Training report Oil India Limited LPG, Duliajan by upal jb
A REPORT ONINDUSTRIAL TRAININGATOIL INDIA LIMITEDDULIAJANLPG DEPARTMENTDECEMBER 2012SUBMITTED BYUPAL JYOTI BARUAH5THSEMESTER,ASSAM ENGINEERING COLLEGE,GUWAHATI - 781013.
AKNOWLEDGMENTWe would like to offer our sincere gratitude to the respected and learned guides of OilIndia Limited, Duliajan especially Shri D. Das ,DSO(i/c) LPG, Mrs. S. Banerjee,CE(O)LPG,Shri R.Bhagawati,SE (i) LPG, Shri M.K. Goswami, CE(E),LPG Shri P Ray ChoudhuryCE(M) i/c LPG, Mrs. E.L.Wahlang Dy.Suptd. Chemist, LPG and Mrs. N.Deka E(PD) LPGunder whom we were deputed. Thanks to Shri Jharna Baruah and Shri D.K. Mahanta forproviding us the environment and other necessary facilities during our stay.We are heartily thankful to all the managers, engineers and operators working in theLPG department who have helped us in different ways to make our training a very productiveone.Apart from them we are grateful to Mrs Nivedita Saikia Tamuli, T&D Officer, OILDuliajan and Prof. Ashok Baruah, HOD, Chemical Engineering, AEC, for their support andencouragement.Upal Jyoti Baruah5thSemester,Department of ChemicalEngineering,Assam Engineering College,Guwahati.
CONTENTSCHAPTERNO.TOPIC PAGENO1 INTRODUCTION TO OIL 12 LPG RECOVERY UNIT 33 SAFETY SYSTEM IN RECOVERY AND FILLING PLANT 74 INSTRUMENTATION IN LPG 135 MECHANICAL MAINTENANCE OF LPG 176 QUALITY CONTROL LAB 217 ELECTRICAL MAINTENANCE 248 LPG FILLING 269 CONCLUSION 30
CHAPTER 1AN INTRODUCTION TO OILThe discovery of oil at Digboi, Assam marks the birth of an oil and gas companybased in Assam. The company was incorporated as a private limited company on February18,1959 under the name “Oil India Private Limited” between the President of India, theBurmah Oil Company Limited and Assam Oil company limited. It became a deemed publiclimited company on May 4, 1961 and thus the word “private” was deleted from its name.Presently the Oil India Limited (OIL) is an Indian public sector company under theadministrative control of the Ministry of Petroleum and Natural Gas of the Government ofIndia. OIL is engaged in the business of exploration, development and production of crudeoil and natural gas, transportation of crude oil and production of liquid petroleum gas. TheCompany presently produces over 3.2 MMTPA (million tons per annum) of crude oil, over5 MMSCMD of Natural Gas and over 50,000 Tones of LPG annually. Most of this emanatesfrom its traditionally rich oil and gas fields concentrated in the North-eastern part of Indiaand contribute to over 65% of total Oil & Gas produced in the region. The search for newavenues has seen OIL spreading out its operations in onshore / offshore Orissa and Andaman,deserts of Rajasthan, plains of Uttar Pradesh, riverbeds of Brahmaputra and offshoreSaurashtra. In Rajasthan, OIL discovered gas in 1988, heavy oil / bitumen in 1991 and startedproduction of gas in 1996. The company has over 100,000 square kilometres of license areasfor oil and gas exploration. It has emerged as a consistently profitable international companywith exploration blocks as far as Libya and sub-Saharan Africa.In recent years, OIL has stepped up E & P activities significantly including Gasmonetization in the North-East India. OIL has set up the NEF (North East Frontier) project tointensify its exploration activities in the frontier areas in North East, which are logisticallyvery difficult and geologically complex. Presently, seismic surveys are being carried out inManbhum, Pasighat and other Trust Belt areas. The Company operates a crude oil pipeline inthe North East for transportation of crude oil produced by both OIL and ONGCL in theregion to feed Numaligarh, Guwahati, Bongaigaon and Barauni refineries and a branch line tofeed Digboi refinery. OIL also sells its produced gas to different customers in Assam viz.BVFCL, ASEB, NEEPCO, IOC (AOD), and APL and to RSEB in Rajasthan.
There are various departments in OIL and a few of them are:Production (Oil&Gas), Civil engineering, Chemical engineering, LPG, Geological,Electrical engineering, Instrumentation, IT, Fire and Safety, Transport, Fieldcommunication, Field engineering, Drilling, Well logging, Geophysics, Materials, Medical,Finance and maintenance, Training and development, Research and developmentThe two major products of Oil India Limited are1.Crude Oil and Natural Gas,2.LPG ( Liquified Petroleum Gas ) being an important value addition to the naturalgasproduced.
CHAPTER 2LPG RECOVERY UNITThe LPG recovery unit of OIL based at Duliajan was incorporated on 1982 and isbased on Turbo Expander Technology. The main objective of this unit is the production ofLPG from Natural Gas. The by-product of this unit is called Condensate or Heavy Gasoline.It is certified to conform to the Quality Management System Standard: OHSAS 18001:2001,ISO 14001:2004 and ISO 9001:2008.LPG department of OIL has two installations, namely, (i) LPG Recovery Plant whichproduces LPG and Natural Gasoline (a by-product) from natural gas and (ii) LPG FillingPlant, which has facilities for filling of LPG cylinders as well as LPG and Natural Gasolineroad tankers. The 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 & AdministrationThe LPG is sold to and marketed by IOCL after being bottled or filled in tankers. Theremaining natural gas is called residue gas at 76MMSCFD which is returned back to LPGtake-off point. The residue gas is supplied to power house, domestic use, BVFCL, NTPS,NEEPCO and AGCL.The LPG recovery unit produces 50:50(w/w) propane-butane product and 12lb RVPgasoline product. Gas is compressed and dehydrated and also chilled by cold liquid and coldresidue gas from top of de-butanizer. Liquid formed during condensation is then removed andsent to de-butanizer. Remaining gas is expanded and pressure is lowered, when the gas getscolder, more liquid condenses. Gas-liquid stream is sent to de-butanizer. The de-butanizeroverhead gas stream is brought back to warm it up. Natural gas at 80MMSCFD (design) fromLPG take-off point of production gas department is received in LPG recovery plant. Thenatural gas is processed in LPG Recovery plant to produce (a) LPG (C3:C4) & (b)Condensate. The remaining natural gas is called residue gas at 76MMSCFD which is returnedback to LPG take-off point.OIL serves about two lakh families in the North East through supply of cooking gas,which replaces equivalent amount of kerosene and helps environment by saving valuabletrees and providing one of the cleanest fuels.
LPG Recovery process comprises of mainly the following units:a) Compressor.b) Dehydrator.c) Heat exchangers.d) Expander.e) De-etheriser.f) De-butaniser.2.1 PROCESS OF LPG PRODUCTIONNatural Gas consists of Methane, Ethane, Propane, Butane, Pentane and Hexane. Thefraction of Butane is maximum. However its fractional percentage has been decreasing.Applying fractional distillation LPG which consists of Propane and Butane and Condensatewhich consists of Pentane and Hexane can be obtained.Natural Gas consists of Hydrocarbons along with moisture. Removal of moisture isvery important in production of LPG especially before compressors are used. These can bemoisture or any solid particle present in the gas. The liquid passes to a closed drain and thegas is passed to a Centrifugal Compressor. The compressor is driven by a 4500 HP H.Tmotor, operating on 11KV power supply. The main purpose of the scrubber is to removemoisture and solid particles so that the power requirement is lessen. The approximateincrease in pressures in the four stages of the centrifugal compressor are as follows:INLET: 14 Kg/cm2STAGE 1: 18 Kg/cm2STAGE 2: 20 Kg/cm2STAGE 3: 28 Kg/cm2STAGE 4: 32 Kg/cm2When a gas is compressed its temperature is increased considerably. This gas isdivided in two paths. The flow of one is controlled and the other is open. The controlled flowis passed through a water based heat exchanger. The opened line is passed through anotherheat exchanger which is heating up deeterniser reflux. Heat of compression fed to de-
ethanizer where temperature of inlet gas is lowered from 215°F to173°F and condensationoccurs. The removal of liquids is very important in the entire process. The gas passes throughscrubber followed by another heat exchanger. The gas which now contains liquid particlesalso now passes through a liquid filter which separates all liquid particles.The liquid flows to the closed drain and the gas goes to a dehydrator. There are twodehydrators in this plant. Each runs for 8 continuous hours. A Dehydrator consists ofmolecular sieves which is of Sodium Alumina Silicate which has the capacity of absorbingwater particles from gas-water mixture. There are approximately 11,000 Kg of such materialin each dehydrator. In order to remove the absorbed water molecules the offline dehydrator anumber of processes takes place. A heat cycle occurs for 270 minutes followed by a coldcycle which runs for about 190 minutes. This is followed by a pressurisation process in whichpressure is build up. This runs for about 15 minutes. For the next 2 minutes bed change overtakes place. Both the dehydrators are online in this period. The controlling of this process isdone using a PLC (programmed logic controller).After dehydration, the gas particles contains dust so it has to be passed through a dustfilter. The outlet of the dust filter is divided into two lines, one contains 70% output and theother the rest 30% both of which is passed through two heat exchanges. The condensed gas ispassed through a cold separator to separate the gas and the liquid. The liquid flows through aheat exchanger to a deetherniser. The gas flows through an expander. The gas flows out asresidue gas and the liquid flows to the deetherniser via a heat exchanger.The deetherniser feed is liquid from cold separator and liquid from expander. A partof this liquid circulated within and this is called deetherniser reflux. This is heated from a partof the gas from the centrifugal compressor. The liquid then passes to a debuteniser wherefractional distillation occurs and LPG and Condensate are obtained as product. A part of theliquid inside the debuteniser circulates within and this is called debuteniser reflux.
CHAPTER 3SAFETY SYSTEM IN LPG RECOVERY AND FILLING PLANTLPG is highly inflammable substance as small leakage as 1.4% can cause 100% lowerexplosive probability. So to carry out any process activity in such flammable environment,there are areas where safety procedures must be adopted. LPG is a colorless liquid whichevaporates easily into a gas, and the leakage of even a small volume can expand into a largehazardous zone. Since it has no smell, a little mercaptan isadded to help detect leaks.It canburn and explode when gets mixed with air and meets a source of ignition and itcan alsocause cold burns to skin. Therefore safety is of utmost importance in LPG plant.Safety inLPG plant.Safety system in LPG Plants includes the following:(1) General safety(2) Electrical safety(3) Work Permit System(1) General safetyFollowing safety facilities are made available in LPG Recovery and Filling Plant: ALARM AND SHUT-DOWN SYSTEM ESD DEVICE SAFETY RELIEF VALVES GAS DETECTION SYSTEM FIRE ALARM SYSTEM, FIRE SIRENS FIRE PROTECTION SYSTEM FIRE EXTINGUISHERS FIRE DRILL REGULAR INSPECTION OF PLANT OTHERS
ALARM AND SHUTDOWN SYSTEM(A) The plant control philosophy has automatic in-built safety shut-down logic to protect thevital equipment and the Plant as a whole from any abnormal condition of operation.Audio-visual alarm and shut-down indications are displayed in LPG Control Room. Thelimits of maximum/minimum flow, pressure, temperature, level etc. of various stages ofthe Plant are also continuously displayed in the computer visual display units formonitoring the plant operation.(B) The exact status regularly comes to computers of DCS in top control room in terms ofthree different colors- (i) yellow color(for standard priority) (ii) blue color(for mediumpriority) and (iii) the red color(for top priority).(C) 24 Nos. of set points on alarm and shut-down indications related to CM 11-01 and EC 12-01 are displayed in static screen named ALARM SHUTDOWN1, 19 nos. of set pointsrelated to other areas are displayed in static screen named ALARM SHUTDOWN2 inDCS.(D)Status monitoring is done round the clock through DCS work stations. Operations ofalarm and shut-down system are tested as and when those conditions arise during day today plant operation and also during planned and non-planned shutdown of the plant.(E) Testing/ Calibration is done as and when required for smooth running of the plant, alsoduring annual maintenance of the plant.ESD DEVICE:(A)It requires to press the ESD switch to stop LPG Recovery Plant in the event of anyemergency that calls for shutdown of LPG Recovery Plant.(B) The ESD switches are provided in three different locations in the plant- (i) Top ControlRoom (ii) Bottom Control Room (iii) Expander Compressor Panel.(C) Testing is done during planned shutdown of the plant.SAFETY RELIEF VALVES(A)Safety Relief Valves(SRVs) are required for protection of storage tanks, pressure vesselsand piping to protect the same from overpressure.(B) 60 nos. of SRVs are provided at storage vessels, pressure vessels and piping to protect thesame from overpressure.
(C) When the pressure of the system goes above the process set point, the SRV opens andreleases the excess pressure.(D)SRVs are provided in the Scrubbers, Inlet Filter Separators, Dehydrators, gas flow lines,all pressure process vessels, LPG storage vessels, LPG despatch piping etc.(E) The discharges of the SRVs of LPG storage vessels are connected to the flare systemthrough a common line for safety and environmental protection.(F) The discharges of the SRVs of LPG storage vessels are connected to the flare systemthrough a common venting system for safety and environmental protection.(G)Calibration and testing is carried out once a year on scheduled date as specified by codeand test results are recorded.GAS DETECTION SYSTEM(A)The gas detection system consists of 28 Nos. of gas detectors which are located at thevulnerable areas of LPG Recovery Plant and LPG Filling plant. The leakage of gasleading to formation of explosive mixture surrounding the detectors get detectedimmediately and the amount of leakage in terms of percentage of lower explosivelimit(LEL) is displayed with alarm in DCS work station of LPG control room.(B) Testing/calibration of gas detectors is done as and when required to ensure that those arein proper working condition. The calibration and testing of gas detectors is carried outquarterly as per OISD guideline with proper documentation and record.FIRE ALARM SYSTEMS, FIRE SIRENS:(A) FIRE ALARM SYSTEM(a) The fire alarm system consists of alarm switch glass boxes installed at 21Nos. of criticalareas in LPG Recovery and LPG Filling Plant with an audio-visual alarm panel in thebottom control room.(b) In case of emergency situation in any area in LPG RP and FP, it is required to break theglass of the switch box of that area. This will give (i)an audio-visual alarm in the bottomcontrol room indicating the location of emergency (ii)siren in LPG Recovery and also inLPG Filling Plantif the glass is broken in LPG Filling Plant (iii)siren in LPG RecoveryPlant if the glass is broken in LPG Recovery Plant.(c) Testing of each point is carried out once in every month. Proper record is maintained.(B)FIRE SIRENS
(a) Two Nos. of power operated fire sirens(ranges are 5km and 1km) are provided in LPGRP and also in LPG FP in suitable locations to cover the whole area.The siren having 1km range is operated in manual mode during normal fire drill, otherwisethe siren having 5km range is operated. The bigger siren is interlocked with Fire Alarmswitches for auto mode operation.In case it is required to raise the bigger siren manually, the switch of siren on the panel of firesirens must be brought to manual mode and then the siren can be raised by ON/OFF switchprovided for that purpose.(b) As per OISD guideline, Fire Siren should be as follows:FIREDISASTERALL CLEARTESTFIRE PROTECTION SYSTEM(A) CLASSIFICATION OF PETROLEUM PRODUCTS(1) CLASS ‘A’ Petroleum(2) CLASS ‘B’ Petroleum below 65 degree celcius(3) CLASS ‘C’ Petroleum below 93 degree celcius(4) Excluded Petroleum Liquefied gases including LPG, do not fall under thisclassification but form a separate category.(B) GENERAL CONSIDERATIONSThe following fire protections are provided in LPG plant:-Fire Water System-Foam System-Portable fire extinguishers-Sand buckets
(C) BASIS OF DESIGNThe fire water system of OIL’s LPG plant is designed to meet the fire water flowrequirement for fighting two major fires simultaneously requiring largest water demand.(D) The fire water system includes continuously pressurized over ground fire water networkof 2KM length (approximately) consisting of(a) 3000 KLS FIRE WATER RESERVOIR WITH ADDITIONAL FACILITY OFANOTHER 3600 KLS FROM CENTRAL TANK FARM.(b) FIRE PROTECTION PUMPS WITH AUTO START FACILITY(c) HYDRANT POINTS, MONITORS, HOSES(d) TEMPERATURE SENSING MEDIUM VELOCITY WATER SPRAY SYSTEMTHROUGH DELUGE VALVES FOR STORAGE TANKS, TANKER LOADINGAREAS, EMPTY AND FILLED CYLINDER SHEDS. FIRE EXTINGUISHERSPortable Fire Extinguishers are provided at critical locations in LPG Recovery Plant andLPG Filling Plant as follows:(1) LPG RP: A-type -- 07 NosB-type – 04 NosC-type – 25 NosD-type – 25 Nos(2) LPG FP: C-type – 31 NosD-type – 07 Nos FIRE DRILLFire drill is carried out forth nightly in LPG Recovery and also in LPG Filling Plant bythe plant personnel from all sections along with personnel from Fire Service Section totest the performance of the Fire Protection System of LPG department and to takecorrective action as necessary. REGULAR INSPECTION OF PLANT
(i) Regular inspection of LPG RP and LPG FP is carried out by sectional In-chargesand representatives.(ii) Important safety related points are noted down.(iii) Decissions are taken at site and responsibilities are defined during the inspection.(iv) Proper follow up actions are taken.FIRE PROTECTION PUMPSThe capacity and number of main fire protection pumps are fixed based on design firewater rate,which is worked out on the basis of design criteria.All pumps are identical withrespect to capacity and head characteristics (410m3/hr at 88m head) except one which ic oflower capacity (275m3/hr at 88m head).Each pump is provided with individual pressure switch on its delivery line.The electric motordriven pumps are kept in AUTO start Mode.The diesel engine driven pumps are kept as standby and is opearated in case of electric Power Failure or during emergency created by failureof any of the electric motor driven pumps.There are two Jockey pumps which are used to maintain the system pressure.OneJockey pump is kept in Auto Start/Stop Mode and keeps the entire hydrant networkpressurized from 4.6kg/cm2to 8.4kg/cm2.DETAILS OF PUMPPUMP CAPACITY HEAD METERWCDRIVE AUTO STARTPRESSURESprinkle pump 275 88 Electric motor 4.0kg/cmsqSpray pump 410 88 Electric motor 1.0kg/cmsqSpray pump 410 88 Electric motor 2.0kg/cmsqHydrant pump 410 88 Electric motor 3.0kg/cmsqDEFP-1 410 88 Diesel Engine NOT ON AUTODEFP-2 410 88 Diesel Engine 2.5kg/cmsqJocky pump 20 88 Electric motor 4.6kg/cmsq
CHAPTER 4INSTRUMENTATION IN LPG PLANT4.1 WHAT IS INSTRUMENTATION?Instrumentation is defined as the art and science of measurement and control of processvariables within a production or manufacturing area. It measures and or regulates physicalquantity or process variables such as flow, temperature, level, or pressure.4.2 ROLE OF INSTRUMENTATION IN LPG RECOVERY UNITThe role of instrumentation is any industry, more specifically in Oil India Ltd. can beclassified as follows:1. Procurement.The instrumentation department is entrusted with the following duties in thefield of process control, drilling and other related areas like laboratory, R&Detc:I. Selection of the process or technology.II. Specifications of the process or technology.III. Scrutinise of the process or technology.2. MaintenanceIn the LPG plant maintenance is given a very high priority because of safety ofthe plant. A very effective maintenance is carried out through both in-houseand outsourcing. There are three types of maintenance process carries out atLPG plant. These are:I. Maintenance in case of break down.II. Routine maintenance.III. Annual maintenance.3. Technical reports:The instrumentation department distributes information outside OIL.Technical presentations and reports given to OSID and other organisations aregiven by this department.The different devices used and maintained by this section are as follows:Gas Chromatography- used for analyzing a mixture of a sample, a fully electronicallycontrolled device. It consists of columns and detectors situated in the oven maintained at80’c.Moisture Analyzer- If the temperature is less than -80’C, the moisture in the gas will becomesaturated 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 moisturepresent and creates an electrical signals.TCD (Thermal conductivity detector)- uses the property of thermal conductivity of gases andconverts into electrical signals unique for each and every gas imitating the same propertywhich are received by the calibrated and programmed computers.Thermocouple is used for sensing temperature. Level transmitters work based on ArchimedesPrinciple. The different types are:Mass flow meter- senses both gravity and volume. It carries out a lot of algorithmsconsidering the resonant frequency of the U wire which gives the inertia of the liquid andtemperature for gravity calculation.Orifice flow meter- works on the Bernoulli’s principle and specifies only volume.4.3 CONTROLLERS IN LPG RECOVERY PLANTFor instrument control, basically two control systems are available. They are asfollows1. Distributed Control System (DCS).2. Programmable Logic Control (PLC).4.3.1 DISTRUBUTED CONTROL SYSTEM (DCS)Distributed control system is a digital control system based on distributed controlphilosophy. It means a control system which works on the principle of power delegation.The control system will be at the top of the power higherchi and sub modules/nodes obtainthe power conferred by the top power higherity. To delegate power there should be someconnectivity to reach the data to all nodes. This is a network backbone associated with thesystem. Basically an Ethernet dual ring network called distributed communication network(DCN).DCS Loops are basically of two types:1. Sourcing type loops:-In this type of loops power flows from the DCS to field’sequipments such as transmitters, RTDs, Thermocouples etc. Here field’s instrument actsas load and obtain power from the loop.2. Sinking type loops:-In this type of loops power flows to DCS to field’s equipment suchas a source and the DCS channel as load. Field instruments are externally powered.
188.8.131.52 System In Detail:To implement a DCS, we need mainly two major components.1. Hardware2. Software184.108.40.206.1 HARDWARE: They are the physically seen objects associated with the systems.First the system has a master controller called advent controller AC460.A dual networkbackbone called dual DCN is basically of Ethernet dual ring.NODE:-Nodes are the terminals for human-machine interface (HMI).Basically theseare computer configured for the system. There are four nodes:-1. Engineering system:- This is the control node.2. Operation station:- This is called sub-node.3. Information management system:- This is the node where wegenerate report. Here oracle is loaded in the system.4. AC460 itself is also a node.I/O PANEL:-This system implements S-100 I/O or S-800 I/O system. The I/O panelsare of four types. They are-1.Analog board:-It is basically a electronic card which provides channelsfor analog I/O. This board provides 4-20 mA input and 4-20 man output.Analog cards are of 16 channels.2.Digital board:-It gives logical I/O for the system.3.Thermocouple I/P board:- It channels to provide measuringthermocouple.4.RTD board:-It provides channels for measuring interfacing RTD. It ishigh sensitive.5. Marsheline panel:-A panel where zener barriers fuses and terminals areinstalled. Here we connect the external world through cables.6. Devices:-Such as transmitters, switches, RTD, thermo couple and otherMVI (multiple vendor interfaces) module ,for example PLC.
220.127.116.11.2 SOFTWARE: These are the programmes that cannot be seen. It includes driverapplications and other related programs written are compiled and executed in the system forproper functioning (interfacing).1. Data base: It is used for storing and accessing of data.2.ADVA(adverb builder):A graphical software package which is used tobuild plant object viewing through video(VDU).The plant object such asvessels, exchanger, pipes equipments, control valves, transmitters,compressors, expander.3. A text package for configuring functions for defining function modules,loops, templates. All user defined functions are inbuilt in the system in theform FCM (function calling module), where we can invoke any functionservices needed by the user.4. A programming language to provide facility to build custom madefunction. This is Taylor code language (TCL) i. e C-like language.
CHAPTER 5MECHANICAL MAINTENANCE OF LPG RECOVERY PLANTThe responsibility of the mechanical department in the LPG Recovery Plant can becategorised as follows:BreakdownAnnual MaintenanceInventoryMaintenance through contractBuilding maintenanceGarden related jobThe mechanical department follows a comprehensive maintenance plan which is certified tocomply with ISO 9001:2008, ISO 14001:2004 and OHAS 18001:2007. The working of themaintenance department can be classified as follows:BreakdownPreventivePredictiveDesign changePredictive is the most desired among all the classes of maintenance. Analysis of drain oil,lube oil, vibrations, photography, sound measurement etc. is used for predicting the working of amachine. These are done in a fixed routine for the analysis of a machine.In LPG recovery plant, the mechanical maintenance is done in three terms. They are:-1. Yearly2. Fixed period (running hours for 500hrs or 1100hrs)3. Break down.The Mechanical Maintenance Section of the LPG department is responsible toperform the following duties :1) Daily plant check up to ensure smooth operation of the plant and to check lube oil leveland vibration & sound and other parameters.2) Monthly vibration measurement to ensure thatvibration levels of critical equipment are within limits and take necessary correctivemeasurements.3) Periodical lube oil testing to test lube oil of three major equipment of LPGrecovery 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 toensure its correct functioning at its Set Pressure.6) Sound level measurement to measure theintensity 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 pulleysto transfer power).8) Replacement of empty Mercaptan drum of LPG storage area.9) Top uplube oil into Expander Surge Tank to maintain a certain oil level in it.10) Air compressor lubeoil top up to maintain the required level of oil.11) Materials inspection and suitability reportfor the acceptability of the materials received against direct charge Indents/purchaseorders.12) Engaging staff on overtime to complete the repairing job within the day in view ofurgent nature of work for operational as well as safety requirements. 13) Workshop jobrequisition to carry out emergency repair and fabrication jobs at general workshop.14)Breakdown maintenance of machines/ equipment.15) Preparation of tentative maintenanceschedule of air compressor.16) Ultrasonic thickness measurement to gauge metal surfaces forthe thickness.17) Handling/cleaning services and day-to-day maintenance in LPG recoveryand filling plant.18) Servicing, Inspection and Testing of LPG storage vessels.19) To replacehot and cold insulation system of LPG recovery plant with new insulation system at aspecified time interval. 20) De-coupling of various motor devices to carry out maintenancework on driver (motor) or driven side (pumps,compressors,fans,etc.)21) Hydro-testing ofpressure vessels and storage vessels to check the condition/health of vessel..22) Storage,handling and disposal of lube oil and other hazardous materials.Some common mechanical parts of the LPG recovery plant are:5.1 Valve:A valve is a device that regulates the flow of a fluid (gases, liquids, fluidized solids, orslurries) by opening, closing, or partially obstructing various passageways.5.1.1 Types of valves:Ball valve: For on/off control without pressure drop, and ideal for quick shut-off since a 90ºturn offers complete shut-off angle, compared to multiple turns required on most manualvalves.Butterfly valve: For flow regulation in large pipe diameters.Choke valve: A valve that raises or lowers a solid cylinder which is placed around or insideanother cylinder which has holes or slots. Used for high pressure drops found in oil and gaswellheads.
Check valve or non-return valve:It allows the fluid to pass in one direction only.Gate valve: mainly for on/off control, with low pressure dropGlobe valve: It is good for regulating flow.Needle valve: It is for accurate flow control.5.2 Bearing:It is used to reduce friction and for smooth running of any mechanical machines5.2.1 Types of bearing:1. Ball bearing2. Roller bearing3. Tapper bearing4. Half type bearing /Boss type bearing5.2.2 Structure of bearing:The bearings are made of soft materials like carbon, copper, brass, etc.The bearing basically consists of three parts1. Inner2. Racer consisting of the ball3. Outer5.3 Pump:A pump is a device that moves fluids by mechanical action. Pumps can be classified intothree major groups according to the method they use to move the fluid viz. directlift, displacement, and gravity pumps. Pumps operate by some mechanism andconsume energy to perform mechanical work by moving the fluid. Pumps operate via manyenergy sources, including manual operation, electricity, an engine of some type, or windpower.5.3.1 Types of Pumps1. Centrifugal pump2. Reciprocal pump3. Rotary pump4. Semi rotary pump
5.4 CompressorA gas compressor is a mechanical device that increases the pressure of a gas by reducingits volume. Compressors are similar to pumps both increase the pressure on a fluid and bothcan transport the fluid through a pipe. As gases are compressible, the compressor also reducesthe volume of a gas. Liquids are relatively incompressible; while some can be compressed,the main action of a pump is to pressurize and transport liquids.5.4.1 Types of compressors:1. Air compressor type (piston)2. Screw type compressor (air)
CHAPTER 6QUALITY CONTROL LABORATORYLPG gas produced has to be maintained at a constant vapour pressure so that it can bestored in cylinder or tanker. This has been standardized by the Bureau of Indian Standardsthrough IS 4576:1999.The vapour pressure of the commercial butane-propane mixture (50%propane-50%butane) has been recommended at 16.87 kgf/cm², maximum at 65ºC. In OIL,Duliajan it is maintained at 830-930KPa(upper limit) and 200KPa(lower limit),maximum at40ºC.Also the composition, density has to be maintained at a standard value.6.1 Tests for Quality Control:6.1.1 Vapour Pressure:Measurement of vapour pressure is done with the help of pressure gauge. Firstly thewhole apparatus is filled with liquid LPG. Then valve is slowly open to let the vapour escapeinto air, so that only liquid LPG is maintained in the apparatus. Temperature at 40ºC ismaintained by the temperature bath, where the apparatus is dipped into. It is checked bymeans of a temperature gauge. The lower apparatus is then removed, which is 20% cc of theupper apparatus. This allows sufficient volume to the upper apparatus.6.1.2 Doctor’s Test:This method is intended primarily for the detection of marcaptan in motor fuel and similarpetroleum products. It is in-applicable in the presence of more than slide trace of peroxides.In this method the sample is shaken with Sodium Plum bite solution small quantity ofpowdered sulpher added and the mixture is shaken again. The presence of marcaptan ofhydrogen sulphide or both is indicated by de-colorization of the sulphar floating at the oil-water interface or by de-colorization of either of the phase.Marcaptans may have adverse effects on certain fuel systems.Illastomers may becorrosive towards fuel system metals and produce an offensive odour the doctor test providesa quick simple method of detecting the presence of marcaptans,hydrogen sulphide,elementalsulphar and trace level of peroxides. A graduated cylinder of 50ml capacity with a groundglass stopper is used as an apparatus for doctor’s test. The complete solution for doctor’s test
is a mixture of sodium plum bite solution(doctor’s reagent),8ml iso-octane,a pinch of sulphurpowder.6.1.3 Density measurement:For this, a chamber of fibre glass with steel cage is used. It contains a Hydro-meter(formeasuring specific gravity and density) and a thermometer(for measuring temperature).LPGvapour is poured into it, which then condenses to liquid at low pressure(atmosphericpressure).Therefore we get the specific gravity(or density) at a certain temperature.6.1.4 Weathering Test:A centrifugal test tube (100 ml) is used.LPG vapour is poured into it, which thencondenses to liquid at low pressure(atmospheric pressure).The temperature is noted with thehelp of a temperature gauge. Temperature at 95% evaporation(ie at 5 ml of the liquid),shouldnot be more than 2ºC.If it is more than 2ºC,it will mean that the LPG contains heavierparticles(hydrogen sulphide,water).6.1.5 Gas ChromatographyGas chromatography (GC), is a common type of chromatography used in analyticalchemistry for separating and analysing compounds that can bevaporized without decomposition. In simple words, gas chromatography is used for theanalysis of different components and its quantity. There are two phases in a Gaschromatograph, a stationary phase and a mobile phase. The stationary phase is a 1m to 20mtube of Stainless Steel inside which a stationary bed of Aluminium Oxide or Alumina isplaced at isothermal condition at 80OC. The mobile phase is H2 which is flows at 30cc/sec.The gas is mixed with the mobile phase and flows through the stationary bed. Depending onsome physical properties like size of the molecule, affinity towards the bed, polarity etc themolecules of different components take different and a unique time, called Retention time, topass through the bed. At the end of the bed there is a Thermal Conductivity Detector (TDC)which has 4 filaments, 2 called reference filament and 2 others called measuring gas filament.These filaments are very precisely calibrated. From the TDC the amount of a component can
be measured. Thus, from the retention time and the TDC the different components and itsquantity can be measured.Apart from this unit there is a GC sample panel. This panel is used to collect thesamples, regulate it and access the multiple samples and convert it into one.The GC instrument used in the Quality Control Lab of LPG Recovery Unit has 4columns for more accuracy in measurement. The GC requires a few gases for analysis. Theseare as follows:Helium: Helium is used for as the carrier gas.Hydrogen: It is used for combustion of the gas to be tested.Nitrogen: Nitrogen is used for the operation of valves.Air: Air is also used for the combustion of gases with higher molecularweight.The gases are present at a constant pressure of 4 Bar. Helium is purchased in cylinders whilethe rest gases are produced by a generator. The gases are dried using Silica Gel and molecularsieves.
CHAPTER 7ELECTRICAL MAINTENANCEThe power house of OIL generates 14.45 MW with the help of two gas turbines whichare alternatively at running and standby modes. The power house supplies 11KV to thesubstation in the LPG plant through two underground cables. This incoming power is sentinto the feeder from two different power houses. These two sections are connected by a buscoupler which is used only when the maintenance job needs to be done. From one the 11KVis supplied to the spare feeder, 4500HP motor starter panel and to a transformer of 1000KVAcapacity which steps 11000V down to 415V. There are 8 vacuum circuit breakers. It ismonitored by protective relays such as VCB, ACB, SF6 of the circuits. UPS system gives anuninterrupted power supply normally of AC current with a battery backup of 120KVAcapacity. There are 2 types of UPS in which input is 415V but outputs are 415V and 110V. Abattery converts a voltage input of AC to DC. A 110V Ni-Cd battery set is used. Anotherauto-transformer other than the two in the feeder circuits produce 450V line. It is a part ofmotor starter panel. During starting of motor the load might reach seven times its full loadand then drop back which cannot be allowed. To reduce this we use this auto-transformerstarter for 20 seconds and then give back to the normal system. Motor control centre (MCC)is provided by the 415V bus. Tripping is a condition when difference between the incomingand outgoing currents of the isolator is more than a given value and the on-off switch of theisolator turns off automatically.7.1 AutotransformerAutotransformer is used for applying reduced voltage to stator during starting. Thereby thestarting current is reduced. The auto-transformer is provided with change-over switch. As themotor comes to full speed, the change-over switch is thrown over to run position.7.2 Circuit breakerCircuit Breaker is an automatic device capable of making and breaking an electric circuitunder normal and abnormal conditions such as short circuits. The part of the circuit breakersconnected in one phase is called the pole. A circuit-breaker suitable for three phase system iscalled a triple pole circuit breaker. Each pole of the circuit breaker comprises one or moreinterrupts 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 bedrawn apart by means of the operating links or the operating medium. The operatingmechanism 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 carryingcontacts is interrupted by a suitable medium and by adopting suitable techniques forextinction. Circuit Breaker is used for opening and closing circuits for normal switchingoperations. During short circuits or abnormal conditions, relay operates and gives openingcommand to circuit-breaker and circuit is opened automatically.7.2.1 Types of Circuit Breaker in LPG plantAir Circuit Breaker (ACB): It utilizes air at atmospheric pressure for arc-extinction.Vacuum Circuit Breaker (VCB): The fixed and moving contacts are housed inside apermanently sealed vacuum interrupter. The arc is quenched as the contacts areseparated in high vacuum.ELECTRICAL LINE DIAGRAM
CHAPTER 8LPG FILLING PLANTTasks carried out at LPG Filling Plant are : LPG cylinder filling and dispatch LPG tanker filling and dispatch Condensate tanker filling and dispatch Regular safety check Routine maintenance of the installationOil India limited introduces a fully automatic bottling system in the LPG filling plantwhich is based on different types of photo-electric sensors, Crisplant universal controller(CUC)and HMI(human-machine interface).The whole filling unit consists a filling machinecalled Carousel filling machine. Chain conveyor with 5 gear boxes operated by 5 motors. TheCarousel machine itself uses a motor of power 1.3 KW.The process works in three stages-weighing unit, filling unit and checking unit.The weighing unit consists of following components. They are- HMI panel with support Pusher Check scaleThe standard weighing range is from 2 to 120 kg in graduating of 100gm.The photocells or photo-electric sensors used in the system are named as B01 , B02……B24and C01,C02…etc.
CAROUSEL MACHINE The carousel machine consists of a carousel frame with 24 filling machines ; runningwheels and running rail, central column for gas and air and driving unit. The carousel frame is a circular aluminium alloy construction and the wholeconstruction is supported by aluminium alloy wheels with ball bearings. The aluminium alloy wheels run on a rail fastened to the floor. Normally gas is led through the bottom and air through the top of the central column. The main LPG conveyor track to carousel is also connected with carousel return line(37.5 mm) along with release valve and safety valve.A 12 mm line is also connected with the carousel return line for filling LPG in the underfilled cylinders
Operation:The LPG is pumped to LPG Filling Plant from LPG storage vessels at LPG RecoveryPlant. The incoming LPG pressure in the pipeline is about 14kg/cm2. The cylinder consists of ahead ring, 3 fins, valve, high pressure seamed cylinder and a foot ring. The inside of the valve isinstalled 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 arefirst marked by tare weight marking and their marked weights are stored by a HMI device calledpre-check scale. The marked cylinders go to Carousel machine by chain conveyor. In Carouselmachine the empty cylinders are first sensed by photo-electric sensors. In each filling gun twosensors are linked which are placed at the top and at the bottom side of the cylinder. The bottomside sensor is called wheel arm sensor. The bottom photo-cell senses the position of the cylinderon the machine. The top photocell senses the cylinder and gives instruction to the gun. Then therespective gun shoots the respective cylinder. The cylinder moves in a revolution for a minute.The gun fills the empty cylinder within one minute. The LPG filled in the cylinder should be ofweight 14.2 kg. If the gun is unable to fill the cylinder within one minute for delay error, thecylinder will again revolve for one minute. In the outlet of the machine has a puller with sensorwhich 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 introducedthrough a check scale, which checks the over weighted cylinders and bypass them to anothersection called correction unit by pusher with photo-electric sensor. The over weighted cylindersare manipulated up to the stander 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 arefed to Gas detector and O’ring detector unit to check the leakages and damages. In this unit thedamaged cylinders are rejected.The tested cylinders are then fed to counting unit to count by asensor and stored. In hot air sealing unit the cylinders are sealed and fed to transportation section.
CONCLUSIONThe vocational training at the LPG Recovery Plant at OIL, Duliajan exposed us to thepractical environment of engineering. We came to know about the practical problems faced inan industry. The measures of safety in an industry are as important as production. We alsocame to know that the smooth functioning of an industry depends to a large extent on themutual co-operation among its different wings. Apart from that we enjoyed interacting withthe employees and came to know about their experience in working at OIL.