetic, magnetoresistive or mechanical and other float level sensors
often involves the opening or closing of a mechanical switch, either through direct contact
with the switch, or magnetic operation of a reed
...

 With a mechanically actuated float, switching occurs as a result of the movement of
a float against a miniature (micro) switch
...
As the float moves up the motion and location are transmitted as the angular
position of the magnetic field
...

Ease of mounting
...

Simplified process takeoffs with minimized connections
...






Unsuitable for dirty applications and processes where magnetite may be produced
...

Suitable only for liquids
...

Accuracy: from 0
...

Drinking water, aggressive liquids, hazardous environments as well as other liquids,
such as clear, clean liquids, wastewater, mud, oil, diesel, etc
...
globalspec
...
engineersgarage
...
sensorsmag
...
iceweb
...
au/Technical/FloatMeasurement
...
com/float-level-measurement/,

2
...


Advantages and limitations:
Advantages:





Magnetostriction is a proven technology for very precisely reading
...

There is the only moving part is the float that rides up and down with the fluid's
surface
...

Their price is relatively high
...

Accuracy:

Key applications:




foam or mist situations
ideal for use in waste and water treatment after initial filtering has occurred
...




In areas where accuracy, reliability and repeatability
magnetostrictive sensors present the far superior technology
...
pollutionequipmentnews
...
sensorsmag
...
com/product/magnetostrictive-level-transmitters/
https://www
...
net/publication/240600701_Overview_of_Magnetostrictive_Sensor_Technol
ogy

3
...


Working principle:
Ultrasonic
level
sensors
measure
distance
by
using
ultrasonic
waves
...
ultrasonic / level sensors measure the distance to the target by measuring the time
between the emission and reception
...
(The value is multiplied by 1/2 because T is the time for go-and-return
distance)

Advantages and limitations:
Advantages:
The ultrasonic level measurement is suitable for measurement in liquid and solid
...

even abrasive or aggressive materials can be measured
They can be used as single point level sensor or continuous level sensors
It does not require contact with processed material
...

It has high accuracy
...


o
o
o
o
o
o
o
o

Limitations:
The ultrasonic level measurement is comparatively expensive
...

If heavy foam is present on the surface it acts as an absorbent which creates errors
...


o
o
o
o

Characteristics:





Operating temperature: -31° to 140°F (-35° to 60°C)
Operating pressure: 30 PSI (2 bar) max
...
8 ft (20 cm to 10m)
Accuracy: 2mm to 4mm
...

Not suitable for liquids containing thick foam
...


More at: https://www
...
com/uses-and-applications-of-ultrasonic-level-sensors/
https://cdn
...
com/static/specs/ultrasoniclltluseries
...
polytechnichub
...
com/ultrasonic-level-transmitter/
https://www
...
com/components/a-dozen-ways-to-measure-fluid-level-and-how-they-work

4
...


Working principle:
Radar level measurement is also based on the principle of measurement of the time elapsed
between the transmission of a microwave pulse and the reception of the reflected echo
...







They can be used as single point level sensor or continuous level sensors
Present a high-accuracy with no contact with the process fluid
...

Detect obstructions in chutes or presses
...

They are very expensive, price increases with accuracy
...

Microwaves will penetrate temperature and vapor layers that may cause problems for other techniques,
such as ultrasonic detectors
...

Accuracy: 3 mm (0
...

Range: 0
...
5 m (1 to 15') application dependant

More at: https://www
...
com/pptst/LVU30
...
engineersgarage
...
instrumentationtoolbox
...
html
https://www
...
com/en/company/technology/radar-level-measurement
https://www
...
com/components/a-dozen-ways-to-measure-fluid-level-and-how-they-work

5
...


Working principle:
Optical level sensors consist of two main parts: an infrared LED coupled with a light transistor, and a
transparent prism tip in the front
...
When the sensor is immersed in liquid,
the light disperses throughout and less is returned to the transistor
...

Advantages and limitations:
Advantages:





They have a compact size,
They are extremely accurate for point level detection in high-stress environments
They lack of moving parts,
Their cost is low
...

Optical level sensors are unsuited for applications where top mounting is necessary
...


Characteristics:





Operating temperature: 40 to 110•°C
Operating pressure: (0 to 17 bar) maximum
Accuracy( Repeatability): ±1 mm
Range: 0
...
5 m (1 to 15') application dependent

Key applications:


They are commonly used in applications like leak detection and tank level measurement

More at: https://www
...
com/different-types-level-sensors-applications/
https://www
...
com/blog/how-do-optical-level-sensors-work/
https://www
...
com/articles/what-is-level-sensor

6
...


Working principle:
This sensor comprises of two concentric tubes immersed in the fluid whose level is to be
measured
...
This capacitance becomes the
function of the fluid level
...

It can detect through containers of certain types also
...

It can detect dense targets and liquids
...

It has very good resolution (as low as 0
...


Limitations:




It is very much sensitive to changes in environmental conditions such as temperature, humidity
...

Can only be used in certain liquids, May require calibration
...

Accuracy: less than 1mm
...


Key applications:
They are commonly used in applications like Tank level monitoring in chemical, water treatment,
food, battery industries and involving high pressure and temperature
...
elprocus
...
rfwireless-world
...
html
https://www
...
com/articles/what-is-level-sensor
https://www
...
com/components/a-dozen-ways-to-measure-fluid-level-and-how-they-work
https://instrumentationtools
...
Air bubbler level detector
Working principle:
An air bubbler system uses a tube with an opening below the surface of the liquid level
...
Pressure in the tube is proportional to the depth (and
density) of the liquid over the outlet of the tube
...

They are very cost effective
...

They cannot be used as point level detectors
...

They are not considered appropriate for use in non-vented vessels
...

They don’t provide much accurate results for level measurement in case of corrosive or
slurry-type applications
...

Accuracy: +- 1-2%
...

Suitable for cooling tower sumps, swimming pools, reservoirs, vented fuel tanks, drain
sumps, air washers
...
com/index
...
instrumentationtoolbox
...
html
https://instrumentationtools
...
hydrostatic level sensor
Working principle:
A hydrostatic level sensor is a submersible pressure transmitter that has a pressure diaphragm
where the inner side of the diaphragm is vented to atmospheric pressure through a vent tube in
the cable and the outer side is in contact with the liquid and measuring the static pressure of the
liquid column above the transmitter
...


Advantages and limitations:
Advantages:






Its simple use and reliable and accurate measurement
It has no moving parts
...

Able to deal with a wide variety of fluids
...

Not suitable for pressurized vessels
...
25m or more
Continuous allowable pressure: 196 kPa (2kgf/cm2)
Momentary allowable pressure 294 kPa (3kgf/cm2)

Key applications:
The hydrostatic level sensor is a specialised sensor for level monitoring, most commonly used
in the water and waste water industry
...

More at: https://en
...
com/newscontentgeneric_ms
...
ydic
...
jp/english/level_meter/pl_E
...
vega
...
iii
...
au/tools/reference/Level%20-%20Hydrostatic
...
Hall based level detector:
Working principle:

A linear Hall sensor is placed at the centre of diametrally magnetised ring magnet, surrounded
by the soft iron magnet to guide the flux
...
Thus as the ring moves with the lever, the component of magnetic field
measured by the Hall Sensor varies
...


Advantages and limitations:
Advantages:




They are highly reliable
...

Offer high speed operation
...




High Temperature affects the conductor resistance
...

Characteristrics:




Level measurement range: from 10mm up to 30 m
...
5 to 5%
Operating temperature: -35 to 60°C(-31 to 140°F)
...

More at: https://www
...
com/articles/what-is-level-sensor
https://www
...
com/dgdl/AppNote_Liquid_Level_Sensing_Rev
...
0
...
com/hall-effect-sensors-work-types-applications-advantagesdisadvantages/



---