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Indian oil corporation limited

An overview

Indian oil corporation limited is an Indian state owned oil and gas company headquartered at

Mumbai ,india. It is indias largest commercial enterprise , ranking 125 on the fortune

global 500 list in 2010.Indian oil and its subsidiaries account for a 47% share in the petroleum products market,

34.8% share in refining capacity and 67% downstream sector piuplines capacity of 65.7

milion metric tons per year.

Indian oil is the largest and widest network of fuel stations in the country ,numbering about

17606. It has also started auto LPG dispensing stations (ALDS). It supplies indane cooking

gas to over 47.5 milion households through a network of 4,990 indian distributors. In addition

Indian oil


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Barauni refinery

Barauni Refinery was built in collaboration with Russia and Romania.Situated 125 kilometres

from Patna, it was built with an initial cost of Rs 49.40 crore. Barauni Refinery was

commissioned in 1964 with a refining capacity of 1 Million Metric Tonnes per Annum(MMTPA) and it was dedicated to the Nation by the then Union Minister for Petroleum, Prof.

Humayun Kabir in January 1965. After de-bottlenecking, revamping and expansion project,

it's capacity today is 6 MMTPA. Matching secondary processing facilities such Resid

Fluidised Catalytic Cracker (RFCC), Diesel Hydrotreating (DHDT), Sulphur Recovery Unit

(SRU) have been added. Theses state of the art eco-friendly technologies have enabled the

refinery to produce environment- friendly green fuels complying with international standards.

IndianOil is the highest ranked Indiancompany in the prestigious Fortune

'Global 500' listing, having moved up 19 places to the 116th position in 2008. It is also the

18thlargest petroleum company in the world.

Awards/Accolades

Barauni Refinery achieved safety award in gold category of Green Tech Foundation

Safety Award on 04.05.09.

BR bagged 2nd prize in Golden Jubilee Indian Oil Album in Aug 09.

Barauni Refinery accredited in Oct 09 with prestigious Jawaharlal Nehru Centenary

Awards (3rd prize) for Energy Performance in Refinery for the year 2008-09 by

MoPNG.

Suggestion Fortnight declared and inaugurated by ED, BR on 09.12.09.

Barauni Refinery has been accredited first prize in the refinery sector for National

Energy

Conservation Awards-2009 by Ministry of Power. Award received by ED, BR on

14.12.09.

Barauni Refinery was initially designed to process low sulphur crude oil (sweet crude) of

Assam. After establishment of other refineries in the Northeast, Assam crude is unavailable

for Barauni . Hence, sweet crude is being sourced from African, South East Asian and Middle

East countries like Nigeria, Iraq & Malaysia. The refinery receives crude oil by pipeline from

Paradip on the east coast via Haldia. With various revamps and expansion projects at Barauni

Refinery, capability for processing high-sulphur crude has been added high-sulphur crude

oil (sour crude) is cheaper than low-sulphur crudes thereby increasing not only the


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capacity but also the profitability of the refinery. Crude oil is separated into fractions

byfractional distillation. The fractions at the top of the fractionating columnhave lower

boiling points than the fractions at the bottom. The heavy bottom fractions are often cracked

into lighter, more useful products. All of the fractions are processed further in other refining

units.

Different boiling points allow the hydrocarbons to be separated by distillation. Since the

lighter liquid products are in great demand for use in internal combustion engines, a modern

refinery will convert heavy hydrocarbons and lighter gaseous elements into these higher

value products.

Oil can be used in a variety of ways because it contains hydrocarbons of varying molecular

masses, forms and lengths such as paraffins, aromatics, naphthenes (or cycloalkanes),

alkenes, dienes, and alkynes. While the molecules in crude oil include different atoms such as

sulfur and nitrogen, the hydrocarbons are the most common form of molecules, which are

molecules of varying lengths and complexity made of hydrogen and carbon atoms, and a

small number of oxygen atoms. The differences in the structure of these molecules account

for their varying physical and chemical properties, and it is this variety that makes crude oil

useful in a broad range of applications.

Once separated and purified of any contaminants and impurities, the fuel or lubricant can be

sold without further processing. Smaller molecules such as isobutane and propylene or

butylenes can be recombined to meet specific octane requirements by processes such as

alkylation, or less commonly, dimerization. Octane grade of gasolinecan also be improved by

catalytic reforming, which involves removing hydrogen from hydrocarbons producing

compounds with higher octane ratings such as aromatics. Intermediate products such as

gasoils can even bereprocessed to break a heavy, long-chained oil into a lighter short-chained

one, by various forms of cracking such as fluid catalytic cracking, thermal cracking, and

hydrocracking. The final step in gasoline production is the blending of fuels with different

octane ratings, vapor pressures, and other properties to meet product specifications.

HIGHLIGHTS

Barauni Refinery achieved highest ever crude processing of 6.2 MMT (outlook)

during the year. Previous best was 5.94 MMT during the year 2008-09.

Achieved highest ever Low Sulphur crude processing of 5.55 MMT (outlook) during

the year surpassing the previous best of 5.16 MMT during the year 2008-09

Achieved highest ever CRU throughputof 288.3 TMT (outlook). Previous best was277 TMT during the year 1999-00.


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Achieved highest ever RFCCU throughput of 1.497 MMT (outlook) during the year

surpassing previous best of 1.454 MMT during the year 2008-09.

Annual Production

(Outlook for the year 2009-10)

Product Qty (TMT) Previous best(TMT)Lpg 291.8 284.5(2008-09)Ms (Total) 763.3 703.2(2008-09)Sko 954.6 894.3(2005-06)Hsd (Total) 3119.7 3087.7(2008-09)RPC 207.8 176.9(2007-08)Fo 26.9


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MEASUREMENT OF PROCESS VARIABLE

FLOW MEASURMENT

Orifice meter

Depending on the type of obstruction, we can have different types of flow meters. Mostcommon among them is the orifice type flowmeter, where an orifice plate is placed in the

pipe line, as shown in fig.2. If d 1 and d 2are the diameters of the pipe line and the orifice

opening, then the flow rate can be obtained using eq. by measuring the pressure difference

(p1 p 2).


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The major advantages of orifice plate are that it is low cost device, simple in construction

and easy to install in the pipeline as shown in fig.3. The orifice plate is a circular plate with a

hole in the center. Pressure tappings are normally taken distances D and 0.5D upstream and

downstream the orifice respectively (D is the internal diameter of the pipe). But there are

many more types of pressure tappings those are in use.


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The major disadvantage of using orifice plate is the permanent pressure drop that is

normally experienced in the orifice plate as shown in fig.3. The pressure drops

significantly after the orifice and can be recovered only partially. The magnitude of the

permanent pressure drop is around 40%, which is sometimes objectionable. It requires

more pressure to pump the liquid. This problem can be overcome by improving the design

of the restrictions. Venturimeters and flow nozzles are two such devices.

Rotameter


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The orificemeter, Venturimeter and flow nozzle work on the principle of constant area variable pressuredrop. Here the area of obstruction is constant, and the pressure drop changes with flow rate. On the other hand Rotameter works as a constant pressure drop variable area meter. It can be only be used in avertical pipeline. Its accuracy is also less (2%) compared to other types of flow meters. But the major advantages of rotameter are, it is simple in construction, ready to install and the flow rate can be directly

seen on a calibrated scale, without the help of any other device, e.g. differential pressure sensor etc.Moreover, it is useful for a wide range of variation of flow rates (10:1). The construction of rotameterThere is cylindrical type inside the tube. The fluid flows upward through the gap between thetube and the float. As the float moves up or down there is a change in the gap, as a result changing thearea of the orifice. In fact, the float settles down at a position, where the pressure drop across the orificewill create an upward thrust that will balance the downward force due to the gravity. The position of thefloat is calibrated with the flow rate.

Fig. 3Basic construction of a rotameter .

Construction of the float

The construction of the float decides heavily, the performance of the rotameter. In general, a float should

be designed such that:

(a) it must be held vertical

(b) it should create uniform turbulence so as to make it insensitive to viscosity

(c) it should make the rotameter least sensitive to the variation of the fluid density.

.


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Temperature measurement Thermocouple

When two conductors made from dissimilar metals are connected forming two common

junctions and the two junctions are exposed to two different temperature. The thermoelectric

emf generated, in fact is due to the combination of two effects: Peltier effect and Thomson

effect . A typical thermocouple junction is shown in fig. 5.

Fig. 5 A typical thermocouple

Thermocouples are extensively used for measurement of temperature in industrial situations.

The major reasons behind their popularity are: (i) they are rugged and readings are

consistent, (ii) they can measure over a wide range of temperature, and (iii) their

characteristics are almost linear with an accuracy of about 0.05%. However, the major

shortcoming of thermocouples is low sensitivity compared to other temperature measuring

devices (e.g. RTD, Thermistor).

Thermocouple Materials

Theoretically, any pair of dissimilar materials can be used as a thermocouple. But in practice, only few

materials have found applications for temperature measurement. The choice of materials is influenced byseveral factors, namely, sensitivity, stability in calibration, inertness in the operating atmosphere and


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reproducibility (i.e. the thermocouple can be replaced by a similar one without any recalibration). Table-I

shows the common types of thermocouples, their types, composition, range, sensitivity etc.

Table-1 Thermocouple materials and Characteristics

(87% Pt,o

1500 C13% Rh)

13.6-14.1no

v/ C

S

Platinu

m- Platinumo

5.4-12.2 1100-15000-1500 CRhodiu

mo

C(90%

P

t,13.6-14.110%

Rh) ov/ C

K

Chrome

l Alumel -200- 15.2-42.6o

0-1000 C

(90%Ni, (Ni94Al2o

1300 C 38-42.910% Cr)

Mn 3Si)o

v/ C

E

Chrome

l Constantan -200- 25.1-80.8 300-800 oC(57%Cu, 1000oC 77.9-80.8

43%Ni) v/oCT Copper Constantan -200-350oC 15.8-61.8 nonlinear

J Iron Constantan -150-750oC 21.8-64.6 100-500 oC54.4-55.9

Reference Junction Compensation


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Fromabove

discussions, it is imminent that the thermocouple output voltage will vary if the reference junctiontemperature changes. So, for measurement of temperature, it is desirable that the cold junction of thethermocouple should be maintained at a constant temperature. Ice bath can be used for this purpose, butit is not practical solution for industrial situation. An alternative is to use a thermostatically controlledconstant temperature oven. In this case, a fixed voltage must be added to the voltage generated by thethermocouple, to obtain the actual temperature. But the most common case is where the reference

junction is placed at ambient temperature.


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Resistance temperature detector

Copper, Nickel and Platinum are mostly used as RTD materials. The range of temperature

measurement is decided by the region, where the resistance-temperature characteristics are

approximately linear. The resistance versus temperature characteristics of these materials is shown in

fig.1, with t as 0 0 C. Platinum has a linear range of operation upto 650 0 C, while the useful range for

Copper and Nickel are 120 0 C and 300 0C respectively.


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Construction

For industrial use, bare metal wires cannot be used for temperature measurement. They must be

protected from mechanical hazards such as material decomposition, tearing and other physical damages.

The salient features of construction of an industrial RTD are as follows:

The resistance wire is often put in a stainless steel well for protection against mechanical hazards.

This is also useful from the point of view of maintenance, since a defective sensor can be

replaced by a good one while the plant is in operation.

Heat conducting but electrical insulating materials like mica is placed in between the well and

the resistance material.


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The resistance wire should be carefully wound over mica sheet so that no strain is developeddue to length expansion of the wire Fig. 2 shows the cut away view of an industrial RTD.

LEVEL MEASUREMENT

Hydrostatic Differential Pressure type

The hydrostatic pressure developed at the bottom of a tank is given

by: p= h g

where h is the height of the liquid level and is the density of the liquid. So

by putting two pressure tapings, one at the bottom and the other at the

top of the tank, we can measure the differential pressure, which can be

calibrated in terms of the liquid level. Such a schematic arrangement is shown in Fig.

1 . The drum level of a boiler is normally measured using this basic principle. However

proper care should be taken in the measurement compensate for variation of density of water


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with temperature and pressure.


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Floats & Displacers

Introduction

Floats and Displacers are simple level measurement devices. They are somewhat identical

in their look but they work on different operating principles.

Float level switches work upon the buoyancy Principle according to which as

liquid level changes a (predominately) sealed container will, providing its density is lower

than that of the liquid, move correspondingly . In other words, the buoyancy principle states

that "the buoyancy force action on an object is equal to the mass of liquid displaced by the

object.


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Displacers operation is based upon the Archimedes Principle which says that

when a body is immersed in a fluid it loses weight equal to that of the

fluid displaced. By detection of the apparent weight of the immersed

displacer, a level measurement can be inferred.

Displacers and floats are strictly applied for level detection in case of moderately non-

viscous and clean process liquids. They present their best operation in switching applications

and over for small periods. One can achieve spans of up to 12m also, but in that case their

use happens to be extremely costly.

Float Level Switches


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Float level switches are mainly employed for level measurement in narrow level differentialfields, for example high level alarm or low level alarm applications. One of the significanttypes of float is a magnetrol float level switch which consists of a plain float and operatesvia Traval in or out of magnetic resulting in its activation. A non-magnetic tube is also

provided in the design which acts as a barrier and helps in separating the switching

arrangement from the controlled fluid.

These float based level switches include: a magnetic piston, a reed switch and a mercury

switch. Among different float switch designs, the oldest and most precise one employed for

continuous level detection is the tape level gage. Float level sensors are usually prepared

from materials like stainless steel, PFA, Hastelloy, Monel, and several other plastic

components. It is always required of floats to have their weights less than the minimum

likely specific gravity of the liquid being measured. There are basically three kinds of Float

level controls which are listed below:

1. Top mounting

2. Side mounting

3. External cage

An extensive choice of float level switches is accessible in the market which may include

mercury, dry contact, hermetically sealed and pneumatic switching devices. The upper

temperature and pressure limits of float level switches are +1000 F and 5000 psig

respectively. They usually work with low specific gravities which can be around 0.32.

They exist in variety of models such as single, dual and three switch models. Besides, for

level detection of interfaces created between two fluids, customary float rides are

available. Float operated control valves are also available which basically perform

combined functions of level detection as well as level control via a single level controller.

However, their use is limited to areas involving small flows with negligible pressure drops

only.

D ISPLACER S WITCHES

In a typical displacer switch design, a spring is provided which is burdened with weighted


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displacers. The displacers having weights greater than the process fluid gets submerged in

the liquid resulting in a buoyancy force change. This will cause a variation in the net force

operating on the spring. In general, the spring will compress with the raise in buoyancy

force. Just like the float level switches, a magnetic sleeve and a non-magnetic barrier tube is

also incorporated in displacer switches. The magnetic sleeve is attached to the spring and it

moves according to the spring movement resulting in activation of switching mechanism. An

in-built limit switch is provided in the design which proves useful in level surge conditions

since it keeps a check on the over stroking of the spring. The operating principle of a typical

Displacer switch is illustrated in the figure below.

Displacer switches are most commonly employed in oil and petrochemical fields as level

transmitters and local level controllers. These switches offer extremely correct and

consistent measurement results in applications where clean liquids having stable densities

are concerned. They are particularly not appropriate for slurry or sludge type applications

since coating of the displacer causes a change in its volume and a resulting change in its

buoyancy force. Temperature adjustments should also be done for these switches,

specifically in areas where changes in process temperature can significantly affect the

density of the process liquid.

The performance of displacers can be influenced by non-stability in process density in view

of the fact that the displacement i.e. the weight loss of the material is equivalent to the

weight of the liquid dislocated. As soon as the specific gravity of the process varies, the

weight of the displaced material also varies accordingly, resulting in a change in the

calibration. Due to this, one can specifically face problems in cases of interface level

detection between two liquids having different densities, where the relative signal depends

upon the difference between two densities. An important requirement while working with

displacers is that even after commissioning, the liquid being detected must retain its density

for getting good repeatability.

Advantage

They perform extremely well with clean fluids.

Use of these level sensors proves to be very accurate.


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.

Floats v/s Displacers

Following are the major points of distinction between floats and displacers:

Float Switches are available with a glandless design and are capable of fail safe

operation in extreme process conditions, unlike displacers, which if the torque tube

fails can provide a leak path.

A float generally rides above the surface of liquid whereas a displacer remains either

partly or totally immersed in process liquid.

Displacer switches are considered to be additionally stable and dependable as

compared to standard float level switches in case of turbulent, surging, frothy and

foamy services. However in case of refineries, the use of displacers is decreasing

owing to their high installation cost and inaccurate performance due to process

density changes. In these applications, float level switches have been found to be

reliable and useful.

Settings of displacers can be changed very easily since they can be shifted at any

place along the length of the suspension cable. Moreover, these level devices have the

provision of interchangeability between tanks. This is due to the fact that the

differences in process density can be endured by varying the tension of the spring

attached to the displacers.

Testing the appropriate working of a displacer switch is much easier than a

customary float level switch since the former requires just lifting of a suspension

whereas the latter necessitates filling of liquid in the tank upto the actuation mark.


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PRESSURE MEASUREMENT

Bourdon gauge

The Bourdon gauge (see Fig. 2a) consists of a bent tube with an elliptic cross section

closed at one end and connected at the other open end to the chamber in which the pressure

is to be measured. Pressure differences between the environment of the gauge and the

interior cause forces to act on the two walls of the tube (Fig. 2b) so that it is bent by an

amount that depends on the pressure difference between the environment and the interior.

The bending is transformed by a lever to a pointer whose position can be calibrated. The

importance of this type of gauge is that it is very robust and that it covers a range of

pressure measurement from pressures higher than atmospheric pressure down to rough

vacuum (about 10 mbar). The accuracy and reproducibility are relatively poor, so that it is

not suitable for precision measurements, and its usefulness for vacuum measurements is

limited.

Diaphragm gauges

If a diaphragm or a bellows separates two regions with different pressures ( p1, p2,) the

difference p ( p = p1 p2) of these two pressures causes a force that deforms the

diaphragm or bellows. There are many possibilities for measuring this deformation, e.g.

mechanically by a lever and a pointer, optically by a mirror and a light pointer, or

electrically by changes of the capacity of a capacitor formed by the diaphragm and an

additional electrode which is usually placed in a region of very low pressure (see Figs. 3a ...

3c). For precision measurements one side of the diaphragm is evacuated to very low

pressure.

This is called a reference vacuum. The other side is exposed to the pressure to be

measured. The deformation of the diaphragm depends on, but is not proportional to,

the pressure difference . These days linearization of the pressure vs. deformation

reading is mostly performed by electronic circuits. Thus it is possible to make

pressure measurements in a range between some hundred mbar and 10-4 mbar with


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such a precision that this type of gauge can be used as a secondary standard gauge.

The lower pressure limit is caused by the thermal dilatation that has the same order

of magnitude as the deformation

Fig. 2 Bourdon gauge, a) principle, b) distribution of forces

at very low pressures. Some special alloys like stainless steel or special ceramics such as

Al2O3 with high density, are used as materials for the diaphragms. Generally the low

pressure in the region of the reference vacuum is maintained by the use of getters. Frequently

the electrodes and the circuits for the pressure reading are placed in the region of the

reference vacuum. Figure 4 shows a diaphragm gauge with electrical reading. The pressure

reading is independent of the gas composition.


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CONTROL VALVE

Introduction

The control action in any control loop system, is executed by the final control element. The

most common type of final control element used in chemical and other process control is the

control valve. A control valve is normally driven by a diaphragm type pneumatic actuator that

throttles the flow of the manipulating variable for obtaining the desired control action. A

control valve essentially consists of a plug and a stem. The stem can be raised or lowered by

air pressure and the plug changes the effective area of an orifice in the flow path. A typical

control valve action can be explained using Fig. 1. When the air pressure increases, the

downward force of the diaphragm moves the stem downward against the spring.

Classifications

Control valves are available in different types and shapes. They can be classified in different

ways; based on: (a) action, (b) number of plugs, and (c) flow characteristics.


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(a) Action: Control valves operated through pneumatic actuators can be either (i) air to open,

or (ii) air to close. They are designed such that if the air supply fails, the control valve will be

either fully open, or fully closed, depending upon the safety requirement of the process. For

example, if the valve is used to control steam or fuel flow, the valve should be shut off

completely in case of air failure. On the other hand, if the valve is handling cooling water to a

reactor, the flow should be maximum in case of emergency. The schematic arrangements of

these two actions are shown in Fig. 2. Valve A are air to close type, indicating, if the air fails,

the valve will be fully open. Opposite is the case for valve B.


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(b) Number of plugs: Control

valves can also be characterized in

terms of the number of plugs

present, as single-seated valve and

double-seated valve . The difference

in construction between a single

seated and double-seated valve are

illustrated in Fig. 3.


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Referring Fig.1 (and also Fig. 3(a)), only one plug is present in the control valve, so it is

single seated valve. The advantage of this type of valve is that, it can be fully closed and flow

variation from 0 to 100% can be achieved. But looking at its construction, due to the pressure

drop across the orifice a large upward force is present in the orifice area, and as a result, the

force required to move the valve against this upward thrust is also large. Thus this type of

valves is more suitable for small flow rates. On the other hand, there are two plugs in a

double-seated valve; flow moves upward in one orifice area, and downward in the other

orifice. The resultant upward or downward thrust is almost zero. As a result, the force

required to move a double-seated valve is comparatively much less.

But the double-seated valve suffers from one disadvantage. The flow cannot be shut off

completely, because of the differential temperature expansion of the stem and the valve seat.

If one plug is tightly closed, there is usually a small gap between the other plug and its seat.

Thus, single-seated valves are recommended for when the valves are required to be shut off

completely. But there are many processes, where the valve used is not expected to operate

near shut off position. For this condition, double-seated valves are recommended.


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(c) Flow Characteristics: It describes how the flow rate changes with the movement or lift

of the stem. The shape of the plug primarily decides the flow characteristics. However, the

design of the shape of a control valve and its shape requires further discussions. The flow

characteristic of a valve is normally defined in terms of (a) inherent characteristics and (b)

effective characteristics.

Ideal Characteristics

The control valve acts like an orifice and the position of the plug decides the area of

opening of the orifice.

the control valves can be classified in terms of their m vs. x characteristics, and three

types of control valves are normally in use. They are:

(a) Quick opening

(b) Linear

(c) Equal Percentage.

The characteristics of these control valves are shown in Fig. 4. It has to be kept in mind

that all the characteristics are to be determined after maintaining constant pressure

difference across the valve as shown in Fig.4.


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