Project (1)

A PROJECT REPORT ON

CONSTRUCTION AND MAINTENANCE OF COMPRESSORS

AT VISAKHAPATNAM STEEL PLANT,

VISAKHAPATNAM.

A project report submitted in Partial fulfillment of

requirements for the award of the Degree of

BACHELOR OF TECHNOLOGY

IN

MECHANICAL ENGINEERING

Submitted By

B.RAJESH KUMAR (08811A0306)

B.NETHRNANDH (08811A0307)

D.KESAVA (08811A0314)

J.SRAVAN KUMAR (08811A0324)

K.ABRAHAM (08811A0328)

UNDER THE GUIDANCE

OF

Sri N.R.RAVI

Asst. General Manager(Mech.)

Utilities Dept.

Visakhapatnam Steel Plant.

RASHTRIYA ISPAT NIGAM LIMITED

VISAKHAPATNAM

Certificate

This is to Certify that this project report entitled ”CONSTRUCTION AND MAINTENANCE OF COMPRESSORS ” has being submitted in partial fulfillment for the award of degree of BACHELOR OF TECHNOLOGY in Department of Mechanical Engineering is a inplant training carried out by

B.RAJESH KUMAR (08811A0306)

B.NETHRNANDH (08811A0307)

D.KESAVA (08811A0314)

J.SRAVAN KUMAR (08811A0324)

K.ABRAHAM (08811A0328)

External Guide:

Sri N.R.RAVI

Asst. General Manager(Mech.)

Utilities Dept.

Visakhapatnam Steel Plant.

Acknowledgement

It is our pleasure to express our thanks to VISAKHAPATNAM STEEL PLANT (RASHTRIYA ISPAT NIGAM LIMITED), our sincere thanks to Training and Development Centre, for allowing us to do our project work for the partial fulfillment of the B.Tech Degree in your reputed organization. It helped us a lot in gaining industrial knowledge and gave us an over view on the practical application of our degree in industries.

We specially thank Sri N.R RAVI, Asst. General Manager of Utilities Department for briefing us the project and guiding us throughout our project time.

We would also thank Mr. J.RAVI, Utilities Department for encouraging and guiding us in completing our project work in spite of his busy schedule.

We would also like to thank Mr. Prabhakar Sir, in-charge of this project, for his support in completing our project.

We also take chance to convey our sincere thanks to all the Utilities Department Employees who helped us in finishing our project.

By

B. Rajesh kumar

B. Nethranandh

D. Kesava

J. Sravan Kumar

K. Abraham

AVANTHI INSTITUTE OF

ENGINEERING AND TECHNOLOGY

(NBA ACCREDITED COLLEGE)

Makavarapalem,Narsipatnam,Visakhapatnam 531113.

Certificate

This is to Certify that this project report entitled ” CONSTRUCTION AND MAINTENANCE OF COMPRESSORS” has being submitted in partial fulfillment for the award of degree of BACHELOR OF TECHNOLOGY in Department of Mechanical Engineering is a inplant training carried out by

B.RAJESH KUMAR (08811A0306)

B.NETHRNANDH (08811A0307)

D.KESAVA (08811A0314)

J.SRAVAN KUMAR (08811A0324)

K.ABRAHAM (08811A0328)

1. ABSTRACT

TITLE: ”CONSTRUCTION AND MAINTENANCE OF COMPRESSORS ”

AIR COMPRESSOR AND ITS WORKING

Air compressor is a mechanical device it used for compressing the air This device used in various applications like vehicle, train, and aero plainsFor controlling over motion (breaks) it is also used for rotating drills .This has a many applications in mechanical.

How it’s working?

Piston type compressor:

It’s working principal similar as compare to diesel engine. Piston it is connected to crank shaft through connecting rod over the piston Over the piston, piston rings are placed the piston is reciprocating in the liner .There is two valves first one inlet valve second one is outlet valve . When crank Shaft rotates clockwise direction piston moves down towards crank , At the same time inlet valve will be open and air will be suck But outlet valve remain closed this will happen in half Rotation . In next half rotation inlet valve will be closed &outlet valve will be Open at the same time piston will move towards valve When piston moving Towards valve air will compress and compressed air will Pass out through outlet valve this compressed air stored in a cylinder through this Cylinder compressed air we can use for required application.

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Maintaining and Caring for Your Air Compressor

If you use pneumatic woodworking tools in your wood shop, you need a quality air compressor to power those tools. Because most air compressors need little day-to-day maintenance, they are easy to overlook. However, there are some items you should keep your eye on to make sure your pneumatic woodworking tools have a proper supply of air.The first, most obvious statement is to read and follow all of the operating and maintenance steps outlined in your air compressor's operating manual. Your compressor's warranty may be voided if you do not follow the steps that the manufacturer outlines.

Most modern air compressors appropriate for all but the largest wood shops are piston-style, oil free air compressors, so you likely won't need to maintain an oil level in your unit. However, you should consult your unit's operating manual to be certain.

Bi-Yearly Maintenance:

Check all gauges for correct readings and all fittings for any leaks. Tighten connectors if needed

Daily Maintenance:You should drain moisture from your air compressor's tanks on a daily basis. Bleed most of the air pressure from the tanks before opening the drain valves, allowing all moisture to drain from the tanks.

Weekly Maintenance:Clean the air intake vents, and remove any obstructions. If your air compressor utilizes an air filter, clean the air filter weekly, and replace when necessary.

Monthly Maintenance:Check the operation of the safety release valve. It should open and relieve air pressure and re-seat properly when closed with no leaks. Also check your electrical cords and hoses for any damage. Do not use your compressor if your electrical cord is damaged.

Portable Air Compressor Care:If you have a portable, gas-powered air compressor, check your engine oil level regularly, and change the oil as recommended. Also clean your engine's air filter at least once a week.

Valves Overhaul Procedure

The compressor must first be electrically isolated with the fuses removed and an electrical isolation and work permit granted by the chief engineer. Thereafter the first stage and the second stage suction and discharge valves should be removed and brought to the workshop for overhauling.

Marine compressors use the HOERBIGER automatic valves. The suction and the discharge valves look similar; however the direction of the operation and the spring stiffness differs. The suction valve springs are of lower spring stiffness than the discharge ones and they must never be mixed up. Also when using new spare parts the part number must be carefully checked from the operation and maintenance manual to avoid mixing them up.

When opened up the suction valves are found to be in clean condition while the discharge valves would have some degree of carbonization. In case a valve is opened up and some parts are found to be broken, all the broken parts must be located to avoid any further damage to the machine. An exploded view of the compressor valve has been shown and the overhaul procedure is as follows:

1. Remove the split pin and open the castle nut.

2. Dismantle all the parts and soak in kerosene or clean diesel oil.

3. Clean all the parts with a soft brush. In case of a hard deposit a copper plate of washer can be used for the scraping action.

4. Check the valve plates and the valve seats for any damage and cracks. If any signs of fatigue cracks on the valve plates are present, then the valve plate must be replaced with new ones. The valve plate must never be turned over and used as it can lead to fatigue failure.

5. The valve plate and the valve seat must be separately lapped on a surface plate using fine and extra fine grinding paste.

6. Thereafter all the parts must be washed with diesel and cleaned with compressed air.

7. The valve should then be assembled, with the lapped surface of the valve plate and the valve seat facing each other.

8. After the assembly of the valve the operation of the valve should be checked by a soft wooden stick.

After the overhaul the valves have to be checked for leakage. The space above the valve plate should be filled up with water or light oil like kerosene. If after a few minutes no drop in level or leakage is there then the valve is satisfactory for the use. While installing care should be taken to avoid the interchange of the suction and the discharge valves, as it could lead to an explosion due to over pressurization of the compression chamber.

WHAT IS BUMPING CLEARANCE

Bumping clearance as the name signifies is a clearance given so that the piston of the marine reciprocating compressor would not bump into its cylinder head. In new compressors this clearance is adjusted by the manufacturers and the marine engineers are blissfully unaware of its importance. However the ship does not remain new for ever and every machine demands overhauling and that is where the problems start. Due to short contract now days the marine engineers normally miss this vital adjustment procedure during their training period and then remain shy to ask through out their sea careers. In this article the art and the science of checking and adjusting the bumping clearance has been explained. It is also beneficial for the junior engineers preparing for their certificate of competency examinations.

How Bumping Clearance Changes over Time

The bumping clearance in a new machine is set properly by the manufacturers during construction but over a period of time the clearance changes because of the following reasons:

1. Wear at the crankpin bearing. The crankpin bearing wears down due to use and this clearance can travel right up to the piston and an unloaded piston can hit the cylinder head. This type of wear can be recognized when the compressor makes impact sounds running unloaded at the starting and stopping operations. This type of wear would also be accompanied by a slow decrease in oil pressure over a period of time.

2. Opening up of cylinder heads. In certain types of reciprocating compressors the cylinder head have to be removed for the changing of the first stage suction and discharge valves. When the cylinder head is put back the correct thickness of the cylinder head gaskets should be used otherwise it would change the bumping clearance.

3. Wear on the main bearings. Over all wear on the main bearings would lower the crank shaft and would thus lower the piston and increase the bumping clearances.

These three are the main reasons for the changing of the bumping clearance.

Significance of Bumping Clearance

The bumping clearance is something which must be adjusted very properly otherwise the marine engineer would lose both by decreasing and increasing it. If the bumping clearance is less and the piston would hit the cylinder head and mechanical damage would occur to both of them.

On the other hand if to keep safe, the marine engineer thinks of giving a few millimeters of extra clearance, the volumetric efficiency of the compressor would decrease and the compressor would struggle to fill up the air bottle. In the case of excess bumping clearance when the compressor reaches the TDC a small amount of air remains in the clearance volume which is re-expanded and re-delivered thus lowering the volumetric efficiency. This would endanger your maneuvering and an accident is waiting to happen.

How to Check Bumping Clearance

The bumping clearance can be checked by the following methods:

1. In case a suitable opening is available the piston can be barred to the top dead centre and then feeler gauges can be put inside and the clearances checked at two three points.

2. The more convenient method is to take lead wire (every second engineers store would have one in some corner) and make a small ball based on the expected clearance and put it between the piston and the head from the valve opening. Then the piston is slowly turned to the top dead centre with the help of a Tommy bar. After that the piston is again turned down and the lead wire ball is extracted and the thickness measured with the help of a micrometer. This measurement would give the bumping clearance.

The caution which must be observed in these methods is that the clearances of the main and the crank pin bearing have not been taken into account. The correct method is thus that after turning the piston to top dead centre the piston connecting rod must be jacked up with the help of a crow bar. It is only after this hidden clearance has been accounted for, will the correct bumping clearance be found.

How to Adjust the Bumping Clearance

The bumping clearance once found to be incorrect would have to be adjusted. The methods of adjusting the bumping clearances are as follows:

1. The cylinder head gaskets can be changed to a different thickness thus altering the bumping clearance.

2. The shims between the foot of the connecting rod and the bottom end bearing can be changed thus changing the bumping clearance.

However after adjusting the bumping clearance the clearance should be checked once again to make sure that there is no error.

AIR COMPRESSOR OVERHAUL

THE OPERATION OF AIR COMPRESSORS IS DANGEROUS!!!! The chance of fatal injury is high. High pressure air escaping from air valves during testing or normal operation is of such a high pitch sound that PERMANENT EAR INJURY AND HEARING LOSS ARE A DIRECT RESULT. High pressure air can CUT THROUGH  THE  SKIN,  DESTROY  TISSUE,  CAUSE  AIR  EMBOLISM, AND DEATH

Air compressors are used throughout the Naval (fig. 8-1) and air compressor controls. In these systems Construction Force (NCF). They supply compressed air the compressor may be smaller than others described in for numerous pneumatic tools, rock drilling, well this chapter, but the operating principles are the same. drilling, diving, and cleaning operations. Certain As a CM-1, it is your job to make sure these units are automotive and construction equipment use air-brake maintained properly and to troubleshoot, repair, and systems in which you will find an air compressor overhaul them.

INTRODUCTION TO

VISAKHAPATNAM STEEL PLANT

AN OVERVIEW OF

VISAKHAPATNAM STEEL PLANT

Visakhapatnam Steel Plant, the first coastal-based steel plan t of India 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 and efficient 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.460 crore 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 a heaven 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.

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. An agreement 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.

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 maximum output 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 and commissioned 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 consumption of 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.

INTRODUCTION TO AIR

SEPERATION PLANT

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 the plant 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.

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 ModeGas 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

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 if buffer 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 m3 water volume at 40KSCG for emergency needs of Blast Furnace.

In addition, Nitrogen storage tanks are provided at desulphurization plant and SMS gas cleaning plant.

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 where cooling 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 as cooling 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.

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 at the time of shut down and defrosting at the time of leakage if any.

INTRODUCTION TO AIR

COMPRESSORS

INTRODUCTION TO AIR COMPRESSORS

The purpose of this chapter is to introduce you to the subject of air compressors. You will learn what an air compressor is mechanically and then its types. After learning these facts, you will find out the many ways in which compressors are put to use.

Lets pass up the technical definition of an air compressor. Simply an air compressor is a machine, which is used for increasing the pressure of air by compression.

The compressed air has many practical uses as driving compressed air engine, driving pneumatic tools, paint spraying, injecting fuel in diesel engines, for boosting internal combustion engines (super chargers), in blast

furnace and boiler furnaces, cleaning surfaces by air blast, cleaning surfaces by air blast, cooling of large building etc.,

DEFINITION:

An air compressor is a device that converts power (usually from an electric or diesel or gasoline engine) into kinetic energy by pressurizing and compressing air, which is then released in quick bursts

CLASSIFICATION:

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.

(B) According to the number of stages:

These are further classified as1. 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.

(C) According to the pressure limits:

Compressors are also classified as per the delivery pressure:

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.

(D) 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.

(E) According to power drives:1. Direct drives.2. Belt drives.3. Chain drives.

(F) According to nature of installation:1. Portable2. Semi-fixed3. Fixed

(G) According to moving parts:1. Reciprocating2. Centrifugal3. Rotary

(H) According to number of power cylinders:

1. Single cylinder2. Multi cylinder

(I) According to the method of cooling:1. Air cooled2. Water cooled

(J) According to number of air cylinders:1. Simplex2. Duplex 3. Triplex

APPLICATIONS OF AIR COMPRESSOR:

The air compressors seen by the public are used in 5 main applications:

To supply a high-pressure clean air to fill gas cylinders

To supply a moderate-pressure clean air to supply air to a

submerged surface supplied diver

To supply a large amount of moderate-pressure air to power pneumatic

tools

For filling tires

To produce large volumes of moderate-pressure air for macroscopic

industrial processes (such as oxidation for petroleum coking or cement

plant bag house purge systems).

Most air compressors are either reciprocating piston type or rotary vane

or rotary screw. Centrifugal compressors are common in very large

applications.

There are two main types of air compressor's pumps:

1. Oil lubed

2. oil-less.

The oil-less system has more technical development, but they

are more expensive, louder and last for less time than the oiled lube

pumps. However, the air delivered has better quality.

Air compressor supplies air into a nail gun

How are air compressors used in off-roading?

Air compressors have a wide variety of uses in off-roading, but the most common is inflating tires. The compressor hose can be attached to a tire pressure gauge to achieve the desired psi rating. Air compressors are also essential for re-seating a tire that has slipped off the rim.

Off-roaders also travel with pneumatic tools like impact wrenches, ratchet wrenches and screwdrivers powered by compressed air (think of the nifty pneumatic wrenches used by NASCAR pit crews to remove tires in seconds). Extendible blow guns can shoot targeted blasts of compressed air on filthy, hard-to-reach engine parts.

For serious off-roaders, compressed air is used to power air lockers. These devices can instantly lock the differential on all four tires, creating intense traction over extreme terrain.

Many people use air compressors in conjunction with on-board air tanks. The tank can be filled with compressed air before a drive to have 5 or 10 gallons (19 to 38 liters) of on-demand pressurized air without waiting for the compressor to power up

Air compressors usually run off of the vehicle's 12-volt power supply. The compressor can be permanently mounted to the vehicle or stowed away in a portable toolbox. For maximum power and air displacement (over 250 psi/1,724 kilopascals and up to 8 cfm/0.23 cubic meters per minute), you can modify an engine-mounted air conditioner pump to work as an air compressor.

An air compressor is a must for any serious off-roader

INTRODUCTION TO

CENTRIFUGAL COMPRESSORS

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 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.

Figure_3.1 – Cut-away view of a turbo-charger showing 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.

Euler’s pump and turbine equation plays an important role in understanding

impeller performance.

Diffuser

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 the diffuser 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 collector’s 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:

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 of rated 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 compressor and HP compressor is a three stage compressor. These are manufactured by SULZER company.

Gear box: 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% UNITSFLOW 15000 16500 Nm3/hrSUCTION PRESSURE

1.5 1.5 Atm

SUCTION TEMPERATURE

25 25 0C

DISCHARGE PRESSURE

40 40 Atm

DISCHARGE TEMPERATURE

42 42 0C

POWER AT MOTOR

2650 2845 kws

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

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 : 450C Cooling water pressure inlet : 3.5atm

Outlet : 2.5 atm

Water requirement : 550 lt/min.

MAINTAINANCE OF IMPELLERS

Impellers are attached to the motor shaft with a keyway and either setscrews or other locking device. Attachment should not require any attention after installation at the factory.

Impellers are subject to damage by debris that may be sucked into the inlet shaft or plenum.

Periodically, the impeller should be inspected and cleared.

First, the blower should be started and run up to full operating speed, then turned off. As the blower accelerates to operating speed, runs at speed, then decelerates, observe the motor and housing for excessive vibration.

If vibration is noted, disconnect the motor from its power source before the unit is further inspected

INSPECTION OF IMPELLERS: It is advisable to careful check the impellers at the opportunity of any overhaul. The operator is recommended to inform the manufacturer about the check results with indication of the applied test methods.

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 of time, 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.

2. General Examination:

Before shutting down the compressor, the vibrations should be judged. Vibrations can occur by a detoriation of the rotor balance, caused by unsymmetrical deposition of dirt or by damages as mentioned before. Before cleaning the impellers, their surfaces are to be checked against signs of uneven dirt deposits, which could point to faults in the impeller surface. Suspicious areas are to be marked and after cleaning thoroughly investigated. After cleaning, a chalk mark should be made on one blade of every impeller. By starting from the chalk marked blade, an accurate sight check of the whole impeller must be made. Check also the shape of the blades at the impeller inlets and compare the blade thickness with the original dimension. On small rotors, the accessibility to the impellers is bad. It is recommended to carry out the sight by the help of a small mirror, fastened to a stick and electric lighting.

3. Special Checks:

Cast or Welded Impellers The 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 be ground slightly and re-checked. For better recognition of a possible crack, it is recommended to apply the visible penetrate( if the required liquids are available). The best test method is the magnetic powder test, which is recommended 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 with a light hammer so as to check whether the rivets are broken or not.

Special care should be taken to the transition points between blades and rivets. These points are especially endangered by electro chemical attacks, caused by corrosive liquid 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 in the surroundings of the rivet holes. In case of doubts, the afore mentioned visible penetrant or magnetic powder tests should be carried out.

4. Inspection Report: Faults and damages reveled during inspection should reported and if necessary augmented by sketches or photographs. If the 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 the cack 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 behind in eventual cracks, pores and laps.

Ensure that last traces of surplus penetrant have been removed 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 film to dry after evaporation, a white porous coat will remain, which sucks the red colored penetrant from the cracks, so that cracks can be recognized on the white background.

The requirements for maximum performance preclude the use of any method of application other than spraying brush application is not recommended.

Impellers of pumps are classified based on the number of points that the liquid can enter the impeller and also on the amount of webbing between the impeller blades.

Impellers can be either single suction or double-suction. A single-suction impeller allows liquid to enter the center of the blades from only one direction. A double-suction impeller allows liquid to enter the center of the impeller blades from both sides simultaneously. The illustration below shows simplified diagrams of single and double-suction impellers

Impellers can be open, semi-open, or enclosed. The open impeller consists only of blades attached to a hub. The semi-open impeller is constructed with a circular plate (the web) attached to one side of the blades. The enclosed impeller has circular plates attached to both sides of the blades. Enclosed impellers are also referred to as shrouded impellers. Figure 5 illustrates examples of open, semi-open, and enclosed impellers.         

The impeller sometimes contains balancing holes that connect the space around the hub to the suction side of the impeller. The balancing holes have a total cross-sectional area that is considerably greater than the cross-sectional area of the annular space between the wearing ring and the hub. The result is suction pressure on both

  sides of the impeller hub, which maintains a hydraulic balance of axial thrust.

MAINTAINANCE OF VOLUTE CASING

INTRODUCTION:

Volute casing maintenance is a very important part of the overhaul of an oxygen compressor plant. Volute casing is the space in the compressor, which comes in contact with the oxygen gas itself. Any kind of contamination leads to great losses in the performance and may also cause accident. However volute casing is the only place, which gets less contaminated compare to other components.

CLEANING OF VOLUTE CASING: The method adopted for cleaning volute casing is usually mechanical cleaning which consists of brushing, sweeping, blowing, scraping, chaining, sand blasting, agitating or otherwise physically removing contaminants from equipment. Ultrasonic method is also employed for cleaning the volute casing. This method employs special equipment to agitate the cleaning fluid, usually a solvent, at high frequency to dislodge particles and break up films.

INSPECTION OF VOLUTE CASING:

Volute casing is very important before correction of the compressor because any contamination with greases or oils will lead to accidents. 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 visible grease or oil films and particulate matter such as filings, rest or mill scale.

Ultraviolet light inspection: It is used in addition to direct visual inspection to detect common oils or greases. Inspection in darkness subdued light using ultraviolet light of 3200-3800mm wavelengths. This method is also adopted because most hydrocarbon oils and greases show florescence under violet light even though they may be invisible under bright light.

CONCLUSION: 1) CLEANING OF VOLUTE CASING.

2) MAINTAINANCE OF IMPELLERS. 3) AN AIR COMPRESSOR IS A MUST FOR ANY SERIOUS OFF-ROADER.

4) CLEANING OF VOLUTE CASING. 5) INSPECTION OF VOLUTE CASING.