NFL summer internship report

DR. B. R. AMBEDKAR NATIONAL INSTITUTE OF TECHNOLOGY JALANDHAR

SIX WEEK INDUSTRIAL TRAINING REPORT IN THE PARTIAL FULFILLMENT FOR THE AWARD OF THE DEGREE OF BACHELOR OF TECHNOLOGY IN INSTRUMENTATION AND CONTROL ENGINEERING

SUBMITTED BY: ICE(6thsem)

A REPORT ON Distributed Control System Prepared in Partial Fulfillment of Industrial Training – I AT National Fertilizers Ltd.

BATHINDA

Submitted to: DR. B.R.AMBEDKAR NATIONAL INSTITUTE OF TECHNOLOGY JALANDHAR June-July 2012 ACKNOWLEDGEMENT The industrial training in an industry / project site is an essential part of curriculum for completion of B.Tech degree. I am grateful to authorities at National Fertilizers Limited, Bathinda for permitting me to undergo six weeks Industrial training in their esteemed organization. During this training I have learnt a lot, for which I pay my heartiest gratitude to the HRD Sr. Manager

Mr. D.K Bora and other staff members of National Fertilizers Limited, Bathinda who helped me in all respects in fulfilling my cherished desire of getting a successful Industrial training. I am very thankful to Mr. Sunil Arora (D.G.M – INST.), Er. B.B Grover (MGR), Mr. R.C Sharma (A.M), Er. Sanjay Yadav(A.M), Mr. S.P Mittal, Er Baltev Singh, Mr. Harvinder and all the supervisors and other officials for providing me complete process details of their respective plants.

ABSTRACT The training report on the working of National Fertilizers Limited, Bathinda has been prepared in accordance with the requirement of scheme of four year B.Tech degree course in Instrumentation and Control engineering being taught at at NIT Jalandhar In this course industrial training is an integral part of the curriculum and can be undertaken in any reputed industry. I have done this training at National Fertilizers Limited, Bathinda which is situated on Bathinda – Goniana road and is very well connected with rail and road. It is very well known for its excellent performance over the past years. I have studied whole plant with Captive Power Plant in detail.

It is pleasure to face the Industrial life that helped me to convert my theoretical concepts into practical knowledge. During this training I came across many emergency situations in the plant that surely explained me, actual industrial life.

KIRANJEET KAUR

TOPIC

INTRODUCTION COMPANY PROFILE STEAM GENERATION PLANT CAPTIVE POWER PLANT INSTRUMENTATION WORKSHOP PROJECT STUDY

CONCLUSION BIBLOGRAPHY

INTRODUCTION NFL is known in the industry for its work culture; value added human resources, safety, environment, concern for ecology and its commitment to social upliftment. All NFL plants have been certified for ISO-9002 for conforming to international quality standards and International Environmental Standard i.e. ISO-14001. With the certification of Corporate Office/Marketing operations under ISO-9001:2000, NFL has become the first Fertilizer Company in the country to have its total business covered under ISO-9001 Certification. On 23rd August 1974, NFL was formed and registered to set up two modern large capacity Nitrogenous Fertilizers plants. NFL, Bathinda (Punjab) NFL, Panipat (Haryana) each with the capacity of 5-11 lakh tones /annum. As to set up any plant there are some essential conditions that support the existence and working of plants for years, so Bathinda was basically selected as one of the site of Fuel based plant as per consumption point of view since Punjab is mainly agriculture based state. NFL was incorporated on 23 rd August 1974 in order to implement this project contract were entered into with M/s " TOYO ENGINEERING CORPORATION " a well known Japanese Engg.

Company and Engg. India Ltd (EIL), a public sector and Engg. Organization .This contract becomes effective on September 26, 1974 with a guaranteed “Feed in “on the Bathinda Fertilizers project to implement within 36 months from the zero date. Due to the power requirements and some other factors, later on it was planned to set up its own power house known as Captive Power Plant (CPP) with 2 turbo generators of 15 MW each. National Fertilizers Limited (N.F.L.) is the largest manufacturer of nitrogenous fertilizers in the Northern India. It is presently operating four large fertilizers plants, two of which are located at Nangal and Bathinda in the Punjab State, one at Panipat in Haryana and one at Guna in M.P. While plants at Nangal, Bathinda and Panipat are fuel-oil based, the one at Guna is gas-oil based. The overall installed capacity of NFL plants is 10.42 lakh MT per annum. The old plant at Nangal was commissioned in 1961 followed by expansion which was commissioned in 1978. Bathinda and Panipat plants were commissioned in 1979. Guna Plant which is the latest plant of NFL was commissioned in Dec, 1978 and is now in full production.

NFL was incorporated on 23rd August, 1974 with two manufacturing Units at Bathinda and Panipat. Subsequently, on the reorganization of Fertilizer group of Companies in 1978, the Nangal Unit of Fertilizer Corporation of India came under the NFL fold. The Company expanded its installed capacity in 1984 by installing and commissioning of its Vijaipur gas based Plant in Madhya Pradesh. NFL Corporate office: Noida

The Vijaipur Plant was a land mark achievement in project management in India. The plant was completed well within time and approved project cost. In recognition of this achievement, the project was awarded the First Prize in Excellence in Project Management by Govt. of India. Subsequently the Vijaipur plant doubled its capacity to 14.52 lakh MTs by commissioning Vijaipur Expansion Unit i.e. Vijaipur-II in 1997. The plant annual capacities have now been rerated w.e.f. 1.4.2000 from 7.26 lakh MT of Urea to 8.64 lakh MT for Vijaipur-I & Vijaipur-II Plants each.

Three of the Units are strategically located in the high consumption areas of Punjab and Haryana.The Company has an installed capacity of 35.49 lakh MTs of Nitrogenous Fertilizers and has recorded an annual sales turnover of Rs.3, 474 crores during 2004-05.

Company Profile NFL Schedule - A & Mini Ratna Category 2004-2005.- I Company, is a market leader in the fertilizer Industry in India with 17.0% share in Urea production during 2004-2005.

PERCENTAGE SHARE OF UREA PRODUCTION IN THE COUNTRY (2004-2005)

NFL

IN

Kisan Urea and Kisan Khad NFL’s popular brands are sold over a large marketing territory spanning the length and breadth of the country. The Company also manufactures and markets Bio fertilizers and a wide range of industrial products like Methanol, Nitric Acid, Sulfur, Liquid Oxygen, Liquid Nitrogen etc. The Company has developed Neem coated Urea which on

demonstration has improved the crop yield by 4-5%. The Company is focusing its thrust to widen the marketing operations of Neem coated Urea. NFL over the years has developed a team of dedicated professionals in the areas STEAM GENERATION PLANT

Steam Generation plant is mainly installed for production of steam and then distributed to various parts of the plant. Here this section of plant installed in National Fertilizers Limited, Bathinda unit produces and supplies steam at 100 Kg / cm2 pressure and nearly 480°C temperature to Ammonia Plant. In today’s world steam has gained importance in Industries. It may be used for power processes and heating purposes as well. BENEFITS OF STEAM It is colorless, odourless and tasteless. Very economical Non polluting Can be used as heat exchanger. It can be easily distributed to various sections of plant. Steam is generated in Boilers (Water tube boilers mounted on common base fitted with mountings and fittings) and then distributed to other parts of plants. For governing the quantity of fuel to be burned and for maintaining the required pressure their are many automatic fuel feeders, equipments and auxiliaries like pressure gauge etc. In the Boilers used at National Fertilizers Limited (Bathinda unit); coal, oil natural gas are used as a fuel for production of steam. NFL , Bathinda is using steam for two purposes ; first and the main reason is for running prime mover and other reason is to exchange heat in the processes taking place their. There are three boilers capable of producing steam at the rate of 150 Tonnes/hr installed in CPP which were supplied and erected b BHEL. Generally two boilers are enough to meet the requirements but third boiler is simultaneously running because if steam load consumption increases then the third boiler plays its part in order to avoid any faulty condition. FUELS USED:

Coal : To obtain steam of desired Temperature and pressure, coal is burned to give major source of heat. Initially coal is stored at Coal Handling plant brought from coal sites. It is this section of plant where coal is crushed by crushers in order to make small pieces of coal, then after crushing it the coal pieces rare passed through heavy electromagnet where iron is separated from coal if present. Coal is then sent to Bunkers from where it goes to Grinding mill. Grinding mill is grinding coal into powder form. Conveyor Belts are being used in the whole plant for transportation of Coal. The powder form of coal is sent to the Boilers through pump as pump sucks the coal from grinding mills and throws it into the boiler for combustion. Fuel Oil : As the Boilers are designed to work on both Coal as well as Fuel Oil so fuel oil can also be pumped to Boiler for combustion. Generally coal alone is not burnt Initially but Fuel Oil (LSHS) is mixed coal and then sent to the furnace for combustion in order to get desired temperature . WHY AND WHERE STEAM IS REQUIRED As National Fertilizers Ltd, Bathinda unit has its own Steam Generation Plant where steam is produced which is used for driving Turbo Compressors, Heating Purposes, for various reactions taking place in the plant itself. Steam is mainly consumed in the Ammonia Plant as nearly 6 to 7 tonne of steam is required to produce 1 tonne of Ammonia. High Pressure Turbines are being used where high pressure and temperature is to be maintained so SGP section plays a important role for maintaining the said condition. There are three boilers (VU-40 type supplied by M/S BHEL) of 150 tonne/hr capacity .These boilers are Water Tube Boilers i.e. water is inside the tubes and hot air surrounds it when coal is burnt, this makes the water in the tubes boil and steam formation takes place. In the beginning coal is burnt with fuel oil in order to get desired temperature.

WATER AND STEAM SYSTEM

As the steam being used should be free from impurities like minerals, silica, oxygen, Iron etc. in order to insure Safe and Efficient working of Steam turbines and Boilers. For this purpose Raw Water is physically and chemically treated and finally supplied to Steam Generation Plant from Ammonia plant. This water is called Boiler Feed water which is further heated to 240º C by the flue Gases and taken to Steam Drum. Steam Drum Acts as storage tank and also separates water from the steam at 315º C and 106 kg/cm2 pressure water then enters the Ring Header formed at on the bottom of outside the furnace and rises by gravity through water wall tubes on the all the four sides, taken heat from furnace and enters steam drum as a mixture of steam and water. FLUE GAS SYSTEM The products of combustion in the furnace consist of carbon-di-oxide, nitrogen, ash, oxygen and sulphur-di-oxide. After leaving the furnace the heat Of these gases called FLUE GASES, is utilized at various levels. First the steam from steam drum is heated in two super heaters to get the required temperatures of 4950C and then feed water in BANK TUBES is also heated and the gases leave bank tubes at around 4970C next the heat is utilized to heat feed water in the ECONOMIZER and gases are cooled down to 3200C. These gases are further cooled down to 150 0C in ROTARY AIR HEATER where the air is required for combustion and conveying the coal is heated up. Temperature is not reduced further because at lower temperature oxides of sulphur present in flue gases are converted to ACID which damages the down stream equipments. These gases then pass through ELECTRO STATIC PRECIPITATOR (ESP) where ash is removed.

CAPTIVE POWER PLANT INTRODUCTION: National Fertilizers Limited has set a Captive Power Plant (CPP) at their complex at BATHINDA, to ensure availability of stable, uninterrupted power and stream to the Ammonia and Urea plant. This will minimize the tripping of the Fertilizer Plant due to transit voltage dips and power cuts. Since inception, Bathinda unit was drawing electric power from Punjab State Electricity Board (P.S.E.B). Electricity is the main driving force after steam in the plant, being used for

moving auxiliary equipments. The unit requires 27MW of power/hr when running at full load. There are two 15 MW turbo-generators to generate power. Under normal running conditions of the plant and healthiness of the P.S.E.B. grid, we generally run in synchronism with the grid merely drawing the power corresponding to the minimum charges to be paid to state electricity board. In case of any disturbance in the grid, our system gets isolated from the grid automatically. With both generators running, we are able to feed power to the whole plant, thus production is not affected. In case only one turbo generator is in line and grid cuts off, urea plant is cut off automatically to balance the load with one generator. As soon as the grid becomes stable, the generators are again synchronized with it. The power generation of each generator can be varied with 2 MW to 15 MW maximum, provision exists to run the generator on 10 % extra load continuously for one hour only. Operation of C.P.P. is based upon microprocessor based computerized instrumentation which allows automatic operation, start up, shut down of the whole or part of the plant. Latest instrumentation has been used in this plant. It allows controlling process variables like flow, pressure, temperature, power factor, voltage, frequency, etc. There is operator interface unit (IOU) Like a TV screen on which various parameters can be displayed and controlled. It allows fully automatic start-up, shut-down of boiler, turbine and other auxiliaries.

NEED FOR C.P.P: It was thought to install a captive power plant in which electric power for our requirement shall be generated in a COAL FIRED BOILER. The benefits envisaged were: 1. Any disturbance in the PSEB grid used to trip the whole plant. Lot of money was lost due to this as each re-startup costs around 40 to 50 lakhs rupees. Moreover, frequent tripping’s had an ill effect on machines and equipments extending the re-startup period. 2. Three boilers of 150Te/hr steam capacity were initially installed in SGP to keep 25 boilers running and one stand by as designed steam requirement was less than 300Te/hr. but in actual operation steam requirement was more and all three boilers had to be run and there was no breathing time for their maintenance. As new boiler was to be installed for CPP, its capacity was so designed that it could export around 60Te of steam for process requirement so that only 2 boilers of SGP would be run keeping the 3rd as stand by. With these points in mind CPP was installed. The functioning of CPP can be sub-divided into parts:

BOILER AND ITS AUXILIARIES: For generation of high pressure superheated steam. TURBO-GENERATOR AND ITS AUXILIARIES: To generate power, using steam from the boiler. Operation of CPP is based upon microprocessor based computerized instrumentation which allows automatic operation, start up, shut down of the whole or the part of the plant. BOILER The basic principle of this boiler is the same as discussed earlier for SGP boiler that is formation of steam by heating boiler feed water inside furnace fired by coal and heavy oil, utilization of heat of the gases and venting these gases at a safe height. Main differences between the two boilers are: SGP boiler is tangentially fired where as CPP boiler is front fired with 6 coal burners and 6 oil gun fixed inside the coal housing. SGP boiler can be loaded up to 30% load with oil firing only whereas CPP boiler can be fully loaded with oil alone. Height of combustible zone in CPP boiler is more and it has residence time of 1.5 sec where SGP boiler has 1.0 sec. Mills used for pulverizations of coal in SGP are negative pressure bowl mills whereas in CPP ball tube mill are used which are positive pressure mills. Due to more residence time and better pulverization the efficiency of CPP boiler is about 4% higher. Boiler feed water required for steam generation can be fully generated in CPP itself. A part of the steam generated is exported for process use in ammonia plant and rest is utilized for power generation in turbo generators as described below:

DESCRIPTION MITSUI RILEY TYPE BOILER Maximum evaporation Design process for boiler

2, 30,000kg/hr 124kg/cm2G

Steam temp at outlet

4950C

Heating surface

1250M2

POWER GENERATION: In C.P.P. two generators of 15MW capacity generate a voltage of 11KV which is fed to the two transformers in the yard. The rating of the transformers is 31.5/25 KVA, these two values depend upon the cooling which we provide, as here 25KVA capacity is when cooling is oil natural air natural and 31.5KVA capacity is when cooling is oil natural air forced. Both these transformers step up the voltage level to 132KV. From the transformers the three phases pass through the lightning arrestors (LA). After this they pass on to the isolator. After this the two lines pass on to the TRANSMISSION pole called DOUBLE CIRCUIT TRANSMISSION. Then these lines go to the M.R.S. i.e. main receiving station. TURBINE: The turbine used is supplied by M/S SGP of AUSTRIA. It is condensing cum extraction turbine designed as single casing reaction turbine with single control stage and high pressure (HP), mild pressure (MP) and low pressure (LP) reaction parts. The turbine is fed with high pressure steam at 100kg from boiler and flows through various control valves for normal and emergency operation. It gets high velocity through the nozzle group and then passes over the impellers fixed on to the rotor and fixed diffusers thus rotating the turbine. The enthalpy of steam is utilized in steps. Steam is also extracted from various stages. HP1 at 10.4kg/cm2, HP2 at 8.1kg/cm2, feed water bleed at 4.3kg/cm2 and LP bleed at 0.9kg/cm2. The exhaust steam from the turbine is condensed in a condenser maintained under vacuum to extract maximum steam enthalpy. The output of the turbine depends on flow of steam and heat difference that is on condition of steam at the main steam valve and the pressure at the turbine outlet or condenser pressure. The turbine is connected to the generator through speed reducing gears. The exhaust steam is condensed in a condenser using cooling water. The resulting condensate can be fed back to LP heater but is normally sent to the polishing water plant. As shall be clear from the attached block diagram various bleeds from the turbine are utilized for heating purpose. HP 1 and HP2 are used for heating boiler feed water in HP 1 and HP2 heaters. Feed water bleeds is used for heating the feed water tank and LP bleed is used for heating the polish water make up to the feed water tank. A lubrication system is also there to lubricate the various bearings of the turbine, gears and generator. Normally the oil pump driven by the turbine shaft supplies oil but auxiliary motor

driven pumps are used for start up and during shutdown. A turning gear has been provided for slow cooling of turbine rotor. Latest instrumentation has been used in this plant. Bailey’s net work-90 microprocessor based instrumentation system is being used. The NETWORK 90 SYSTEM is a distributed process control system. Using a series of integrated control nodes. The network 90 system allows controlling process variables like flow, pressure and temperature according to a control configuration. There is operator interface unit (OIU) like a TV screen on which various parameters can be displayed and controlled. It allows fully automatic start-up/shut-down of boiler, turbine and other auxiliaries. DESCRIPTION:Make

Simmering Graz Panker, Austria

Type

Multifunction (28 stages)

Capacity RPM

65 T/H at 15 MW 6789 at 50 Hz

Critical speed

3200-3600 RPM

GENERATORS CPP is having two number turbo generators of capacity 15MW each. The generators are type SAT three phase, 50Hz, 11kV, 984amps, at 0.8 power factor rating supplied by M/S JEUMONT SCHNEIDER OF FRANCE. These are totally enclosed self ventilated type with two lateral airs to water coolers for cooling. The alternators are able to bear 10% overload for one hr with an increase in temp. of 10 0C while maintaining the voltage as near as possible to the rated one. The excitation is compound and brush less with exciter rotor and Rectifier Bridge mounted on the extended main shaft on non driving end. The excitation is controlled automatically with automatic voltage regulator and a PLC controller. All protection relays installed for protection of generator are solid state having high accuracy, quick response and low power consumption. Under normal running conditions of the plant and healthiness of the PSEB grid, we generally run in synchronism with the grid merely drawing the power corresponding to minimum charges to be paid to state electricity board. In case of any disturbance in the grid measured by higher low frequency, high rate of change of frequency, low voltage etc. our system gets isolated from the grid automatically. With both generators running, we are able to feed power to the whole plant, thus production is not affected.

UNINTERRUPTED POWER SUPPLY: The uninterruptible power supply system is connected between a critical load, such as digital drives & automation, distributed digital process control system, telecom equipment, programmable logic controller, mission critical applications, computer and its three phase mains power supply under all rated load and input supply conditions. The system offers the user with the following advantages: Increased power supply: The UPS has its own internal voltage and frequency regulator circuits which ensure that its output is maintained within close tolerances independent of voltage and frequency variations on the mains power lines. REDUNDANT Vs NON REDUNDABT CONFIGURATIONS:In a non-redundant configuration the system is sized such that both UPS modules are required to feed the potential load and if one of the two modules develops a fault or for some reason shut down, the other module also automatically shuts down. In such an event the load is transferred to an unprocessed bypass supply. In a redundant module configuration the system is sized such that the potential load can be provided by just one of the two modules. Under normal circumstances both modules are operational and share the load current equally; but if one module develops a fault, or

is shut down, the second module is able to take over the full load demand and continue to provide it with processed, backed-up power. 7400 Module Design:The UPS basically operates as an AC- DC-AC converter. The first conversion stage (from AC to DC) uses a 3 phase fully controlled silicon controlled rectifier (SCR) bridge rectifier to convert the incoming mains supply into a regulated 432V DC bus bar. The DC bus bar produced by the rectifier provides both battery charging power and power to the inverter section-which is of a transistorized / IGBT based pulse width modulation (PWM) design

and provides the second conversion phase i.e. reconverting the DC bus bar voltage back into an AC voltage waveform.

INSTRUMENT WORKSHOP Workshop is the important area of industry.in the workshop all engineering designs are implemented practically. Repair, maintainence and design work are done here. all instruments whether it is pneumatic or electronic are repaired in this workshop. In NFL many pneumatic systems are replaced by electronic instruments, stripchart recorders are replaced by chartless recorder. the plant is having pneumatic system in field but electronic signal requires current signal so pneumatic signals are converted to current signals with the help of I/P converter.

In this industry different parameters are to be controlled like pressure, temperature, flow, level etc. For these parameters there are different instruments like for Pressure:bourden tube Level:radar system,dp transmitter Flow:venturimeter,orifice DEADWEIGHT TESTER A dead weight tester apparatus uses known traceable weights to apply pressure to a fluid for checking the accuracy of readings from a pressure gauge. A dead weight tester (DWT) is a calibration standard method that uses a piston cylinder on which a load is placed to make an equilibrium with an applied pressure underneath the piston. Deadweight testers are so called primary standards which means that the pressure measured by a deadweight tester is defined through other quantities: length, mass and time. Typically deadweight testers are used in calibration laboratories to calibrate pressure transfer standards like electronic pressure measuring devices.

Operating Principle Fluid Pressure generated by a screw pump acts on the bottom of a vertically free floating piston. The force produced pushesthe loaded free piston vertically upwards. The piston floatsfreely in its cylinder and the pressure in the circuit will be determined by the weights loaded on the piston

divided by theeffective area of the piston with corrections for value of acceleration due to gravity, air buoyancy, surface tension and datum level difference. The formula on which the design of a DWT is based basically is expressed as follows : p

=

F/A

[Pa]

where : p :reference pressure [Pa] F :force applied on piston [N] A :effective area PCU [m2]

PRESSURE GAUGES Basic Principle of Bourdon tube pressure gauge: when an elastic transducer ( bourdon tube in this case ) is subjected to a pressure, it defects. This deflection is proportional to the applied pressure when calibrated. Operation of Bourdon tube:

The pressure to be measured is connected to the fixed open end of the bourdon tube. The applied pressure acts on the inner walls of the bourdon tube. Due to the applied pressure, the bourdon tube tends to change in cross – section from elliptical to circular. This tends to straighten the bourdon tube causing a displacement of the free end of the bourdon

tube.

This displacement of the free closed end of the bourdon tube is proportional to the

applied pressure. As the free end of the bourdon tube is connected to a link – section – pinion arrangement, the displacement is amplified and converted to a rotary motion of the

pinion.

CONTROL VALVES Control valve is a device which controls fluids passing through a restriction by regulating the travel of stem or plug. The control valve works as a variable resistance in the pipeline. FUNCTION OF CONTROL VALVE The Control Valve plays a very important role in the automatic control of modern plants. The control valve manipulates a flowing fluid such as gas ,steam ,water, or chemical compounds to compensate for load disturbances and keep the required process variable as close as possible to the desired set point.Basically it is a flow control device so by controlling the flow of fluids a control valve indirectly controls the process variable that may be LEVEL,TEMPERATURE, and PRESSURE ETC.

.Control valve parts •

ACTUATOR: A fluid -powered or electrically powered device that supplies force and motion to a valve closure member (plug).

•

BODY:The body of the valve is the main pressure boundary. It provides the pipe connecting ends and the fluid flow passageway. Selection of valve body material depends upon mechanical strength and resistance to errosion it

PARTS OF ACTUATOR DIAPHRAGM A flexible pressure responsive element that transmits force to the diaphragm plate and actuator stem. FORCE PLATE The support plate which gives support to the diaphragm and exerts force uniformly SPRING

This is required for single acting actuators to return to normal position when air supply is failed. YOKE Yoke is the fixed connection (mounting) between body and actuator. PARTS OF BODY •

BONNET: The bonnet is that portion of the valve pressure retaining boundary which may guide the stem and contains the PACKING BOX and STEM SEAL.

•

TRIM Includes all the parts that are in flowing contact with the process fluid except the body, BONNET, and body flanges and gaskets. It includes the plug, seats, stem, guides, bushing & cage.

•

STUFFING BOX The chamber located in the BONNET which surrounds the stem and contains the PACKING and other stem-sealing components. PACKING a part of valve assembly used to seal against leakage around the valve disk or stem.

FLOW COEFFICIENT (Cv): It is the no.of US gallons per minute of water at 60 deg F which will pass through a valve at maximum opening with a pressure drop of one psi.i.e Cv means of understanding the relative capacity of each size of valve. Its most basic form is Where Q is flow rate P is press.drop across the valve The Cv value increases if flow rate increases or if press. drop decreases. Cv = AD Where A is constant called valve discharge coefficient B is another constant D is valves diameter in inches

Cv = Q  G/P

Control valves are classified according to – -

Body types

-

Characteristics

-

Seat Leakage

TYPES OF CHARACTERISTICS •

LINEAR: A characteristic where flow or (Cv) increases linearly with valve travel. Flow is directly proportional to valve travel. Q = ky k = constant , y = valve opening , Q = Flow at constant press. Drop.

•

EQUAL PERCENTAGE: With an equal % ch., each increments of valve plug movement produces a change in flow rate which is proportion to the amount flowing, before the change is occurred. In this, flow change to the lift is small, when the valve travel is small.As the travel becomes large,however the flow change corresponding to the same lift tends to becomes greater, means the change is always proportion to the flowing quantity.

Q = b eay •

QUICK OPENING: These are used when maximum valve capacity must be obtained quickly (I.e for ON OFF control).A quick opening valve has a linear ch. For about one forth of its travel from shut off ,when sized to operate in this range, it becomes a linear valve. Beyond this point ,it has a little use, except for an ON OFF control.

PROBLEMS FACED •

CAVITATION : Cavitation happens between the two-stage process of vaporization and condensation of a liquid. As fluid passes through a valve just downstream of the orifice area, there is an increase in velocity or kinetic energy that is accompanied by a substantial decrease in pressure or potential energy. This occurs in an area called the VENA CONTRACTA. If the pressure in this area falls below that of the vapor pressure of the flowing fluid, vaporization (boiling) occurs. Vapor bubbles then continue downstream

where the velocity of the fluid begins to slow and the pressure in the fluid recovers. The vapor bubbles then collapse or implode. •

FLASHING : Flashing is a one stage phenomenon.Flashing is similar to Cavitation except the vapor bubble do not collapse,as the downstream pressure remains less than the vapor pressure.The flow will remain a mixture of vapor and liquid. When the vapor pressure downstream of a control valve is less than the upstream vapor pressure, part of the liquid changes to a vapor and remains as a vapor unless the downstream pressure recovers significantly. This is called Flashing The vapor bubbles along with the fluid ( dual face flow) can also cause mechanical damage to the valve and piping system

•

CHOKED FLOW: This condition exists when at a fixed upstream pressure the flow through valve cannot be further increased by lowering the downstream pressure.

•

Fluids flow through a valve because of a difference in pressure between the inlet (Pl) and outlet (P2) of the valve. This pressure difference (Delta-P) or pressure drop is essential to moving the fluid. Flow is proportional to the square root of the pressure drop. Which means that the higher the pressure drop, more will be fluid flow through the valve. How to reduce cavitation & Flashing

By using anti cavitating trims effect of cavitation can be reduced. The pressure reduction is done in stages to decrease the velocity by providing a volume in between. By doing this the pressure never falls below the vapour pressure of the liquid.

ANALYZERS There are various types of analyzers with different principle Some of them are: 1)electrochemical analyser 2)thermal conductivity based analyser 3)ir analyser Electrochemical analyzer These type of analyzers based on chemical reaction.Under these type of analyzers we study H2S analyzer.in the process we have to measure .1ppm of H2S ie we use these type of analyzer. Lead Acetate Tape. Methodology.

This method relies on the chemical reaction of H2S with lead acetate

impregnated paper tape to form lead sulfide. The lead sulfide appears as a brown stain on the paper tape. A light source is used to illuminate the tape where the reaction is to occur and light detector

is

used

to

monitor

the

reflection

of

the

source

from

the

tape.

A concentration of H2S can be determined by the rate of staining on the tape. Lead acetate, Pb(CH3COO)2, is a white salt. Light illuminating the tape reflects on the white surfaceand a photodiode detects the reflected light. The H2S reacts with the lead acetate to produce leadsulfide (PbS) which forms a dark brownish stain on the white tape. Less light reflects when the colorof

the tape changes from white to brown due to H2S. The decreasing amount of reflected light isproportional to the amount of sulfur in the sample.

THERMAL CONDUCTIVITY ANALYZER Each gas has a known thermal conductivity, that is how well heat transfers through it. This property can be measured. Thermal conductivity is measured with a sensor that employs four matched filaments that change resistance according to the thermal conductivity of the gas passing over it. The thermal conductivities of some gases can be found in Table A below. GAS THERMAL CONDUCTIVITY ACETYLENE 4.400 AMMONIA 5.135 ARGON 3.880 CARBON DIOXIDE 3.393 CARBON MONOXIDE 5.425 CHLORINE 1.829 ETHANE 4.303 ETHYLENE 4.020 HELIUM 33.60 HYDROGEN 39.60 HYDROGEN SULPHIDE 3.045 METHANE 7.200 NEON 10.87 NITRIC OXIDE 5.550 Table A. Thermal conductivities of common gases.Theory & Principle of Operation The sensor uses four matched filaments that change resistance according to the thermal conductivity of the gaspassing over it. These four filaments are connected in a Wheatstone Bridge configuration as shown below in Figure 1.

(Figure 1. Wheatstone Bridge of the thermal conductivity detector.) When all four resistances are the same, VOUT is zero and the bridge is considered balanced. When zeroing, the reference gas is passed over all the filaments, the resistances will be the same (because filaments are matched) andthe bridge is balanced. When the sample gas is passed over half of the bridge, then VOUT’s value correlates to the content of the sample gas in the reference.The detector is a four element Katharometer having two elements situated in the reference gas and two elements in the sample gas shown in Figure 2 below.

(Figure 2. Cut-away view of the thermal conductivity sensor.) The four elements are electronically connected in a bridge circuit and a constant current is passed through thebridge to heat the elements. If each element is surrounded by the same gas, then the temperature, and hence theresistance, of each element will be similar and the bridge circuit will be balanced.

APPLICATION Measure the gas sample content of a sample/reference mixture by comparing the thermal conductivity of the mixture with that of a reference. For example, hydrogen has a thermal conductivity which is approximately seven times greater than that of nitrogen, so small changes are readily detected. All other common gases have thermal conductivities similar to nitrogen so the method of measurement is fairly selective.

Other gases that may be measured using this technique are: 

Carbon Dioxide



Oxygen



Argon



Methane



Sulphur Dioxide



Ammonia In NFL we are using this type of analyzer for hydrogen

IR ANALYZERS Gases to be detected are often corrosive and reactive. With most sensor types, the sensor itself is direct exposed to the gas, often causing the sensor to drift or die prematurely.The main advantage of IR instruments is that the

detector does not directly interact with the gas (orgases) to be detected. Principle of Operation The infrared detection principle incorporates only a small portion of the very wide electromagnetic spectrum .The portion used is that which we can feel as heat. This is the region close to the visible region of the spectrum to which our eyes are sensitive. Electromagnetic radiation travels at close to 3 x 10^8m/sec and has a wave-like profile. Let’s review the basic physics of electromagnetic radiation by defining the terminology involved with it. The major functional components of the analyzer are protected with optical parts .In other words, gas molecules interact only with a light beam. Only the sample cell and related components are directly exposed to the gas sample stream. These components can be treated, making them resistant to corrosion, and can be designed such that they are easily removable for maintenance or replacement. Today, many IR instruments are available for a widevariety of applications. Many of them offer simple, rugged, and reliable designs. In general, for toxic and combustible gas monitoring applications, IR instrumentsare among the most user friendly and require the least amount of maintenance. There is virtually an unlimited number of applications for which IR technology can be used. Gases whose molecules consist of two or more dissimilar atoms absorb infrared radiation in a unique manner and are detectable using infrared techniques.

PROJECT ON DCS INTRODUCTION

INTRODUCTION Before the introduction of dcs we have pneumatic system, due to the limitation of pneumatic system , electronic system come into the process and after that dcs comes into picture. Due to the several advantages of dcs it come into existence. Stage I Stage II Stage III

Pneumatic Instrumentation Electronic Stand alone Controllers Distributed Control System

A Distributed Control System (DCS) refers to a control system usually of a manufacturing system, process or any kind of dynamic system, in which the controller elements are not central in location (like brain) but are distributed throughout the system with each component subsystem controlled by one or more controllers. The entire system of controllers are connected by networks for communication and monitoring A DCS typically uses custom designed Processors or Controllers and uses both proprietary inter connections and protocols for communication. Input and output modules form component parts of DCS. The processor receives information from input modules and sends information to output modules. Input module receives information from input instruments in the process (field) and output modules transfer instructions to the output instruments in the field. Computer buses or electrical buses connect the processor and modules. Buses also connect the distributed controllers to the Human-machine Interface (HMI) or control consoles. Main functions of DCS          

Measurement Analog, Binary and pulse signal conditioning Programming Control logic development performing closed & open loop control Data processing Data display Alarm monitoring & printing History Data archiving Report

DISTRIBUTION COMMUNICATION (CNET)

PCU1 TG#2

PCU2 SYSTEM

COMMON TG#1

PCU4

PCU5

TG#1

TG#2

MARSALLING / RELAY

Input from field INTRODUCTION → This PP system which was very recently installed in the Captive Power Plant NFL Bathinda on 8th March 2005. This is a completely automated plant, which is based upon very modern technologies in the control system. The working explanation could be given as follows: The signal from the field is received from the field which is received from the transmitter which is present in the field. The transmitter could be of any variable like temperature, pressure; flow level etc. This signal is received in the control section and is named under a tagging system. For example, “FR100”, this is representing flow in Turbine#1. The signal in the control room is a current signal. The signal could be changed to voltage signal by using a 250 ohm resistor. But due to prime advantage of current signal of not being affected by wire resistance is preferred. This current signal are sent to the field to operate a particular valve which is based upon the pneumatic system so I/p converter is to be used to change current signal to a pneumatic (pressure) signal. The signal received from the field is received in the MARSALLING /RELAY. These signals are then send to the PCU (Process Control Unit), from where the signal is sent to the C-NET. This signal is picked from the C-NET

by the server. This is then transferred to the clients who are connected to the server by O-NET Ethernet connection. Similarly in the reverse cycle, the signal is send from clients to the server then transferred to C-NET then to PCU and then signal is sent to the field. The information regarding each element in the diagram is given as follows:MARSALLING /RELAY → It is the end point of the control section. Here the signal is received form the field and then is sent to the terminating unit of the PCU. PCU (Process Control Unit) → The PCU is the most important section of the plant. PCU consists of a number of subsections. Signal from Marshalling/Relay is received at the termination unit of PCU consisting of termination modules. Signal is then sent to the slave unit and then to the Master Unit. Master Unit consists of MFP (Multi Function Processor). MFP sends and receive signal to field by using I/O modules (explained later). All these units are interconnected inside PCU by specific wire. These MFPs are connected to NIS (Network Interface Module) and NPM (Network Processing Module) which finally connects PCU to C-NET. C-NET→ It is the Communication Network also known as the PCL (Plant Communication Loop). The C-NET allows the signals from various PCUs and from the server and EWS to be entered and retrieved. C-NET consists of a redundant loop, which takes over in case of failure of the primary loop. O-NET→ This is the Ethernet Connection which is used to form LAN (Local Area Network) in the plant. This network is built under the bus Topology system in which all the units are connected as nodes. Since all nodes are connected in Bus topology each can access the data equally. It provides maximum speed of 100 MBPS. Client → Clients are HIU (Human Interface Unit) which are the computer which have GUI based software. Clients are used by the operator to perform any task. All clients have equal data sharing. Operator can send command from this mouse enabled unit which is used to perform specific tasks in the field. Server → Server is pathway which allows the request from client to be sent to the C-NET. It is the server which records the actions taken by the clients. The server installed is a non-dedicated server, meaning thereby, this server can also function as a client. Two servers available are primary and secondary servers. One of them is in use and other is a stand by. A number of server like historian, real time data server etc which are present in the plant have been explained later. Engineering Work Station (EWS) → EWS is a special computer which has direct access to the ONET as well as C-NET. It is used by an engineer to design, configure, monitor, change, trouble shoot and reinstall the Process portal system. EWS has inbuilt features of CAD with control drawing. EWS is also used to change and monitor functioning of modules. Connecting Cables → A number of connecting wires are to be used whose choice is made on the basis of speed, type of connections, type of data, operating environment etc. most of the connections in PCU are through SCSI cable.

The entire hardware is non-dedicated, which means hardware of various manufacturers could be connected together very easily. Hence all parts are manufactured on international standards. All the systems present are redundant for backup. All the connections shown also have redundant cables. DCS Components  The hardware Control Station  Software and licenses for control  Human Interface Station (HIS)  Engineering Station  Communication Network Control Station It consists of the Main controllers, it’s slave and termination modules, power supplies and their interconnections.The main controllers are hot redundant. All the logic and control strategy is built in the main controller. These controllers can handle very large number of control loops involving any complex functions. They are attached to various slave cards(analog, Digital, Pulse etc) which do all the signal conditioning of the data handled. These slave cards are linked to termination cards where the field wires are physically terminated. The Slave and termination card combination provides the required power supplies from a redundant source to the field devices (Transmitters, Relays etc.)

CONTROL STATION

Control Module The control module is a multiple loop analog, sequential, batch and advanced controller, that provides powerful solutions to process control problems. It also handles data acquisition and information processing requirements providing true peer-to-peer communications. The comprehensive set of function codes supported by these modules handles even the most complex control strategies. The system uses a variety of analog and digital I/O modules to communicate with and control the process. The control module can communicate with a maximum of 64 modules in any combination. The module has three operating modes: execute, configure and error. • In the execute mode, the module executes control algorithms while constantly checking itself for errors. When an error is found, the front panel LEDs displays an error code corresponding to the type of error found. • In the configure mode, it is possible to edit existing or add new control algorithms. In this mode, the module does not execute control algorithms. • If the module finds an error while in execute mode, it automatically goes into error mode. Software and licenses for control

There are different types of Software required for DSC. Licenses are to be obtained for using most of these software. Licenses comes in the form of a Dongle with a key no. to activate the Licenses. These software can be categorized as follows : 1. Software for operating system : This is the basic software on which other control software is being loaded. This software may be Microsoft windows based or Unix based software. Microsoft windows are most popular and user friendly whereas Unix based are most powerful. In CPP Windows 2000 professional and in SGP Windows XP are used as operating system. 2. Software for engineering station : A dedicated Licensed software is used for Engineering workstation. Functions of this software is given under the head Engineering station below. In CPP and SGP we are using COMPOSER for this purpose. 3. Software for front end operator station or Human interface station : A dedicated Licenses software used for HIS and functions are explained below. we are using Process portal B in CPP & Power generation portal in SGP for this purpose. 4. Software for Configuration Servers : A licensed software is used for configuring the data bases in bulk configuration manager to configure tags, their engg. units , ranges, limit values, alarm values and for automatic updating of any changes done from different HIS. Complete information of whole tag database are centrally stored in configuration server. We are using Windows server 2003 for this purpose. 5. Software for optimization, efficiency calculation etc. : These are the special & optional software used for optimization of plant efficiency , calculation of plant efficiency automatically obtaining available process data and manual feed data. This software also maintains a maintenance log sheet algorithm and provides information regarding maintenance of different equipments. 6. Software for printers : Recommended and compatible Software used for taking printouts of control logics, trends , alarms , graphics etc.

Human Interface Station ( HIS )

• The HIS is mainly used for operation and monitoring of the plant – it displays process variables, control parameters and alarms necessary for users to quickly grasp the operating status of the plant. It also incorporates open interfaces so that supervisory computers can access trend data, messages and process data & events. • Physically it consists of mostly general purpose PC with CRT, LCD based screens and normal keyboards with an option for dust and drip proof flat keys, which enable one touch operation. •

Advantages of the DCS displays. – High speed data update. – Multi-monitor function permitting to display more information.

– – – – – – – – –

Multi-window display mode. System message window display. Tuning trend displays. Dynamic graphics displays. Alarm handling functions. Print screen functions. Long term data archiving functions. Voice messaging functions. Security functions.

Engineering Station No matter how good a system is, it cannot succeed if the system configuration is extremely time consuming and difficult. So mostly the engineering functions are designed for efficient engineering- they are designed for ease of use and software reusability. It contains all the control logic templates, function codes, macros, shapes, and borders that are used to create controller configurations (control logic documents). Engineering tool consists of Memory blocks (locations and capacity ). Specific functions. Connecting tools. Constant value blocks.

Programming • • • • • • • •

Build the logic / control strategy using the various function blocks. Compile the logic. Check for any errors. Remove the errors one by one. If no errors then a configuration file is generated. Download this file to the controller and putting the controller to configure mode. Change the mode of the controller to execute mode. New configuration is downloaded in the controller.

Communication Modules The communication cards connects Communication network -to-HMI interface. controllers to:

It enables

• Communicate field input values and states for process monitoring and control. • Receive control instructions from plant personnel through human system interfaces to adjust process field outputs. • Provide feedback to plant personnel of actual output changes through human system interfaces. • Communicate controller function block configuration information and parameters. These parameters determine the operation of functions such as process control, data acquisition, alarming, trending, and logging. • Report status. • Download firmware. Data is transferred in messages that contain system data, control, and configuration information and also in exception reports. Communication network -to-control Unit Interface • Communication network provides a plant-wide communication network. • It provides time-synchronization across the control system plant wide. • Each node can operate independently of other Communication network nodes. • Control Unit interface modules provide localized startup and shutdown on power failure without operator intervention. • Fast response time. The 10-MHz communication rate gives timely information exchange. • The modules process information for maximum transmission efficiency. • The Control Unit interface modules handle four message types: broadcast, timesynchronization, multicast, and NIS poll. • All messages contain cyclic redundancy check codes and checksums to insure data integrity. CPP DCS SYSTEM 1. 2. 3. 4. 5.

Distributed control system for CPP was originally of “BAILEY NETWORK 90” Later on it was up graded with Symphony Harmony Industrial IT System for turbine side The boiler side is remained with Network 90 System. In this way CPP have to separate DCS System. Both systems are connected to a pair of redundant server.

OPERATING STATIONS DISTRIBUTION OF CPP DCS SYSTEM  A. B. 

Four Operating Station Are Connected Through Redundant O-Net To RTDS 1 & 2. Two Stations Are Loaded with History. One Station Is Loaded with Configuration Software. The Operating Station System Is Windows 2000 Professional Based.

NODE DISTRIBUTION OF CPP DCS SYSTEM 

It Has 15 (fifteen) Nodes connected to C – NET

HSI (Human System Interface) is achieved by using user friendly environment which is provided by using HIU (Human Interface Unit) which is a computer based upon GUI. PP is based upon graphics functions which are easily understood and presents a livelier picture. For example: - The graphics view of a steam boiler will not only have pictorial shape of boiler but also will show current state of the fire in graphical form which shows fire intensity as well as temperature. Any section of the plant can be viewed by just clicking upon the particular area as shown in the figure. MODULES Modules are the hardware components of the process portal. There are a number of modules which perform functions like input and output interaction with controller, address identification etc. Basic modules which are a necessary part of PP are:Digital Input Module

Description: - Digital input module IMDSI03 has a single printed circuit board that occupies one slot in MMU (Module Mounting Unit). It monitors two separate groups of eight inputs; hence there are totally 16 input lines. There are 12 inputs which are mutually isolated remaining 2 pair have common positive input lines. 16 LED’s are on the panel which shows the current status of the module. This module has 3 card edge connector as follows: P1  P2  P3 

Connects common and +5VDC. Connects module to I/O expander bus to the controller. Inputs digital signal using cable to terminating unit.

Inputs to the module are 120VAC, 24VDC, 48VDC or 125VDC. Some of digital input modules are IMDSI13, IMDSI14, and IMDSI22.

Parts of Input Module Input Isolation: - Low isolation capacitance allows protection against fast transient bus disturbance. Threshold Detection: - Test the input voltage to determine it is proper voltage on or off. Control Logic: - Takes the signal from threshold detection and energies proper LED. It consists of buffer to hold the input and I/O bus interface is used to read these bytes. I/O Expander Bus: - It is a high speed parallel bus which allows the bytes to travel along and provides communication path between controller and I/O module and form a major part of PCU (Process Control Unit).

Digital Output Module Description: - Digital output module IMDSO14, has 16 open-collector, digital output channels that can switch at 24 VDC and 48 VDC load voltages. The digital outputs are used by controller to switch field devices for process control. The controller communicates with its I/O modules on an I/O expander bus. Each I/O module on the bus has a unique address set by its address dipswitch. Digital output module has a single printed circuit board that occupies one slot in MMU (Module Mounting Unit). It outputs two separate groups of eight inputs; hence there are totally 16 input lines. There are 12 inputs which are mutually isolated remaining 2 pair have common positive

input lines. Upper two red and green LEDs shows operating status. 16 red LEDs are on the panel which shows the current status of the module for group A and B. This module has 3 card edge connector as follows: P1  P2  P3 

Connects common and +5VDC. Connects module to I/O expander bus to the controller. Outputs digital signal using cable to terminating unit.

The voltage energies or de-energies a field device or a relay. Inputs to the module are 24VDC or 250mA, 48VDC or 125mA. Functions of output Module: 1. Controls digital output switching. 2. Transmits operating status back to a controller. Open collector transistor provides switching in output circuit. Opto-couplers isolate module from process field device.

Digital Output Circuit This is digital output circuit which sends a field output in correspondence to the signal from output circuitry. Sixteen open-collector transistors in the digital output block function as digital switches. Optocouplers for each output pro-vide isolation between the module circuits and the process field device. All outputs are normally de-energized (off) until a signal from the data selector block causes them to energize (on). The output circuits provide 1.5 kilovolts isolation between output and logic circuits, and other output channels. Output Control Logic Output register holds the data that controls the output. The input expander bus interface writes control data to this register. This data is sent to the data selector determines the output state (on or off). Default data from the controller is sent to default register. Default values can be fixed before hand. If a time-out (hanged state) is happening, means (controller is unable to perform in a fixed time) then a special signal code may be obtained. O/p connections are obtained by a 30 pin card edge connector P3 of the DSO module from termination unit. I/O Expander Bus

Provides high speed, synchronous parallel bus. Provides a communication path between controller and I/O module. Controller and I/O modules form an individual subsystem with in a Process control unit. Provides following functions:  Address comparison and detection.  Function code ditching and decoding.  Read strobe generation.  Data line fitting of bus signals.  On board bus drivers. Status of Module  Status data consists of three separate 8 bit signals.  First and second represent group A and B signals.  Third is for module identification and module status.  I/O module identification by four MSB.  LSB represent module status. Bus Fault Timer Reset to default signal if it takes more than 10ms, Red LED in front panel shows Bus fault. The module has an address selection Dipswitch with eight switches. First two are always kept closed and rest 6 decides the address. Module status indicator There are 2 LEDs for indicating module status which are red and green. The status with the LED is shown in following table. Red 0 0 1 1

Status NO power Enabled Bus fault Not allowed

Single loop of HP1 heater

Green 0 1 0 1

Loop of the hp1 heater is shown below and its components are given as: 1.Analog transfer function This function selects one of the two inputs depending on Boolean input s3. The output equals the input that is selected. There are two time constants to provide smooth transfer in both directions. S1 S2 N T S3 2- input Summer This function performs a weighted sum of two inputs. By choosing the proper gains and inputs this block can perform proportional. Bias or difference functions.it can also be used as a scalar for a non- zero biased signal by referencing the second input to a constant block. This operation of this function is described by the equation : Output = (s3) + (s4) S1 S2

∑(k)

N

3.Rate limiter The output of a block using this function code is the same as the input as long as the rate of change on the input does not exceed a limit value. When the rate of change of the input is greater than the limit, the output will change at the rate established by the limit until the output agains equals the input. S1 S2

V>

N

4.PID Error Input This function provides proportional, integral and derivative operations on an error Signal. It has 3 inputs and 1 output. Besides the error input,there are also provisions for track reference and track switch input signals.the parameters for this function include an overall gain specification (s5), a proportional constant(s6), an integral (s7) and derivative specification(s8). S1 S3 N S4 PID 5.Test Quality The test quality function code is used to check the point quality of up to 4 inputs. It is a 4 input logical OR fuction that sets the output to a logical 0 if all tested points are good, and to a logical 1 if one or more tested inputs is bad. Only process i/o , module bus inputs can be tested for quality. Quality is not propagated through a module’s function blocks. All internal points have good quality.

S1 S2

TSTQ

N

S3 S4 6.Timer The Timer function code is used to perform timing, pulsed timming, or timed out delay function depending on the function specified(s2), duration of timming interval(s3), and the logic state of the input.

NTD-DIG

s1 7.Control Station (MFC)

The Control Station (MFC) function code provide an interface between the MFC and the following interface device: Digital Control Station(DCS), Operator Interface unit(OIU), Management Command System(MCS), and computer interface unit(CIU). The function code cannot be placed in any block numbered higher than 1023 because the current plant loop message size allows the loop to access blocks through 1023 only for control. S1

N

S2 S3

M/A

S4

MFC/P

N+1 S5 N+2 S18 S19 N+3 S20 S21 N+4 S22 S24

N+5 S25 S26

S27 S28 S29 S30

S4

DCS or PLC This plant consists of both the DCS (Distributed Control System) and PLC (Programmable Logic Controller). Hence a brief description of their difference is to be considered.

Distributed Control System: - In a DCS, all the variables in the plant from various remote locations are brought to operator’s observation. Each of the variable are interrelated to one another so controlling of all is achieved through best possible combinations. In a stand alone controller, all variables are completely independent and are not related to one another. For example, if a particular pressure and flow are to be maintained in a pipe. Then, in stand alone controller, if flow maintenance goes out of reach, even then pressure would be kept on maintained which are useless in many cases. But in DCS, programmed software itself performs the best solution hence controlling all the variables. Therefore, DCS is totally automatic system which can run the plant even without operator. Programmable Logic Controller: - A PLC consists of following main parts:

PLC Block Dig. Inputs and outputs to the PLC are: INPUT Sensing Devices Switches and Pushbuttons Proximity Sensors Limit Switches Pressure Switches

OUTPUT Valves Solenoids Motor Actuators Pumps

DCS is better to PLC as:  System Upgrades and expansions → In a PLC, the adding a new facility is a tough job on the control layer.  PLC is totally dedicated system which work only on factory support.  DCS enables High Speed peer to peer instruments but PLC does not → Suppose 3 different signals are to be controlled. These all must be mapped into 3 PLC slots. Thus, all wiring from transmitter is send to PLC. But in DCS, signal is mapped to 1 st controller then copied to 2nd and 3rd controller without rebuilt, thus reducing wiring.  PLC do not provide Security, Alarm, Advanced math function (PID).  HMI on PLC is far difficult to work with as compared to DCS.  Open communication Protocols in PLC→ Make it difficult for 3rd part instruments and software. PLC Advantages  Low Cost  The PLC are low cost system compared to DCS in many applications.  Easy decision making and easy maintenance of PLC.  Fast project implementation of PLC makes it more beneficial.

But the biggest benefit in using a PLC is the ability to change and replicate the operation or process while collecting and communicating vital information.

HARMONY RACK I/O ARCHITECTURE

Digital Input Termination Unit: The NTDI01 digital I/O Termination Unit is a Harmony rack I/O device. It provides a signal path for 16 input signals to the following I/O modules. The inputs are used by the controller to monitor and control a process. A Harmony area controller and the Harmony rack controllers can use the rack I/O module and termination units for I/O interface. Analog Input Termination Unit: The NTAI05 Analog Input Termination Unit is a Harmony rack I/O device that is part of the Symphony Enterprise Management and Control System. It provides a signal path for 15 input signals to the IMFEC11 or IMFEC12 Analog Input Module. The inputs are used by the controller to monitor and control a process. Terminating O/P module P1 → Logic power P2 → I/O bus communication P3 → Provide digital O/P.

CNET-to-Computer Interface CNET  Unidirectional, high speed data network, 10 MBPS communication.  Control network with 250 modes.  Multiple Satellite CNET can link to central Network.

Computer Transfer module: The INICT03 Computer Transfer module handles all communication with a host computer. The module is command driven through software on the host computer. The INICT03 module receives a command from the host computer, executes it, and then replies. It performs system functions such as security, time-synchronization, status monitoring, and module configuration. The INICT03 module can store up to 30,000 point definitions. Multifunction Processor Interface Module: The IMMPI01 Multifunction Processor Interface module handles the I/O interface between the host computer and the INICT03 module. Computer: A computer can access Cnet for data acquisition, system con-figuration, and process control. It connects to Cnet through a Cnet-to-computer interface. The computer connection to Cnet enables plant personnel, for example, to develop and maintain control configurations, manage the system database, and create HSI displays remotely using Composer engineering tools. Features of CNET to computer Interface  Provides a plant- wide communication network.  Provides time synchronization in control system.

  

Each note can operate independently. Support cyclic Redundancy check codes. Fast response (10 mbps).

CNET to HCU Interface

HCU (Harmony Control Unit) comprises of controller and I/O devices. Actual process management takes place at this level. CONTROLWAY → It is a high speed link which provides peer to peer communication link between controller and module. It consists of 32 connections.

HCU – CNet Interface allows  Communicate field input value and state for control.  Receive control instruction from plant personal and adjust process field O/P.  Provide feed back to plant personal via HIS.  Determine, process control, data acquisition, alarming, logging and trending.  Report status and download firmware. Complete redundancy of HCU and its module are provided to tackle situation of a failure. Network Interface Module (INNIS01): NIS provides node to node communication in process portal system. The NIS connects to its CNet communication network through a cable attached between P3 connector and a terminating unit. The communication is through coaxial or twisted pair cable that connects the termination units of each node. Network Processing Module (INNPM12): NPM holds HCU database and directs communication process between modules and controlway and NIM (Network Interface Module). The INNPM12 Network Processing Module acts as a gateway between Cnet and Controlway.

Multi Function Processor

MULTI FUNCTION PROCESSOR

A MFP (Multi Function Processor) IMMFP12 is the main part of the HCU. It is the main controller which takes the particular actions on the requests from the client via server. MFP is a double printed circuit board that occupies two slots in MMU. A MFP can provide PID transfer function hence can control different variables like temperature, pressure, flow etc. derivative control is used to control temperature variable.

BLOCK DIG. Multi Function Processor

MFP consists of a number of units which are explained as follows: 1. Microprocessor: - The microprocessor, operating at 16 megahertz, enables module operation and control. Since the microprocessor is responsible for overall module operation, it communicates with all the functional blocks. 2. Memory: - The MFP module contains 512 kilobytes of ROM memory, 512 kilobytes of random memory (RAM), and 256 kilobytes of non-volatile random access memory (NVRAM). The RAM memory provides temporary storage and a copy of the modules configuration. 3. I/O Expander Bus: - The I/O expander bus resides on the backplane of the module mounting unit. This bus, an eight-bit parallel bus, provides the communication path for I/O data between rack controllers and rack I/O modules. 4. I/O Section: - The input and output section interface allows the microprocessor to read the switches that tell it how to operate and what address it has. This section contains the latches whose outputs connect to LEDs one through eight and the status LED. 5. DMA Section: - The microprocessor sets this section for direct memory access Or DMA. The DMA section allows data being received or transmitted over the various communication paths to be transferred directly to or from the RAM memory without microprocessor intervention. This process is known as cycle stealing. 6. Station Link: - The station link controls the serial communication between the MFP module and stations. This link has two modes of operation: 40 kilobaud and five kilobaud.

Module Mounting Unit This is the cabinet in which all the modules and there connecting cables are placed. Input AC and DC power is supplied to the IEMMU11 and IEMMU12 units through the input power bus bar located inside the cabinet. Power is transferred to the mounting unit from the bus bar through cables.

All input power to the mounting unit is fused and filtered through a power entry panel. The power supplies providing the regulated voltages are fused and filtered. Regulated power supply voltages (+5 VDC, +15 VDC, –15 VDC, and +24 VDC), PFI, and STATUS signals are distributed to the system through the system power bus bar located inside the cabinet. Power is transferred to the mounting unit from the bus bar through cables.

CONCLUSION After performing the training I have concluded that in a process industry, a chemical plant like N.F.L. a large number of processes are to be controlled. Each process includes large number of variables which are to be maintained simultaneously. Therefore, large numbers of control mechanisms are involved. Hence electronics, mechanical, instrumentation, electrical and chemical knowledge go hand in hand. From the study in Captive Power Plant, one can conclude that plant’s non-stop working is a prime factor as rest of the plants are completely dependent upon CPP. For efficient working of the plant, the control system must be excellent and

Process Portal fulfills all the needs. PP which supports DCS (Distributed Control System), provides the best results with complete automation. The system provides a very user friendly environment which is easy to understand and operate. The PP system can also tackle emergency situations very effectively thus reducing the large number of hazards present in the plant. The PP also has the ability to generate reports and show the current and previous trends just on a click. As all the instruments are redundant hence chances of failure are reduced to minimum. Though this system has number of merits, the negative aspect of the plant is that in some cases DCS cannot be used as the process happens very fast. For example, in dedicated controllers like ETS 301 and ETS 302, which are used to control speed and load of turbines are standalone and only display is given to DCS because of there high speed. Also with the upgrading technology, the replacement of malfunctioning circuits becomes tough as they become obsolete in the market.

BIBLOGRAPHY

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NFL manuals

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Engineer lecture’s

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Internet sites - www.scribd.com