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AN OVERVIEW OF
VISAKHAPATNAM STEEL PLANT
Visakhapatnam Steel Plant, the first coastal-based steel plan t ofIndia is located 16km south east of destiny i.e., Visakhapatnam.
Bestowed with technologies, VSP has an installed capacity of 3 million
tones per annum of liquid steel 2.56 million tones of saleable steel. At
VSP there is emphasis on total automation, seamless integration andefficient up gradation, which result in wide range of long and structural
products to meet stringent demands of discerning customers within India
and abroad.
VSP products meet exalting International quality standards such
as JIS, DIN, BIS, BS, etc.VSP has the distinction to be the first
integrated steel plant in India to become a fully ISO-9001 certified
company. The certificate covers systems of all operational, maintenance,services units. Besides purchase systems, Training and marketing
functions spreading over 4 regional marketing offices and 22 stockyards
located all over the country.
VSP by successfully installing & operating efficiently Rs.460crore worth of pollution control and environment control equipments
and converting the barren landscape by planting more than 3 million
plants has made steel plant township and the surrounding areas into aheaven of lush greenery. This has made Steel Township a greater,
cleaner and cooler place, which can boast of 3 to 4 degrees lesser
temperature even in the peak summer as compared to Visakhapatnam
city.
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VSP exports pig iron & steel products to Srilanka, Myanmar,
Nepal, Middle East, USA & South East (Pig Iron). RINL-VSP was
awarded Star Trading House status during 1997-2000. Having
established a fairly dependable export market, VSP plans to make a
continuous presence in the export market.
Having a total manpower of about 17250 VSP has envisaged a
labour productivity of not less than 230 tones per man-year of liquid
steel, which is the best in the country and comparable with the
international levels.
BACKGROUND:
With a view to give impetus to industrial growth and to meet the
inspirations of the people from south India, Government of India
decided to establish Integral steel plants in public sectors at
Visakhapatnam(AP) and Hospet (Karnataka) besides a special steel
plant at Salem(Tamilnadu). The announcement was made in the
parliament on 17th April 1970 by the prime minister of India late Smt.
Indira Gandhi.
A site was selected near balacheruvu creek near Visakhapatnam
city by a committee set up for the purpose, keeping in view the
topographical features, greater availability of land proximity to a future
port. The foundation stone for the plant was laid down by late Smt.
Indira Gandhi on 20-01-1971.
Seeds were thus sown for the construction of a modern
sophisticated Steel Plant having 3.4 million tones annual capacity. Anagreement was between Governments of India and erstwhile and Soviet
Union on June 12th 1979 for setting an integrated Steel Plant to produce
structural and long products on the basis of detailed project prepared by
Dr. M.N. Dastur Company was submitted in Nov.1980 to Govt. of India.
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The construction of plant started on 2nd feb.1982.Govt of India on
18th feb.1982 formed a new company called Rashtriya Ispat Nigam
Limited (RINL) and transferred the responsibility of constructing,
commissioning and operating the plant at Visakhapatnam from Steel
Authority of India ltd. to RINL.
Due to poor resource availability, the plant construction could not
keep pace with the plans, which led to appreciable revision of the plant
cost. In the view of the critical fund situation, and need to check further
increase in the plant costs, a rationalized concept was approved which
was to cost Rs.6849 crores on 4th quarter of 1988.
The rationalized concept was based on obtaining the maximumoutput from the equipments already installed, planned/ordered for
procurement and achieving higher levels of operational efficiency and
labour productivity. Thus, the plant capacity was limited to 3 million
tones of liquid steel per annum.
The availability of resources were continued to be lower than
what was planned and this further delayed the competition of the
construction of the plant. Finally all the units were constructed andcommissioned by July 1992 at a cost of Rs.8529crores. The plant was
formally dedicated to the nation on 1st august 1992 by the prime minister
of India Sri P.V Narsimha Rao.
VSP has already crossed many milestones in the fields of
production, productivity and exports. Coke rate of order 543 Kg/ton of
Hot metal, average converter life of 649 heats an average of 11.5 heats
per sequence in continuous bloom caster. Specific energy consumptionof 7.51G kal/ton of liquid steel, a specific refractory consumption of
15.2 kg and labour productivity of 192 ton/man years are some of the
peaks achieved(during the year 1999-2000) in pursuit of excellence.
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AIR SEPERATION PLANT
Air separation plant is one of the major auxiliary units and is
adjusted to meet the maximum daily demand of gaseous Oxygen,
gaseous Nitrogen and gaseous Argon. The plant has the provision for the
production of liquid Nitrogen and liquid Oxygen for storage and
utilization during the period of shutdown of the plant. The plant has
three air separation units, which produce 500 tones/day of
Oxygen(supplied by M/S B.H.P.V).
MAJOR CONSUMERS:
Total requirements of Oxygen, Nitrogen and Argon all over theplant for three million tones stage is 24.248 Nm3/hr and 32 Nm3/hr
respectively. Out of this Steel Melting Shop(SMS) requires 97.3% of
Oxygen for LD converters blowing and LD vessel heating. 65.47% of
Nitrogen produced is consumed by Blast Furnace concasting department
requirement of Argon for homogenization of steel is 93.75%.The basic principle is separation of main constituents of air i.e.
Oxygen(Boiling Point of -182.8 degrees centigrade at 1atm pressure)
and Nitrogen(Boililg Point of 195.7 degrees centigrade at 1 atm
pressure) that is carried out by liquefying the air and separating by
utilizing the boiling point difference for distillation.
BRIEF PROCESS:
Air is sucked from the atmosphere through a pulse type filter
where the dust is removed and then compressed in an air compressor to
7.4KSCA(kg per square cm absolute). This air is precooled in air water
tower to 10 degrees centigrade and sent to purification unit for removal
of moisture, carbon dioxide and other hydrocarbons.
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The purified air passes through the main heat exchanger where it is
cooled to its dew point, currently with the outgoing product i.e. Oxygen,
Nitrogen and waste Nitrogen from the rectification column. A part of air
is taken at an intermediate point and expanded in an expansion turbine to
provide necessary cold to compensate the thermal losses of the system.
The air from the exchangers will be sent to distillation system, which
separates air into Oxygen, Nitrogen and Argon.
For the production of Argon, a gaseous flow is picked at a suitable
point in the upper column of the distillation system(where Argon
contents are maximum) and sent to crude Argon rectification column to
produce crude Oxygen containing 2-3% Oxygen and small amount of
Nitrogen as impurities. Oxygen is separated in a warm Argon
purification unit where Oxygen is reacted with hydrogen in the presence
of a palladium catalyst. Hydrogen required will be taken from water
electrolysis plant(capacity 30 Nm3/hr). Nitrogen is separated by
distillation in pure Argon column.
TABLE:
Gaseous Mode Mixed Mode
Gas Nm3/hr Purity Gas(Nm3/hr) Liquid
(Nm3/hr)
Oxygen 148000 99.5% 12750 875
Nitrogen 296000 99.9% 25500 1000
Argon 100 99.9% -------- 100
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STORAGE AND DISTRIBUTION:
Gaseous Oxygen and Nitrogen from cold box is compressed to
40KSCA, 10KSCA respectively by centrifugal compressors and
supplied directly to the consumers by pipelines. The liquid Oxygen and
Nitrogen will be stored in storage tanks and pumped to 40KSCA by
centrifugal pumps and vaporized by water bath type with steam injection
and supplied to consumers at the time of emergency. Liquid Argon from
cold box is collected in the liquid Argon tanks and cold converters. From
cold converters liquid Argon is vaporized in atmospheric vaporizers and
supplied to con casting department at 7 KSCA.
CYLINDER FILLING STATION:
Liquid Oxygen, Nitrogen and Argon will be pumped by
reciprocating pumps to a pressure of 165KSCA, vaporized, filled and
delivery into cylinders through manifolds of 4, 2, 2 respectively.
GASEOUS STORAGE SYSTEM:
Gaseous Oxygen from the storage will be stored in 8 numbers ifbuffer vessels near SMS (Steel Melt Shop) of 100m3 water volume at
40KSCA. This pressure is reduced to 18KSCG and supplied to SMS.
Gaseous Oxygen is stored near ASP in 3 numbers of 100m3
water volume buffer vessels and pressure is reduced to 12-18KSCG and
supplied for autogenic needs all over the plant.
Gaseous Nitrogen is stored in 6 numbers of buffer vessels of
125m3 water volume of 40KSCG, 2 numbers buffer vessels of 100 m3water volume at 40KSCG for emergency needs of Blast Furnace.
In addition, Nitrogen storage tanks are provided at
desulphurization plant and SMS gas cleaning plant.
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REQUIREMENTS:
ELECTRICITY:
Electric power requirements of ASP are set by LBSS-2. Total power requirement of ASP at 3 million tones stage is 64MW
approximately. Total connected load is 123.7MVA.
COOLING WATER:
There is a closed cycle cooling water system in ASP wherecooling water at 36 degree centigrade is drawn from pump house-14,
which is used as a cooling medium for gas and oil coolers of
compressors and expansion turbine and air pre-cooling system. The hot
water at 45 degree centigrade is returned back to cooling tower for
cooling at 36 degree centigrade.
CHILLED WATER:
Chilled water is taken from chilled water plant and is used ascooling medium in air-conditioning and ventilation systems.
STEAM:
Steam is available near the battle limits at 5-12KSCA(MTN)
for regeneration of absorbers, vaporization of liquids, deriming of
heaters etc.
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PUMP HOUSE:4 pumps of each 3500m3/hr capacity and discharge pressure of
3.5 kg/cm2 are provided to pump the cooled from cooling water for
ASP.
COOLING TOWER:
There are 5 cells of cooling towers and total water flow rate is
12000 m3/hr warm water from different units will be coming back at 2.5
kg/cm2 and cooled in cooling water tower.
DERIMING HEATERS:
2 deriming heaters are provided for warming up of the plant atthe time of shut down and defrosting at the time of leakage if any.
INTRODUCTION TO AIR COMPRESSORS
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The compressors may be classified as follows:
(A) According to design and principle of operation:
There are two basic types:1. Positive Displacement compressors.
2. Non-positive or steady flow compressors.
Positive displacement compressors are further classified as
reciprocating compressors and rotary compressor. In positive
displacement compressors the fluid is prevented by a solid boundary.
Non-positive compressors are the rotary compressors of centrifugal
and axial flow design. In these compressors the fluid is not contained by
solid boundaries but is continuously in a steady flow through the
machine undergoing changes in pressure primarily by means of dynamic
effects.
(A) According to the number of stages:
These are further classified as
1. Single stage compressor : delivery pressure upto 5 bar.
2. Double stage compressor : delivery pressure from 5 to 35 bar.
3. Three stage compressor : delivery pressure from 35 to 85 bar.
4. Fourth stage compressor : delivery pressure above 85 bar.
(A) According to the pressure limits:
Compressors are also classified as per the delivery pressure:
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1.Low pressure compressor:delivery pressure upto 1 bar
2.Medium pressure compressor:delivery pressure from 1 to 8 bars
3. High pressure compressor:delivery pressure from 8 to 10 bars
4.Super high pressure compressor:delivery pressure above 10 bars.
(B) According to the capacity:
Compressors are also classified according to the volume of air
delivered per unit time. They are:
1.Low capacity compressor : volume delivery 0.15m3/s pr less.
2.Medium capacity compressor : volume delivery 0.15 to 5 m3/s.
3.High capacity compressor : volume delivery above 5 m3/s.
(C) According to power drives:
1. Direct drives.
2. Belt drives.
3. Chain drives.
(D) According to nature of installation:
1. Portable
2. Semi-fixed
3. Fixed
(A) According to moving parts:
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1. Reciprocating
2. Centrifugal
3. Rotary
(A) According to number of power cylinders:
1. Single cylinder
2. Multi cylinder
(A) According to the method of cooling:
1. Air cooled
2. Water cooled
(A) According to number of air cylinders:
1. Simplex
2. Duplex
3. Triplex
CENTRIFUGAL COMPRESSOR:
Centrifugal compressor is a non positive or steady flow rotary
compressor. A centrifugal compressor consists of an impeller rotating at
high speed (20000-30000rpm). The impeller consists of a disc on which
radial blades are attached. The air enters the impeller eye and flows
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radially outward with increasing pressure and temperature. In impeller a
static pressure of air increases from eye to the tip in order to provide the
centripetal force on the air. From the impeller the air enters a diffuser,
which provides a gradually increasing area to convert velocity energy to
pressure energy.
In Single stage centrifugal compressors a pressure ratio of 4:1
can be obtained. Pressure in multi stage compression can go upto 10 bar.
The impeller may be a single sided or double sided. In double sided
impeller suction takes place from both sides.
The figure shows the schematic diagram of centrifugal
compressor.
Components of a simple centrifugal compressor
A simple centrifugal compressor has the following four components: inlet, impeller/rotor,
diffuser, and collector. If you look carefully at Figure_3.1 you will be able to identify each
of these 4 components of the flow path. With respect to the figure, the flow (working
gas) enters the centrifugal impeller axially from right to left. As a result of the impeller
rotating clockwise when looking downstream into the compressor, the flow will pass
through the volute's discharge cone moving away from the figure's viewer.
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Figure_3.1 Cut-away view of aturbo- chargershowing the centrifugal compressor (blue) on the
right end of the rotor
Inlet
The inlet to a centrifugal compressor is typically a simple pipe. It may include features
such as a valve, stationary vanes/airfoils (used to help swirl the flow) and both pressure
and temperature instrumentation. All of these additional devices have important uses in
the control of the centrifugal compressor.
Centrifugal impeller
The key component that makes a compressor centrifugal is the centrifugal impeller. It is
the impeller's rotating set of vanes (or blades) that gradually raises the energy of the
working gas. This is identical to an axial compressor with the exception that the gases
can reach higher velocities and energy levels through the impeller's increasing radius. In
many modern high-efficiency centrifugal compressors the gas exiting the impeller is
traveling near the speed of sound.
Impellers are designed in many configurations including "open" (visible blades),
"covered or shrouded", "with splitters" (every other inducer removed) and "w/o splitters"
(all full blades). Figure 3.1 show open impellers with splitters. Most modern high
efficiency impellers use "backsweep" in the blade shape.
Eulers pump and turbine equation plays an important role in understanding impeller
performance.
Diffuser
http://en.wikipedia.org/wiki/Turbo-chargerhttp://en.wikipedia.org/wiki/Turbo-chargerhttp://en.wikipedia.org/wiki/File:Turbocharger.jpghttp://en.wikipedia.org/wiki/Turbo-charger -
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The next key component to the simple centrifugal compressor is the
diffuser. Downstream of the impeller in the flow path, it is the diffuser's responsibility to
convert the kinetic energy (high velocity) of the gas into pressure by gradually slowing
(diffusing) the gas velocity. Diffusers can be vaneless, vaned or an alternating
combination. High efficiency vaned diffusers are also designed over a wide range of
solidities from less than 1 to over 4. Hybrid versions of vaned diffusers include: wedge,
channel, pipe and pipe diffusers. There are turbocharger applications that benefit by
incorporating no diffuser.
Bernoulli's fluid dynamic principal plays and important role in understanding diffuser
performance.
Collector
The collector of a centrifugal compressor can take many shapes and forms. When thediffuser discharges into a large empty chamber the centrifugal compressors collector
may be referred to as a Plenum. When the diffuser discharges into a device that looks
somewhat like a snail shell, bull's horn or a French horn, the collector is likely to be
referred to as a volute or scroll. As the name implies, a collectors purpose is to gather
the flow from the diffuser discharge annulus and deliver this flow to a downstream pipe.
Either the collector or the pipe may also contain valves and instrumentation to control
the compressor. For example, a turbocharger blow-off valve.
OXYGEN COMPRESSOR
INTRODUCTION:
http://en.wikipedia.org/wiki/Bernoulli's_principlehttp://en.wikipedia.org/wiki/Bernoulli's_principle -
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To ensure uninterrupted supply of Oxygen to the consumers
there are six numbers of oxygen compressors in air separation plant.
These oxygen compressors are supplied by M/S. SULZER,
SWITZERLAND & erected and commissioned by M/S. BHPV Ltd.
DESCRIPTION:
Oxygen compressor is a large centrifugal compressor, which
operates on the combination of the following systems.
Power supply:
Power is supplied by main motor manufactured by BHEL ofrated power 3200Kw and of supply voltage of 11000 +/- 10%.
Bearing sealing system/pneumatic valves:
This is system provided for easy supply of air 6 atm and 300C
to all pneumatic operated valves and to seal the bearing pedestal.
Cooling water systems:
Cooling water of 3.5 atm and 360C is supplied to cool down
the lube oil, cool down the air of the driving motor and to cool
down the Oxygen after the individual compressor stages.
Lubricating oil systems:
This system is included to lubricate the bearing of the driving
motor, gear and compressor. This lubricating oil system includes
oil tank, oil mist fan, main oil pump, oil coolers & oil filters.
LP & HP compressor:
This compressor train consists of two compressors namely
LP & HP compressors. LP compressor is a two stage compressorand HP compressor is a three stage compressor. These are
manufactured by SULZER company.
Gear box:
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Gear box is used between the motor and the LP compressor
to transfer the motion from one position to the other. It increases
the speed of the rotor from the power given by the shaft of the
motor. It is manufactured by MAAG.
TECHNICAL SPECIFICATIONS:
LP COMPRESSOR:
Manufacturer : SULZER ESCHER WYSS.
Type : RZ 35 2 + 2
OPERATING CONDITIONS:
100% 10% UNITS
FLOW 15000 16500 Nm3/hr
SUCTION
PRESSURE
1.5 1.5 Atm
SUCTION
TEMPERATURE
25 25 0C
DISCHARGE
PRESSURE
40 40 Atm
DISCHARGE
TEMPERATURE
42 42 0C
POWER ATMOTOR
2650 2845 kws
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OIL MIST FAN:
Manufacturer : LUESCIHER
Air flow capacity : 3 m3/min.
Pressure difference : 70 mm WC
OIL TANK:
Manufacturer : SULZER ESCHER WYSS
capacity : 2700lt.
MAIN OIL PUMP:
Manufacturer : ALL WEITER
Type : SNG*210-40
Capacity : 5 atm
Speed : -3315 rpm
AUXILLARY OIL PUMP:
Manufacturer : ALL WEITER
Type : SNH 210 R 4647 WI
Capacity : 412 lit/min
Pressure : 4 atm
TWIN OIL COOLER:
Manufacturer : CALORIFIER
Heat exchanger each element : 120 w
Oil temp in & : 630C
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Out : 500C
Water temp in & : 360C
Out : 41.20C
Oil flow : 333 lit/min
TURBO GEAR:
Manufacturer : MAAG
Type : GN*60
Speed : 1500/16080 rpm
Power : 3200 Kw
TOOTHED COUPLING:
Manufacturer : RENK
Type : ZNX100
Oil Filling : 2.7 litres
MAIN MOTOR:
Manufacturer : BHEL
Rated power : 3200 Kw
Rated current : 219.6 amps
COOLING WATER SYSTEM:
Cooling water temperature inlet : 360C
Outlet : 450CCooling water pressure inlet : 3.5atm
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Outlet : 2.5 atm
Water requirement : 550 lt/min.
MAINTAINANCE OF IMPELLERS
INSPECTION OF IMPELLERS:
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It is advisable to careful check the impellers at the opportunityof any overhaul. The operator is recommended to inform themanufacturer about the check results with indication of the applied testmethods.
1. Sources of Damage:Depending on the operating conditions and on the nature of
the compressed gas, the impeller can be affected in the course oftime, by the following:
Aspired dust, if no, or only insufficient intake filters are installed,or when the filter are badly maintained.
Aspired humidity, originating from coolers or cleaners.
Surface corrosion, caused by: Corrosive liquids aspired together with the handled gas. Condensate, containing chemical pollutants from the ambient
air.
1. General Examination:
Before shutting down the compressor, the vibrations should
be judged. Vibrations can occur by a detoriation of the rotorbalance, caused by unsymmetrical deposition of dirt or by damagesas mentioned before.
Before cleaning the impellers, their surfaces are to bechecked against signs of uneven dirt deposits, which could point tofaults in the impeller surface. Suspicious areas are to be marked andafter cleaning thoroughly investigated.
After cleaning, a chalk mark should be made on one bladeof every impeller. By starting from the chalk marked blade, anaccurate sight check of the whole impeller must be made. Checkalso the shape of the blades at the impeller inlets and compare the
blade thickness with the original dimension.
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On small rotors, the accessibility to the impellers is bad. Itis recommended to carry out the sight by the help of a small mirror,fastened to a stick and electric lighting.
2. Special Checks:
Cast or Welded ImpellersThe following components are to be examined thoroughly:
Blade inlet edges Blade roots along the impeller discs Inlet ring
If a rupture is suspected, the area in question must beground slightly and re-checked. For better recognition of a
possible crack, it is recommended to apply the visiblepenetrate( if the required liquids are available). The besttest method is the magnetic powder test, which isrecommended to apply if a specialist is on site.
Riveted Impellers
The impellers are to be checked against missed rivet heads
or cut-off rivet shafts. Projecting rivets are to be knocked witha light hammer so as to check whether the rivets are broken ornot.
Special care should be taken to the transition pointsbetween blades and rivets. These points are especiallyendangered by electro chemical attacks, caused by corrosiveliquid penetrating into the space between the holes and rivets.Lying in the said space, the concentration of the liquid can
even increase and cause a supplementary source of danger.
The discs are to be checked against incipient fracture inthe surroundings of the rivet holes. In case of doubts, the aforementioned visible penetrant or magnetic powder tests should
be carried out.
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1. Inspection Report:
Faults and damages reveled during inspection shouldreported and if necessary augmented by sketches or photographs. Ifthe checks do not show any problems a corresponding note should
be written.The methods applied when remedying faults should be
described likewise in the report. Inspection for the application of thecack test(penetrant process)
Surface to be inspected must be free from oil, grease, rust
and paint. Apply the red-colored spray penetrant and allow a contact
time of 10-20 minutes. Carefully clean surface, first by wiping with the cloth, then
with liquid dissolvent. The red penetrant will remain behindin eventual cracks, pores and laps.
Ensure that last traces of surplus penetrant have beenremoved and that the surface of the component is dry.
Shake the can of the Developer liquid thoroughly and spray
a thin even film onto the component. Allow developer filmto dry after evaporation, a white porous coat will remain,which sucks the red colored penetrant from the cracks, sothat cracks can be recognized on the white background.
The requirements for maximum performance precludethe use of any method of application other than spraying
brush application is not recommended.
MAINTAINANCE OF VOLUTE CASING
INTRODUCTION:
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Volute casing maintenance is a very important part of theoverhaul of an oxygen compressor plant. Volute casing is the space inthe compressor, which comes in contact with the oxygen gas itself. Any
kind of contamination leads to great losses in the performance and mayalso cause accident. However volute casing is the only place, which getsless contaminated compare to other components.
CLEANING OF VOLUTE CASING:
The method adopted for cleaning volute casing is usuallymechanical cleaning which consists of brushing, sweeping, blowing,scraping, chaining, sand blasting, agitating or otherwise physicallyremoving contaminants from equipment.
Ultrasonic method is also employed for cleaning the volutecasing. This method employs special equipment to agitate the cleaningfluid, usually a solvent, at high frequency to dislodge particles and breakup films.
INSPECTION OF VOLUTE CASING:
Volute casing is very important before correction of thecompressor because any contamination with greases or oils will lead toaccidents.
Two methods are adopted for inspection Direct visual inspection Ultraviolet light inspection
Direct visual inspection:
This method is adopted to verify the cleanliness of casing.Look at or in the casing under bright white light to detect the presence of
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visible grease or oil films and particulate matter such as filings, rest ormill scale.
Ultraviolet light inspection:
It is used in addition to direct visual inspection to detect
common oils or greases. Inspection in darkness subdued light usingultraviolet light of 3200-3800mm wavelengths. If a bluish whiteflorescent screen is present readen the item. This method is also adopted
because most hydrocarbon oils and greases show florescence underviolet light even though they may be invisible under bright light.
CONCLUSION:
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