STUDY OF HYDRAULIC SYSTEMSIN BLAST FURNACE

A report submitted for fulfillment of the MINI PROJECT

By

ASISH KUMAR (10131A0303)

R.RAJENDRA PRASAD (10131A0340)

M.V.S.SRIKAR (10131A0328)

Under the esteemed guidance of

T.V.SESHAGIRI RAO

AGM, BLAST FURNACE

VIZAG STEEL PLANT

Department of Mechanical engineering

GAYATRI VIDYA PARISHAD COLLEGE OF ENGINEERING (AUTONOMOUS)

(Affiliated to JNTU Kakinada, Approved by AICTE)

VISAKHAPATNAM

CERTIFICATE

This is to certify that the mini-project report entitled STUDY OF

HYDRAULIC SYSTEMS IN BLAST FURNACE that is being submitted

by ASISH KUMAR (10131A0303), R.RAJENDRA PRASAD (10131A0340),

M.V.S.SRIKAR (10131A0328) in partial fulfillment for the award of the

Degree of Bachelor of Technology in MECHANICAL ENGINEERING to

GAYATRI VIDYA PARISHAD COLLEGE OF

ENGINEERING(A) is a record of bonafied work carried out by him

under our guidance and supervision.

Signature of Project Guide

T.V.SESHAGIRI RAO

Asst. General Manager

BLAST FURNACE DEPARTMENT

Visakhapatnam Steel plant

2

Acknowledgement

We sincerely thank our guide T.V.SESHAGIRI RAO

Asst. General Manager, BLAST FURNACE Dept. for his

encouragement and guidance in completing the project work.

We should thank our H.O.D. Sri. B.Govindarao, MECH

Dept. For his co-operation and support for successfully

completion for the project.

We would like to express our immense gratitude to Sri.

JEETENDRA KUMAR (Sr. Manager), Sri K.VENKATA

RAMANA (Deputy Manager), Mr. HARI PRASAD (Asst.

Manager) and all executives of BF Dept. who provided the aid

facilities through the course of my project work.

We also extend our thanks to all those who directly &

indirectly helped us in completing the project work

successfully.

Students of GVPCE(A)

ASISH KUMAR (10131A0303)

R.RAJENDRA PRASAD (10131A0340)

M.V.S.SRIKAR (10131A0328)

3

ABSTRACT

Visakhapatnam Steel plant (VSP) is the first shore based integrated steel plant in India producing high quality value added steel of 3.4 million tons per annum. Blast Furnace is one of the major departments of VSP where the conversion of raw materials like iron ore, Sinter and coke into molten metal (pig iron) takes place. To charge raw material into Blast Furnaces, which are operated at 2kg/cm2 pressure, Bell-less top (BLT) charging system supplied by M/s PAULWORTH, LUXUMBURGE is provided.

In this project various hydraulic systems used in top charging of blast furnace are studied and noted. Based on this failure of Sealing valve is taken for further study which is causing highest production loss to the company.

Major causes contributing to the failure of Sealing Valve are analyzed and different procedures for changing valve components are examined.

4

CONTENTS

1. INTRODUCTION - 7

2. BLAST FURNACE -16

3. HYDRAULIC SYSTEM - 20

4. FAILURE ANLYSIS OF SEALING VALVE - 29

5. REPAIR PROCEDURES FOR SEAL VALVE FLAP AND SEAT - 31

6. CONCLUSION - 36

7. BIBLOGRAPHY - 36

5

6

CHAPTER-1

INTRODUCTION

VISAKHAPATNAM STEEL PLANT

Visakhapatnam Steel Plant, the first coastal based Steel plant of India is located, 16km

southwest of city of destiny, i.e. Visakhapatnam. Bestowed with modern technologies, Visakhapatnam

Steel Plant has an installed capacity of

• 3 Million Tons per annum of liquid steel, and,

• 2.656 Million Tons of saleable steel.

Visakhapatnam Steel Plant products meet exalting International Quality Standards such as

JIS, DIN, BIS, BS etc.

Visakhapatnam Steel Plant has the distinction to be the first integrated Steel Plant in India to

become a fully ISO-9002 certified company. The certificate covers quality systems of all Operational,

Maintenance, Service units besides Purchase systems, Training and Marketing functions spreading over

4 Regional Marketing Offices, 20 Branch offices and 22 stock yards located all over the country.

Visakhapatnam Steel Plant by successfully installing and operating efficiently Rs.460 corers

worth of Pollution Control and Environment Control equipments and converting the barren landscape

by planting more than 3 million plants has made the Steel Plant, Steel Township and surrounding areas

into a heaven of lush greenery- This has made Steel Township a greener, cleaner and cooler place,

which can boast of 3 to 4 degrees centigrade lesser temperature even in peak summer compared to

Visakhapatnam city.

Visakhapatnam Steel Plant exports quality pig iron and steel products too Sri Lanka,

Myanmar, Middle East, USA and Southeast Asia (pig iron). RINL-VSP was awarded “Star Trading

House” status during 1997-2000.

7

Having a total manpower of about 17250 Visakhapatnam Steel Plant has envisaged a labour

productivity of not less than 230 tones per annum year of Liquid Steel which is the best in the country

and comparable with the international levels.

The major production departments of Visakhapatnam steel plant are the Raw materials handling

system, Coke ovens, Sinter plant, Blast furnace, and Steel melting shop and Rolling mills.

RAW MATERIAL LINKAGES :

The steel plant is getting its supply of iron ore- lumps and fines from the Bailadilla deposits in

Madhya Pradesh (MP) blast furnace grade lime stone from Jaggayyapeta in Andhra Pradesh, SMS

grade lime stone from Badnapur in MP, blast furnace grade lime stone from the Kotni-sonor deposits in

MP. 20% of cocking coal requirements will be met by imports through the Visakhapatnam harbor

while the balance will come from the Bengal-Bihar. Coal for power generation will come from Talcher

in Orissa.

POWER SUPPLY :

A peak construction power requirement was about 12MVA. This was arranged from the

Gajuwaka substation of APSEB at 33KV.

The plant have captive power generation unit consists of 3 nos. turbo generators, each having

60 MW capacity. An additional requirement of operational power around 150 MVA is being met from

the APSEB grid.

Operational power supply is initially at 220 KV, which are subsequently stepped down to 400 KV

WATER SUPPLY :

Requirements f water during the peak of construction was of the order of 4.5, Mgd. This was

met from the Meghadrigedda, and Raiwada schemes of Andhra Pradesh state government.

Operational water requirements of 70 Mgd. Of the steel plant are being met from the Yeleru

water supply scheme provided by the AP government. This involved construction of a storage reservoir

8

at Yeleswaram and a 153 KM long linked canal to the plant site apart from Kanithi Balancing

Reservoir (KBR).

REPAIR AND MAINTENANCE SHOPS :

The repair and maintenance shops are required to manufacture spares and replaceable items and

will cater to the capital and running maintenance of the various units of the steel plant. The activities of

the repair and maintenance shops are extremely wide and varied in nature. The experience of the Indian

steel plants has been kept in view in planning the repair and maintenance facilities.

Raw Material Handling Plant(RMHP):

VSP annually requires quality raw materials viz. iron ore, fluxes (limestone, dolomite) coking

and non-coking coals, etc. to the tune of 12-13 million tons for producing 3 million tons of liquid steel.

To handle such a large volume of incoming raw materials received from different sources and to ensure

timely supply of consistent quality of feed materials to different VSP consumers, Raw material

Handling Plant serves a vital function. This unit is provided with elaborate unloading, blending,

stacking and reclaiming facilities viz. Wagon Tipplers, Ground and Tank Hoppers, Stock yards

Crushing Plants, Vibrating Screens, Single/ twin boom stackers, Wheels on boom and Blender

Reclaimers.

In VSP Peripheral unloading has been adopted for the first time in the country.

Fig RMHP

9

Coke ovens and Coal Chemical Division:

Blast Furnaces, the mother units of any steel plant requires huge quantities of strong, hard and

porous solid fuel in the form of hard metallurgical coke for supplying necessary heat for carrying out

the reduction and refining reactions besides acting as a reducing agent.

Coke is manufactured by heating of crushed coking coal ( below 3mm) in the absence of air at

temperature of 10000 c and above for about 16 to 18 hours . A coke oven comprises of two hollow

chambers namely coal chamber and heating chamber. In the heating chamber a gaseous fuel such as

blast furnace gas, coke oven gas, etc is burnt. The heat so generated is conducted through the common

wall to heat and carbonize the coking coal placed in the adjacent coal chamber.

Number of ovens built in series one after the other form a coke oven battery.At VSP there are

three coke oven batteries, 7 meters tall and having 67 ovens each. Each oven is having a volume of

10

41.6 cu. meters and can hold up to 31.6 tons of dry coal charge. The carbonization takes place at 1000 0

c to 10500 c in the absence of air for 16 to 18 hours.

Red hot coke is pushed out of the ovens and sent to coke dry cooling plants for cooling to avoid

its combustion. There are three coke dry cooling plants (CDCP), each having four cooling chambers.

The capacity of each cooling chambers is 50 to 52 TPH. Nitrogen gas is used as cooling medium. The

heat recovery from nitrogen is done by generating steam and expanding in two back pressure turbines

to produce 7.5 MW power each.

The coal chemicals such as benzyl (and its products), tar (and its products) and ammonium

sulphate, etc. are extracted in coal chemical plant from CO gas. After recovering the coal chemicals,

the gas is used as by – product fuel by mixing it with gases such as BF gas, LD gas, etc. A mechanical,

biological and chemical treatment plant takes care of the effluents.

SINTER PLANT:

Sinter is a hard and porous ferrous material obtained by agglomeration of iron ore fines, coke

breeze, limestone fines; metallurgical wastes viz. flue dust, mill scale, LD slug, etc.

Sinter is a better feed material to blast furnace in comparison to iron ore lumps and its usage in

blast furnace help in increasing productivity decreasing the coke rate & improving the quality &

improving the quality of hot metal produced.

Sintering is done in 2 nos. of 312 Sq. meter, sinter machines of Dwight Lloyd type by heating

the prepared feed on a continuous metallic belt made of pallets at 1200 c- 1300 c.

Hot sinter discharged from sintering machine is crushed to sizes between 5mm and 50mmsize

and cooled before dispatching to blast furnaces.

The dust laden air from the machines are cleaned in scrubbers and electrostatic precipitators to reduce

the dust content to 100 mg/m3 level before allowing to escape into the atmosphere and thus helping in

maintaining a clean and dust free environment.

11

BLAST FURNACES:

Hot metal is produced in blast furnaces, which are tall vertical furnaces. The furnace is named

as Blast Furnace as it is run with blast at high pressure and temperature. Raw materials such as sinter,

iron ore lumps, fluxes (limestone, dolomite) and coke arecharged from the top and hot blast at 1100 0 c

to 13000 c and 5.75 KSCH pressure is blown almost from the bottom. The furnaces are designed for

80% sinter in the burden.

VSP has two 3200cu.meters blast furnaces (largest in India) equipped with Paul worth Bell less

top equipment with conveyor charging. Rightly named as Godavari and Krishna after the two rivers of

A.P., the furnaces will help in bringing prosperity to the state of Andhra Pradesh.

Provision exists for granulation of 100% liquid slag at blast furnace cast house and utilization of

blast furnace gas-top pressure (1.5 to 2 atmospheric pressure) to generate 12 MW of power in each

furnace by employing gas expansion turbines.

The two furnaces with their novel circular cast house and four tap holes each are capable of

producing 9720 tons of hot metal daily or3.4 MT of hot metal annually.

12

STEEL MELTING SHOP (SMS):

Steel is an alloy of iron with carbon up to 1.8%. Hot metal produced in blast furnace contains

impurities such as Carbon (3.4 to 4.25%), Silicon (0.4 to 0.5%) Manganese (0.3 to0.4%), Sulphur

(0.04% maximum) and Phosphorous (0.04% maximum) is not suitable as a common Engineering

Material. To improve the quality, the impurities are to be eliminated or decrease by oxidation process.

VSP produces steel employing three numbers of top blown oxygen converters called LD

Converters (L and D stands for Linz and Donawitz- two towns in Austria where this process was first

adopted) or Basic Oxygen Furnaces/Converters. Each converter is having 133cu.mts volume capable of

producing 3MT of liquid steel annually. Besides hot metal, steel scrap, fluxes such as calcinated lime

or dolomite from part of the charge to Converters.

99.5% pure Oxygen at 15-16 KSCG pressure is blown in the Converter through oxygen lance

having convergent divergent copper nozzles at the blowing end. Oxygen oxidizes the impurities present

in the hot metal, which are fluxed as slag with basic fluxes such as lime. During the process heat is

generated by exothermic reactions of oxidation of metalloids viz. Si, Mn, P and Carbon and

temperature rises to 17000 c enabling refining & slag formation.

13

Different grades of steel of superior quality can be made by this process by controlling the

Oxygen blow or addition of various ferroalloys or special additives such as FeSi, FeMn, Si-Mn, Coke

breeze, Aluminum etc. in required quantities while liquid steel is being tapped from the converter into a

steel ladle. Converter / LD gas produced as by product is used as a secondary fuel.

CONTINUOUS CASTING DEPARTMENT: Continuous casting may be defined as teaming of

liquid steel in a mould with a false bottom through which partially solidified ingot/bar (Similar to the

14

shape & cross section of the mould) is continuously withdrawn at the same rate which liquid steel is

teamed in the mould.

Facilities at a continuous casting machine include a lift and turn for ladles, copper mould,

mould oscillating system tundish, primary and secondary cooling arrangement to cool the steel bloom,

gas cutting machines for cutting the blooms in required lengths (Avg. 6 meters long).

At VSP we have six-4 strand continuous casting machines capable of producing 2.82 MT/Year

Blooms of size 250X250 mm and 250X320 mm. Entire quantity of molten steel produced (100%) is

continuously cast in radial bloom casters which help in energy conservation as well as production of

superior quality products.

Fig Continuous Casting Machine

ROLLING MILLS:

Blooms produced in SMS-CCD do not find many applications as such and are required to be

shaped into products such as billets, rounds, squares, angles (equal and unequal), channels, IPE beams,

HE beams, wire rods and reinforcement bars by rolling them in 3 high capacity, high speed fully

automatic rolling mills namely Lightand Medium Merchant Mills (LMMM), Wire rod mill (WRM)

LMMM PRODUCTS WRM PRODUCT

CHAPTER-2:

15

BLAST FURNACE DEPARTMENT

2.1INTRODUCTION TO BLAST FURNACE

Blast furnace department is one of the major departments in Visakhapatnam steel plant. It is having two

India's biggest blast furnace named Godavari and Krishna having useful volume of 3200 m3 per furnace

and production capacity of 11315 tons / day. Raw material like iron ore, sinter, coke and additives like

limestone and dolomite are charged from top of the furnace and hot blast at around 1000°C. is sent into

furnace through 32 numbers of tuyeres from the bottom of the furnace.

The line diagram of blast furnace is shown in figure 2.1 Blast furnace is cylindrical, tapered,

counter vessel where several reactions take place at different zones. The process of reduction will tap

hot metal as the main product and slag as by product from four tap holes, which are provided at the

bottom side of the furnace.

Blast furnace is designed to operate at 2 kg/sqcm working pressure at furnace top to get the

rated production. To charge the material in the furnace 2 kg/sqcm pressure is to be maintained in the

bin. A separate bell less top charging system is provided. The system is provided exactly on the top of

the furnace and the main purpose of it is to distribute the required quantity of material uniformly into

furnace as and when the furnace required. As the volume of blast furnace is very high - its raw material

requirement is also very high hence the charging equipment should operate continuously without any

break. In addition to this blast furnace department is having a slag granulation unit and 4 pig casting

machines also. Fig 2.1.1 shows schematic diagram of Blast furnace.

16

17

2.2 SECTIONS IN BLAST FURNACE

1. BURDEN HANDLING SECTION (BHS):

In this section, the raw materials like iron ore, sinter, coke, limestone, manganese ore, quartz are

made to prepare as a stock and is transferred to top charge of the blast furnace by means of conveyors

in the form of batches. The raw materials are stored in bunkers. The raw materials from different

conveyors reach the top charge of the blast furnace. An amount of 20T coke and 6T sinter is used for

every batch of production in blast furnace. All these raw materials are made in stock by a series of

bunkers as shown in figure.

2. FURNACE:

Two furnaces named Godavari and Krishna of 3200 cubic meters of volume, each

capable of producing 1.7MT of hot metal per year

Position : 33,100mm

Height of Hearth : 4600mm

Height of Bosh : 3400mm

Height of Belly : 1900mm

Height of shaft : 20,000mm

Dia. of Hearth : 12000mm

Dia .of Belly : 13300mm

18

Dia. of Top : 8900mm

No of Tuyeres : 32

No of Tap Holes : 4

4.CAST HOUSE – SLAG GRANULATION PLANT (SGP):

In blast furnace, liquid iron and slag are the products formed due to heating of raw materials.The

liquid iron is transferred to SMS while slag is transferred to slag granulation plant (SGP) where the slag

is granulated and transferred to slag yard. This slag is used mainly in preparation of cement..

2.3 BELL LESS TOP CHARGING SYSTEM

It has mainly two bins having useful volume of 47m3. Each bin is having two sealing valves to

avoid from BF gas leakage, one at the top of the bin and other at the bottom. Each bin is having one

material gate at the lower portion to hold the burden and is located above the lower sealing valve.

There is a receiving hopper to receive the material from the main charging conveyors and to guide to

either of the bins. Receiving hopper is having one material gate at the bottom of the hopper. The

function of the material gate is not to allow any material to fall when the hopper is in transition from

one bin to the other bin. At the bottom of the bins and just above the furnace there is a distributiosn

chute gearbox. The main function of the gearbox is to hold, rotate and tilt the main distribution chute.

The length of the chute is 4m. The main purpose of the chute is to receive the material from the bins-

and to distribute uniformly in the furnace. The chute is having two motions one is rotation and the other

is tilting.

The chute rotates at an angle of 3600 and tilts up to 540 from the vertical axis. The provision of chute

rotating and tilting facilitates to charge the material into the furnace in concentric circles. It is N 2

cooled gearbox having a lubrication interval of 8 minutes.

19

Raw material charging will be charged into the furnace, in batches. In which iron ore material is

one batch and coke as another batch. Either of the batches is first taken into one bin through receiving

hopper from the main charging conveyor. Then the bin will be pressurized up to 2 Kg/sqcm pressure by

using semi cleaned B.F. gas and nitrogen.Due to hot blast, the pressure will be maintained on the bin.

This

obstructs the

flow of raw

materials in to

the furnace. In

order to

avoid this, N2

gas and BF gas

is circulated in

the bin such that

it can with stand the hot blast pressure. Thus the pressure is equalized. After pressure equalization,

lower sealing valve is opened fully and lower material gate is opened partially to regulate the flow. Due

to gravity the material falls into the chute and gets distribute into the furnace.

Chapter-3

HYDRAULIC SYSTEMS

3.1 HYDRAULIC COMPONENTS IN BELL-LESS TOP CHARGING SYSTEM:

Hydraulic Oil Tanks:

There are two hydraulic tanks of volume 1000l, each in Bell less top hydraulic system. They are

located at 44mts elevation of the blast furnace complex. Either of the tanks is kept in working and the

other is standby. These tanks act as a reservoir of hydraulic oil, receives oil from the system and supply

oil to the pump whenever it is required. These tanks are located above the main pumping unit So as to

20

maintain positive head in the suction line. If we see the cross section of the hydraulic tank, it is divided

into three chambers.

1. Receiving chamber : Hydraulic oil from valve stands comes to the receiving chamber through return

filters, and it settles there and flows to the suction chamber.

2. Suction chamber : This chamber acts as a supply reservoir to the pumping units.

3. Cooling chamber : This chamber is connected to cooling circulation pump. This pump circulates

cooling oil through heat exchanger by which the oil gets cooled in the process.

Pumps:

There are two main pumps in the bell less top charging system. Each pump is connected to one

tank. Pumps are axial piston pumps with fixed displacement and bent axis pumps. One pilot operated

relief valve with directional valve unloading is provided in the delivery side of the pump. Pump always

generates flow but whenever systems do not require flow, the above unloading valve simply unloads

the oil back into the tank and whenever system requires oil it loads oil to the system. This way

operation of the pump and frequent starting and stopping is avoided.In addition to the above main

pump, there will be another circulation pumping unit. The function of the circulation-pumping unit is to

keep the temperature of hydraulic oil under control.

Valve Stands:

Bell less top hydraulic system is having two control valve stands.

1. Control Valve Stand-I 2. Control Valve Stand - II.

Control Valve stand-I consists of valves connecting to

a. Receiving hopper d. LMG (lower material gate)

b. UMG (upper material gate) e. LSV (lower sealing valve)

c. USV (upper sealing valve) f. Main goggle valve clamping

Control Valve - 2 consists of valves connecting to primary equalizing valves (PEV), secondary

equalizing valve (SEV), purging valves, and pressure relief valves.

21

Valve stands consists of direction control valves, flow control valves, and shutoff valves and

check valves. Mainly two types of direction valves are fitted in control valve stand 1.3/4 valves for

material gates and main google movement and 2/3 way valves for all sealing valves. Flow control will

be done according to the speed requirement of the valve. Whenever a particular valve is to be isolated

from the system corresponding shutoff valves will be close.

Hydraulic Cylinders:

The entire bell less top charging equipment except the chute is connected with hydraulic

cylinders. All these cylinders are turn-on rounded and are having spherical bearings at rod eye. Speed

of these cylinders regularly checked and accordingly flow control will be done. Since these cylinders

are located at the site, they are subjected to dust. To prevent the dust entrapment into the cylinder a

wiper seal is provided to the piston end.

Accumulator:

Bell less top hydraulic system is having two piston accumulators of volume 251ts each and one

bladder accumulator. Each piston accumulator is connected with 4 number of N2 bottles of each 251ts

of volume. A free moving piston separates the nitrogen gas and hydraulic oil in piston accumulator.

Piston accumulator is being operated between the pressures rating from 165 bars to 185 bars. Filling

pressure of N2 bottles is 160 bars.

Hydraulicoil:

Hydraulic oil used in bell less top hydraulic system is servo system HLP 46 supplied by M/s

IOCL. Once in three months oil will be sent for testing and based on the suggestion the oil replacement

will be done. As the clearances of all the hydraulic parts are in microns, effect of contamination is very

high on the equipment. Hence, oil should be maintained always clean.

Upper Sealing Valve:

22

Upper sealing valve is a flap with gas tight seal. The purpose of this valve is to maintain

2-kg/sqcm pressure in the bin. Upper sealing valve is operated by hydraulic system. Cylinder (actuator)

mounting for this is turn-on type to reduce the thrust on the system. The hydraulic force pushes the

piston, so that it operates a crank, which rotates half circle and closes or opens the flap in the bin

through a long curved shaft.

Lower Material Gate:

Operation : Hydraulic force pushes the piston and itself operates the gate. After upper sealing valve has

been opened, the lower sealing valve and the lower material gate will be closed. Then the receiving

hopper comes to the position and fills the bin with material. Then closing of upper sealing valve and

getting required pressure is done. Then after opening of lower sealing valve, the material is allowed to

fall and the bin pressure is relieved. Then the opening of upper sealing valve takes place after the

material gate is closed.

Receiving Hopper:

The purpose of receiving hopper is to take the material coming from the BHS (Burden Handling

Section) through conveyors and directs the material into the bin.The hopper is free to move in linear

direction to cover the two bins one after other in sequential manner. The load on the hopper is constant

and somewhat less compared to other components in the system. Upper material gate' is fixed to the

receiving hopper. Receiving hopper is also operated by '4-way 2 position' DC valve.

Distribution Gear Box:

Distribution gearbox is the major part in distributing in the form of concentric circles in blast

furnace using the "CHUTE", which is in a sectioned cylinder form. Distribution gear box is an

epicyclical gearbox with two motions.

a) Rotating movement. b) Tilting movement

This gearbox is cooled by nitrogen. Distribution gearbox is operated by electrical motor, and the

gearbox is to be lubricated with grease for every 8min. that is located at top of blast furnace.

Pressure Relief Valve:

23

Pressure relief valve is used to relieve pressure in the bin. Pressure relief valve has piston with

double piston rods. 4/2 valves operate it. For relief valves hydraulic force is used only for operating

purpose, closing of valve is automatically done by spring force.

3.2 BASIC CIRCUIT FOR WORKING OF HYDRAULIC CYLINDER IN BELL LESS

TOP CHARGING SYSTEM

The pump (driven by motor) sucks fluid from the tank and discharges into the line through

different valves to the cylinder. So long as, there is no resistance to the flow, thefluid will be pushed

further and thus increases the pressure till the cylinder moves. But the maximum pressure must be

limited in order to prevent any damages to the system due too high load. For this, a pressure relief

valve is used in which a spring as a mechanical force presses the ball on the seat. The ball opens when

the force exceeds spring force. Thus, the fill flow delivery by the pump flows to the tank. Fig 2.1.3

shows Hydraulic circuit.

3.3 MAIN COMPONENTS IN THE HYDRAULIC CIRCUIT

Hydraulic Cylinder:

The cylinder comprises mainly cylinder cap, cylinder tube, cylinder head, tie rod, piston with

piston rod, guide bush and the mounting device (in this case mounting flange.)

LOA

D

cylinder

Oil reservoir

pump

Pressure relief valve

Direction control valve

Piston rod

piston

Hydraulic circuit

24

Cylinder cap, cylinder tube, and the cylinder head are assembled and then held together by 4 tie rods.

Piston seal is fitted between the piston side and the rod side. A "stick - slip" free wheeling motion

(smooth) is achieved at the lowest speeds and low pressure, by the selected seal types and the surface

quality of the cylinder tube, piston rod guide. Figure shows Hydraulic Cylinder.

Fig Hydraulic Cylinder

COMPONENTS:

1. Cylinder cap 2. Cylinder tube

3. Cylinder head 4. The rod piston

5. Piston rod 6. Guide bush

7. Mounting flange

Direction Control Valve:

The control valve used in the hydraulic circuit is the Direction spool valve. The purpose of

this valve is to direct the flow of fluid and to change the direction of flow. A 4/3 -way spool valve is

mainly used to direct the flow of fluid.

cylinder

pistonPiston rod

Gland seal Piston seal

Oil inlet/out let Oil inlet/out let

cap

25

Working of a 4/3-Way Direction Spool Valve:

Annular ports are cast around a longitudinal bore in a housing I. The annular ports interrupt the

longitudinal bore. If the control spool is moved it connects or divides the annular ports in the housing.

Each annular port is connected to an outlet terminator in the housing. Separation and combination of

the ports is synchronous. The operating sequence can be determined exactly.

The different control functions result relatively simply due to the spool shape. The housing

does not generally change. All the ports P,T,A and B are separate at outlet

position, i.e., without external operation. If the spool is pushed to the right, for example connections P

to B and A to T occurs sealing for individual annual ports is achieved via the tolerance between the

spool and the housing. Figure Show Direction Control Valve and circuit diagram.

T A P B

26

1.Housing 3.Control lands

2. Annular port 4.Control spool

A, B, P, T are different switching positions.

Fig Direction Control Valve

Advantages of Direction Spool Valves:

1. They are relatively simple in design.

2. Very good pressure balance is obtained and thus low operating pressures are

required.

3. These valves have comparatively low losses.

Flow Control Valve:

The flow control valve used in the hydraulic circuit is a double throttle / check valve.

Working:

Double throttle check valves comprise two throttle check valves arranged symmetrically in one

block. They are fitted between the direct operated directional valve and the sub plate to influence the

speed of the user (main flow limiter). With flow from the bottom to the top, pressure acts via bore I on

the mounting face of the check valve, designed as a throttle pin.The throttle pin is pushed back and no

throttling takes place. With flow from top to bottom the pressure acts via bore 2 on the rear side of the

throttle pin. It is pushed against the stop 3 and occupies a throttle position according to the position of

adjustment screw. Fig shows flow control valve.

27

1. Pressure acts via bore. 3. Spring pushed against the top .

2. Pressure acts via bore 4.Adjustment screw.

Fig Flow Control Valve

Pressure Relief Valve:

The pressure relief valve used in the hydraulic circuit is the direct operated pressure relief valve. It

serves to influence pressure in a unit or in part of a unit.

Working of a Direct Operated Pressure Relief Valve:

The housing or the control contains the sleeve 2, spring 3, advance mechanism 4, poppet with

cushioning the housing or the control contains the sleeve 2, spring 3, and advance mechanism 4, poppet

with cushioning spool 5 and as a separate part the hardened seat. The spring pushes the poppet in its

seat. The spring force can be steplessly adjusted by means of a rotary knob. The pressure is also set

accordingly. Port P is connected with the system. Pressure in the system acts on the poppet surface. If

the pressure lifts the poppet from its seat, the connection to the T port is opened. A pin limits the

poppet stroke.

Since the spring force also increases according to the spring constant as stroke increases,

the underside of the spring retainer is a special shape. The impulse forces of the oil flow are

used in such a way that the increase in spring force is almost balanced out. Fig shows

pressure relief valve.

1. Control block

2. Sleeve

3. Spring

4. Advanced mechanism

5. Cushion spool

6. Hardened seat

28

Fig. Pressure Relief Valve

CHAPTER-4

FAILURE ANALYSIS OF THE SEALING VALVE OF BELL LESS

TOP CHARGING SYSTEM

4.1 Selection of problem:

To select a problem for this project data regarding various failures in Bell less top charging system is

collected from past records. Table 3.1.1 shows the data of major problems identified for the past three

years:

Table. Failure analysis of BLT charging system

29

From this data table it is clear that the failure of Sealing Valve is resulting in maximum loss

5577 tones of hot metal production. Fig 3.1.2 shows bar graph of Failure analysis of BLT

charging system.

30

S.n

o

Problems Off

blast

Low blast

Wind

restriction

Loss of hot

metal(tons)

1. Sealing valve failure Nil Nil 71.5 5577

2. Hydraulic problems 8.15 5.30 6.10 3106

3. Bleeder valve 10.20 Nil Nil 2553

4. Sealing valve seat leakage 6.25 Nil Nil 1584

5. Hatch cover leakage 3.25 1.25 0.25 1014

6. Main charging conveyor Nil 1.35 3.45 453

7. Mobile hopper wheel

failure

4.45 Nil Nil 1128

8. Up takes leakage Nil 3.20 Nil 437

Sealing valve problem Hydraulic problems

Bleeder valve failure Sealing valve seat leakage

Mobile hopper wheel failure Hatch cover leakage

Main charging conveyor failure Up takes leakage

4.2 PROBLEM DEFINITION AND ANALYSIS:

Sealing valve description: Sealing valve plays an important role in Bell Less Top Charging System.

These valves are meant for sealing the bin from Blast Furnace gas leakage which is driven by

Hydraulic cylinder. They consist of flap and a seat with silicon rubber seal. Flap closes against the seat

during closing, once the valve is closed, it will not allow any leakage through the valve. These valves

are located one at top of the bin and other at the bottom. These are very critical valves. Fig 3.1.3 shows

process flow diagram of sealing valve.

CHAPTER-5

REPAIR PROCEDURES FOR SEAL VALVE FLAP AND SEAT

5.1 PREPARATIONS PRIOR TO THE REPAIR WORK:

1. If access to seal valve is required, then fill material hopper with coke or install a

temporary platform inside. The platform may only be installed after the hopper is

degassed.

2. Disable and lock the burdening installation.

3. Move the rocker in a horizontal position and secure mechanically, open the cylinder

bypass valve.

31

4. Lock lower seal valve and material gate of serviced hopper in closed position. Use

safety pins.

5. Lock upper seal valve to be serviced in required position .Use safety pins.

6. Lock equalizing valves in closed position as required. Use safety pins.

7. Lock goggle valve in the equalizing lines in closed position.

8. Lock relief valve in the open position. Use safety pin.

9. Lock goggle valve in closed position.

10. Disable and lock the hydraulic, steam and electric circuits of the above mentioned

components.

11. Degas the material hopper.

12. Switch off and disable radar/microwave probe of hopper (if installed).

13. Post warning notes

5.2 EXCHANGING FLAP SEAL RING:

5.2.3 Exchanging procedure: Make sure that all the safety precautions described in section 1

and the preliminaries of this section are respected.

1. Perform steps per chapter 5.1 and lock upper seal valve in open position (see PIC 5.2.1)

2. Open material hopper access door and degasify properly.

3. Access to the seal valve flap via the burden material or install a platform inside the hopper.

4. Remove fixing bolts of seal hold-down ring (see PIC 5.2.2).

5. Remove 3 M16 plugs of seal flap and release seal hold down ring by means of three M16

screws see PIC 4.5.3.2 & 4.5.3.3). Reinstall plugs with grease.

6. Remove hold-down ring from seal flap (see PIC 5.2.3).

7. Replace seal ring (see PIC 5.2.3).

WARNING! - GAS HAZARD! Prior to entering any BLT components, check environment for blast furnace gas, using gas detectors. If necessary, use gas masks for the following repair work.

32

LOCK

SAFETY PIN

PROTECTION HOOD

FIXING BOLT OF SEAL HOLD DOWN RING

8. Reinstall hold-down ring (install new bolts and nuts, if necessary).

9. Put equipment in operation.

PIC 5.2.1 LOCKING UPPER SEAL VALVE DRIVE

PIC. 5.2.2: SCREWS SEAL VALVE FLAP

33

SEAL HOLD DOWN RING

FIXING BOLT OF SEAL

SEAL RING

RELEASING SCREWS

LOCK

PROTECTION HOOD

SAFETY PIN

PIC 5.2.3. REEASING SEAL RING

5.3.3 Exchanging procedure:

Make sure that all the safety precautions described in section 1 and the preliminaries of this

section are respected.

1. Perform steps per Chapter 5.1 and lock upper seal valve in open position (see

PIC. 5.3.1).

2. Open material hopper access door and degasify properly.

PIC. 5.3.1: LOCKING UPPER SEAL VALVE DRIVE

WARNING! - GAS HAZARD! Prior to entering any BLT components, check environment for blast furnace gas, using gas detectors. If necessary, use gas masks for the following repair work

34

SEAL HOLD DOWN RING

SEAL RING

FLAP AXLE

PROTECTION COVER

LOOSE BEARING PART

DISC SPRINGS

COUNTER & FASTENING NUTS

PRESSURE WASHER

RECTANG-ULA R OPENING

ACCESS DOOR

CONICAL PROTECTION COVER

PIC. 5.3.2: SECURING SEAL VALVE FLAP

PIC. 5.3.3: CONICAL PROTECTION COVER OF SEAL VALVE FLAP

PIC. 5.3.4: PRESSURE WASHER OF SEAL PIC. 5.3.5: SPRINGS & LOOSE VALVE FLAP SPHERICAL BEARING PART

PIC. 5.3.6: FLAT PROTECTION COVER PIC. 5.3.7: FLAP AXLE

35

BEARING HALF FLAP

3. Access to the seal valve flap via the burden material or install a platform inside the

hopper. 4. Introduce two chain hoists through the rectangular opening on top of the upper

seal valve casing and hook to upper eyelets of seal valve flap. Hook two further chain

hoists between lower eyelets of seal valve flap and the chains of the upper chain hoists (see

PIC 5.3.2). Tighten up the chain hoists.

5. Remove conical protection cover from inner side of seal flap (see PIC 5.3.3).

6. Loosen and remove the safety counter nut, fastening nut, pressure washer and springs

with loose spherical bearing part (see PIC 5.3.4 & PIC 5.3.5).

7. Remove the flat protection cover with sealing on the lever arm and dismantle the flap

axle (see PIC 5.3.6 & PIC 5.3.7).

8. Introduce one additional chain hoist through material hopper access door and hook to

seal valve flap (see PIC 5.3.2).

9. Remove seal flap through the material hopper access door while releasing

simultaneously the chain hoists through the rectangular opening on top of upper seal valve

casing and tightening up the chain hoist through the material hopper access door.

10. Check spherical bearings, springs, fixing elements and seat axle if these can be reused.

11. Install bearings to lever arm and new seal flap (see PIC5.3.8 & PIC5.3.9).

Remark: The spherical bearing must be free of grease prior mounting.

CONCLUSIONS:

1. Bell-Less top charging system of blast furnace is intended for distribution of

charging ingredients into the furnace as per preset requirements.

2. Most of the components of the system are hydraulically operated and any failure of

these leads to the stoppage of blast furnace.

36

3. From the problems that exist in Bell-Less top charging system “Sealing Valve crank

and gland of Hydraulic Cylinder” failure is of serious concern as it involves major

loss in production.

4. Hydraulically operated systems are more efficient and are extremely suitable in case

of noise reduction.

5. They are self lubricating and hence require less maintenance cost when compared to

other mechanical drives.

6. As the furnace is in continuous operation for every 6 months seal valve flap is

inspected and replaced where as seal valve seat is replaced once in a year.

7. For replacement 12 hours of shutdown is required and valve components should be

centered properly and made air tight for preventing leakage during equalizing

process.

BIBLOGRAPHY:

1. The Hydraulic trainer – Instruction and information on oil Hydraulics by A Schmit

2. Fluid mechanics by R.K. RAJPUT.

3. Hydraulics and hydraulic machines by P.N. Modi and S.M.Seth.

37