training report oil india limited lpg, duliajan by upal jb

A REPORT ON

INDUSTRIAL TRAINING

AT

OIL INDIA LIMITED

DULIAJAN

LPG DEPARTMENT

DECEMBER 2012

SUBMITTED BY

UPAL JYOTI BARUAH

5TH SEMESTER, ASSAM ENGINEERING COLLEGE,

GUWAHATI - 781013.

AKNOWLEDGMENT

We would like to offer our sincere gratitude to the respected and learned guides of Oil

India 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 Choudhury

CE(M) i/c LPG, Mrs. E.L.Wahlang Dy.Suptd. Chemist, LPG and Mrs. N.Deka E(PD) LPG

under whom we were deputed. Thanks to Shri Jharna Baruah and Shri D.K. Mahanta for

providing us the environment and other necessary facilities during our stay.

We are heartily thankful to all the managers, engineers and operators working in the

LPG department who have helped us in different ways to make our training a very productive

one.

Apart from them we are grateful to Mrs Nivedita Saikia Tamuli, T&D Officer, OIL

Duliajan and Prof. Ashok Baruah, HOD, Chemical Engineering, AEC, for their support and

encouragement.

Upal Jyoti Baruah

5th Semester, Department of Chemical Engineering, Assam Engineering College, Guwahati.

CONTENTS

CHAPTER

NO.

TOPIC PAGE

NO

1 INTRODUCTION TO OIL 1

2 LPG RECOVERY UNIT 3

3 SAFETY SYSTEM IN RECOVERY AND FILLING PLANT 7

4 INSTRUMENTATION IN LPG 13

5 MECHANICAL MAINTENANCE OF LPG 17

6 QUALITY CONTROL LAB 21

7 ELECTRICAL MAINTENANCE 24

8 LPG FILLING 26

9 CONCLUSION 30

CHAPTER 1

AN INTRODUCTION TO OIL

The discovery of oil at Digboi, Assam marks the birth of an oil and gas company

based in Assam. The company was incorporated as a private limited company on February

18,1959 under the name “Oil India Private Limited” between the President of India, the

Burmah Oil Company Limited and Assam Oil company limited. It became a deemed public

limited 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 the

administrative control of the Ministry of Petroleum and Natural Gas of the Government of

India. OIL is engaged in the business of exploration, development and production of crude

oil and natural gas, transportation of crude oil and production of liquid petroleum gas. The

Company presently produces over 3.2 MMTPA (million tons per annum) of crude oil, over

5 MMSCMD of Natural Gas and over 50,000 Tones of LPG annually. Most of this emanates

from its traditionally rich oil and gas fields concentrated in the North-eastern part of India

and contribute to over 65% of total Oil & Gas produced in the region. The search for new

avenues has seen OIL spreading out its operations in onshore / offshore Orissa and Andaman,

deserts of Rajasthan, plains of Uttar Pradesh, riverbeds of Brahmaputra and offshore

Saurashtra. In Rajasthan, OIL discovered gas in 1988, heavy oil / bitumen in 1991 and started

production of gas in 1996. The company has over 100,000 square kilometres of license areas

for oil and gas exploration. It has emerged as a consistently profitable international company

with exploration blocks as far as Libya and sub-Saharan Africa.

In recent years, OIL has stepped up E & P activities significantly including Gas

monetization in the North-East India. OIL has set up the NEF (North East Frontier) project to

intensify its exploration activities in the frontier areas in North East, which are logistically

very difficult and geologically complex. Presently, seismic surveys are being carried out in

Manbhum, Pasighat and other Trust Belt areas. The Company operates a crude oil pipeline in

the North East for transportation of crude oil produced by both OIL and ONGCL in the

region to feed Numaligarh, Guwahati, Bongaigaon and Barauni refineries and a branch line to

feed 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, Field

communication, Field engineering, Drilling, Well logging, Geophysics, Materials, Medical,

Finance and maintenance, Training and development, Research and development

The two major products of Oil India Limited are

1.Crude Oil and Natural Gas,

2.LPG ( Liquified Petroleum Gas ) being an important value addition to the naturalgas

produced.

CHAPTER 2 LPG RECOVERY UNIT

The LPG recovery unit of OIL based at Duliajan was incorporated on 1982 and is

based on Turbo Expander Technology. The main objective of this unit is the production of

LPG 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 which

produces LPG and Natural Gasoline (a by-product) from natural gas and (ii) LPG Filling

Plant, which has facilities for filling of LPG cylinders as well as LPG and Natural Gasoline

road 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 & Administration

The LPG is sold to and marketed by IOCL after being bottled or filled in tankers. The

remaining natural gas is called residue gas at 76MMSCFD which is returned back to LPG

take-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 RVP

gasoline product. Gas is compressed and dehydrated and also chilled by cold liquid and cold

residue gas from top of de-butanizer. Liquid formed during condensation is then removed and

sent to de-butanizer. Remaining gas is expanded and pressure is lowered, when the gas gets

colder, more liquid condenses. Gas-liquid stream is sent to de-butanizer. The de-butanizer

overhead gas stream is brought back to warm it up. Natural gas at 80MMSCFD (design) from

LPG take-off point of production gas department is received in LPG recovery plant. The

natural 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 returned

back 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 valuable

trees 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 PRODUCTION

Natural Gas consists of Methane, Ethane, Propane, Butane, Pentane and Hexane. The

fraction of Butane is maximum. However its fractional percentage has been decreasing.

Applying fractional distillation LPG which consists of Propane and Butane and Condensate

which consists of Pentane and Hexane can be obtained.

Natural Gas consists of Hydrocarbons along with moisture. Removal of moisture is

very important in production of LPG especially before compressors are used. These can be

moisture or any solid particle present in the gas. The liquid passes to a closed drain and the

gas is passed to a Centrifugal Compressor. The compressor is driven by a 4500 HP H.T

motor, operating on 11KV power supply. The main purpose of the scrubber is to remove

moisture and solid particles so that the power requirement is lessen. The approximate

increase in pressures in the four stages of the centrifugal compressor are as follows:

INLET: 14 Kg/cm2

STAGE 1: 18 Kg/cm2

STAGE 2: 20 Kg/cm2

STAGE 3: 28 Kg/cm2

STAGE 4: 32 Kg/cm2

When a gas is compressed its temperature is increased considerably. This gas is

divided in two paths. The flow of one is controlled and the other is open. The controlled flow

is passed through a water based heat exchanger. The opened line is passed through another

heat 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 condensation

occurs. The removal of liquids is very important in the entire process. The gas passes through

scrubber followed by another heat exchanger. The gas which now contains liquid particles

also 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 two

dehydrators in this plant. Each runs for 8 continuous hours. A Dehydrator consists of

molecular sieves which is of Sodium Alumina Silicate which has the capacity of absorbing

water particles from gas-water mixture. There are approximately 11,000 Kg of such material

in each dehydrator. In order to remove the absorbed water molecules the offline dehydrator a

number of processes takes place. A heat cycle occurs for 270 minutes followed by a cold

cycle which runs for about 190 minutes. This is followed by a pressurisation process in which

pressure is build up. This runs for about 15 minutes. For the next 2 minutes bed change over

takes place. Both the dehydrators are online in this period. The controlling of this process is

done using a PLC (programmed logic controller).

After dehydration, the gas particles contains dust so it has to be passed through a dust

filter. The outlet of the dust filter is divided into two lines, one contains 70% output and the

other the rest 30% both of which is passed through two heat exchanges. The condensed gas is

passed through a cold separator to separate the gas and the liquid. The liquid flows through a

heat exchanger to a deetherniser. The gas flows through an expander. The gas flows out as

residue 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 part

of this liquid circulated within and this is called deetherniser reflux. This is heated from a part

of the gas from the centrifugal compressor. The liquid then passes to a debuteniser where

fractional distillation occurs and LPG and Condensate are obtained as product. A part of the

liquid inside the debuteniser circulates within and this is called debuteniser reflux.

2.2 FLOW DIAGRAM OF LPG PRODUCTION

Simplified flow diagramRESIDUE GAS

LPG

CONDENSATE

INLETGASCOMPR.

GAS- GAS EXCHANGER

GAS - LIQUIDEXCHANGER

TURBO-EXPANDER

EXPANDERSEPARATOR

DE-ETHANIZERDE-BUTANIZER

BOOSTERCOMPRESSORFEED

GAS

COLD SEPARATOR

DEHYDRATOR

CHAPTER 3 SAFETY SYSTEM IN LPG RECOVERY AND FILLING PLANT

LPG is highly inflammable substance as small leakage as 1.4% can cause 100% lower

explosive 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 which

evaporates easily into a gas, and the leakage of even a small volume 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 safety is of utmost importance in LPG plant.Safety in

LPG plant.

Safety system in LPG Plants includes the following:

(1) General safety

(2) Electrical safety

(3) Work Permit System

(1) General safety

Following 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 the

vital 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. The

limits of maximum/minimum flow, pressure, temperature, level etc. of various stages of

the Plant are also continuously displayed in the computer visual display units for

monitoring the plant operation.

(B) The exact status regularly comes to computers of DCS in top control room in terms of

three different colors- (i) yellow color(for standard priority) (ii) blue color(for medium

priority) 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 points

related to other areas are displayed in static screen named ALARM SHUTDOWN2 in

DCS.

(D) Status monitoring is done round the clock through DCS work stations. Operations of

alarm and shut-down system are tested as and when those conditions arise during day to

day 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, also

during annual maintenance of the plant.

ESD DEVICE:

(A) It requires to press the ESD switch to stop LPG Recovery Plant in the event of any

emergency that calls for shutdown of LPG Recovery Plant.

(B) The ESD switches are provided in three different locations in the plant- (i) Top Control

Room (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 vessels

and piping to protect the same from overpressure.

(B) 60 nos. of SRVs are provided at storage vessels, pressure vessels and piping to protect the

same from overpressure.

(C) When the pressure of the system goes above the process set point, the SRV opens and

releases 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 system

through a common line for safety and environmental protection.

(F) The discharges of the SRVs of LPG storage vessels are connected to the flare system

through 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 code

and test results are recorded.

GAS DETECTION SYSTEM

(A) The gas detection system consists of 28 Nos. of gas detectors which are located at the

vulnerable areas of LPG Recovery Plant and LPG Filling plant. The leakage of gas

leading to formation of explosive mixture surrounding the detectors get detected

immediately and the amount of leakage in terms of percentage of lower explosive

limit(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 are

in proper working condition. The calibration and testing of gas detectors is carried out

quarterly 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 critical

areas in LPG Recovery and LPG Filling Plant with an audio-visual alarm panel in the

bottom control room.

(b) In case of emergency situation in any area in LPG RP and FP, it is required to break the

glass of the switch box of that area. This will give (i)an audio-visual alarm in the bottom

control room indicating the location of emergency (ii)siren in LPG Recovery and also in

LPG Filling Plantif the glass is broken in LPG Filling Plant (iii)siren in LPG Recovery

Plant 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 LPG

RP 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, otherwise

the siren having 5km range is operated. The bigger siren is interlocked with Fire Alarm

switches for auto mode operation.

In case it is required to raise the bigger siren manually, the switch of siren on the panel of fire

sirens must be brought to manual mode and then the siren can be raised by ON/OFF switch

provided for that purpose.

(b) As per OISD guideline, Fire Siren should be as follows:

FIRE

DISASTER

ALL CLEAR

TEST

FIRE 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 this

classification but form a separate category.

(B) GENERAL CONSIDERATIONS

The following fire protections are provided in LPG plant:

-Fire Water System

-Foam System

-Portable fire extinguishers

-Sand buckets

(C) BASIS OF DESIGN

The fire water system of OIL’s LPG plant is designed to meet the fire water flow

requirement for fighting two major fires simultaneously requiring largest water demand.

(D) The fire water system includes continuously pressurized over ground fire water network

of 2KM length (approximately) consisting of

(a) 3000 KLS FIRE WATER RESERVOIR WITH ADDITIONAL FACILITY OF

ANOTHER 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 SYSTEM

THROUGH DELUGE VALVES FOR STORAGE TANKS, TANKER LOADING

AREAS, EMPTY AND FILLED CYLINDER SHEDS.

FIRE EXTINGUISHERS

Portable Fire Extinguishers are provided at critical locations in LPG Recovery Plant and

LPG Filling Plant as follows:

(1) LPG RP: A-type -- 07 Nos

B-type – 04 Nos

C-type – 25 Nos

D-type – 25 Nos

(2) LPG FP: C-type – 31 Nos

D-type – 07 Nos

FIRE DRILL

Fire drill is carried out forth nightly in LPG Recovery and also in LPG Filling Plant by

the plant personnel from all sections along with personnel from Fire Service Section to

test the performance of the Fire Protection System of LPG department and to take

corrective action as necessary.

REGULAR INSPECTION OF PLANT

(i) Regular inspection of LPG RP and LPG FP is carried out by sectional In-charges

and 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 PUMPS

The capacity and number of main fire protection pumps are fixed based on design fire

water rate,which is worked out on the basis of design criteria.All pumps are identical with

respect to capacity and head characteristics (410m3/hr at 88m head) except one which ic of

lower capacity (275m3/hr at 88m head).

Each pump is provided with individual pressure switch on its delivery line.The electric motor

driven pumps are kept in AUTO start Mode.The diesel engine driven pumps are kept as stand

by and is opearated in case of electric Power Failure or during emergency created by failure

of any of the electric motor driven pumps.

There are two Jockey pumps which are used to maintain the system pressure.One

Jockey pump is kept in Auto Start/Stop Mode and keeps the entire hydrant network

pressurized from 4.6kg/cm2 to 8.4kg/cm2.

DETAILS OF PUMP

PUMP

CAPACITY

HEAD METER

WC

DRIVE

AUTO START

PRESSURE

Sprinkle pump 275 88 Electric motor 4.0kg/cmsq

Spray pump 410 88 Electric motor 1.0kg/cmsq

Spray pump 410 88 Electric motor 2.0kg/cmsq

Hydrant pump 410 88 Electric motor 3.0kg/cmsq

DEFP-1 410 88 Diesel Engine NOT ON AUTO

DEFP-2 410 88 Diesel Engine 2.5kg/cmsq

Jocky pump 20 88 Electric motor 4.6kg/cmsq

CHAPTER 4 INSTRUMENTATION IN LPG PLANT

4.1 WHAT IS INSTRUMENTATION?

Instrumentation is defined as the art and science of measurement and control of process

variables within a production or manufacturing area. It measures and or regulates physical

quantity or process variables such as flow, temperature, level, or pressure.

4.2 ROLE OF INSTRUMENTATION IN LPG RECOVERY UNIT

The role of instrumentation is any industry, more specifically in Oil India Ltd. can be

classified as follows:

1. Procurement.

The instrumentation department is entrusted with the following duties in the

field of process control, drilling and other related areas like laboratory, R&D

etc:

I. Selection of the process or technology.

II. Specifications of the process or technology.

III. Scrutinise of the process or technology.

2. Maintenance

In the LPG plant maintenance is given a very high priority because of safety of

the plant. A very effective maintenance is carried out through both in-house

and outsourcing. There are three types of maintenance process carries out at

LPG 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 are

given 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 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:

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.

4.3 CONTROLLERS IN LPG RECOVERY PLANT

For instrument control, basically two control systems are available. They are as

follows

1. 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 control

philosophy. 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 obtain

the power conferred by the top power higherity. To delegate power there should be some

connectivity to reach the data to all nodes. This is a network backbone associated with the

system. 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’s

equipments such as transmitters, RTDs, Thermocouples etc. Here field’s instrument acts

as load and obtain power from the loop.

2. Sinking type loops:-In this type of loops power flows to DCS to field’s equipment such

as a source and the DCS channel as load. Field instruments are externally powered.

4.3.1.1 System In Detail:

To implement a DCS, we need mainly two major components.

1. Hardware

2. Software

4.3.1.1.1 HARDWARE: They are the physically seen objects associated with the systems.

First the system has a master controller called advent controller AC460.A dual network

backbone called dual DCN is basically of Ethernet dual ring.

NODE:-Nodes are the terminals for human-machine interface (HMI).Basically these

are 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 we

generate 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 panels

are of four types. They are-

1.Analog board:-It is basically a electronic card which provides channels

for 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 measuring

thermocouple.

4.RTD board:-It provides channels for measuring interfacing RTD. It is

high sensitive.

5. Marsheline panel:-A panel where zener barriers fuses and terminals are

installed. Here we connect the external world through cables.

6. Devices:-Such as transmitters, switches, RTD, thermo couple and other

MVI (multiple vendor interfaces) module ,for example PLC.

4.3.1.1.2 SOFTWARE: These are the programmes that cannot be seen. It includes driver

applications and other related programs written are compiled and executed in the system for

proper 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 to

build plant object viewing through video(VDU).The plant object such as

vessels, 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 the

form FCM (function calling module), where we can invoke any function

services needed by the user.

4. A programming language to provide facility to build custom made

function. This is Taylor code language (TCL) i. e C-like language.

CHAPTER 5 MECHANICAL MAINTENANCE OF LPG RECOVERY PLANT

The responsibility of the mechanical department in the LPG Recovery Plant can be

categorised as follows:

Breakdown

Annual Maintenance

Inventory

Maintenance through contract

Building maintenance

Garden related job

The mechanical department follows a comprehensive maintenance plan which is certified to

comply with ISO 9001:2008, ISO 14001:2004 and OHAS 18001:2007. The working of the

maintenance department can be classified as follows:

Breakdown

Preventive

Predictive

Design change

Predictive 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 a

machine. 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. Yearly

2. Fixed period (running hours for 500hrs or 1100hrs)

3. Break down.

The Mechanical Maintenance Section of the LPG department is responsible to

perform the following 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) De-coupling of various motor devices to carry out maintenance

work on driver (motor) or driven side (pumps,compressors,fans,etc.)21) Hydro-testing of

pressure 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, or

slurries) 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 90º

turn offers complete shut-off angle, compared to multiple turns required on most manual

valves.

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 inside

another cylinder which has holes or slots. Used for high pressure drops found in oil and gas

wellheads.

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 drop

Globe 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 machines

5.2.1 Types of bearing:

1. Ball bearing

2. Roller bearing

3. Tapper bearing

4. Half type bearing /Boss type bearing

5.2.2 Structure of bearing:

The bearings are made of soft materials like carbon, copper, brass, etc.

The bearing basically consists of three parts

1. Inner

2. Racer consisting of the ball

3. Outer

5.3 Pump:

A pump is a device that moves fluids by mechanical action. Pumps can be classified into

three major groups according to the method they use to move the fluid viz. direct

lift, displacement, and gravity pumps. Pumps operate by some mechanism and

consume energy to perform mechanical work by moving the fluid. Pumps operate via many

energy sources, including manual operation, electricity, an engine of some type, or wind

power.

5.3.1 Types of Pumps

1. Centrifugal pump

2. Reciprocal pump

3. Rotary pump

4. Semi rotary pump

5.4 Compressor

A gas compressor is a mechanical device that increases the pressure of a gas by reducing

its volume. Compressors are similar to pumps both increase the pressure on a fluid and both

can transport the fluid through a pipe. As gases are compressible, the compressor also reduces

the 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 6 QUALITY CONTROL LABORATORY

LPG gas produced has to be maintained at a constant vapour pressure so that it can be

stored in cylinder or tanker. This has been standardized by the Bureau of Indian Standards

through 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 at

40ºC.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 the

whole apparatus is filled with liquid LPG. Then valve is slowly open to let the vapour escape

into air, so that only liquid LPG is maintained in the apparatus. Temperature at 40ºC is

maintained by the temperature bath, where the apparatus is dipped into. It is checked by

means of a temperature gauge. The lower apparatus is then removed, which is 20% cc of the

upper 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 similar

petroleum 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 of

powdered sulpher added and the mixture is shaken again. The presence of marcaptan of

hydrogen 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 be

corrosive towards fuel system metals and produce an offensive odour the doctor test provides

a quick simple method of detecting the presence of marcaptans,hydrogen sulphide,elemental

sulphar and trace level of peroxides. A graduated cylinder of 50ml capacity with a ground

glass 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 sulphur

powder.

6.1.3 Density measurement:

For this, a chamber of fibre glass with steel cage is used. It contains a Hydro-meter(for

measuring specific gravity and density) and a thermometer(for measuring temperature).LPG

vapour is poured into it, which then condenses to liquid at low pressure(atmospheric

pressure).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 then

condenses to liquid at low pressure(atmospheric pressure).The temperature is noted with the

help of a temperature gauge. Temperature at 95% evaporation(ie at 5 ml of the liquid),should

not be more than 2ºC.If it is more than 2ºC,it will mean that the LPG contains heavier

particles(hydrogen sulphide,water).

6.1.5 Gas Chromatography

Gas chromatography (GC), is a common type of chromatography used in analytical

chemistry for separating and analysing compounds that can be

vaporized without decomposition. In simple words, gas chromatography is used for the

analysis of different components and its quantity. There are two phases in a Gas

chromatograph, a stationary phase and a mobile phase. The stationary phase is a 1m to 20m

tube of Stainless Steel inside which a stationary bed of Aluminium Oxide or Alumina is

placed 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 on

some physical properties like size of the molecule, affinity towards the bed, polarity etc the

molecules of different components take different and a unique time, called Retention time, to

pass 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 its

quantity can be measured.

Apart from this unit there is a GC sample panel. This panel is used to collect the

samples, 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 4

columns for more accuracy in measurement. The GC requires a few gases for analysis. These

are 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 molecular

weight.

The gases are present at a constant pressure of 4 Bar. Helium is purchased in cylinders while

the rest gases are produced by a generator. The gases are dried using Silica Gel and molecular

sieves.

CHAPTER 7

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. These two sections are connected by a bus

coupler which is used only when the maintenance job needs to be done. From one the 11KV

is supplied to the spare feeder, 4500HP motor starter panel and to a transformer 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 cannot be allowed. To reduce this we use this auto-transformer

starter 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 incoming

and outgoing currents of the isolator is more than a given value and the on-off switch of the

isolator turns off automatically.

7.1 Autotransformer

Autotransformer 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.

7.2 Circuit breaker

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.

7.2.1 Types of Circuit Breaker in LPG plant

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.

ELECTRICAL LINE DIAGRAM

CHAPTER 8 LPG FILLING PLANT

Tasks 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 installation

Oil India limited introduces a fully automatic bottling system in the LPG filling plant

which 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 machine

called Carousel filling machine. Chain conveyor with 5 gear boxes operated by 5 motors. The

Carousel 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 scale

The 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……B24

and C01,C02…etc.

CAROUSEL MACHINE

The carousel machine consists of a carousel frame with 24 filling machines ; running

wheels and running rail, central column for gas and air and driving unit.

The carousel frame is a circular aluminium alloy construction and the whole

construction 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 under

filled cylinders

Operation:

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 device called

pre-check scale. The marked cylinders go to Carousel machine by chain conveyor. 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 moves in a revolution for a minute.

The gun fills the empty cylinder within one minute. 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 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 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.

CONCLUSION

The vocational training at the LPG Recovery Plant at OIL, Duliajan exposed us to the

practical environment of engineering. We came to know about the practical problems faced in

an industry. The measures of safety in an industry are as important as production. We also

came to know that the smooth functioning of an industry depends to a large extent on the

mutual co-operation among its different wings. Apart from that we enjoyed interacting with

the employees and came to know about their experience in working at OIL.