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Industrial Training in

Numaligarh Refinery Limited (NRL)

Under the guidance of: Presented by:Instrumentation Department, Alok Saikia (Gau-C-12/L-201)Numaligarh Refinery Limited (NRL) B.Tech 4th year, 7th semester

CENTRAL INSTITUTE OF TECHNOLOGY KOKRAJHAR

(A Centrally Funded Institute under Ministry of HRD, Govt. of India)

BODOLAND TERRITORIAL AREAS DISTRICTS :: KOKRAJHAR :: ASSAM :: 783370

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ContentsIntroduction

Objectives of NRL

Overview of NRL

Area covered by Instrumentation Department

Instrument observed in various plants

Distributed Control System

Programmable Logic Controller

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Introduction

• Numaligarh Refinery Limited (NRL), popularly known as “Accord Refinery”

was proposed in the historic Assam Accord on 15th August 1985.

• The foundation stone was laid by former Prime Minister Shri P. V. Narasimha Rao

on 3rd July 1992.

• On 9th July 1999 Numaligarh Refinery was dedicated to the nation by Hon’ble Prime

Minister Shri Atal Bihari Vajpayee.

• Commercial Production commenced from 1st October 2000 with 3 MMTPA

capacities.

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Objectives of NRL

• To process the crude available in the North-East region.

• To achieve highest standards in product quality, safety, health and environment

protection.

• Focus on development and growth of human resource through proper training and

career planning.

• To remain at the technological forefront by continuous upgradation of in-house

expertise and absorption of latest technologies.

• To adopt measures/ technologies for energy efficient systems in refining.

• To facilitate economic and industrial development of the region.

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Overview of NRL

• Numaligarh Refinery is situated at Numaligarh in the Golaghat district of

Brahmaputra valley(Assam)

• NRL is a refinery owned by Numaligarh Refinery Limited, a joint venture among

Bharat Petroleum Corporation Limited(61.65%), Oil India Limited(26%) and Govt.

of Assam(12.35%).

• With its concern, commitment and contribution to the socio-economic development

of the state combined with a track record of continuous growth, NRL has been

conferred the status of Mini Ratna PSU.

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Major units of NRL:

• Crude and Vacuum Distillation Unit (CDU/VDU)

• Delayed Coker Unit (DCU)

• Hydrogen Unit (H2U)

• Hydrocracker Unit (HCU)

• Sulphur Recovery Block (SRB)

• Coke Calcination Unit (CCU)

• Motor Spirit Plant (MSP)

• Naphtha Splitter Unit (NSU)

• Solvent De-oiling Unit (SDU)

• Hydrogen Fixing Unit (HFU)

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Products

• Liquefied Petroleum Gas (LPG)

• Naphtha

• Motor Spirit (MS)

• Aviation Turbine Fuel (ATF)

• Superior Kerosene Oil (SKO)

• High Speed Diesel (HSD)

• Raw Petroleum Coke (RPC)

• Calcined Petroleum Coke (CPC)

• Sulphur

• Wax

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Block Flow Diagram

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Area covered by Instrumentation Department

Instrumentation Workshop• Calibration and servicing

• Public Address (PA) system

• Very High Frequency (VHF) system

• Fire Alarm (FA) system

• CCTV system

• Analyzer system

• Gas Detector system

• Clean Agent system

• RIM seal system

• Lab Instrument

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Central Control Room (CCR)• Crude and Vacuum Distillation Unit (CDU/VDU)

• Delayed Coker Unit (DCU)

• Hydrogen Unit (H2U)

• Hydrocracker Unit (HCU)

• Sulphur Recovery Block (SRB)

• Coke Calcination Unit (CCU)

• Motor Spirit Plant (MSP)

• Naphtha Splitter Unit (NSU)

• Solvent De-oiling Unit (SDU)

• Hydrogen Fixing Unit (HFU)

• Numaligarh Refinery Marketing Terminal (NRMT)

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Captive Power Plant And Utility

• Gas Turbine(GT)

• Steam Turbine (STG)

• Utility Boiler (UB)

• Heat Recovery Steam Generator (HRSG)

• Effluent Treatment Plant (ETP)

• Raw Water Treatment Plant (RWTP)

• Fire Water Pump House (FWPH)

• Nitrogen Plant (N2P)

• Raw Water Intake Plant

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Instruments observed in the various PlantsPressure Measurement• Pressure Gauges:1. Bourdon Tube type pressure gauges:

• The bourdon tube consists of a thin walled tube i.e flattened diametrically on opposite sides to

produce a cross-sectional area elliptical in shape.

• Pressure applied fluid present in the gauge enters the tube and pushes the tube in proportion

with the pressure applied.

• The inside of the tube causes distention of the flat sections and tends to restore its original

round cross-section.

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• There is a light spring called hair spring attached to the coil to bring the indicator to starting position.

• Since the tube is permanently fastened at one end, the tip of the tube traces a curve that is the result

of the change in angular position with respect to the center.

• Bourdon tube type gauges are very widely used in NRL in all process and utility plants.

2. Diaphragm type pressure gauges:

• In diaphragm elements, measurements are taken from the elastic deformation of the diaphragm,

which is held by its edges and loaded on one side.

• This deformation is converted by known methods into a rotary movement.

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• Pressure Transmitters:

1. Capacitive type pressure sensor:

• In capacitive type pressure sensor, the sensing element is a taut metal diaphragm located

equidistant between two stationary metal surfaces, forming a complementary pair of

capacitances.

• An electrically insulating fluid transfers motion from the isolating diaphragm to the sensing

diaphragm.

• Any pressure difference of pressure across the cell will cause the diaphragm to flex in the

direction of least pressure.

• Since capacitance between conductors is inversely proportional to distance separating them

there will be a change in capacitance between two plates.

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2. Piezo resistive type pressure sensor

• Piezoresistive means pressure sensitive resistance, or a resistance that changes with pressure

applied.

• Attaching a strain gauge with a diaphragm results in a device that changes resistance with applied

pressure.

• Pressure forces the diaphragm to deform, which in turns causes the stain gauge to change

resistance.

• By measuring the change in resistance we can measure the applied pressure.

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Temperature measurement

• Temperature Gauges:

1. Bimetallic devices

• A bimetallic strip thermometer uses a helical metal strip that unwinds when heated and

rotates a pointer over a calibrated scale.

• When warmed, one metal expands more than the other ( usually Invar), so causing the

bimetallic strip to unwind. Invar is an alloy of iron and nickel, which has a low

coefficient of thermal expansion.

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Fig – Bimetallic Thermometer

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2. Gas/ Liquid expansion device

• It consist of a stem, capillary and bourdon tube in a case.

• The complete measuring system is filled with an inert gas as standard or mercury

under pressure.

• A temperature change cause the internal pressure in the stem to change. The

deflection of the bourdon tube thus caused is transmitted to the pointer by a

movement.

• A bimetallic element is fitted in between the movement and bourdon tube to

compensate for fluctuations of ambient temperature at the case.

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• Temperature Transmitter

1. Thermocouples

• It is the most popular type of sensor.

• It is based on the principle that two wires made of dissimilar materials connected

at either end will generate a potential difference between the two ends.

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• In NRL , most of the thermocouples used are K,R,E.

Type Materials of construction Temperature range

(continuous)

Temperature range

(short term)

K Chromel (90% nickel and 10% chromium)-

Alumel (95% nickel , 2% manganese, 2%

aluminium and 1% silicon)

0 to +1100 -180 to +1300

R Platinum-Rhodium alloy containing 13%

rhodium for one conductor and pure

platinum for the other conductor

0 to +1600 -50 to +1700

E Chromel (90% nickel and 10% chromium)-

Constantan(55% copper and 45% nickel)

0 to +800 -40 to +900

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• To protect the thermocouple from the pressure, flow-induced forces, and

chemical effects of the process fluid, thermocouples are inserted in a tubular

fitting called thermowell.

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2. Resistance Temperature Detector(RTD)

• RTD’s are made of a metal wire or fiber or of semiconductor material that

responds to temperature change by changing its resistance.

• Platinum, nickel, and tungsten and other metals are used that have high

resistivity, good temperature coefficient of resistance, good ductile or tensile

strength, and chemical inertness with packaging and insulation materials.

• The change in resistance can be determined using a bridge circuit.

• RTD’s are manufactured with 2,3,or 4 lead wires per element. The 3-wire

RTD is most common.

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Fig- 3 wire RTD

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3. Pyrometer

• A Pyrometer is an instrument for measuring very high temperature without

any physical contact with the hot body.

• Two common types of pyrometer are the optical type and the radiation

pyrometer.

• An optical pyrometer determines the temperature of a very hot object by the

colour of the visible light it gives off.

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Fig- Optical Pyrometer

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Flow measurement

• Flow Transmitters

1. Differential Pressure:

I. Orifice Plate

• It comprises a metal plate with a concentric round hole (orifice) through which

the liquid flows.

• When an orifice plate is installed in a flow line(usually clamped between a pair

of flanges), increase of fluid flow velocity through the reduced area at the

orifice develops a differential pressure across the orifice.

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II. Venturi Tubes

• A Venturi tube can be used where high pressure loss is not tolerable.

• Because of its gradually curved inlet and outlet cones, almost no permanent

pressure drop occurs.

• In NRL, Venturi Tubes are used in compressor suction flow measurement of

Hydrocracker RGC, MSP RGC and in DCU Off-gas compressor.

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IV. Pitot Tubes

• Pitot tube comprises a small tube inserted into a pipe with the head bent so that

the mouth of the tube faces into the flow. As a result, a small sample of the

flowing medium impinges on the open end of the tube and is brought to rest.

Thus, the kinetic energy of the fluid is transformed into potential energy in the

form of a head pressure.

• By measuring the static pressure with a convenient tapping, the flow velocity can

be determined from the difference between the head pressure and the static

pressure.

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Fig- Pitot tube

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Level Measurement

1. Level Gauges:

• In level gauge, a tube is attached to the bottom and top of tank is monitored.

• The height of the liquid in the tube will be equal to the height of the level in the tank.

• There are different types of level gauges for different application.

• Some of them are-

a) Reflex level gauge

b) Magnetic level gauge

c) Transparent level gauge

d) Tubular level gauge

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2. Level Transmitters:

i. Float Type:

• The float is connects via a cable or tape to a measuring device outside the tank that precisely

measures the length to the float.

• In NRL float type transmitters are used in offsite area.

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iii. Radar type:

• These measurements work by sending a pulsed wave signal from the top of the tank that

hits the surface and then reflects back to the instrument.

• The distance or level of the surface is then determined by the transmission time.

• Radar has the advantage that it is broadly applicable to most of the liquids and

measurement independent of temperature, pressure and vapour.

• In NRL for level measurement of vessels side mounted pulse radars are used at some

cases. Top mounted pulse radars are used in CBD vessels of HCU and utility area.

• In offsite area level of storage tank is measured by Frequency-Modulated Continuous

Wave radar (FMCW radar) are used.

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iv. Radioactive Type:

• A radioactive source either point or strip is placed on one side of and outside of the tank,

and a radiation detector(Geiger counter), of series of detectors is placed on the other side.

• The amount of radiation reaching the detectors is depend on the amount of material in the

tank.

• This type is highly expensive and requires stringent personal safety requirements and

licensing.

• In NRL this type of level transmitters are used only in DCU for coke chamber level

measurement.

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Distributed Control System (DCS)

• A distributed control system (DCS) refers to a control system usually of a manufacturing

system, process or any kind of dynamic system, in which the controller elements are not

central in location but are distributed throughout the system with each component sub-

system controlled by one or more controllers.

• Basic Components of DCS:

• FCS (Field Control Station):It is used to control the process. All the instruments and

interlocks created by software reside in the memory of the FCS. All the field instruments like

transmitters and control valves are wired to the FCS.  

• OPS (Operator Station):It is used to monitor the process and to operate various instrument 

• Communication : It is used to communicate between the FCS and the OPS

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Advantages of DCS:

• Control function is distributed among multiple CPUs (Field Control Stations). Hence

failure of one FCS does not affect the entire plant.

•  Redundancy is available at various levels.

•  Instruments and interlocks are created by software.

•  Generation and modifications of the interlocks are very flexible and simple.

•  Information regarding the process is presented to the user in various formats.

•  Field wiring is considerably less.

•  Maintenance and trouble shooting becomes very easy.

•  Cost effective in the long run.

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Programmable Logic Controllers(PLC):

• In earlier plant operation, Electrical Relay based system was utilized for logic and

shutdown operation of process plant .

• These relays allow power to be switched on and off without a mechanical switch. It is

common to use relays to make simple logical control decisions.

• The development of low cost computer has brought the most recent revolution, the

Programmable Logic Controller (PLC).

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PLC Control Loop:

• The control loop is a continuous cycle of the PLC reading inputs, solving the ladder logic,

and then changing the outputs.

• Figure below shows the basic operation cycle of a PLC. When power is turned on initially

the PLC does a quick sanity check to ensure that the hardware is working properly. If

there is a problem the PLC will halt and indicate there is an error.

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• PLC inputs are easily represented in ladder logic. In Figures below there are three types of

inputs shown. The first two are normally open and normally closed inputs.

• Immediate inputs will take current values, not those from the previous input scan.

• This instruction is actually an output that will update the input table with the current

input values. Other input contacts can now be used to examine the new values.

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Thank You