dgkccl affan internshipp report

Submitted by Muhammad Affan Usmani(UET-11-F-BSC-ET-CASE_05) Includes brief points about the topics covered in training as per trainer instruction.

T r a i n e r : M r . H a f i z S a j i d H a b i b

Internship Report (Electrical Department)

DG Khan Cement Company Limited Internship Report (Electrical Department)

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Muhammad Affan Usmani Dated: July21, 2014

In the name of ALLAH, the most merciful, The most beneficent.


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Acknowledgement

First of all, we are very thankful to the almighty “ALLAH”, the most Beneficent and the most Merciful for his blessing to all of us.

I would like to convey my sincere gratitude to my internship advisor Mr Hafiz Sajid Habib, who believed in me and for his kind interest

and guidance without which this endeavor would not have been materialized. Special thanks to him for his encouragement and

support.I would like to thank all those who directly or indirectly helped me in making this report fruitful.


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ABSTRACT

This Report is concerned with DG-Cement manufacturing and all the processes involved starting from raw material to the packing of

final product. It mainly describes all the Electrical components present in DG-Cement Plant. The plant was established in 2007 at Khairpur near Kallar Kahar and it is producing 7000 tons cement per day. It is equipped with all latest equipment required for the

production of cement and has the major role in exporting ordinary Portland cement from Pakistan which has maximum setting strength

of about 10000Psi. The report cover all the areas which are important from study point of view. Hope everyone will find it as a

best material to study.


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Plant Visit


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Safety Section It is the first portion of internship in which we have learned about safety precautions in DG-Cement. In Khairpur plant all equipment of firefighting is available at every place and every person is equipped with safety helmets and jackets. Internee are also provided with security helmet to prevent any damage. Fire alarms are attached and one main security alarm which indicates any emergency. In case of major emergency when the alarm rings, all the workers are advised to come out of plant and stop working till that security team covers the danger. There is a red line spread all around the plant which also covers tunnel area so that in case of any damage workers can even pull a single wire and emergency can be felt. AFF is added in 3% with water which produces foam and used in firefighting. The company has firefighting Van which is of about 10Million cost. Very costly equipment is present and all the environment is safe and sound. There is no such danger while working at DG. Pipes are present which sprays the water on fire during working in form of mist and thus prevent the fire fighter also they have different kind of nozzles which exhaust water at 7Bar pressure and covers an area of 100ft. Security buzzers are present and also they are connected through cello phones with each other. Main firefighting or danger area is of Kiln because in this region the temp is almost around 1600’C so there is a chance of fire spreading. After visiting the plant we can say that it has best equipment of safety and has full

security of workers working over there.


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INtroduction

Cement is a mixture of argillaceous and calcareous minerals and has the major portion of Calcium Carbonate (60-80%) and Silica (20-30%) and has the additives Aluminum Oxide (0-10%) and Fe2O3 (0-10%). Additives are added to perform reactions at low temperature of 1600’C otherwise 2000’C temp is required to perform Kiln reactions and to decompose Calcium Carbonate into CaO and CO2. By mixing all of the above reactants the product formed is called clinkers which has ball like shape and they are stored in clinker silo. They are then mixed with gypsum in proper portion as additive (5%) to increase setting time of cement and are grinded in two cement mills having capacity of producing 175tons cement per hour. They are then stored in cement Silo having 22000tons capacity each (total 3). After that they are transferred to packing plant for packing of cement into bags. All automation is present in packing plant. Plant has designed with a capacity of 7000Tons/day. When we talk about power supply, the plant has 33MW power units and they also have supply through wapda. The plant is under Nishat Group of industries and a paper manufacturing shop is also present. It has complete safe and healthy environment which has complete control of dust. Also coal manufacturing from RDF is present. Canteen is also present and it is equipped with laboratory and clinic facility also it has CCR and other main units for meetings like admin block. All the workers are well corporation especially with Mr Safdar Kamal.


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Quarry and Crusher Quarry is the place from where raw material in extracted. Drilling and blasting is done to extract the material. A hole of about 10-15 m is drilled and ammonium nitrate in filled as an explosive in these holes. When this explosive is ignited the rocks are broken into pieces of different sizes. These pieces are then loaded on the dumper trucks and conveyed to the crusher. It is located about 3-4 Km from the plant. Drilling takes place firstly and then blasting of calcium carbonate take place which is then feed to apron feeder and move towards crusher. Two main crushers are present which are CaCO3 crusher (1500-1700tons/hour and additive crusher. Both have same mechanism but number of hammers and their weights are different. CaCO3 Crusher is of bigger size and comparatively hard to crush lime stone into small pieces of almost 1-2inch.

Quarry and raw materials: The following raw material is required in the production process: 1. Lime stone: This raw material is company owned and is extracted from the nearby quarry Unit. Limestone has the highest composition in the cement product. 76% of the cement constitutes of limestone. 2. Clay: Clay is another natural resource. This raw material is also company owned. 24% of cement composition comprises of clay. 3. Iron Ore, Bauxites and silica sand: Iron Ore is the only resource that is bought from contractors. Iron Ore, Bauxites and silica sand are added in small quantities less than one percent and it helps to strengthen the cement. 4. Gypsum: Gypsum acts as a retarding agent. It slows down the hardening process which in turn gives the constructor enough time to use it. Gypsum Clay Limestone


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Limestone Crusher: Capacity: 1500 tons/hr. Supplier: FLSmidth. Type: Hammer type crusher Hammer weight: 92 to 95 kg approx. Rotor drive source: 1540 kW motor (with reduction gear box) Input size: up to 2m Output size: 125mm Number of shafts on rotor: 4 Number of hammers on each shaft: 12 Total hammers: 48 Mechanism: Raw material such as limestone, clay, marl and shale are dumped into hoppers by dump trucks and entered into a hammer crusher through an apron feeder. Inside hammer crusher there are 48 Hammers attached to four main rotor shafts each having 12 hammers each and each having weight of 100Kg approx. They rotate at a speed of 1200-1300 rpm and is capable of crushing feed of very large sizes.

Input is through hopper and then apron feeder takes the lime stone pieces to main crusher where a rotating disk and steel chains are present to prevent backward movement of broken pieces. Lamella plates are used for movement of raw stones of crusher. Magnet separator is attached to conveyor belt to prevent metallic particles from reaching the raw mill. When we talk about additive crusher it has only one shaft having 12 hammers, smaller in size and attached to a single shaft. They are then transferred to main storage section and then move towards raw mill through belts.


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Storage Area: The crushed material is stored in the form of piles in the storage yard. There are 6 piles in the storage yard. Mixed piles are used in larger quantity where as high grade and additive piles are used in small quantity.6 piles are made in the storage area.

Pile # Material Capacity Pile #1 Bauxite 1500t Pile #2 Iron ore 2800t Pile #3 HG lime stone 3000t Pile #4 HG lime stone 3000t Pile #5 Mix 35000t Pile #6 Mix 35000t

Stacker: A stacker is a device which form conical piles of the crushed material. Feed is conveyed to the stacker through conveyor belts. This stacker then moves to and fro to make a pile. The stacker belt is called “Jib” in engineering terms. Now, for conveying this material from piles to the conveyor following equipment are used :

Side Scraper Reclaimer


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Raw Mill Section

Raw Mill Feed Area: The raw mill feed area consists of 4 feed hoppers:

Mixed feed hopper. Pure Limestone hopper. Bauxite hopper.

Iron ore hopper. The capacity of first two hoppers is 800 tons while the other two hoppers have a capacity of 600 tons. The feed from each pile is conveyed to the hoppers through conveyor belts in relevant hoppers. Each hopper has 4 load cells. This section is one of most important section of plant where the crushed material in form of piles is transferred to bins through belts and then to Raw Mill through rotary feeder (28rpm) which permits only raw material to fall inside the raw mill and air is not allowed to fall.


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Main Specification:

Manufacture: FLSmidth number of rollers: 3 Fan Motor: 4300kw weight of each roller: 60t Capacity: 500tph Model name: Atox 52.5 Table diameter: 5.25m

Mechanism: The raw feed from the belt conveyer directly falls on the rotating table of the raw mill. The table contains on 3 crushing rollers.The raw feed is crushed into fine powder with these rollers. At the top of raw mill there is a separator section. Hot gases come from pre heater at the bottom of raw mill. A suction fan with a motor of 5500kw.Here the dusty air rotates and air is separated from dust nearly 80% dust from air is separated in four cyclones. These four cyclones sent the crushed material into CF silo with the help of air slides and bucket elevators.

Sections of Raw Mill: There are 3 sections of a raw mill.

Three Rollers Bottom Scrapper Seperator

Three Roller: The raw feed from the belt conveyor directly falls on the rotating t able of the raw mill. The table contains 3 crushing rollers. The raw fed is crushed to fine powder with these rollers. The coarse particles are collected at the bottom of raw mill and are sent to the vibrator from where they are sent to the raw feed belt conveyor and again recycled to the ram mill for re crushing. The vibrator is use to handle the quantity of the material being put on the belt.


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Seperator: At the top of the raw mill, there is separator section. Hot gases from the kiln comes from the bottom of the raw mill and lift very fine particles with it. A suction fan with motor power of 4500 kw produces suction and sends dusty air into the cyclones at the top. Here the dusty air rotates and particles are separated from the air. These particles are collected at the bottom of the cyclone and sent to the CF silo with the help of air slides. The air which still contains dust particles are separated in Conditioning tower and Electrostatic precipitator.

Two input ducts are coming inside the raw mill which provide hot air having temp 108’C almost and there in single outlet duct which takes material and exhaust air in form of cyclones. Id fan is attached which is used for rapid movement of air b/w inlet and outlet ducts. Material transfer in form of cyclones prevents the raw material from reaching Id fan. This material is then transferred to silo’s four in number and the dusty air is transferred to conditioning tower where foggy drops are sprayed from 30 nozzles each having 3mm dia to decrease dusty air temp to a lower limit (80-100’C) before it reaches EP (Electrostatic Precipitators) In this section cooled dusty air is passed between electrical plates where ionization of dust take place, they are ionized into positive and negative plates and then stick to respective plates. After this process hammering or shock is produced in plates which removes dust from plates and this dust is then transferred through bucket elevators to the CF-silo. The same process occurs with grinded material, they are conveyed through duct to bucket elevators and then transferred to CF-Silo through bucket elevators. Air from EP and exhaust air from raw mill is exhausted to the atmosphere using chimneys so that fresh air cycle can be started again.


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KILN area And Pre heater

Preheater: It is in-line double string five stages consigner. Double string means at both

sides’ cyclones are present. Five stages mean total five cyclones are present on

side.At consigner and kiln 900 ton/day coal use to produce 7000 ton/day. 12%

ash allow in cement according to ISO standards.At different heights of consigner,

temperature is different. 900 degree centigrade temperature at the upper side of

consigner.


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Kiln: ROTAX-2 kilin use at plant .Its have maximum revolution are 4.5 per minute.

Mostly it run at 4.1 to 4.3 rpm. Hydraulic system use for self-aligning of bearing.

Its diameter is 5.5 m and length is 65.5 m. 7 to 10 min material stay in kiln at 4.3

rpm. It takes approximately 24 hours for pre heating. Otherwise fuel more use.

Clinker cooler Clinker is cooled in this chamber at a temperature of 105-110 degree Celsius. Water showering takes place in this chamber to cool down the gases that are going to EP.This chamber is not inclined. So to move the clinker to the other end, moving plate’s mechanism has been used.Many plates are present at a specific distance from each other to transfer material to the other end.Plates move to and fro through hydraulic cylindrical mechanism and drag the material to the other end.This material is then crushed and finally moved to clinker silo through deep bucket elevator.


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Waste heat Recovery Plant It is largest waste heat recovery plant of world in cement industry.Its totlal

capacity of 8.6 MW. It is invented by scientist whose name was “Kalina.Kalina

system is efficient of low temperature sources geothermal energy and waste heat

recovery.It works on the base of Rankine cycle. It contains two HRVG’s (heat

recovery vapor generator) at preheater strings and one at cooler side.Gases

coming from preheater having temperature 310-320 Ċ and WHR stakes

temperature is 110 degree centigrade. WHR efficiency is 24-25%.

Main parts of WHR:

Boiler: Here three boiler use. These are gas tube boiler. In the boiler, water ammonia

mixture use.We use ammonia to enhance the water energy storage capacity. 55-

60% ammonia solution use. Percentage of ammonia at different points of WHR

are vary according to situation. All boiler have three main sections i.e.

economizer, evaporator and super heater. But one boiler have two extra sections

i.e. condensate preheater (CPH) and flash super heater (FSH). After the super

heaters of other two boilers steam also come in FSH of his boiler. In the boiler we

use treated water for minimize the scaling. From two boilers we use partial heat

because rest heat use to remove moisture from RAW Mill. At third boiler use

complete heat.

Turbine: In WHR turbine install of General Electric (GE) Company. Its rated capacity is 10

MW. It is working on 8.6 MW. It is axial flow back pressure turbine. Its working

rpm is 4200. It has 11 stages and last stage has titanium coated blades.

Generator: ABB company generator use in WHR. The medium which join generator to turbine is gear box. Generator rpm is 1500. Its oil also cooled by cooling tower water.

Condenser: In WHR, shell and plate type four heat exchangers are used. Water comes from

cooling tower which cool and convert steam into water. In the condenser lean

solution of ammonia will come.It separate earlier from water. Because due to

ammonia heat dissipation of water decrease


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Pump: Axial flow centrifugal pumps use of FLOW SERVE Company. These are

multistage pumps. It is used to feed the water in boilers.

Cooling tower: Induced draft counter flow cooling tower use. It has three cells. It has different

components. Fill is made by PVC material which is used to increase contact time

between water and air. Drift eliminator here also present make by same

material. It prevents water vapors go to atmosphere.

Compressor House: There are 8 compressors. 7 working at a time and 1 for emergency which has

lesser capacity. Rest compressor capacity is 8.5 bar pressure each. Its company

name is ATLAS OPCO and model GA200 W.All compressors are screw type. Each

compressor has 3 oil filter and 1oil separator. For lubrication,roto inject oil use

108 liter per compressor.

Centrifugal pumps: Three pumps present in compressor house. Two work at a time and one for

stand by position.Each has 2 bar pressure. These pumps are manufactured by

“KSB PUMP.It is German company also working in Pakistan. Pumps use here for

compressor cooling.

Dry unit: This unit used to remove moisture from compressed air.Because moisture cause

corrosion of machine parts. It contains silica gel. It absorbs moisture when air

passes through it.In dry unit heater also present which dry silica gel.

Colour coding of pipes: Red color pipe show, this is for firefighting. Green color use for fresh water.Grey

color use for compress air. Blue color use for treated water.

Types of valves:

Butterfly valve: These valves present at compressed air pipe lines of larger diameter.

Ball valve: These are present at smaller diameter air pipe line.


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Gate valve: It was on water pipe lines. In this valve small plunger present. It stop the

passage in pipe when we close valve.

Non return valve: This valve use for unidirectional flow. It allows the fluid forward motion but

prevent reverse.

Safety valve: At the top of vessels, this valve present. When pressure increase from specific

value in vessel, it open and release the pressure.

Cement Mill Area

Mill name is “OK36-4”. Its turning table diameter is 3.64m. Its capacity is 175

ton/hr. It contains four rollers. Each roller weight is 34 ton. These rollers are

mounted on spherical roller bearing. For roller alignments nitrogen gas use.

Rollers dive by heavy motors in which hydraulic oil present. This oil is cooled by

water coming from cooling tower. During the cement making process, material

also remove by rollers due to extensive grinding. This material is recovered by

hard facing. “MAGG Company” give gears of raw mill and cement mill. In cement

mill air separator present which suck the grinded material upward. Cement mils

have 3400kw motors each.


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Bag filter: Largest bag filter present after the cement mill. Bag filter actually use to absorb

the dust.Bag material of different types use in different bag material.Mostly use

materials are polyester, normax and anti-static. In coal mill bag filters anti-static

material use. Normax material can bear high temperature.Bag filter purging may

be time base or pressure type. Rotary valve open for dropping down the material

on belt conveyor from bags.It has 8 solinide valves.Each valve has 1 coil.each coil

have24 volt dc supply.

Storage Silos: There are 3 cement storage silos in which crushed cement is stored up till packing. To convey the cement to the other 2 silos air slides are used. From these silos the cement enters air slides by air circulations through blowers. Now these air slides take the cement to the packing plant.


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Packing and Baging The packing plant comprises of 6 packers and 12 terminals. Each packer has a capacity of 100 tons/hr. Each Packer has 8 nozzles and shooting of bag on these nozzles is done by shooters which are latest techniques applied over there. Also manual installing of bags on packing is done through workers. Alarm is attached with each packing unit so that it can be turned on whenever there may be a demand of cement. From slide bars the cement falls to hopper through screen to remove any impurities. There is a weight sensor attached with each packing unit which dispose of any bag having weight more than 50.5Kg or less than 49.5Kg. A blower is present which removes dust present on cement bags. Nylon and paper bags are used according to requirement and they have valves made up on the top side for automatic sealing. The cement bags are attached manually to the rotating packer which fills the cement bag. When the bag is filled up to the required weight, it automatically falls on the conveyor belt which takes the bags to the roller conveyor. From these rollers the bags slide to different channels and finally cement bags are loaded on the trucks for dispatch.


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Dispatching Section

Power Plant(Gas and Oil):

It is a power plant which produces electricity by the internal combustion (I.C)

engines. Its have total capacity is 33MW. It is captive power plant. 200g diesel

use to produce one kilowatt of electricity. In summer natural gas use 0.24

cm3/kwh .In winter season 0.27cm3/KWH. Price of unit produce by gas six

rupees.Furnace oil unit price seventen rupees respectively.WAPDA unit price is

14 rupees.Power plant efficiency is 45%.

Main parts of power plant:

Generator: Three generators are installed at power plant. Two couple with I.C engine for

producing electricity and one for future plan Gear box couple I.C engine with

generator and also decrease rpm for increasing torque.Generator cooled by

treated water. After cooling, water go in pipe line towards cooling tower pipe

lines. In cooling tower untreated water cooled. Both pipe lines come in contact

and treated water cooled as a result of it.


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Fuel treatment unit: Use this treatment for furnace oil.Furnace oil passes from fuel treatment unit

where cleaning of wax, small metal parts carbon and other types Impurties.

Storage tanks: There are two storage tanks with each has capacity of 1000 ton.

Engines (dual fire): Engines of WARTISLA Company working at plant. Its project of operation and

maintenance also given to same company. Two engines are working with 16.5

MW capacities each. These are 18 cylinder engines and can work by try fuels i.e.

gas, diesel, and gas and diesel mixture. Diesel use as pilot in engine for auto

ignition. In the engine no spark plug present.

Grid station

Grid station has two transformers. They have 20 MVA and 26 MVA capacities

respectively. Output Voltages of transformers is 6.3 KV. Lines which come from

WAPDA go to CT/PT. then go to transformer after passing to jumper and

disconnect respectively. Vacuum circuit breakers are working at grid station.

Different relays also present there.

Paper mill Nishaat group is making cement paper bags for different cement industries. Paper mill is equipped with highly automated machines. Proximity sensors also working at mill.Craft paper used to make paper bags.Craft paper imported from Sweden, Spain, and Austria. Craft paper roll is of 1 ton and from that we can make nearly 6000 bags. Paper mills of different plies can be made with this machine Nishaat paper mill makes usually 2 and 3 ply paper bags. Process starts from the mounting of paper roll on real stand. Paper printing is done with water based ink. Printing can be done in four different color.After that the papers are joined together depending on the type of bag, for triple ply bag three layers are joined together.In the next step glue applied on the sides of papers and then they are joined together or folded and thus a tube is formed. Then there is a perforation unit from here the tube goes to separator rollers that consist of two rollers now tube comes in a bag shape.Then there is a pressing unit from their bags goes to next phase.


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Devices Study


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Belt conveyor (BC) Side where motor is connected to drive the belt is known as driven drum.Driven drum is connected to a motor through a gear assembly. Other end is known as tail driven drum. Speed of motor, n = 120f/p, f= 50 Hz, p= no. Of poles. Motors with the speed 3000, 1500, 1000, 750rpm etc. are designed by changing the no. of poles. Most of the motors are designed with 4 poles to run at 4000rpm.After slip canceling, such motors rotate at 1460-1480rpm.Belt conveyors are run at speed of 0.8-1.5m/s. A gearbox is used with the motor to run conveyor belt at such speed.n1 /n2 = d2 /d1 , where n and d are speed and diameter of the gears respectively. Speed is reduced and torque is increased using gears Rotational motion is converted into linear motion by taking the path covered in one rotation as a circumference and then considering it as a linear distance travelled by the belt.

Circumference c= pi*d.

Protection Sway switch is used to detect sway. Motion sensor, speed monitor or rpm meter to detect any breakage in the belt, in the gears, in the shaft or any undesirable variation in the belt speed.

Substation (Raw Mill,Cement Mill,Kiln,Crusher,WHR,Packing) It has 6.3kV feeder coming from main substation.From feeder, supply goes to respective motor and a transformer that drives all other motors of the area. Substation panels contain relays SIPROTEC 75J62. SF6 circuit breakers. motors operates on fixed speed. Frequency drives are present for the other motors of the crusher area.UPS set up is present for back up of control supply in case of power shutdown at any time. The main transformer of the area is of 1600kVA. It’s a 3 phase and output is 415V. Has Delt-Vye connection topology.

Weigh feeders All the material is stored in the hopper feeders. From these feeders meal is passed onto conveyor belts for transportation. Hoppers openings are controllable to control the flow rate of the meal.These belts have load cells and they combine make up weigh feeders to measure weight/meter of material. Other controllable parameter is velocity of the belt which is due to rpm of the drive drum.An optical encoder has been mounted to account for the linear distance covered by the belt by sensing the complete revolution of the drum. Motor, which drives the drive drum, has a frequency drive to vary its speed accordingly.An installed controller multiply load cell reading and velocity of the belt to calculate flow rate of the meal.Hopper opening usually wears out due to continuous flow of material for a long time; this leads to more kg/m of material. So to achieve continuous flow rate, speed of the belt should be reduced from the frequency drive of the motor.Installed controller automatically adjusts the flow rate up to certain limit.


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Metal detector Material is transported to raw mill through a main duct that has two openings. One opening goes to raw mill and the other one goes to waste.An automatic gate is present in between them to select for the desirable path for the material.If any non-ferromagnetic metal is present in the material, metal detector is present to detect it.Automatic gate switch is moved so that this metallic material goes into the waste instead of going to raw mill.After passing that metallic material to the waste, switch gate comes to original position for passing of material to the raw mill through rotary lock.

Screw conveyer It has a mechanism that uses a rotating helical screw blade. This blade when moves, drags material with it and transport it further on.

Air slide It is used for transportation of fine powder material.Always inclined downward towards destination point. It has two compartments and a special cloth present between them. Hot air is passed at a greater speed through lower compartment that causes the cloth to vibrate. Powder material present on the cloth moves forward due to vibration of cloth.

Bucket elevator It is a vertical belt conveyer. Used to transport material straight upward or downward. A belt runs in a straight vertical position. Running belt has buckets attached to it. Material is filled into the buckets and the belt takes it to the destination point.

Chain conveyer/drag chain It has blades or dragging plates like structure attached to moving chain. These plates drag the spilled material and avoid its wastage.

Packer A rotary bin is present above the packer. Cement is passed through a grate and sent to a bin. Gate is present between the bin and the packer, which open to fill the packer and closes when the packer fills. Packer is a rotating body, so it gets its power and control supply through slip rings. Packer has 8 nozzles to fill the cement in the bags. A turbine is present before each nozzle to push the cement from the packer out of the nozzle. Fluidizing air comes into the running turbine for smooth flow of cement out of the nozzle. Nozzle contains a proportional opening shutter for filling. A load cell is present above the nozzle. A motor and gearbox is present below the packer to provide rotary motion. Communication IR sensors are present and communication takes place between static and rotary part of the packer. Bag packed with the weight of 49.5 – 52 kg is dropped on the transportation belt and the one which is under weight, is dropped in the path below where blades are present to cut the bag and obtain the cement out of it. Bags are then loaded through the belts in the transportation vehicles.

http://en.wikipedia.org/wiki/Screw_(simple_machine)


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Protection devices

Relay It is an electrically operated switch. It is used to connect two terminals of power circuit with low control voltage. Its working principal is based on electromagnet. DC source is applied to it and coil present in it gets energized to form an electromagnet. Energized coil, and then attract the metallic piece towards its self to connect two terminals of power circuit with each other. In this way power circuit gets completed with low control voltage. Some auxiliary contact are also present for control and indication purposes.

Magnetic contactors In 3-phase circuits, a Magnetic Contactor is used instead of relay. It makes and breaks 3 contacts at same time because any delay in phase availability can be very harmful for machine.Working principal is magnetization of coil.Coil is energized by an external dc or ac source.When coil gets energized it pulls out a mechanical assembly which in turn makes or breaks power contacts.Some auxiliary NO and NC contacts are also available for indication and interlocking purposes.

Circuit breakers It is an electromagnetic automatic switch.Operates when current drawn by machine is not as per requirements. C.Bs are of different types depending on their working principal i.e electromagnetic and thermal type. Electromagnetic type operates when coil inside it gets energized by main power source current, only when current exceeds some specific value. Thermal type operates under working principal of bimetallic strips, made by special selected metals for specific ratings.Thermal expansion of bimetallic strip makes or breaks main power contacts. Auxiliary contacts are also present.

Over load protection These devices used specifically for over load (over current) protection.Consists of bimetallic strips .Main power wire is wound across insulated strip which produces heat in strip. Thermal expansion of strip is controlled in such a way, it breaks the main contacts when current (heat) value exceeds a specific value. A current controlling knob is also present to adjust stress of mechanical structure.

Motor control circuit (MCC) A motor control circuit (MCC) is an assembly of one or more enclosed sections having a common power bus and principally containing motor control units.MCC is used to control motor. MCC modules are of different sizes selected with respect to motor ratings. Cable sizes also increase or decrease with respect to module sizes because of current. Connections are taken out by bus bars and MCC modules are detachable. Simocode is the sub-PLC system in MCC module. In MCC module firstly circuit breaker is used for protection. After this magnetic contactor is used. Main Contactor used for flow of power. Magnetic contactor also has a varistor to control current. CT’s are used to monitor and measure


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current located inside simocode. Simocode is powered up by 24Vdc. Simocode also has other 24Vdc power supply to check test position. Command relay located inside simocode. Emergency start/stop switches are wired with MCC. Emergency start/stop switches connected to respective simocode. Motor can be started by emergency start/stop switch only when operator provides local permission. BO1_N2 MCC module has 4 DI’s (MCC ready, Test position, Motor ready and Local start) and 2 DO’s. Simocode also monitor temperature variations with the help of thermistor, which is located inside motor casing, which is positive temperature coefficient thermistor. Simocode CPU continuously monitors thermistor. Profibus is used for communication with simocode. For testing: MCC connections are broken with main PLC in such a way that main PLC receives no current and main PLC gets test acknowledgement signal. Test position basically used to check controls of MCC. DI’s are taken out by several points (e.g: after CB, MC, OL etc.) to get feedback (to check normal/abnormal conditions). Simocode can take some decisions, which are authorized by main PLC. If motor takes overcurrent then simocode takes decisions etc. Basic data for simocode is current. Simocode has its own microprocessor. Main PLC communicates with simocodes with respective addresses. Scan time for executing instructions is less than 200 or 300msec. Executing all instruction and returns to first one is the known as scan time. Flow of power from cable chamber to motor.

Instrumentation devices

Proximity sensor Proximity sensor detects metallic objects without touching them.The proximity sensor used in DGKCCL 2 gives about 6-150 pulses per minute. These types of sensors can be used for speed sensing. The purpose of a motor speed sensing is to take a signal representing the speed, and to check a motor speed. Here we checked the speed of motor by pulses that are sent by proximity sensor to electronic circuit, which has a comparator.Comparator compares the pulses or time between the two pulses is noted, if there is time delay in pulses, there is a possibility of fault due to reduction of speed of motor . This feedback is sent to main plc.

Pt-100 A family of RTD. It is a transducer, which converts temperature signal into an

electrical signal. Made of platinum wire. Its resistance changes almost linearly

within a specific range of temperature change. Pt-100 means, 100 Ω resistance at

0°C. Initially calibrated for values of m Amps against the corresponding values of

resistances. Rate of change is 0.385 Ω/°C. Can read from 0 to 300°C. The wire of

platinum wound on ceramic material enclosed in a steel capsuled filled with

ceramic powder.

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


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CTs Current transformers. Used to measure current. Works on the principle of electromagnetic induction. A very high value current is stepped down to a measurable value and then measured by CT.

N2/N1 = I1/I2 Always operated in a short circuit. CTs of specific measurable current rating are available. If current is too small to be measured with CT then a turn is given to primary wire. In this way CT reads double current, which is now in its range, than the real stepped down value. In the PLC, the current value is then divided by # of turns of the primary wire to get the original current value.

Vibration measurement Old vibration measurement devices had a ball of magnet placed on a spring attached to a solid base. A coil is present around the magnetic ball. When surface vibrates, magnetic ball moves and voltage is induced in the coil due to change in flux. Amplitude of the voltage gives vibration and frequency gives repeatability. Now a days a piezoelectric material is used which produces voltage when vibrated or pressure is applied on it. Vibration is measured in mm/s.

PLC Programmable Logic Controller. It consists of a power supply, CPU and some

digital and analog inputs and outputs. Different DPs are available for controlling

real I/O sub PLCs, MV panels, VFDs, LV simocodes. 10 main units of PLCs are

installed.9 schneider electric. 1 siemens. Some sub PLCs are also installed.

Overall communication is done through Profibus, optical fiber and Ethernet

cable. Profibus can travel the signal upto 100m of length without using

repeaters. For more than 100m distance, optical fiber is used. Windows based

Expert Control Supervision (ECS) is also used. Machine Status Word (MSW) links

between ECS and PLC.

Motor’s Frequency drives Also known as vvvf (variable voltage variable frequency). N=120f/p N α f. So by varying frequency, speed can be varied.

Eemf =4.44ΦBfN Eemf α f. When f decreases, back emf Eemf decreases, so difference between applied voltage and Eemf increases which increases current at no load. So to decrease current at no load applied voltage V should be decreased to the value near to Eemf. Also when f decreases impedance Z decreases since Z= R+2πfL. Since I=V/Z. So both V & Z should be decreased simultaneously to decrease current at no load. Frequency drive’s input is AC, which goes to a bridge rectifier. Bridge rectifier converts 3 phase AC into pulsating DC which is then smoothened using a capacitor. Input to the rectifier is usually from both star and delta configuration simultaneously which are 30 degrees electrically apart. So output of the rectifier for such input is a DC with 12 pulses in a cycle, which is then smoothened easily


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with a capacitor of small RC. This DC is then fed to inverter to convert it into variable voltage variable frequency Sine wave output. Inverter has H-bridge configuration. Switches used are usually thyristors. Their firing angle is controlled through PWM generated by a CPU. Output of the bridge is square wave. Changing the pulse time in each cycle changes frequency of the output. Average voltage is changed by changing the Ton & Toff time of the output pulse, which is changed through firing of thyristors using PWM. Thus motor can be operated at desired frequency & desired voltage keeping in mind the current at no load. Basic principle V/f = constant. In high power frequency drives, many low power frequency drives are operated in parallel.

Capacitor forming To wake up capacitor dielectric when not in use for many years. Starting from low voltage and increasing it in steps, voltages are applied for certain time.

References:

www.sick.com/.../cement/Pages/cement.aspx www.siamrefractory.com/cement_cyclone.php www.freepatentsonline.com www.DGcement.com

http://www.dgcement.com/


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Report Prepared By:

Muhammad Affan Usmani (UET-11-F-BSc-ET-CASE-05) Electrical Engineering Department, CASE, Islamabad. DG-Cement Internship 2014 ( June 26- July 5) Contact 92- 0313-5421168

dgkccl affan internshipp report

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