A REPORT ON INDUSTRIAL TRAINING AT OIL INDIA LIMITED DULIAJAN LPG DEPARTMENT Submitted by : P. Yashaswini, Aakanksha Prerona Das, Rijumoni Boro Bachelor of Technology 4th Semester Department of Chemical Engineering Indian Institute of Technology (IIT) Guwahati
ACKNOWLEDGEMENTWith due respect, we express our deep sense of gratitude to the respected and learnedguides of Oil India Limited, Duliajan for providing their painstaking and untiring supervision.We are thankful to the training center for giving us the opportunity to learn deeper insidethe basics of LPG production. We also express our sincere thanks to Mr. B.K Buragohain, Deputy Chief Engineer(Safety & Training, LPG), OIL, for providing us with a conducive environment and necessaryfacilities, allowing us to reach the desired accomplishment. We are heartily thankful to all the Managers, Engineers and all Shift Operatorsworking under them to give us direction and valuable inputs on each and every sections ofLPG production. P. Yashaswini, Aakanksha Prerona Das, Rijumoni Boro B.Tech 4th semester Chemical Engineering IIT Guwahati
CONTENTSSERIAL TOPICNUMBERs1. INTRODUCTION2. FAMILIARIZATION AND STUDY OF LPG RECOVERY PROCESS3. STUDY OF FIRE PROTECTION SYSTEM AND GENERAL SAFETY4. STUDY OF INSTRUMENTATION INCLUDING DCS5. FAMILIARIZATION OF QUALITY CONTROL LABORATORY6. STUDY OF ELECTRICAL MAINTENANCE ACTIVITIES7. STUDY OF MECHANICAL MAINTENACE ACTIVITIES8. STUDY OF LPG FILLING PLANT
INTRODUCTION Oil India Limited (OIL), an E & P company is a premier National Oil Company engaged in the business of Exploration, Production and Transportation of crude oil and natural gas. A Navratna Company under The Ministry of Petroleum and Natural Gas, Government of India, it is the second largest national oil and gas company in India as measured by total proved plus probable oil and natural gas reserves and production. Incorporated as a private company in 1959, OIL has been present in the Indian oil and gas exploration and production industry for over five decades. The company presently produces around 3.90MMTPA(Metric Million Ton Per Annum) of crude oil, around 7.93MMSCUMD(Metric Million ) of natural gas and more than 45,010 tons of LPG annually.• Main Producing Areas: Assam, Arunachal Pradesh and Rajasthan in India.• Customers:- Assam-AGCL, BVFCL, ASEB, NEEPCO, IOC and APL- Rajasthan-RRVUNL• The company operates a crude oil pipeline in the North-East for transportation of crude oil produced for both OIL and ONGCL in the region to feed Numaligarh, Guwahati, Bongaigaon and Barauni refineries and a branch line to feed Digboi refinery.• Moreover it has also extended its blocks overseas in Iran, Libya, Gabon, Nigeria, Sudan, Yemen, Egypt and Timor Leste.• A reservoir of hydrocarbons from where natural gas and oil are collected through a drilling in the earth is called a well.• Types- Oil and gas well Oil well – crude oil + associated gas Gas well – natural gas(unassociated gas) + condensate
There are various departments in OIL a few are :• Production (Oil & Gas)• Civil engineering• Chemical engineering• LPG• Geological• Electrical engineering• Instrumentation• IT• Fire and Safety• Transport• Field communication• Field engineering• Drilling• Well logging• Geophysics• Materials• Medical• Finance and maintenance• Training and development• Research and development
OIL’S LPG PLANT (ISO-9001:2008,ISO-14001:2004 and OHSAS 18001:2007 certified)The two major products of Oil India Limited are Crude Oil and Natural Gas,LPG ( Liquified Petroleum Gas ) being an important value addition to the naturalgas produced. It is the first diversification of OIL active since the last 29 years.LPG department has two installations:(i) LPG Recovery Plant(ii) LPG Filling PlantThe various sections at LPG department are :(a) Recovery Plant Operation(b) Filling Plant Operation(c) Mechanical and General Maintenance(d) Electrical(e) Instrumentation(f) Quality control(g) Safety(h) Planning & Administration
LPG RECOVERY PLANTThis plant indulges in production of LPG and a by-product ,i.e , NaturalGasoline ( Condensate ) from natural gas.Designed and commissioned in 1982 by The Randall Corporation, USA, it isthe second plant in India where LPG is produced from natural gas.Maintenance of high productivity, quality and concern for safety, health andenvironment in a professional manner has always been the main motto of thisdepartment.The plant was originally designed to handle 2.215 MMSCM/day of natural gasto produce 60,000 TPA of 50:50 (w/w) C3H8 : C4H10 LPG and 12,000 TPA ofcondensate on 350 days working. But due to changes in the feed gascomposition the plant design capacity has been re-rated as 55,000 TPA of49:51 (w/w) C3H8 : C4H10 LPG and 25,000 TPA of condensate.
LPG is liquefied petroleum gas which is a mixture of certain lighthydrocarbons, derived from petroleum, which are gaseous at ambienttemperature and atmospheric pressure but may be condensed to liquid stateat ambient temperature by the application of moderate pressure. Liquefactionis accompanied by a considerable decrease in the volume, thus the liquidformed requires much less storage space stored in the liquid phase inpressurized containers and systems, finally allowed to revert to the vapourphase at or near the point of eventual utilization. The feed gas, i.e ,natural gas is first drilled from oil well and gas well andthen collected at the OCS from where it is sent via pipelines to the main plantarea. In the process of LPG production, the plant also produces a high revenue-earning by-product, i.e, Natural Gasoline, which contains pentane and hexaneand it is sold to solvent-manufacturing companies like EPC International,Sikkim Organics, etc.25-Aug-12 8
FEED GAS ANALYSIS COMPONENTS DESIGN PRESENT COMPOSITION COMPOSITION N2 0.26 0.96 CO2 1.10 0.82 C1H4 86.80 89.88 C2H6 6.50 3.96 C3H8 3.30 2.32 iC4H10 0.72 0.51 nC4H10 0.86 0.71 iC5H12 0.18 0.25 nC5H12 0.13 0.16 C6H14 + 0.15 0.43Out of the total composition, 3.54 % accounts for LPG production from the feedgas.
Important Properties of LPGLPG is colourless , odourless , highly volatile and hazardous liquid that mixesquickly with air. It is heavier than air and one litre of LPG when expands producesabout 250 litres of vapor.Max. vapour pressure at 40 deg. C = 1050 kPa, gaugeVolatility i.e. evaporation temp. in deg. C for 95 % by volume at 760 mm of Hgpressure, Max = 2.0Hydrogen sulphide = pass, i.e. Hydrogen sulphide is not more than 5 ppmFree water content = NoneMin. 20 ppm of ethyl mercaptan for odor. Auto-ignition temperature = 410 to 580 degree Celsius Flash Point =-104.4 degree Celsius In a closed liquid filled vessel or pipe , for 1 degree rise in temperature ,the pressure increases by 14 to 15 kg/cm^2 Explosive Limit = 1.85 to 9.5 % v/v in air
PROCESSThe process comprises of broadly the following:(a) Compression(b) Dehydration(c) Product extraction through: (i) On stream cooling by heat exchanger (ii) Turbo expansion (iii) Removal of non-condensable and undesired lighter fractions(d) Product fractionationThe different stages are as follows:• Compression: 1st stage -> Inlet Gas Compression Suction Scrubber The inlet gas enters at 14kg/cm^2, is compressed to 33.8kg/cm2 in a 4 stage centrifugal compressor driven by York Manufacturer’s 4500HP electric motor operating on 11KV power supply. The heat of compression is partly used in re-boiling the bottom liquid of de-ethanizer and then cooled to 37.8’c in water cooled heat exchanger.
2nd stage -> Booster Compression Suction Scrubber The gas is then compressed to 41.9 kg/cm2 driven by the turbo expander and then cooled to 37.8’c. It is then sent through an inlet filter separator wherein any water that may condense out is knocked out.• Dehydration: The gas is dried in one dehydrator while the other is being regenerated. The pressure of compressed gas decreases to 39.6 kg/m2 as it reaches dehydrator. Dehydrator consists of molecular sieve made of crystallized metal Aluminum Silicate of 4A’ size of approx 11650kg weight in which water particles are retained. This process is required as the temperature of the gas can go down up to minus 100’c where ice crystals form. The dehydrated gas passes through a dust filter to remove sieve dust etc.• Product extraction: 70%(by volume) of inlet gas is exchanged with cold residue from de-ethanizer and expander separator overhead, 30%(by volume) exchanges heat with the cold separator liquid in the gas-liquid exchanger and also with the expander separator liquid. These two streams combine to enter the cold separator. Liquid condensed is separated by cold separator and then the liquid is pressurised through the de-ethanizer reflux condenser.
The inlet gas from the cold separator enters the expander where the pressure is lowered, following Joule-Thompson Effect. The gas liquid mixture out of the expander of 1670 HP and 27000 rpm speed reducing temperature to -84’c, is separated in the expander separator. Liquid thus collected flows to the de-ethanizer feed pre-heater and then to the de- ethanizer.• Product Fractionations: A de-ethanizer column with three separate packed sections and a reboiler. The liquid formed at the cold separator and the expander separator enter it, by maintaining proper bottom temperature with reboiler and reflux, the undesirable liquefied fraction methane, ethane and excess of propane are knocked out from the top. The temperature of LPG is increased by exchanging heat with residue gas, whose refrigeration is in turn used in heat gas exchangers. A de-butanizer column having 34 trays and reboiler provision through closed circuit hot oil systems with direct fired heater. The bottom liquid flows on to de-butanizer tower where LPG and condensate are separated out. LPG comes out at the top which is cooled to ambient temperature and sent for storage in bullets and Horton spheres. The bottom condensate(Natural Gasoline) is similarly stored in separate storage tanks.
Simplified flow diagram RESIDUE GAS INLET COLD GAS- GAS GAS SEPARATOR BOOSTER EXCHANGER COMPR. COMPRESSORFEEDGAS LPG DEHYDRATOR GAS - LIQUID EXCHANGER DE-BUTANIZER DE-ETHANIZER TURBO-EXPANDER EXPANDER SEPARATOR CONDENSATE
Fire Protection & SafetyLPG is a colorless liquid which evaporates easily into a gas, and the leakage of even a smallvolume can expand into a large hazardous zone. Since it has no smell, a little mercaptan isadded to help detect leaks.It can burn and explode when gets mixed with air and meets a source of ignition and itcan also cause cold burns to skin.Therefore, Fire Protection & safety is of utmost importance in LPG plant.Safety in LPG plant includes: FIRE PROTECTION SYSTEM ALARM AND SHUT DOWN SYSTEM ESD DEVICE SAFETY RELIEF VALVES FIRE ALARM SYSTEM GAS DETECTION SYSTEM FIRE EXTINGUISHERS FIRE DRILL COMMUNICATION SYSTEM REGULAR INSPECTION OF PLANT
Fire Protection SystemIt comprises of :1) A continuously pressurized water network of approximately 2 km length , consisting of one 3000 kLs water reservoir, pumps, hydrant points, monitors(water and foam) , hose reels , temperature sensing medium velocity water spray system.2) Portable fire extinguishers and sand buckets.3) Fire water pumps.4) Manual fire call points at different locations.One of the most important components of the safety system is the Deluge Valve, which isthe controlling valve of the pressurized water network.It can be operated either on auto mode or manually.Auto Operation :1) Water pressure is maintained in the hydrant system through a jockey pump.2) DV is kept closed by maintaining air pressure in the network.3) Due to rise in temperature, a heat detector bulb ( Quartzoid bulb ) in the air networkbursts releasing air pressure.4) When air pressure drops, DV opens spraying water on the vessel.Manual Operation :DV can be opened locally through a valve provided at the DV or by operation of a switchprovided in the control room.
FIRE SAFETY SYSTEMS.NO. EQUIPMENT QUANTITY 1 FIRE WATER PUMPS 06 (04+02) 2 JOCKEY PUMPS 02 3 HYDRANTS 28 (21+7) 4 MONITORS 16 (9+7) + 2 5 FIRE ALARM POINTS 21 (12+9) 6 GAS DETECTION SYSTEM : % LEL 28 (20+8) 17
DETAILS OF PUMPS:Pump Capacity Head Drive Auto start pressure M3/ Hr meter WC (on discharge line)Jockey 20 90 Electric Motor 4.6 kg/cm2Pump (02 Nos.) [Auto stop pressure = 8.4 kg/cm2]Sprinkler 275 88 Electric Motor 4.0 kg/cm2PumpSpray 410 88 Electric Motor 1.0 kg/cm2Pump ‘B’Spray 410 88 Electric Motor 2.0 kg/cm2Pump ‘A’Hydrant 410 88 Electric Motor 3.0 kg/cm2PumpDEFP -1 410 88 Diesel Engine 18DEFP -2 410 88 Diesel Engine 2.5 kg/cm2
Alarm And Shutdown SystemThe plant has got automatic in-built shutdown system to protect the vital equipment andthe plant as a whole from any abnormal condition of operation. Audio-visual alarms andshutdown indications are displayed in LPG control room. All the important equipment are provided with alarm and shutdown devices for critical operating parameters. All the storage devices are provided with high level alarms. Emergency shutdown switch is provided in control room to shutdown the plant in any case of emergency. Remote shutdown switches are provided in the local panels of two most important equipment- inlet gas compressor and expander compressor.Status monitoring is done round the clock through DCS work stations. Operation testedduring running condition, planned and non-planned shutdown of the plant.Testing/calibration is done as and when required for smooth running of the plant and alsoduring the annual maintenance of plant.
EMERGENCY SHUT-DOWN SYSTEM(ESD)The plant is equipped with ESD switches which calls for shut down in emergencysituations . The plant has these emergency switches in three locations –(a) Top ControlRoom (b) Bottom Control Room (c)Expander Compressor Panel SAFETY RELIEVE VALVESSRVs are required to release the excess pressure build-up in the system due to processupset etc. so that they are protected from failure due to over-pressure . These valvesare provided in the scrubbers , inlet filter separators , dehydrators , gas flow lines and ineach of the process pressure vessels. FIRE ALARM SYSTEM The fire alarm system consists of alarm switch glass , which when broken will lead to an audio –visual alarm at the bottom control room indicating the location of emergency , and also hooting of sirens in LPG Recovery and Filling Plant areas. GAS DETECTION SYSTEMGas Detectors , located at the vulnerable areas of the plant , detects the leakage of anyexplosive gas displaying the amount of leakage in terms of %LEL , together with hootingof an alarm in the DCS system of the control room.
FIRE EXTINGUISHERSFire Extinguishers are classified into the following categories ,as per the nature ofassociated fire- Type A : for general fire out of wood , paper and other such stationary sort of stuffs. Type B : for fire from liquid ,as diesel ,petrol ,diesel etc. utilizing dry chemical powder Type C : for gaseous fire , as LPG gas , Natural Gasoline etc. utilizing carbon dioxide Type D : for electrical and metallic source fire FIRE DRILLFire drill is carried out forth nightly in LPG Recovery and also in LPG FillingPlant by the plant personnel from all sections along with personnel fromFire Service Section ( General Engineering Department ) to test theperformance of the Fire Protection System of LPG Department and to takecorrective action as necessary. COMMUNICATION SYSTEMBoth LPG Recovery and Filling Plant are provided with 2 fire sirens (1 km and 5 kmregion) incorporating the entire area. The smaller siren is operated in manual mode innormal fire drill , else the bigger siren is operated. The bigger siren is inter-lockedwith fire alarm switches which run in auto-operation mode.
Instrumentation The role of this section is to quantify all physical parameters such as pressure, temperature, flow rate and liquid level. It is an integral part of LPG department of OIL. LPG implements PLC other than DCS dedicated to equipment control only, sequential start and stop of all devices and tripping of plants during emergency is done by PLC. Whereas DCS controls the entire process temperature, flow and level. Two types of control systems are-• Distributed Control System (DCS)- is a digital control system based on distributed control philosophy. It means a control system which works on the principle of power delegation, for which there should be some connectivity to reach the data to all nodes i.e. Ethernet dual ring network called distributed communication network .• Programmable Logic Control (PLC)- is a digital computer used for automation of electromechanical processes, designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact.• AC 460 is the heart of the system used to execute any function to maintain it, acts as interface and reads and writes over the I/O panel.• Ethernet connection is used to communicate or integrate all the nodes.• Graphics package are used to built plant objects.• Text package provides libraries through which the system is configured and started.• Database management might be there and uses oracle to send report.• Input devices- transmitter
The different devices used and maintained by this section are as follows:• Gas Chromatography: used for analyzing a mixture of a sample, a fully electronically controlled device. It consists of columns and detectors situated in the oven maintained at 80’c.• Moisture Analyzer- If the temperature is less than -80’C, the moisture in the gas will become saturated and form ice crystals which blocks the pipelines and hence has to be prevented. This is done by placing a device at different locations for checking the amount of moisture present and creates an electrical signals.• TCD (Thermal conductivity detector)- uses the property of thermal conductivity of gases and converts into electrical signals unique for each and every gas imitating the same property which are received by the calibrated and programmed computers.• Thermocouple is used for sensing temperature. Level transmitters work based on Archimedes Principle. The different types are: Magnetic level gauge Radar level gauge Servo level gauge Floatation method on the basis of buoyancy force
Flow rate indicator:• Mass flow meter- senses both gravity and volume. It carries out a lot of algorithms considering the resonant frequency of the U wire which gives the inertia of the liquid and temperature for gravity calculation.• Orifice flow meter- works on the Bernoulli’s principle and specifies only volume. Types of valves:• Shutdown valve• Deluge valve• Solenoid valve- is a logical valve and operated by solenoid coil which opens up at 110V of AC current or 240V DC.• Safety relief valve- are protection devices used in the worst conditions and are always maintained.• Remotely operated valve(ROV)- It is a logical valve which either closes or opens and requires 60-70psi. The feedback signal is received through PLC in control room and is used only for shutdown, cant be controlled.• Control valves are the ultimate output devices.• Audio, visual, olfactory and vibration are the four types of alarms used.
Pressure gauges , based on the Hooke’s law relating stress and strain, consists of the following components:• C-type tubes• Spiral type• Bello• Diaphragm• Dead weight tester• Manometer• DP (Differential Pressure) transmitter- measures the difference in pressure through micro-controller.• LEL (Lower Explosive Limit)- calibrated optimum quantity of a combustible substance which can support a self propagating flame when ignited. The device uses the infrared radiation emitted by the gas which is dependent on its concentration. The inner part is maintained at a higher temperature causing convection i.e. the hot air rises due to its lower density sucking in the air below which is at a lower temperature.• LELs of substances in terms of percentage present in the atmosphere are- CH4- 5% LPG- 1.2% Condensate- 1.8%• If LEL exceeds 10% sparking is prohibited.
Process water• The pH must be maintained in the alkaline range i.e. more than 7 as acidic process water may cause scaling in the heat exchangers. This can be done by treating the water with NaOH and KOH.• The viscosity should not be very high.• This water cannot be released into the environment without being treated for its salinity, pH, minerals added and oil accumulated. The methods employed to dispose off this water without causing any damage are: Flocculent(gravity) and coagulant(sand) filters Aerobic and anaerobic treatment UV rays cleaning system Bleaching(chlorine) Demineralization- is a series of anion and cation exchanger to maintain the pH around 7. The minerals such as Ca, Mg, SO4-2, Cl-1 can be removed completely but the water cannot be polished off silica if its concentration is below 2ppm. The water is heated in a high pressure water boiler.• If the toxic level of water is very high and cannot be treated it is injected back into the well.
Quality Control LaboratoryIt is a branch of the Chemical department of OIL, and being a service section its main roleis to evaluate the quality of products, LPG and Residue Gas, along with the feed gas that is,Natural Gas.It mainly performs two types of tests , viz., compositional and physical.1.Physical Analysis :It includes Volatility and Vapor Pressure tests as per IS 4576: 1999 certification,depending on which one can decide whether the product is good or bad.a) Volatility : It is measured by Weathering Test. In this test, the sample is taken in a tube called weathering tube and a thermometer is put in it. The temperature is noted at 25, 50, 90 and 95 percent(by volume) evaporation and the temperature corresponding to 95% evaporation is called the Weathering Temperature and it should be in the range of +2 degree C and -2 degree C.b) Vapor Pressure : For this we take the sample in a sampler and put it in a temperature bath which is maintained at 40 degree C and we check the pressure building up at this temperature indicated by the pressure gauge.Apart from these tests, some other tests are also performed to measure the density ofsample, moisture level and also the Ethyl Mercaptan (C2H5SH) level in LPG. Ahydrometer is used to measure density.We use Doctor’s Test to check minimum value of Mercaptan added to LPG. For this,Sodium Plumbate solution is taken in a cylinder and LPG sample is added which mixes withit. A positive Doctor’s Test gives a yellow precipitate/solution indicating presence ofMercaptan.
Dew Point Test :We have to check dew point at dehydrator inlet and outlet, gas inlet and air inlet. As thefeed gas, after compression, needs to be dehydrated using dehydrator, hence we need tocheck whether the molecular sieves (which are made of alumina silicate) are working.2. Compositional Analysis :It includes compositional analysis of the natural gas coming from production department,LPG and Residue gas, done by Gas Chromatography (GC), as explained below :GC , a common type of chromatography performed in a Gas Chromatograph, is used inanalytical chemistry for separating and analyzing compounds that can be vaporizedwithout decomposition. It is based on different boiling points and retention time fordifferent components. It is used for testing the purity of a particular substance, orseparating the different components of a mixture.GC consists of two phases : a mobile phase and a stationary phase. Here the mobile phaseis a carrier gas, usually an inert gas like Helium or a non-reactive gas like Nitrogen.The stationary phase is a microscopic layer of a liquid or a polymer on an inert solidsupport, inside a piece of glass or metal tubing called a column.The molecules move to the wall of the column, coated with different stationary phases,which causes each compound to elute at a different time, known as the Retention Time ofthe compound.
GC Analysis :In a GC analysis, a known volume of gaseous or liquid analyte is injected into the columnusing a micro-syringe. As the carrier gas sweeps the analyte molecules through thecolumn, this motion is inhibited by the adsorption of the analyte molecules either onto thecolumn walls or onto packing materials in the column. The rate at which moleculesprogress along the column depends on the strength of adsorption, which in turn dependson the type of molecules and on the stationary phase materials. As each type of amolecule has a different rate of progression, the various components of the analytemixture are separated as they progress along the column and reach the end of the columnat different times (retention time). A detector is used to monitor the outlet stream fromthe column, hence the time at which each component reaches the outlet and the amountof that component can be determined.Generally substances are identified by the order in which they emerge from the columnand by the retention time of the analyte in the column. The chromatographic data ispresented as a chromatogram, which is a graph of detector response (y-axis) againstretention time (x-axis). This provides a spectrum of peaks for a sample representing theanalytes present in a sample eluting from the column at different times. The area under apeak is proportional to the amount of analyte present in the chromatogram, and bycalculating it, the concentration of an analyte in the original sample can be determined.
Electrical maintenance• The power house of OIL generates 14.45 MW with the help of two gas turbines which are alternatively at running and standby modes.• The power house supplies 11KV to the substation in the LPG plant through two underground cables.• This incoming power is sent into the feeder from two different power houses, #1 and #2. These two sections are connected by a bus coupler which is used only when the maintenance job needs to be done.• From #1 the 11KV is supplied to the spare feeder, 4500HP motor starter panel and to a transformer1 of 1000KVA capacity which steps 11000V down to 415V.• There are 8 vacuum circuit breakers. It is monitored by protective relays such as VCB, ACB, SF6 of the circuits.• UPS system gives an uninterrupted power supply normally of AC current with a battery backup of 120KVA capacity. There are 2 types of UPS in which input is 415V but outputs are 415V and 110V.• A battery converts a voltage input of AC to DC. A 110V Ni-Cd battery set is used.• Another auto-transformer other than the two in the feeder circuits produce 450V line. It is a part of motor starter panel. During starting of motor the load might reach seven times its full load and then drop back which cant be allowed. To reduce this we use this auto-transformer starter for 20 seconds and then give back to the normal system.• Motor control center(MCC) is provided by the 415V bus.• Tripping is a condition when difference between the incoming and outgoing currents of the isolator is more than a given value and the on-off switch of the isolator turns off automatically.
ELECTRICAL LINE DIAGRAM INCOMER 1 INCOMER 2 11 KV 4500 HP, 11 KV MOTOR TR 1 TR 2 STARTER PANEL 11/ 0.415 KV 11/0.415KV ACB ACB 415 V MCC 1 A MCC 1 B RECOVERY BUS RECOVERY PLANT COUPLER PLANT MCC 2 A RECOVERY PLANT MCC 2 B ELECTRICAL LOADS MCC 3 AIR FILLING PLANT FILLING PLANT COMPRESSOR
AUTOTRANSFORMER• Auto-transformer is used for applying reduced voltage to stator during starting. Thereby the starting current is reduced. The auto-transformer is provided with change-over switch. As the motor comes to full speed, the change-over switch is thrown over to run position. CIRCUIT BREAKER AND ITS TYPES• Circuit Breaker is an automatic device capable of making and breaking an electric circuit under normal and abnormal conditions such as short circuits. The part of the circuit- breakers connected in one phase is called the pole. A circuit-breaker suitable for three phase system is called a triple pole circuit-breaker.• Each pole of the circuit-breaker comprises one or more interrupts or arc-extinguishing chambers. The interrupters are mounted on support insulators. The interrupter encloses a pair of fixed and moving contact. The moving contacts can be drawn apart by means of the operating links or the operating medium. The operating mechanism of the circuit-breaker gives the necessary energy for opening and closing of contacts of the circuit-breakers.• The arc produced by the separation of current carrying contacts is interrupted by a suitable medium and by adopting suitable techniques for extinction.• Circuit Breaker is used for opening and closing circuits for normal switching operations. During short circuits or abnormal conditions, relay operates and gives opening command to circuit-breaker and circuit is opened automatically. TYPES OF CIRCUIT BREAKERs IN LPG PLANT• Moulded Case Circuit Breaker (MCCB):• Air Circuit Breaker (ACB): It utilizes air at atmospheric pressure for arc-extinction.• Vacuum Circuit Breaker (VCB): The fixed and moving contacts are housed inside a permanently sealed vacuum interrupter. The arc is quenched as the contacts are separated in high vacuum.
POWER HOUSEPower House generates power for the entire plant using the concept of a Gas Turbine,which is based on the Bryton Cycle.The following components comprise a Gas Turbine –(a) Axial Air Compressor(b) Combustor(c) Turbine(d) AuxiliariesAxial Air Compressor : Air after passing through the filter enters the axial compressor and flows parallel to theaxis .it consists of a stationary body called Casing and a moving part called Rotor, andBlades , some of which are attached to the casing and some to the rotor . A pair ofstationary and moving blades is called a Stage and the compressor has got 15 suchstages. Air gets compressed as it passes through the different stages.Combustor : Air from the compressor enters the combustor which has 2 parts –a transition piece anda combustor, the latter being divided into 3 zones , viz, primary , secondary and tertiary ,each consisting of a number of holes . Fuel is injected in the primary zone and ignited using spark from the spark plug, therebycreating a cyclone.
In the secondary zone , complete burning of fuel is ensured. As the temperature of airrises to a high value of 1200 degree C ,it needs to be cooled down to 899 degree C at leastbefore entering the transition piece. For this more air is to be supplied to the tertiaryzone. The transition piece has a nozzle which increases the velocity of air.Turbine :Air from combustor enters the turbine where it expands and exits as exhaust gas. Therotating turbine then generates power via a generator. The exhaust gas is at a temperatureof 370 degree C and this energy can be utilized to produce more electricity using thesteam turbine . For this DM(De-Mineralized) plant is required but this is a costly process.This produces about 7Mwatt power in addition to the actual power of 14.45Mwatt. As the Gas Turbine is not self starting , a starter diesel engine is required.A total of 14.45Mwatt electricity is the output from the generator. Out of this 10.4Mwattis utilized to fulfill the electricity requirement of the different units of the industry.
Mechanical MaintenanceThe Maintenance Section of the LPG department is responsible for the following :1) Maintaining the plant availability to achieve MOU target.2) Maintenance of all rotary and stationary equipment of the LPG plant to keep them in proper working conditions.3) Execution of various contract jobs under the department related to maintenance of the plant.4) Planning of maintenance activities for annual plant maintenance.5) Spare part management for maintenance of the plant.This section aims to achieve the following targets :1) To reduce the cost of maintenance activities by 1 % of the previous year.2) To keep the minimum MTTR of critical equipment for achieving the MOU target.3) To keep good relations and understanding with the different sections of the LPG department.4) To keep good relations and understanding with the other departments of the company.5) To keep close watch on various activities so that there is no misuse of approved funds and that these are properly utilized.
The Mechanical Maintenance Section of the LPG department is responsible to perform thefollowing duties :1) Daily plant check up to ensure smooth operation of the plant and to check lube oil level and vibration & sound and other parameters.2) Monthly vibration measurement to ensure that vibration levels of critical equipment are within limits and take necessary corrective measurements.3) Periodical lube oil testing to test lube oil of three major equipment of LPG recovery section, namely, Inlet Gas Compressor, Gear Box and Expander-Compressor.4) Cleaning of cooling tower top chambers to ensure its proper functioning.5) Testing of SRV to ensure its correct functioning at its Set Pressure.6) Sound level measurement to measure the intensity of sound at specified locations and compare it with permissible limit.7) Replacement of damaged or worn out Vee-Belt ( Endless belts used between driving pulleys to transfer power).8) Replacement of empty Mercaptan drum of LPG storage area.9) Top up lube oil into Expander Surge Tank to maintain a certain oil level in it.10) Air compressor lube oil top up to maintain the required level of oil.11) Materials inspection and suitability report for the acceptability of the materials received against direct charge Indents/purchase orders.12) Engaging staff on overtime to complete the repairing job within the day in view of urgent nature of work for operational as well as safety requirements.
13) Workshop job requisition to carry out emergency repair and fabrication jobs at general workshop.14) Breakdown maintenance of machines/ equipment.15) Preparation of tentative maintenance schedule of air compressor.16) Ultrasonic thickness measurement to gauge metal surfaces for the thickness.17) Handling/cleaning services and day-to-day maintenance in LPG recovery and filling plant.18) Servicing, Inspection and Testing of LPG storage vessels.19) To replace hot and cold insulation system of LPG recovery plant with new insulation system at a specified time interval.20) Major overhauling of Inlet Gas Compressor and Expander Compressor to ensure smooth and trouble free operation.21) De-coupling of various motor devices to carry out maintenance work on driver (motor) or driven side (pumps, compressors, fans, etc.).22) Hydro-testing of pressure vessels and storage vessels to check the condition/health of vessel.23) Periodical testing of lifting tools.24) Storage, handling and disposal of lube oil and other hazardous materials.
LPG Filling Plant• In LPG Filling Plant – (i) LPG is bottled into cylinders (packed form) in Carousel machine containing 24 number of filling points or guns. (ii) LPG is filled into road tankers (bulk form). These cylinders and road tankers are handed over to IOCL for marketing.• The LPG is pumped to LPG Filling Plant from LPG storage vessels at LPG Recovery Plant.• The incoming LPG pressure in the pipeline is about 14kg/cm2. The cylinder consists of a head ring, 3 fins, valve, high pressure seamed cylinder and a foot ring.• The inside of the valve is installed with an O-ring and a valve pin. The valve needs to be checked for any leak possible.• The bottling capacity of the plant is about 6000-7000 cylinders per day.• The empty cylinders are first marked by TARE WEIGHT MARKING and their marked weights are stored by a HMI (Human Machine Interface) device called pre-check scale.• The marked cylinders go to Carousel machine by chain conveyor, run by 14 motor driven Gear boxes. In Carousel machine the empty cylinders are first sensed by photo-electric sensors.• In each filling gun two sensors are linked which are placed at the top and at the bottom side of the cylinder.
• The bottom side sensor is called wheel arm sensor. The bottom photo-cell senses the position of the cylinder on the machine. The top photocell senses the cylinder and gives instruction to the gun. Then the respective gun shoots the respective cylinder.• The cylinder is filled in the course of one rotation of the carousel, the filling time is approximately 60 seconds.• When the regulator’s pin when pressed together with the valve pin, two holes are opened.• The LPG filled in the cylinder should be of weight 14.2 kg. If the gun is unable to fill the cylinder within one minute for delay error, the cylinder will again revolve for one minute.• In the outlet of the machine has a puller with sensor which allows only those cylinders filled up to the standard weight to go out of the machine, otherwise it will return back the cylinder to the machine again.• The cylinders are introduced through a check scale, which checks the over weighted cylinders and bypass them to another section called correction unit by pusher with photo-electric sensor.• The over weighted cylinders are manipulated up to the standard by manual filling. This over weighted range is considered as +200gm.Now the corrected cylinders are lined up with the other cylinders.• Now the cylinders are fed to Gas detector and O-ring detector unit to check the leakages and damages. In this unit the damaged cylinders are rejected. The tested cylinders are then fed to counting unit to count by a sensor and stored. In hot air sealing unit the cylinders are sealed and fed to transportation section.
• The evacuation unit takes care of the rejected cylinders which are found defective by applying suction pressure on the LPG cylinder and the valuable LPG is sent back in the form of vapor to the storage tanks.• In the sealing unit i.e. Hot air seal unit, a plastic cap is placed over the cylinder along with a thin PVC seal which then is exposed to 265’C of hot air.• Compressed air of 7.5kg/cm2 is required for the functioning of the plant, which is done by using V-type, screw-type and vertical air compressor which are manually checked after the working hours which can be done.• In bulk filling, LPG and condensate are filled into tankers following the same procedure as that of packed form.• The tanker is checked for a hydraulic testing certificate valid for a period of 5 years from the date of issue.• The tanker evacuation unit is utilized when excess is sent into the tanker. The liquefied form of LPG filled into the tank is 18% less than the total tanker capacity.
CONCLUSIONThe vocational training enhanced our practical knowledge . Most importantly , wewere oriented to the industrial scenario and its many challenges and subtleties . Thesmooth functioning of an industry depends to a large extent on the mutual co-operation among its different wings.Nevertheless , we did enjoy the training to the fullest and are very sure that thistraining will help us in our future endeavors.Thanking You