Control and Instrumentation - Copy

8/12/2019 Control and Instrumentation - Copy

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Brief about company NPCIL a government-owned corporation of India based in Mumbai.One of the public sector undertakings, it is wholly owned by the Union

Government and is for the generation of nuclear power for electricity.

NPCIL is administered by the Department of Atomic Energy (DAE).

NPCIL was created in September 1987 as public limited company. The company has 21 nuclear reactors in operation at seven locations, a

total installed capacity of 5780 Mwe.

India's first research nuclear reactor with assistance from Canada. The

40 MW CIRUS achieved first criticality in 1960. The agreement for India's first nuclear power plant at Rajasthan,

RAPP-1, was signed in 1963, followed by RAPP-2 in 1966..

The 200 MW RAPP-1 reactor was based on the CANDU reactor

at Douglas Point and began operation in 1972.



PRINCIPLE OF NPCILFISSION REACTION

Fission is the splitting of a nucleus into two or more separate nuclei of comparable mass

One neutron interacts with one “fissionable” nucleus (Uranium for example)

Results are:

Fission Products – Two heavy nuclides

One heavier than the other (Average ratio of ~ 2 : 3 )

It is based on the EINSTEIN EQUATION:

E=MC^2

One fission reaction can lead to more fission reactions in a process called a chain reaction.

CHAIN REACTION OF URANIUM -235



FUSION REACTION The combining of atomic nuclei to form a larger atom

is called fusion.

Nuclear fusion occurs in the sun where hydrogen

atoms fuse to form helium

4 H + 2 0 e- He + energy

Fusion reactions also release very large amount of

energy but require extremely high temperatures to

start.



COMPLETE LAYOUT OF NPCIL



Can the atomic reactor explode like an atom bomb?

Atomic bomb uses 100% U235 or Pu239, whereas in the reactors

either it is natural uranium or enriched uranium of 1.5% to 4.5%

enrichment. The effort in the bomb is to generate maximum

energy in the smallest possible time there by resulting in the

explosion, whereas in the reactor the effort is to generate rated

power on a continuing basis. So, various controls are put to ensure

that the power generated is within its capacity at all the times.Thus, design of Nuclear reactor does not permit such explosions.



CONTROL&INSTRUMENTATION

The term control and instrumentation is used as collective term to

encompass all instruments, equipment, systems and special

features intended to monitor, control and promise protection for

the nuclear power plant. These are broadly categorized as

follows:

INFORMATIONSYSTEM

CONTROLSYSTEM

PROTECTIONSYSTEM



• Monitoring of plant parameters

• Display and annunciate the status of plant parameter at all states of the plant.

• Storage of selected data for review andanalysis

INFORMATION

SYSTEM

• Maintains plant parameters with

specified limits of operational states orinitiate change in plant parameters inorder to return to parameter withinspecified limits.

CONTROLSYSTEM

• Detects departure from acceptable plantconditions and issues command to maintainthe plant within safety limits.

• This system over rides information andcontrol systems fail to maintain plant parameters within acceptable values.

PROTECTIONSYSTEM



Main parts ofcontrol room

PLC DCS



PLC(programmable Logic Controller)

•A programmable logic controller (PLC) is a special purpose computer

aimed at implementing control solutions.

•

Historically PLC’s have been used mainly for on-off or logic typeapplications. Modern PLC’s have become increasingly sophisticated

and can now cover quite complex control tasks.

•A PLC is simply an industrial computer designed to be durable

enough to withstand the rigors of industrial applications

•It is common in the mining industry to have PLC’s on large mobile

equipment to monitor and control everything from lights to largeelectrical drives.

The programming methods can be with Logic Ladder Diagram,

mnemonic (statement list), and / or function block diagram.

•The method is practical and easy to understand.•The programmer in charge of writing a program should describe an

electronic switch circuit.

•It can be designed to perform the conversion of electronic circuits

that already exist, and then replace the switch function according to

the functions available to software programmers.

Ladder Logic



Every PLC has associated programming software that allows the user to

enter a program into the PLC.

Software used today is Windows based, and can be run on any PC.

Different products may require different software: PLC5, SLC, and

Control Logix each require their own programming software.

Programming a PLC

Example of PLC programming software



Ladder Logic Instructions

few more ladder logic instructions:

OTL - Output Latch - turns on the output and keeps it even if the rung goes

false

OTU - Output Unlatch - turns off the output when the rung is true .

Timer On Delay - when the rung is true the timer will run. It will store the

elapsed time in the “Accum” field (accumulator). As long as the rung

remains true it will count until it reaches the preset value. If the preset value

is hit the DN bit will go on (Done bit). When the rung goes false the timer

will be reset.



Programming a PLC – Conveyor example

When a box is placed on the conveyor in front of Photoeye 1, Light1,and Motor 1 will turn on, causing the box to move down the

conveyor to the left. When the box passes in front of Photoeye 2,

Motor 1 and Light 1 will turn off, stopping the conveyor.



Here’s the program for the conveyor: The first line of code turns on

the motor and the light when a box is detected by photoeye1.

Likewise, the motor and light are turned off when photoeye2

detects the box in the second line of code



The third line begins a timer when the box passes by photoeye1,

and if the box does not pass by photoeye2 in 30 seconds (the

timer counts in milliseconds), the motor and light are shut off by

line 4. This is the indication of a jam condition



Most PLCs have the ability to communicate with other devices.

These devices include computers running programmingsoftware, or collecting data about the manufacturing process, a

terminal that lets an operator enter commands into the PLC, or

I/O that is located in a remote location from the PLC. The PLC

will communicate to the other devices through a network

interface.

Network Interface



PLC Control Panel



Instrumentation is defined as "the art and science of measurement and control".

Instrumentation also can refer to the available methods of measurement and control.

It include four type of measurements:

INSTRUMENTATION

Temperature

sensor

Pressuremeasurements

Flowmeasurement

Levelmeasurement



1. TEMPERATURE SENSORS:

There are 3 types of temperature sensors:

Thermistor

RTD(resistance temperature detector)Thermocouple

THERMISTORThermistors measure the change in resistance with temperature.

Thermistors are very sensitive (up to 100 times more than RTDs and 1000

times more than thermocouples) and can detect very small changes in

temperature. They are also very fast.

Due to their speed, they are used for precision temperature control and any

time very small temperature differences must be detected.

They are made of ceramic semiconductor material (metal oxides).

The change in thermistor resistance with temperature is very non-linear.



APPLICATION OF THERMISTOR

•PTC thermistors can be used as current-limiting devices for circuit protection, as fuses.•Current through the device causes a small amount of resistive heating

• NTC thermistors are used as resistance thermometers in low-temperature measurements of

the order of 10 K.

• NTC thermistors can be used as inrush-current limiting devices in power supply circuits.

THERMISTOR NONLINEARITY

•Standard thermistors curves are not provided as much as with

thermocouples or RTDs. We need a curve for a specific batch of

thermistors.

•Thermistors do not do well at high temperatures and show instability

with time (but for the best ones, this instability is only a few millikelvin

per year)

http://en.wikipedia.org/wiki/Fuse_(electrical)

http://en.wikipedia.org/wiki/Resistance_thermometer

http://en.wikipedia.org/wiki/Resistance_thermometer

http://en.wikipedia.org/wiki/Fuse_(electrical)



THERMOCOUPLE:

It is based on principle of “SEE BACK EFFECT”

•If two wires of dissimilar metals are joined at both ends and one end is heated,

current will flow.

•If the circuit is broken, there will be an open circuit voltage across the wires.Voltage is a function of temperature and metal types.

•For small ∆T’s, the relationship with temperature is linear

•For larger ∆T’s, non-linearities may occur.

V T



RTDs (Resistance Temperature Detectors)

•Resistivity of metals is a function of temperature.•Platinum often used since it can be used for a wide temperature

range and has excellent stability. Nickel or nickel alloys are used aswell, but they aren’t as accurate. •These RTDs are very small but aren’t as stable (and henceaccurate).RTDs are more accurate but also larger and more expensive than

thermocouples.RTD GEOMETRY



Working principle- when the temperature of the metal changes, their

resistance also changes and the change in resistance is alphato the change in temperature .this relationship is given by:-

Rt=Ro(1+at+b+….)

Where ,Rt= resistance at temperature to

t = changes in temperature

Ro=resistance at 0 degree

a,b,c=constants and depends upon alpha and ∆

∆=maximum non-linearity of changes in resistance from the

straight line.

a=α(1+∆) b =-(∆α)

if ∆ is zero then Rt is given by

Rt=Ro(1+αt)



RTD material and their ranges-

RTD material range

resistivity (Micro/cm)

Pt - 250°c to 900°c

9.83 Ni -150°c to 300°c 6.38

Cu -200°c to 120°c 1.56

Pt-200 is used

Pt is best metal for RTD’ s because it follows a very linear resistance

temperature relationship and it follows the R vs T relationship in highly

repeatable manner over a wide range of temperature range and used because of chemical inertness.





Temperature Sensor Installation and Laboratory Response Time Data

for a Slow and Fast RTD

Tim(sec)

NEW RESEARCH FOR TEMPERATURE MEASUREMENTS



2.Pressure measurement

•Pressure is the force exerted per unit area.

•. The pressure P of a force F distributed over an area A is defined as

P = F/A.•The units of measurement are either in pounds per square inch (PSI) in

British units or Pascals (Pa) in metric. As one PSI is approximately 7000Pa,

we often use kPa and MPa as units of pressure.

TOTAL VACUUM - 0 PSIA

PRESSURE

ABSOLUTE

GAUGE

COMPOUND

BAROMETRIC RANGE

ATMOSPHERIC PRESSURE

NOM. 14.7 PSIA



PRESSURE INSTRUMENT

Types of Pressure Instruments

Pressure Gauges (Vacuum, Compound, Absolute, Gauge)

Differential Pressure Gauge

Pressure Switch (Vacuum, Absolute, Gauge)

Differential Pressure Switch

Pressure Transmitter (Vacuum, Absolute, Gauge)

Differential Pressure Transmitter

PRESSURE

GAUGE PRESSURESWITCH

DIFFERENTIALP

RESSURE

TRANSMITTER



PRESSURE GAUGE

Measuring Principle

Bourdon tube measuring element is made of a thin-walled C-shape tube orspirally wound helical or coiled tube.

When pressure is applied to the measuring system through the pressure port

(socket), the pressure causes the Bourdon tube to straighten itself, thus causing

the tip to move.

The motion of the tip is transmitted via the link to the movement which converts

the linear motion of the bourdon tube to a rotational motion that in turn causes thepointer to indicate the measured pressure.

C” Type Bourdon

Helical Bourdon

Coiled Bourdon



•A Pressure Transmitter is used where indication and/or

record of pressure is required at a location not adjacent tothe primary element.

•A Pressure Transmitter is used for both indication and

control of a process.

•A Pressure Transmitter is used where overall highperformance is mandatory.

Pressure Transmitter



Sensing Line Connecting a Pressure Transmitter to the Process

NEW RESEARCH FOR PRESSURE MEASUREMENT



3.FLOW MEASUREMENT

Flow is measured as a quantity (either volume or mass) per unit timeVolumetric units

Liquid

G pm, bbl/day, m3/hr, liters/min, etc.Gas or Vaporft3/hr, m3/hr, etc.

Mass units (either liquid, gas or vapor)lb/hr, kg/hr, etc.

Flow can be measured in accumulated (totalized) total amounts for a timeperiod

gallons, liters, meters passed in a day

FLOWDETECTORS

•Velocity will vary directly with the flow and as the flow

increases a greater pressure differential will occur across

the restriction.

•To measure the rate of flow by the differential pressure

method, some form of restriction is placed in the pipeline

to create a pressure drop.



ORIFICE PLATE

A simple device, considered a precision instrument.

It is simply a piece of flat metal with a flow-restricting

bore that is inserted into the pipe between flanges.

The orifice meter is well understood, rugged and

inexpensive.

It’s accuracy under ideal conditions is in the range of

0.75-1.5%.

It can be sensitive to a variety of error-inducingconditions, such as if the plate is eroded Orifice Plate

are damaged.

Orifice Flanges Orifice Plate



VENTURI TUBE

In a Venturi tube, the fluid is accelerated through a converging cone, inducing a local

pressure drop.

An expanding section of the meter then returns the flow to near its original pressure.

These instruments are often selected where it is important not to create a significant

pressure drop and where good accuracy is required.

• Used when higher velocity and pressure recovery is required.

• May be used when a small, constant percentage of solids is present.



4.LEVEL MEASUREMENT

Accurate continuous measurement of volume of fluid in containers has

always been a challenge to industry. This is even more so in the nuclear station

environment where the fluid could be acidic/caustic or under very high pressure/temperature.

Level Measurement Basics

The pressure at the base of a vessel containing liquid is directly proportional

to the height of the liquid in the vessel. This is termed hydrostatic pressure. As

the level in the vessel rises, the pressure exerted by the liquid at the base of thevessel will increase linearly.

Mathematically, we have:

P = S·H

Where P = Pressure (Pa)

S = Weight density of the liquid (N/m3) = .g H = Height of liquid column (m)

ῤ. = Density (kg/m3)

g = acceleration due to gravity (9.81m/s2)

Th h d f l l



There are two methods for level measurements:

Direct method

In direct method

Direct method: Level is measured by direct contact with the fluid

surface. Either the fluid surface is visible to be compared directly

to a scale, or direct contact is made with the fluid surface.

Indirect method: Level is inferred by means other than direct

contact with the Fluid surface. Fluid level is inferred by its effect

on some type of device.

Sightglass

•It is quite straight forward method. In these the level in the glass

seek the same position as the level in the tank.

•It provides a continuous visual indication of liquid level in processvessel or small tank, more convenient than other direct method.

•This method for local indication, during the power failure ,

maintenance ,this method is used manually.

•The main disadvantage ;may be chance of breakage when hot,

corrosive& flammable liquid is handled.

B bbl M h d



Bubbler Method

“Bubbler systems are ideal for level measurement of open

channel run off systems or duct and tank situations where

debris, foam, steam, or surface turbulence makes standardmethods of level measurement impractical.”

This technique of level detection is employed for vessels

which work below atmospheric pressure.

This arrangement basically comprises of :A pipe i.e. a dip tube: It usually has its open end mounted in proximity to

the vessel base.

A purge gas: It is normally an air supply but an inert gas can also be used

specifically in areas which are susceptible to contamination or an oxidative

reaction with the medium. “As gas flows down to the dip tube's outlet, the

pressure in the tube rises until it overcomes the hydrostatic pressure

produced by the liquid level at the outlet. That pressure equals the process

fluid's density multiplied by its depth from the end of the dip tube to thesurface.”

A pressure transmitter or transducer: It is connected to the dip tube for

the purpose of monitoring the pressure.

A differential pressure regulator: It is mainly needed to create a constant

flow of gas necessary for avoiding variations in calibration.

http://automationwiki.com/index.php?title=Level_Measurement

http://automationwiki.com/index.php?title=Level_Measurement



Capacitance Method

•Capacitance is the property of circuit that stores electron & opposes a change

in the circuit.

•The value is determined by area of the conductor ,the distance between the

plates & the dielectric constant of the two insulators.

•Capacitance level measuring application, one plate is probe &while other is

tank level .The dielectric is material in the vessel which determines the

capacitance value when it rises or fall.

•The probes are mostly used for on/off application for alarm& switches&control function.

•This method is highly used in manufacturing & processing industries.



Control and Instrumentation - Copy

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