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Internship Report

Dated 06/08/2012-to-25/09/2012

Submitted By:

Muhammad Arshad

Reg.no. 10ES-155

Department Of Electronics Engineering.

University College Of Engineering & Technology (IUB)

Bahawalpur.

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ACKNOWLEDGEME

In the Name of Allah, the Most Gracious, the Most Merciful.

I am very thankful to Almighty ALLAH who gave me power and ambitious mind

to make this report possible. With Allah’s will and mercy I have been able to

achieve all of this. As is the case in most human productions, this thesis was the

result of the collective efforts of a number of important and valued people who

directly or indirectly supported me during my doctoral studies. To these people, I

owe my gratitude and thanks.

I wish to express my sincere appreciation and gratitude to my Senior Engineers

Mr.Amjad, Mr.Imran & Mr.Irfan. Thank you for your guidance, encouragement,

and support. I have appreciated your patience, input, and positive criticism and

comments throughout the development of this study. I should also like to thank the

Management of KAPCO for giving me the chance to do work with them.

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ABSTRACT

The report is about my internship tenure which made me learn the basics of

Instrumentation and control system of a combined cycle power plant. The Power

Plant comprises of 10 multi fuel (HSD, BFO &Gas) fired gas turbines and 5 steam

turbines. These turbines are divided into 3 energy Blocks with each Block having a

combination of gas and steam turbines. The Power Plant's combined cycle

technology enables KAPCO to use the waste heat from the gas turbine exhaust to

produce steam in the Heat Recovery Steam Generator, which in turn is used to run

the steam turbines thereby resulting in fuel cost efficiency and minimum wastage.

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Table of Contents:

1) ACKNOWLEDGEME…………………………………………………………….2 2) ABSTRACT………………………………………………………………………………………………….3 3) Table of contents………………………………………………………………………………………...4 4) Over View Of The Power Plant……………………………………………………………………..5 5) Kot Addu Power Company Limited (KAPCO)……………………………..6 6) Inside KAPCO……………………………………………………………………………………………….7 7) GAS TURBINE POWER STATION (1-4)…………………………………………………………..9 8) TREATMENT OF FURNACE OIL……………………………………………………………………10 9) FORWARDING SKID…………………………………………………………………………………….11 10) Combine Cycle…………………………………………………………………………………………….12 11) Gas Turbine…………………………………………………………………………………………………13 12) Steam Turbine……………………………………………………………………………………………..14 13) Boiler (HRSG)……………………………………………………………………………………………..16 14) INSTRUMENTATION AND CONTROL…………………………………………………………….17 15) Process Control Loop…………………………………………………………………………………...18 16) The Element Used In The Process Control Loop…………………………………………….19 17) Controller…………………………………………………………………………………………………….20 18) Sensors ……………………………………………………………………………………………………………….21 19) Temperature Sensor…………………………………………………………………………………….21 20) Pressure Sensor…………………………………………………………………………………………...24 21) Flow Sensor………………………………………………………………………………………………...28 22) Level Sensor…………………………………………………………………………………………………31

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Over View of The Power Plant:

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Kot Addu Power Company Limited (KAPCO)

Introduction: Kot Addu Power Plant (the "Power Plant") was built by the

Pakistan Water and Power Development Authority ("WAPDA") in five phases between

1985 and 1996 at its present location in Kot Addu, District Muzaffargarh, Punjab ,Pakistan.

KAPCO is Pakistan's largest Independent Power Producer (IPP) with a name plate capacity

of 1600 MW. . In April 1996, Kot Addu Power Company Limited ("KAPCO") was

incorporated as a public limited company under the Companies Ordinance, 1984 with the

objective of acquiring the Power Plant from WAPDA. The principal activities of KAPCO

include the ownership, operation and maintenance of the Power Plant.

In KAPCO three type of fuel are used in the gas turbine to produce electricity these

three are Natural gas, Low Sculpture Furnace Oil and High Speed Diesel. The Power Plant is

also the only major plant in Pakistan with the ability to self-start in case of a country wide

blackout.

On June 27, 1996, following international competitive bidding by the Privatization

Commission Government of Pakistan (the "Privatization Commission"), the management of

KAPCO was transferred to National Power (now International Power) of the United

Kingdom, which acting through its subsidiary National Power Kot Addu Limited (NPKAL),

bought shares representing a 26% stake in KAPCO. Later, NPKAL bought a further 10%

shareholding in KAPCO increasing its total shareholding to 36%.The other majority

shareholder in KAPCO is WAPDA with a present shareholding of 46%.

Following the successful completion of the offer for sale by the Privatization

Commission (on behalf of WAPDA) in February 2005, 20% of KAPCO’s shareholding is now

held by the General Public. On April 18, 2005 KAPCO was formally listed on all three Stock

Exchanges of Pakistan.

The Power Plant is situated in District Muzaffargarh, Punjab, 90 K.M. north west of

Multan on the left bank of the River Indus at a distance of 16 K.M. from Taunsa Barrage.

The area is surrounded by agricultural land on the north and west side of Kot Addu.

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Inside KAPCO:

General information of the power plant

Gas Turbines 10

HRSGs 10

Steam Turbines 5

Installed Capacity 1600MW

Max. Load Generation 1541MW

Load According to IDC Test (1996) 1345MW

Load According to ADC Test (2010) 1355MW

No. of Feeders 6 x132KV; 6 x220KV

Max. Generation in one day 35,667Mwh

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GAS TURBINE POWER STATION (1-4)

Three different type of fuels used in KAPCO .These are given below.

1) Natural Gas.

2) High Speed Diesel (HSD)

3) Blended Furnace Oil (BFO)

KAPCO use natural gas which is given by the pipe lines and for the HSD and the BFO

storage it has Storage Tanks.

Tanks:

There are total 27 tanks for the storage of BFO and HSD. 5 tanks are used for the

storage of HSD. The numbering of these are 4, 5, 6, 11&20. HEH keep ambient

temperature.

Other 22 tanks are use for the storage of BFO. The viscosity of the BFO is too much high

to decrease the viscosity of the BFO special type of electric heater is used in the BFO

tanks. If we will not use this electric heater the viscosity of the BFO is increased and this

oil can freeze in the pipe lines. BFO is not in pure form so before using the BFO some

type of treatment taken place on BFO.

The distribution of the Tanks is as follow,

1) For untreated Oil , 11 Tanks

2) For treated Oil , 11 Tanks

3) For HSD ,5 Tanks

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TREATMENT OF FURNACE OIL:

Treatment of LSFO is quite necessary before it can be used in the combustion

chambers because it may contain a no. of impurities in the form of water soluble salts, oil

soluble salts and compounds, and suspended particles. These impurities can cause a

considerable damage to combustion chambers, Turbine blades and other necessary

equipment that are very expensive and these impurities thus lower the overall efficiency

and increase the maintenance costs. Generally these impurities are classified in three types:

1) Water Soluble ( Na, K and other 2nd group elements)

2) Oil Soluble (Pb, Ni, Co, V etc.)

3) Suspended particles and dust particles

Now there are different methods to remove these impurities. We first discuss the method

to remove water soluble impurities as follows:

There are two methods to remove water soluble impurities from raw FO:

Electrostatic Method

Centrifugal Method

There are five FUEL OIL TREATMENT PLANTS (FOTPs) at KAPCO for the treatment of

Furnace Oil. FOTPs nos. 1, 2, 3 and 4 are for Electrostatic Method and FOTP no. 5 is for

Centrifugal Method. KAPCO is the only company that has the facility of removing water

soluble impurities through Centrifugal method. Centrifugal Method is so far the most

efficient method for the purpose.

Electrostatic Method :

In an electrostatic method basically the salts are ionized and made to collect at their

respective electrodes. A large drum is used for this purpose in which there are Cathode and

Anode. Untreated FO is mixed with water in the drum at a specific temperature. The water

soluble salts get mixed with water and +ve and –ve ions are formed. For example in case of

NaCl two ions are formed i.e. Na+ & Cl−. When electrodes are connected to power supply of

high voltage, these ions move to their respective electrode. Thus these salts are thus

removed from the electrodes later on.

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Now a chemical called DEMULSIFIER is added into the oil water mixture. The function of

Demulsified is to make the oil droplets separate from water droplets. It makes water

droplets larger in terms of its diameter due to which its surface area increases and due to

gravity water droplets settle down and drained to effluent water tanks. This water is called

EFFULANT WATER. Thus this treated Oil is obtained and pumped to treated oil tanks.

Centrifugal Method:

In centrifugal Method, water is first added in Oil in the same way as before. Water

soluble salts get dissolved in water and are separated from Untreated Oil. This water containing

salts is removed from oil by centrifugal action. The water Oil mixture is rotated at a very large

speed in a large drum. The centrifugal force pushes the heavier fluid i.e. water containing salts in

it towards outer radial direction and oil gets deposited in the center and drained to Treated oil

tanks.

FORWARDING SKID

Booster pumps carry FO from treated tanks or from FOTP to Forwarding skid at

pressure of 3 bars. Pumps to maintain pressure of 6.5 to 7 bar. Nitrogen

Accumulator to bear the pressure jerks while changing the pump. Pumps to carry FO

from Forwarding Skid to Filtration Skid.

FILTERATION SKID

Dosing of KI200 (with 25% Mg.) to FO to eliminate vanadium effect. Plate type Heat

Exchanger to recover heat of fuel coming back from GT (Excess fuel).

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Combine Cycle:

In a combined cycle power plant (CCPP), or combined cycle gas turbine (CCGT) plant, a gas

turbine generator generates electricity and the waste heat is used to make steam to

generate additional electricity via a steam turbine; this last step enhances the efficiency of

electricity generation. Most new gas power plants in North America and Europe are of this

type. In a thermal power plant, high-temperature heat as input to the power plant, usually

from burning of fuel, is converted to electricity as one of the outputs and low-temperature

heat as another output. As a rule, in order to achieve high efficiency, the temperature

difference between the input and output heat levels should be as high as possible. This is

achieved by combining the Rankin (steam) and Braxton (gas) thermodynamic cycles. Such

an arrangement used for marine propulsion is called combined gas (turbine) and steam

(turbine) (COGAS).

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Gas Turbine:

Now first we discuss gas turbine of the combine cycle. In an open cycle gas turbine, air and fuel follow several types of thermodynamic cycles. The simplest gas turbine cycle consists of Compression of air, burning the fuel, Expansion of flue gases etc.

The gas turbine unit consists of the following main components: The name of main components and the working principle are given below.

Starting motor

Intake air filters

Compressor

Combustion chamber

Turbine

Generator

Starting Motor:

A starting motor is an Asynchronous motor; it used to start the machine. This motor is designed at 6.6 KV and it takes 1MW power. In starting it take power from the unit (1-4) common bus bar or black start diesel engine bus bar (COBDA). After that when this machine is able to produce power. Then automatically change its own power. Approximately at 1900 rpm it becomes cut off from the system. Because at this time burnt gases become able to rotate itself to the machine.

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Steam Turbine:

Main components of a steam Turbine are:

1. Boiler(HRSG)

2. Turbine

3. Condenser

4. Pump

A steam turbine is a prime mover which continuously converts energy of high pressure, high temperature steam supplied by the steam generator in to the shaft work with the low temperature steam exhausted to a condenser. The energy conversion essentially occurs into steps:

1. The high pressure high temperature steam first expands in nozzles and comes out at high velocity 2. The high velocity jets of steam coming out of the nozzles, impinge on the blades mounted on a wheel, get deflected an angle and suffer a loss of momentum which is absorbed by the rotating wheel in producing torques.

Steam turbine power plants operate on a Rankin cycle. The steam is created by a boiler, where pure water passes through a series of tubes to capture heat from the firebox and then boils under high pressure to become superheated steam. The heat in the firebox is normally provided by burning fossil fuel (e.g. coal, fuel oil or natural gas). However, the heat can also be provided by biomass, solar energy or nuclear fuel. The suprerheated steam leaving the boiler then enters the steam turbine throttle, where it powers the turbine and connected generator to make electricity. After the steam expands through the turbine, it exits the back end of the turbine, where it is cooled and condensed back to water in the surface condenser. This condensate is then returned to the boiler through high-pressure feed pumps for reuse. Heat from the condensing steam is normally rejected from the condenser to a body of water, such as a river or cooling tower.

Steam turbine plants generally have a history of achieving up to 95% availability and

can operate for more than a year between shutdowns for maintenance and inspections.

Their unplanned or forced outage rates are typically less than 2% or less than one week

per year.

Modern large steam turbine plants (over 500 MW) have efficiencies approaching 40-

45%. These plants have installed costs between $800 and$2000/kW, depending on

environmental permitting requirement

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Boiler (HRSG)

The exhaust gases of a gas turbine are at a high temperature and such hot gases are

utilized in Heat Recovery Steam Generator (HRSG). The efficiency of HRSG is relatively

higher than conventional boilers i.e. 40% to 45 % whereas the efficiency of

conventional boilers is about 35 % and that of Burners Boiler is 32% to 40 %.

The HRSG has the capacity of about 200 tons of steam production in it. There are

different stages of a HRSG. There are generally four stages:

1. LP Evaporator

2. HP Economizer

3. HP Evaporator

4. Super Heater

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INSTRUMENTATION AND CONTROL: Process control is the automatic control of an output variable by sensing the amplitude of the output parameter from the process and comparing it to the desired or set level and feeding an error signal back to control an input variable. Instrumentation is the base of the process control in industry .However it comes in many forms from domestic water heaters and HVAC, where the variable temperature is measured and used to control gas, oil, or electricity flow to the water heater, or heating system, or electricity to the compressor for refrigeration, to complex industrial process control applications such as used in the petroleum or chemical industry.

Importance The instrumentation and control (I&C) systems of power plant (PP) have

three major roles. Firstly, they are the ‘eyes and ears’ of the operator. If properly planned, designed, constructed and maintained, they provide accurate and appropriate information and permit judicious action during both normal and abnormal operation. They are therefore, with the human operator, vital for the safe and efficient operation of the plant.

Secondly, under normal operating conditions they provide automatic control, both of the main plant and of many ancillary systems. This allows the operator time to observe plant behavior and monitor what is happening so that the right corrective action can be taken quickly, if required. Thirdly, the I&C safety systems protect the plant from the consequences of any mistakes which the operator or the automatic control system may make. Under abnormal conditions they provide rapid automatic action to protect both the plant and the environment. The I&C requirements of an PP are, in most cases, more complex and diverse than those of a conventional power plant

Process Control Loop:

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The Element Used In The Process Control Loop The following are used in the process control loop.

Feedback loop is the signal path from the output back to the input to correct for any variation between the output level from the set level. In other words, the output of a process is being continually monitored, the error between the set point and the output parameter is determined, and a correction signal is then sent back to one of the process inputs to correct for changes in the measured output parameter.

Controlled or measured variable is the monitored output variable from a process. The value of the monitored output parameter is normally held within tight given limits.

Manipulated variable is the input variable or parameter to a process that is varied by a control signal from the processor to an actuator. By changing the input variable the value of the measured variable can be controlled.

Set point is the desired value of the output parameter or variable being monitored by a sensor. Any deviation from this value will generate an error signal.

Instrument is the name of any of the various device types for indicating or Measuring physical quantities or conditions, performance, position, direction and the like.

Sensors are devices that can detect physical variables, such as temperature, light intensity, or motion, and have the ability to give a measurable output that varies in relation to the amplitude of the physical variable.

Transducers are devices that can change one form of energy to another, e.g., a resistance thermometer converts temperature into electrical resistance, or a thermocouple converts temperature into voltage. Converters are devices that are used to change the format of a signal without changing the energy form, i.e., a change from a voltage to a current signal.

Actuators are devices that are used to control an input variable in response to a signal from a controller. Atypical actuator will be a flow-control valve that can control the rate of flow of a fluid in proportion to the amplitude of an electrical signal from the controller. Other types of actuators are magnetic relays that turn electrical power on and off. Examples are actuators that control power to the fans and compressor in an air-conditioning system in response to signals from the room temperature sensors

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Controller Controller are devices that monitor signals from transducers and take the necessary action to keep the process within specified limits according to a predefined program by activating and controlling the necessary actuators.

Programmable logic controllers (PLC) are used in process-control applications, and microprocessor-based systems. Small systems have the ability to monitor several variables and control several actuators, with the capability of being expanded to monitor 60 or 70 variables and control a corresponding number of actuators, as may be required in a petrochemical refinery. PLCs, which have the ability to use analog or digital input information and output analog or digital control signals, can communicate globally with other controllers, are easily programmed on line or off line, and supply an unprecedented amount of data and information to the operator. Ladder networks are normally used to program the controllers. An error signal is the difference between the set point and the amplitude of the measured variable. A correction signal is the signal used to control power to the actuator to set the level of the input variable. Transmitters are devices used to amplify and format signals so that they are suitable for transmission over long distances with zero or minimal loss of information. The transmitted signal can be in one of the several formats, i.e., pneumatic, digital, analog voltage, analog current, or as a radio frequency (RF) modulated signal. Digital transmission is preferred in newer systems because the controller is a digital system, and as analog signals can be accurately digitized, digital signals can be transmitted without loss of information. The controller compares the amplitude of the signal from the sensor to a predetermined set point.

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Sensors Sensors are devices that can detect physical variables, such as temperature, light intensity, or motion, and have the ability to give a measurable output that varies in relation to the amplitude of the physical variable. In industry major four type of sensors are used,

1) Temperature Sensor 2) Pressure Sensor 3) Flow Sensor 4) Level Sensor

Now we discuss these four types of sensors.

Temperature Sensor: Name of the different temperature sensors are

Resistance temperature detectors (RTD) Thermistor NTC and PTC Thermocouples Pyrometers

RTD (Resistance Temperature Detector)

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Thermocouple: Thermocouples (T/C) are formed when two dissimilar metals are joined together to form a junction. Joining together the other ends of the dissimilar metals to form a second junction completes an electrical circuit. A current will flow in the circuit if the two junctions are at different temperatures. The voltage difference between the two junctions is measured, and this difference is proportional to the temperature difference between the two junctions.

Resistance Temperature Detector: RTD’s are built from selected metals (typically Platinum), which change resistance with temperature change. The resistance temperature detector (RTD) measures the electrical conductivity as it varies with temperature. The electrical resistance generally increases with temperature, and the device is defined as having a positive temperature coefficient. The magnitude of the temperature coefficient determines the sensitivity of the RTD. Apart from Platinum, other metals are used for RTD’s such as Copper and Nickel. Platinum is the most common and has the best linear characteristics of the three, although Nickel has a higher temperature coefficient giving it greater sensitivity.

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Thermistors:

A thermistor is a semiconductor device formed from metal oxides. The principle of temperature measurement with a thermistor is that its resistance changes with temperature. Most thermistors differ from normal resistors in that they have a negative coefficient of resistance, this means that the resistance decreases with an increase in temperature. Negative (NTC) thermistors are the more common although positive(PTC)

are also available.

Pyrometer: Pyrometric methods of temperature measurement use the electromagnetic radiation that is emitted from a material. The emitted radiation is proportional to the temperature. Any object with a temperature above absolute zero will radiate electromagnetic energy. Infrared pyrometers measure the amount of energy radiated from an object in order to determine its temperature. There are a number of different types of infrared pyrometers:

1)-Total radiation

2)-Single wavelength

3)-Dual wavelength

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Pressure Sensor Pressure is defined as a force per unit area, and can be measured in units such as psi (pounds per square inch), inches of water, and milli meters of mercury, Pascal (Pa, or N/m²) or bar. Until the introduction of SI units, the 'bar' was quite common. Pressure= Force/Area Pressure Transducers and Elements

Bourdon tube Helix and spiral tubes Spring and bellows Diaphragm Manometer Single and Double inverted bell Piezoelectric

Bourdon Tube The Bourdon tube works on a simple principle that a bent tube will change its shape when exposed to variations of internal and external pressure. As pressure is applied internally, the tube straightens and returns to its original form when the pressure is released.

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Helix and spiral tubes are fabricated from tubing into shapes as per their naming. With one end sealed, the pressure exerted on the tube causes the tube to straighten out. The

amount of straightening or uncoiling is determined by the pressure applied.

Manometer Manometers are good examples of pressure measuring instruments. U-tube manometers consist of “U” shaped glass tubes partially filled with a liquid. When there are equal pressures on both sides, the liquid levels will correspond to the zero point on a scale.

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Piezoelectric When pressure is applied to crystals, they are elastically deformed. Piezoelectric pressure sensing involves the measurement of such deformation. When a crystal is deformed, an electric charge is generated for only a few seconds. The electrical signal is proportional to the applied force. Quartz is commonly used as the sensing crystal as it is inexpensive, stable and insensitive to temperature variations. Tourmaline is an alternative which gives faster response speeds, typically in the order of microseconds

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Flow Sensors Basic concept

Velocity: This is the speed at which the fluid passes a point along the pipe. The velocity is used to calculate volume and mass flow rates.

Volumetric flow rate: The volumetric flow rate represents that volume of fluid which passes through a pipe per unit of time. This form of measurement is most frequently achieved by measuring the velocity of a fluid with a DP sensor as it travels through a pipe of known cross sectional area.

Mass flow rates: Mass flow is a measure of the actual amount of mass of the fluid that passes some point per unit time. Different sensors are used to measure the flow of the fluid.

Orifice Plate Venturi Tube Pitot Tube Rota meter Annubar Tube Turbine meter Magnetic Flow meter

Orifice Plate A standard orifice plate is simply a smooth disc with a round, sharp-edged inflow aperture and mounting rings. In the case of viscous liquids, the upstream edge of the bore can be rounded. The shape of the opening and its location do vary widely, and this is dependent on the material being measured. Standard orifice meters are primarily used to measure gas and vapor flow. Measurement is relatively accurate.

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Venturi Tube A number of obstruction devices are available that are specially designed to minimize the pressure loss in the measured fluid. These have various names such as Venturi, flow nozzle and Dallflow tube. The Venturi Tube is often selected because pressure drop is not as significant as with the orifice plate and accuracy is better maintained.

Pitot tube: The Pitot tube measures flow based on differential pressure and is primarily used with gas flows. The Pitot tube is a small tube that is directed into the flow stream. Pitot tubes have the advantage that they cause negligible pressure loss in the flow. They are also cheap, and the installation procedure consists of the very simple process of pushing them down a small hole drilled in the flow-carrying pipe.

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Turbine Meter A turbine flow meter consists of a multi-bladed wheel mounted in a pipe along an axis parallel to the direction of fluid flow in the pipe. The flow of fluid past the wheel causes it to rotate at a rate that is proportional to the volume flow rate of the fluid. As an important application of the turbine meter is in the petrochemical industries, where gas/oil mixtures are common.

Magnetic Flow meter Electromagnetic flow meters, also known as magmeters, use Faradays’ law of electromagnetic induction to sense the velocity of fluid flow. Faradays law states that moving a conductive material at right angles through a magnetic field induces a voltage proportional to the velocity of the conductive material. The conductive material in the case of a magmeter is the conductive fluid. The advantages of magnetic flow meters are that they have no obstructions or restrictions to flow, and therefore no pressure drop and no moving parts to wear out.

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Level Sensors

Level sensing devices can be divided into four categories

Direct sensing, in which the actual level is monitored

Indirect sensing, in which a property of the liquid, such as pressure, is sensed to determine the liquid level

Single point measurement, in which it is only necessary to detect the presence or absence of a liquid at a specific level. Different types of sensors are used in Level measurement.

Float Sensor Displacer Switches Conductive Probes Capacitive Probes Ultrasonic Level Sensor Radar measurements

Float Sensors There are two types of floats shown: the angular arm and the pulley .The advantages of the float sensor are that they are almost independent of the density of the liquid or solid being monitored, are accurate and robust, and have a linear output with level height. One of the significant types of float is a magnetrolfloat level switch which consists a

plain float and operates via a magnetic coupling action.

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Conductive Probes Conductive probes are used in single and multiple point measurements systems. Low voltages are applied to the electrodes as they are immersed in the liquids. The conductive liquid completes the electrical circuit of the control, which activates a semiconductor switch. The advantage of conductive probes is their low cost and simple design. The disadvantage is that they are limited to point measurement and can be only used with conductive liquids.

Capacitive Probes They are used for continues measurements. The value of the capacitance can be change by varying the dielectric. The probe and the metal wall of the tank form the two plates of a capacitor, and the contents in the tank are the dielectric. When the tank is empty the dielectric is the air. As the level changes the dielectric constant changes and causes the capacitance change.

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Ultrasonic Level Sensors Ultrasonic or sonic devices can be used for single point or continuous level measurement of a liquid or a solid. A pulse of sonic waves (approximately 10 kHz) or ultrasonic waves (more than 20 kHz) from the transmitter is reflected from the surface of the liquid to the receiver, and the time for the echo to reach the receiver is measured. The time delay gives the distance from the transmitter and receiver to the surface of the liquid, from which the liquid level can be calculated, knowing the velocity of ultrasonic waves (approximately 340 m/s).

Radar Measurement Radar gauges differ from ultrasonic in that they use microwaves instead of sound waves. Like ultrasonic devices they measure from the top of the vessel to determine the product level. Two examples of radar gauges are the 5.8GHz and 24GHz systems. The higher transmission frequency can be used to detect dry, non-conductive materials with very low bulk density.

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