Training at HINDUSTAN ZINC, Chittorgarh

CHAPTER 1

INTRODUCTION

1.1 REQUIREMENT OF PRACTICAL TRANING:

Engineering profession is full of practical challenges as every engineer has to

confront various problems in his/her professional career. Therefore an engineer

must be aware of practical challenges right from the college level. Sometimes

it becomes essential to find the solutions to the problems practically, and then

comes the need to implement the theoretical knowledge gained during study

life into the practical environment.

This practical implementation not only requires thorough knowledge of

the subject but also the skill and real time decision making so that the task can

be performed with full efficiency and accuracy. This skill and decision making

power comes only when one should be aware of the live processing and

working of an industry, therefore every Engineer has to undergo a practical

summer internship in an organization so that he can practically visualize the

working, management, and various techniques of the industry and can simulate

on real machines and gadgets with his own hands.

Therefore Rajasthan Technical University, Kota has prescribed 30 days

practical summer training for every Engineer after the completion of the VIth

Semester to enhance one’s practical approach and also the application of the

theoretical knowledge.

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1.2 ROLE OF INDUSTRIAL AUTOMATION:

Life has become simpler and luxurious after the development of science and

engineering. Everything has become automatic and can be operated by just one

click or one press of a button. This has led to revolution in current scenario. It

has reduced labor and has increased efficiency and accuracy as the tasks

considered too difficult and impossible for human being can now be

accomplished with the help of automatic machines. This requires low

manpower and can save a lot time.

Automation in industries play a major role as everyday, the

requirements are increasing and accordingly the production needs to be

increased to earn maximum profits. Today every production industry rely on

heavy machinery which works automatically and saves both power and

money with least risk to human life. Thus automation is a necessary tool for

the increment in production as well as profit for an organization. Therefore it

is both essential and beneficial to learn the role of automation as it requires

core Electronics & Instrumentation along with Computer applications.

1.3 AUTOMATION AT HZL:

Hindustan Zinc Limited is a world renowned organization producing millions

of tons of Zinc (Zn) and Lead (Pb) every year. It requires a lot of sophisticated

machinery and equipments, costing millions of rupees to produce such a huge

amount of concentrate. Therefore skilled labor and proper conditioning is very

essential. Every task on this level cannot be performed by human being for

such huge quantities with proper accuracy and efficiency in the given time

slot, here comes the role of automation. Each equipment works automatically

under the prescribed measurements and norms with complete human

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supervision. Various sensors, transducers, motors, pumps run automatically

24x7 for zinc and lead production. The working of these equipments is

monitored by Programmable Logic control which fetches each and every

information of equipment connected in the stream. It visualizes the functioning

of the plant on a computer screen which is supervised by an Engineer.

Automation system comes under the supervision of Electronics and

Instrumentation department which is responsible for proper functioning of

Smelters. The company profile and training report is accommodated in

forthcoming chapters.

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CHAPTER 2

ORGANIZATION PROFILE

2.1 HISTORY:

Hindustan Zinc Limited, a Vedanta Group Organization the only integrated

Zinc manufacturer in India and is the world`s second largest and India`s largest

integrated Zinc producer and also one of the lowest cost Zinc producer in the

world, with a global share of 6% in Zinc. The company has four mines & four

smelting operations, captive mines are located at Rampura Agucha (Bhilwara),

Rajpura Dariba (Udaipur), Sindesar Khurd and Zawar (Udaipur) with smelters

at Chanderiya, Debari and Dariba located in Rajasthan & Vizag (Andhra

Pradesh).

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Fig .1 HZL Distributions in India

Chanderiya Smelting Complex is located 110kms from north of

Udaipur in the State of Rajasthan,India.It was commissioned in year 1991 with

an initial production capacity of 70,000 tonnes of per annum Zinc & 35,000

tonnes of Lead per annum.

It is basically the single largest Zinc Smelting Complex in the world.

Now the metal production capacity is 610,000 tonnes per annum.With a talent

pool of over 6400 employees and about 16% women employees in the fresh

intake, HZL is emerging as one of the most preferred employer in the industry.

The company has tried to maintain and upkeep the quality of life of its

employees.

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Fig 2. Chanderiya Lead Zinc Smelter

2.2 EXCELLENCE AT HZL:

You set a vision and you build a road map to achieve it, Hindustan Zinc was

no different, but the most important was the approach to excel- to make

Hindustan Zinc Ltd a world class company that is focused to achieve

excellence and set global benchmark. This is what lies in the working culture

at HZL, and this is best reflected in their mission and vision.

MISSION: Be a world class company, creating value, leveraging mineral

resources and related core competencies.

VISION: To be a global lowest cost Zinc producer, maintaining market

leadership with a million tonne Zinc-Lead metal capacity by 2012 by

innovating, customer oriented and eco-friendly environment and maximizing

stake-holder value.

QUALITY POLICY: Ensure involvement, participation and motivation of

employees and contractor employees in implementation of our environment,

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health and safety management systems through training, awareness and

continual competence building.

2.3 IMPORTANT KEY FEATUERS:

In the past 3 decades, Chanderiya Smelting Complex has continuously made

progress in terms of production, cost and consumer satisfaction, it has made

several milestones in this period. To count a few Key facts are:

1. Annual Production Capacity:

a. Zinc: 525,000 tons per annum

b. Lead: 85,000 tons per annum

c. Silver: 168 tons per annum

2. Products: SHG Zinc & Zinc alloys, PW Zinc, Lead, Silver

2.4 AWARDS AND RECOGNITIONS:

Hindustan Zinc Limited has received various awards in production, consumer

satisfaction, environment, health and safety. Even, it has got various

certifications from government of India and state government. The

organization is been certified by:

1. ISO-9001 (Quality control)

2. ISO-14001 (Environment Management)

3. OHSAS (Occupational health and safety advisory services)

4. SA-8000 (Social accountability)

Besides these major certifications HZL has been recognized by various

prestigious awards in different categories, the few to mention are:

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1. FIMI National Environment award under best open cast mechanized

mine – 2006.

2. Bhilwara Udyog Ratna Award – 2006, 2009.

3. Greentech safety silver award – 2006.

4. “First” overall performance in safety week in Ajmer region – 2006.

5. Golden Peacock Award for environ management – 2009.

6. Ranked second in the top 25 for best employers in India – 2009.

7. 9th Annual Excellence Award in the best manufacturing process – 2008.

8. ROSPA gold award for prevention against accidents – 2008.

9. National energy conservation award – 2008.

10. Gold Pegasus CSR award – 2008.

11. FICCI annual award for Rural and Community development – 2007

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CHAPTER 3

PROCESS

3.1 PYRO PLANT

1. SINTER GROUP

- Sinter Plant

- Acid Plant

- Effuel Treatment Plant

- Tall Gas Treatment

- Reverse Osmosis

2. ZINC CIRCUIT

- Imperial Smelting Furnace/plant

- Zinc Refinery Plant

3. LEAD CIRCUIT

- AUSMELT

- Lead Refinery Plant

- Copper Refinery Plant

- Silver Refinery Plant

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Fig 3 Sinter plant

3.1.1 RAW MATERIAL STOCK YARD WITH LOADING

STATION

Concentrates and fluxes are unloaded from the trucks into grizzly. The

unloading system of belt conveyors takes the material to the respective bay in

the storage yard through a tripper conveyor. The capacities of various

materials and fluxes bay are as follows:

Zinc concentrates (Total) 9450MT

Bulk concentrates 3500MT

Lead concentrates 7500MT

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Limestone fluxes 450MT

Iron fluxes 700MT

From the above storage yard they are carried to proportioning bins by a series

of conveyor system.

3.1.2 CHARGE PROPORTIONING AND CONDITIONING SYSTEM

The raw material can be made to pass through a disintegrator when they

are over size, there are 13 storage bins each having a capacity of 50 cu M, six

bins are for zinc concentrate 3 bins for lead concentrate 1for bulk concentrate

1 for iron flux and 2 for limestone are earmarked in that order lastly, two bins

with capacity of 25 cu M are provided for return fines. All bins are equipped

with vibrator and shock cannons to prevent blockage. Generally, the ratio

between crude charge and return fines will be in ratio of 1:3 to 1:5 in order to

have supplied sulphur of 6% in feed to sinter machine. Plant ventilation dust,

which is removed in a bag filter and stored in a 35 cu M. Bins are being added

to the final stream of charge component entering the mixing drum, moisture

addition is done in a controlled way at mixing and conditioning drums so as to

get a moisture content of 6% in the feed to sinter machine. All the various

sources of input are controlled through weigh feeders located at the bottom of

the proportioning bins.

3.1.3 SINTER MACHINE

The updraft sinter machine has an area of 120 sq m and 109 pallets each

measuring 3m x 1m in size. There are 444 grate bars in a pallet above the

sinter machine, the main and ignition layer bins are located. The ignition layer

thickness is generally adjusted to give 30 mm height and the total layer

thickness maximum is up to 400 mm. The ignition layer is fired by two

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burners operating on L.S.H.S. to get about 1000 C hood temperature. The

ignition gases are drawn by the ignition waste gas fan through the wind box

and conveyed to recalculating gas main. Dust and spillage are removed in a

solid separator. The ignition wind box is equipped with two conveyors, which

are to seal and discharge the sinter machine dust collecting through from the

sinter hood, the rich sulphur dioxide gases are drawn and sent to wet gas

cleaning plant through a HGP with the help of booster blower.

Beside the ignition fan, there are three fresh air fans and one

recirculation fan supplying fresh air and recirculated to 17 wind boxes of the

sinter machine. The gases above the both updraft wind boxes are low in

sulphur dioxide extremely humid and at low temperature. These gases are

mixed with the hot gases from the discharge end of the sinter machine

recirculated to the last three wind boxes at the discharge end of the sinter

machine. There are five cyclones for dust removal of ventilation air and

recirculation gases in order to avoid any dust build up in the ducts and also to

avoid wear of the fans.

3.1.4 SINTER AND RETURN FINES HANDLING

The lumps discharge from sinter m/c at 800 deg. C are first crushed by a claw

breaker up to about 250 mm. a vibrating feeder feed the materials to a spike

roll crusher to get particles of size 130 mm which are conveyed to a vibrating

feeder and a Ross classifier . The 65-130 mm fraction is sent to ISF by a tray

conveyor. The 7-65 mm fraction from classifier is sent to an intermediate bin.

From here the material can either go to intermediate storage or to crushing

circuit for return fines. In the return crushing circuit the material goes to a

corrugated roll crusher and a smooth roll crusher through vibrating feeders to

get a size less than 8 mm, the finally crushed hot material is sent to cooling

drum where the bay house dust is also added. The cooling is accomplished by

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addition of different slurries generated in ISF plant, cadmium plant, copper

plant and industrial water. The moisture content of the cooled material is in the

industrial water. The moisture content of the cooled material is in the range of

2-35% and this material is carried back to sinter proportioning plant.

3.1.5 VENTILATION SYSTEM

The dry ventilation gases from all machines, belt conveyors and material

transmission point are cleaned in a central bag filter. The mixing and cooling

drum dusts are removed at above 100 deg. C. by a burner system and the gases

are dusted in a separate bag filter. The removed dust is sent to return fines

circuit.

Ventilation gases and vapors from the return fines bin are treated in

venture scrubber units. The washed gases are vented after passing through

hydro clones. The wash solution is collected in an agitated tank from where the

solution is recalculating to the venture scrubber units.

3.1.6 SLURRY HANDLING

In general, the slurry received from ISF, cadmium plant and copper plant are

treated in agitated tank and fed into cooling drum. The various slurry-handling

units are located in the crusher building.

3.1.7 RECIRCULATION FAN

The Main uses of recirculation fan as depicted above are:

1. It is used for reutilization of the heat of SO2 gas and supply it to bed

again

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2. It is used for cooling purpose.

3.2 ZINC CIRCUIT

3.2.1 IMPERIAL SMELTING PLANT

The I.S.F. is one of the plants of the C.L.Z.S. in this plant, the small sized

clinkers coming from the sinter plant are melted and lead, silver, zinc, and

copper are obtained in their impure form. These impure metals are then sent to

refinery in order to obtain the highest purity form.

Fig 4 Imperial Smelting Furnace

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Fig.5 Process Flow Diagram

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3.2.1.1 PROCESS:

In sinter plant, the raw material after conveyed through a belt, is mixed with

water and heated in a furnace and it forms spherical shaped clinkers of size

about 25-30 kg. After this, these are subjected to hammering in a big machine

and small sized products of 1-2 kg are formed.

In Imperial smelting furnace (I.S.F.), these clinkers are kept in sinter

bins of capacity 300 tones. These are two bins, one on the left and other on the

rights. After this, these sinter products reaches the screen feeder (vibrator) a

dare stored in way hopper, which works as small storage having open for a

definite time period and it closes as soon as it fills completely.

The coke required for combustion is stored in coke yard and is

transferred through cold coke bin. This coke is sent to coke screen feeder.

There is preheated at a temperature of 400-500 deg Celsius the CO gas is

obtained from this heating.

Air is blown into the stove by the help of an 1800 KW blower. The

reaction between air and coke produces carbon monoxide. Enormous amount

of heat is obtained by firing the air. This heat basically smelts the metal oxide

into elemental metal. Molten Lead metal falls into the bottom of the furnace

from where it is tapped together with slag of molten gangue material. At the

temperature of operation, metallic zinc is formed as a vapor and rises up the

furnace shaft with the furnace gases. These zinc containing gases pass through

a furnace off take into the condenser containing molten lead. Here zinc is

condensed to a liquid by shock cooling, the gases with a spray of finely

divided droplets of lead generated by rotors immersed in the lead. After

absorbing condensed zinc, this lead is pumped out of the condenser into an

adjacent cooling launder where it is cooled by tube banks immersed in the

launder from above. At the end of the launder the zinc lead is treated with flux

and flows into a separation bath where, at the cool temperature of 440 deg.

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Cent., zinc separates as a molten layer on the top of lead. Zinc continuously

overflows via a V – notch into a adjacent liquation bath whilst the main lead

stream passes from the separation bath under the underflow weir and then

into a return launder leading back into the condenser. The liquation bath is

small bath in which any final separation of lead and iron from the zinc can

occur before the zinc overflows to the final holding bath. Here it is allowed to

accumulate before being tapped for casting or further treatment in zinc

refinery. The waste gases leaves the condenser after zinc is condensed from

them are passed into a gas. These gases contain carbon monoxide and have a

low calorific value. After cleaning, calorific value is utilized in preheating the

furnace blast air and in preheating the cokes any remaining excess is used in

the site power plant boilers.

3.2.2 ZINC REFINERY PLANT

Fig. 6 Zinc Refinery

3.2.2.1 OBJECTIVES FOR REFINING:

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The I.S.F zinc is not suitable for zinc’s prime user i.e. galvanizers due to

1) High cadmium percentage

2) Occasional high arsenic

Hence zinc produced from I.S.F. needs a suitable refining tobecome of

economic industrial use. The process followed in CLZS is by distillation in

“new jersey type distillation columns”

3.2.2.2 INTRODUCTION:

Zinc refinery is situated east of I.S.F. the basic engineering is given by

mechim-engineering of Belgium and process by novellas-godault of France.

Main construction is done by TATA DAVY LTD.

3.2.2.3 FEATURES:

1. Since the main refining is done in columns consisting of superimposed

silicon-carbide trays, the trays can’t take thermal shock, so the process

can’t be stopped more than 2-3 minutes. Only after the life (2 to 3 yr) of

the columns finishes can be stopped. So the equipments which are

responsible for feeding and heating must run 24hr/day.

2. Due to above reason, there are some conditions before start up. Otherwise

huge expenditure & time will be taken to rebuild the trays consisting

columns.

3.2.2.4 PROCESS

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The I.S.F. Zinc is feed to the storage f/c through tilting device or by the

loading door in form of 1.1T ingots. This Zn by gravity goes to the feeding

furnace. In emergency 1 zinc pump is used or ladles are tilted in the feeding f/c

directly. The feeding furnace through the needle valve and float valve feeds

the I.S.F. Zinc to the lead columns in requite amount and temp. The lead

columns which have 59 trays each are having two parts up to the 30th tray. It is

having a combustion chamber around it and is known as the boiling part. The

top portion above the 34th tray (feed tray) is insulated, it is the refluxing part.

Only during the start up this top part of lead columns are electrically

heated.

If we consider the column erected by superimposition the trays, has got 8

types of trays. The top tray is different at it is connected to the condensers by a

mall-rack (electro-fused silica) cross over the bottom tray, the tray above feed

tray. The 30thtray is having double opening and extra electric coils around it.

33rd tray is having different outer shape. All the rest trays are of 2 types.

1. flat type: located in the reflux part

2. w-type: located in the bottom part (boiling part)

If we consider the composition of I.S.F. Zn and see the action of combustion

chamber which is having 8 burners in each column drawing 10% of total

combustion air from the burner and the rest 90% preheated air from

recuperator, we find that full cadmium, half Zn vaporizes and full lead and half

Zn comes down, the top product is condensed in condensers of each lead

column and then again in hot condition they are fed to cadmium columns. Feed

system is same as lead columns, Here the number of trays are 56 only and 2

columns are there (rest everything is same for cadmium columns) this feed is

known as Zn-Cd alloy. This Lead is separated in liquation f/c. some hard Zn

also comes and rest Zn having only the minimum lead comes out as G.O.B.

Zinc i.e. good ordinary brand or prime western (PW) zinc. The top Zn-Cd

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alloy is separated in cadmium columns. The bottom product of this is very

high grade Zinc known as Special High Grade Zinc (SHG).The top product

after condensation becomes Cd-Zn enriched alloy and is casted moulds to be

sent to Cd refinery. The SHG & GOB are casted in separate casting m/c.

CHAPTER 4

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TRANDUCERS & INSTRUMENTS

4.1 DISTRIBUTED CONTROL SYSTEM

A distributed control system (DCS) usually refers to a manufacturing system,

process or any kind of dynamic system, in which the controller elements are

not central in location (like the brain) but are distributed throughout the system

with each component sub-system controlled by one or more controllers. The

entire system of controllers is connected by networks for communication and

monitoring.

DCS is a very broad term used in a variety of industries, to monitor and

control distributed equipment. A DCS typically uses custom designed

processors as controllers and uses both proprietary interconnections and

Communications protocol for communication. Input & output modules form

component parts of the DCS. The processor receives information from input

modules and sends information to output modules. The input modules receive

information from input instruments in the process (a.k.a. field) and transmit

instructions to the output instruments in the field.

4.1.1 APPLICATIONS

Distributed Control Systems (DCSs) are dedicated systems used to control

manufacturing processes that are continuous or batch-oriented, such as oil

refining, petrochemicals, central station power generation, pharmaceuticals,

cement production, steelmaking, and papermaking. DCSs are connected to

sensors and actuators and use set-point control to control the flow of material

through the plant. The most common example is a set-point control loop

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consisting of a pressure sensor, controller, and control valve . Pressure or flow

measurements are transmitted to the controller, usually through the aid of a

signal conditioning Input/output (I/O) device. When the measured variable

reaches a certain point, the controller instructs a valve or actuation device to

open or close until the fluidic flow process reaches the desired set-point. Large

oil refineries have many thousands of I/O points and employ very large DCSs.

Processes are not limited to fluidic flow through pipes, however, and can also

include things like paper machines and their associated variable speed drives

and motor control centers, cement kilns, mining operations, ore processing

facilities, and many others.

A typical DCS consists of functionally and/or geographically distributed

digital controllers capable of executing from 1 to 256 or more regulatory

control loops in one control box. The input/output devices (I/O) can be integral

with the controller or located remotely via a field network. Today’s controllers

have extensive computational capabilities and, in addition to proportional,

integral, and derivative (PID) control, can generally perform logic and

sequential control.

DCSs may employ one or several workstations and can be configured at

the workstation or by an off-line personal computer. Local communication is

handled by a control network with transmission over twisted pair, coaxial, or

fiber optic cable. A server and/or applications processor may be included in

the system for extra computational, data collection, and reporting capability.

4.1.2 USE OF DCS IN PLANT

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1. Distributed Control Systems (DCSs) are used to control manufacturing

processes that are continuous or batch-oriented, such as refining Process

(lead, zinc silver).

2. The whole process of the plant is controlled by DCS so that the plant can

work automatically

4.2 PROGRAMMABLE LOGIC CONTROLLER (PLC):

INSTALLED AT: Serve as the centre for monitoring, controlling and

measuring all the parameters in control room. PLC in short act as the important

computer to control the process flow.

FIG.7 PLC Working

4.2.1 PRINCIPLE:

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A programmable logic controller (PLC) or programmable controller is a digital

computer used for automation of electromechanical processes, such as control

of machinery on factory assembly lines, amusement rides, or lighting _xtures.

PLCs are used in many industries and machines, such as packaging for

multiple inputs and output arrangements, extended temperature ranges and

semiconductor machines unlike general-purpose computers, the PLC is

designed immunity to electrical noise, and resistance to vibration and impact.

Programs control machine operations are typically stored in battery-backed or

non-volatile memory. A PLC is an example of a real time system since output

results must be produced in response to input conditions within a bounded

time, otherwise unintended operation will result.

4.3 THERMOCOUPLE

Fig 8 Thermocouple

A thermocouple is a junction between two different metals that produces a

voltage related to a temperature difference. Thermocouples are a widely used

type of temperature sensor and can also be used to convert heat into electric

power. They are cheap and interchangeable, have standard connectors, and can

measure a wide range of temperatures. The main limitation is accuracy;

System errors of less than one Kelvin (K) can be difficult to achieve.

24

Thermocouples are widely used in science and industry; a few applications

would include temperature measurement for kilns, measurement of exhaust

temperature of gas turbines or diesel engines, and many other industrial

processes.

4.3.1 PRINCIPLE OF OPERATION

When any conductor is subjected to a thermal gradient, it will generate a

voltage. This is now known as the thermoelectric effect or See beck effect.

Any attempt to measure this voltage necessarily involves connecting another

conductor to the "hot" end. This additional conductor will then also experience

the temperature gradient, and develop a voltage of its own which will oppose

the original. Fortunately, the magnitude of the effect depends on the metal in

use. Using a dissimilar metal to complete the circuit creates a circuit in which

the two legs generate different voltages, leaving a small difference in voltage

available for measurement. That difference increases with temperature, and

can typically be between 1 and 70 micro volts per degree Celsius (µV/°C) for

the modern range of available metal combinations. Certain combinations have

become popular as industry standards, driven by cost, availability,

convenience, melting point, chemical properties, stability, and output. This

coupling of two metals gives the thermocouple its name.

Thermocouples measure the temperature difference between two points,

not absolute temperature. In traditional applications, one of the junctions—the

cold junction—was maintained at a known (reference) temperature, while the

other end was attached to a probe

4.3.2 APPLICATIONS

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Thermocouples are suitable for measuring over a large temperature range, up

to 2300 °C. They are less suitable for applications where smaller temperature

differences need to be measured with high accuracy, for example the range 0–

100 °C with 0.1 °C accuracy. For such applications, thermistors and resistance

temperature detectors are more suitable.

4.4 RTD

There are two broad categories, "film" and "wire-wound" types.

Film thermometers have a layer of platinum on a substrate; the layer may be

extremely thin, perhaps one micrometer. Advantages of this type are relatively

low cost and fast response. Such devices have improved in performance

although the different expansion rates of the substrate and platinum give

"strain gauge " effects and stability problems.

Fig 9 Film Type

Wire-wound thermometers can have greater accuracy, especially for wide

temperature ranges. The coil diameter provides a compromise between

mechanical stability and allowing expansion of the wire to minimize strain and

consequential drift.

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Fig 10 Wire Wound

4.4.1 WORKING

Resistance thermometers require a small current to be passed through in order

to determine the resistance. This can cause resistive heating, and

manufacturers' limits should always be followed along with heat path

considerations in design. Care should also be taken to avoid any strains on the

resistance thermometer in its application. Lead wire resistance should be

considered, and adopting three and four wire connections can eliminate

connection lead resistance effects from measurements - industrial practice is

almost universally to use 3-wire connection. 4-wire connections need to be

used for precise application.

4.4.2 ADVANTAGES:

Advantages of platinum resistance thermometers:

● High accuracy

● Low drift

● Wide operating range

● Suitability for precision applications.

4.4.3 LIMITATIONS:

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● RTDs in industrial applications are rarely used above 660 °C. At

temperatures above 660 °C it becomes increasingly difficult to prevent

the platinum from becoming contaminated by impurities from the metal

sheath of the thermometer. This is why laboratory standard

thermometers replace the metal sheath with a glass construction. At very

low temperatures, say below -270 °C (or 3 K), due to the fact that there

are very few phonons, the resistance of an RTD is mainly determined by

impurities and boundary scattering and thus basically independent of

temperature. As a result, the sensitivity of the RTD is essentially zero

and therefore not useful.

● Compared to thermistors, platinum RTDs are less sensitive to small

temperature changes and have a slower response time. However

thermistors have a smaller temperature range and stability.

BIBLIOGRAPHY

1. Vedanta Resources

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2. Industrial Instrumentation and Control (S.K. SINGH)

29