IMPROVED HOPPER WEIGHING AND CONTROL SYSTEM FOR LD
CONVERTORS IN STEEL PLANTS.
FIELD OF INVENTION
The present invention relates to a hopper weighing and control system for LD
converters in steel plants. More particularly the present invention deals with a
simplified low cost hopper weighing instrument including its control system for the
LD converters used in the steel plants.
BACKGROUND ART
The blast furnace process is essentially a continuous batch process. The batches
of material are repeatedly charged into the furnace on a periodic basis as hot
metal, slag and hot gases are produced. Batches of hot metal and slag are
tapped from the furnace from time to time while hot gas outflow occurs
continuously.
Maximum furnace productivity and operating efficiency can be achieved if
predetermined hot metal, slag and hot gas endpoint conditions are met. In
particular, the endpoint chemistry of the hot metal should meet specifications
required for input of the metal to a steelmaking furnace such as a basic oxygen
furnace, and the endpoint chemistry of the slag should meet specifications
required for making the slag commercially usable as a separate product.
To meet productivity and efficiency objectives it is essential that the iron
making process be held in thermal and chemical imbalance.
In turn, process balance requires control over the quantity of materials charged
into the furnace. It is particularly important that a predetermined ratio of input

carbon to input iron be held reasonably accurately on a continuing basis. If
material inputs are imbalanced and particularly if the input carbon iron ratio is
imbalanced, the thermal and/or chemical balance of the process is disturbed.
As a consequence one or more of the endpoint conditions would deviate from
specifications causing loss in productivity or operating efficiency.
In the conventional blast furnace material handling system, scheduled amounts
of charge materials are weighed and transported to the furnace by a skip hoist or
conveyor belt system and the charging process thus generally provides for
thermal and chemical balance in the furnace operation. However, some degree
of imbalance often results in the furnace operation for various reasons. The flux
addition system of SMS-1 in the Rourkela Steel Plant, consists of 6 loaded
bunkers per LD converter having flux material like lime, dolomite, mn ore, coke
etc. The present developed system is used for mainly lime and dolomite in
converter IV and V. (Reference Fig 2 (a) & 3(a)). The bunker with flux material is
used during LD hot metal blow. The bunker gives the material to the specific
quantity of flux set from the hopper through vibrator designed to feed material as
per requirement. The flux material is added in batches as per metallurgical
requirements
In particular undesirable or unacceptable process imbalance can result from
varying moisture content in porous input materials, principally the carbon
containing materials such as coke and/or sinter. For example, varying
atmospheric humidity and other conditions can cause the weight percentage of
water in bin stored coke to vary typically over a range of 2% to 15%. The
prescribed weight of coke to be charged into the furnace can thus have a
corresponding range variation in total carbon weight Accordingly, although
accurate weighing of coke and iron containing materials can result in accurate
maintenance of a fixed coke to iron ratio, a variation in coke water content will
cause the input carbon/iron ratio to vary and thereby produce a corresponding

degree of furnace process imbalance. Similarly, for general background
purposes, it is also noted that problems like the carbon iron ratio problem in the
blast furnace process can and often do exist in other processes in which variable
water content materials are used.
Once the hot metal with scrap is charged in the LD converter, the blow starts with
O2 injection. The flux material like lime & dolomite is taken from hopper as per
pre-decided quantity. The hopper rests on 3 load cells of 2.2 ton capacity with
2.85 mV per volt sensitivity. The hopper capacity is 4000 Kg with tare weight of
1800 kg the material inside the hopper is weighed and discharged during blow in
batches as per requirement. The required material quantity is set in kgs with 10
kg resolution and when loading is started the material gets loaded in the hopper
till the set value is reached through the working of the vibrator placed in between
bunker & hopper. As per the process requirement time the material is released
with hopper get open and during empty condition of the hopper gate closes
automatically and the similar operations continue during the entire blow. The
following flow diagram can explain the system.
Set the Required Value - Start Hopper loading-Vibrator starts with gate closing
& minimum level indication - Material gets loaded up to the set value and stops
automatically - Hopper weight is displayed -When the hopper gate is opened
material gets released till minimum level is reached - Hopper gate closes
automatically with Hopper gate close indication - Ready for next cycle .
The original system was provided by Ms. Schenk Ltd with ( 3 nos of load cells
fitted with the hopper and the vibrator placed between the bunker and hopper -
Part I) Disomate , Diso-C, Relay Panel having 25 nos. of relays with GNT power
supply unit, Calibration box individually for all the material batching process in
computer/Auto/ Manual and service modes Part II. The load cell signal through
calibration box was processed and controlled for material addition during blow.
The system (Part II), Fig 2(a) gave repeated problems and units became

obsolete and could not be repaired. To overcome this Ms. Johnson & Nicholson
System was installed in converter P for (Part II) with complex electronic circuitries
for each material separately.
Also, different applications require different mixtures of metals and it is
necessary to measure the quantities of each metal being melted. In many cases,
a particular composition is first approximated in a batch which is melted, and then
samples of that batch are analyzed to determine what adjustments need be
made to obtain the desired composition. A selected mix and weight of metals is
then added to make the necessary adjustments. However, making these
adjustments involves the same drawbacks as discussed above.
The old system, Fig. 1(a) to Fig. 6(a) could not work for long and had started
giving problems and customer complaints from the beginning of system
commissioning. Regular queries were made with Ms. J&N for smooth operation
of the supplied system. Since it involved a number of hardware devices and
relays so the troubleshooting was very difficult and time consuming. The blows in
LD converter were getting delayed because of need of required flux material
addition.
The basic purpose of going for the innovation in Part II is because of regular
problems faced in the earlier J&N system having the following sections.
oTarring circuit
oDiso- C device Fig 4(a)
oDiso - D device
oCommon Relay panel Fig 6(a)
oIndividual relay panel Fig 6(a)
oDNT power supply unit
oProcessor and other cards

The present invention is directed toward overcoming one or more of the
problems as set forth above.
SUMMARY OF THE INVENTION
The object of the invention is to provide a novel, simple, and highly efficient
weighing machine for rapidly and accurately weighing flowable solid material.
A further object of the invention is to provide a new improved weighing
mechanism which may be economically manufactured and possesses structural
and operating features which render it superior for any weighing purposes to
weighing elements of the prior art of: which we are aware.
Therefore such as herein described the improved hopper weighing and control
system for LD converters in steel plants comprising of a power supply circuit
comprising four different supplies; a load cell excitation unit; a signal processing
and tarring network; a comparator configured for comparing the outputs; a set the
required weight circuit configured for measuring the current output; a display
configured for displaying the weights.
With these general objects in view, and such others as may appear, the invention
consists in the weighing machine, in the weighing mechanism, and in the various
structures, arrangements and combinations of parts hereinafter described.
In order that the invention may be more clearly understood and readily carried
into effect reference will now be made to the accompanying drawing.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1 (a) illustrates the block diagram of hopper weighing and control system as
per the prior art;
Fig. 1 (b) illustrates the block diagram of a simplified low cost hopper weighing
and control system for the LD converters in steel plants in accordance with the
present invention;
Fig 1 (c) illustrates a detailed circuit diagram of the hopper weighing and control
system in accordance with the present invention;
Fig 2 (a) illustrates the block diagram of the prior hopper weighing and control
system;
Fig 2 (b) illustrates the circuit diagram of the modified relay control logic for
hopper weighing and control system in accordance with the present invention;
Fig 3 (a) illustrates the relay location of flux weighing for the hopper weighing and
control system as per prior art;
Fig 3 (b) illustrates the modified relay location of flux weighing for the hopper
weighing and control system in accordance with the present invention;
Fig 4 (a) illustrates the DISOMAT C Connections as per the prior art;
Fig 4 (b) illustrates the transformer and the circuit components of the hopper
weighing and control system in accordance with the present invention;
Fig 5 (a) illustrates the housing and panel details of the hopper weighing and
control system as per the prior art;
Fig 5 (b) illustrates the housing for the digital weighing indicator of the hopper
weighing and control system in accordance with the present invention;
Fig 6 (a) illustrates the details of the circuit (relay panels) of the control system as
per the prior art.
Fig6(b) illustratesthecalibrationof thefluxweighing DWI andthe
corresponding load cell output chart of the hopper weighing and control system in
accordance with the present invention;
Fig 7 illustrates the dimensions of the hopper weighing controller panel in
accordance with the present invention;

DETAILED DESCRIPTION
Since hopper weight display along with material addition in batches as per the
process requirement was utmost important for metallurgical parameter control
during steel preparation in LD converters, was to overcome the difficulties by
optimum system designing and making the system functioning with available in
house resources by providing trouble free service for steel making process
improvement and customer's satisfaction.
The present in house designed system consist of digital weight indicator with
inbuilt power supply & system tarring circuit, 2 sets of potential free relay
contacts (No- Nc) with seven no of plug in type relays for the complete process
requirement function of the system. Since shortcomings of earlier system were
carefully noted and observed so in the designed circuit care was taken in every
step so that problem faced during process requirement operation does not get
repeated as in earlier system during the entire blow campaign of steel production
in the LD converter. By this innovation of the in-house designed single digital
weight indicator with less number of hardware devices /sections made the
complete setup a safe and trouble free control system. Total designed and
development cost is much less than the original system giving smooth troubles
free service with easy maintenance and troubleshooting approach.
The system is designed in-house with available spares from local markets. Spare
components, connector can easily be replaced. No of working PCBs reduced
with aim to ease the maintenance system, reduce downtime and make the unit
customer friendly. The system requirement was the weighing and batching of 3
materials in 3 Weigh-Hoppers i.e lime, Manganese ore, dolomite and then
discharge the same as and when it is desired. This type of Batching System was
known as GIW or GAIN-IN-WEIGHT batching system. In GIW batching, material

is allowed to fall into the Weigh Hopper from a silo. When the predetermined
amount of material has filled the Weigh Hopper, filling process is stopped.
The Digital Weighing Indicator such as herein described is having the following
sections:
a) Power supply circuit.
b) Load cell Excitation
c) Signal processing & Tarring Network.
d) Comparator Output
e) Weight Display
f) Set Weight Ckt.
g) 4-20 mA Analog Output for PC / Remote Applications.
a) The enclosed circuit provides 4 types of power supplies such as (Fig 1&4)
i) +/-15 V ,1 Amp. For Load Cell Excitation. IC LM 317 & IC LM 337 are used.
ii) + 12 V Unregulated supplies for Min. & Max. Relay operation and use of
potential free contactsfor controller network,
iii) +/-5V for A/D & Display Circuits,
iv) +/- 9 V for Analog Supplies & other associated circuits.
Normal Power supply IC s 7805, 7905, 7809 & 7909 are used.
b) The Load Cell output is directly fed Instrumentation Amplifier through a divider
network. The output of the Inst, amp is fed to the Buffer Amplifier to A/D
conversion circuit to display the weight value of the Hopper. The external manual
tarring network has been provided to make the Display system to zero when
required. The circuit involves IC 1 to IC 4 for the purpose.
c) The control options are met with IC 5, 6, 9,DR1, TR1 & TR2 for Minimum relay
operation with indication of minimum weight in the Hopper. Potential free
contacts are used for both Min and Max relays to set the value for Hopper

loading with IC 5,10,11,12,DR2,TR3 & TR4 .Set the required weight circuit is
associated here with along with the comparator circuit.
d) Weight display with IC 7135 and seven segment display chip is achieved with
the Buffer output from the Instrumentation amplifier where analog output is
converted into digital output and drives the display directly for 4 and !/2 digit
displays.
e) 4-20 mA current loop circuit is developed with the fact that current output is
proportional and linear to weight display in the Hopper considering Zero Kg
weight = 4 mA output and 2500 Kg = 20 mA output with IC 6,7 & 8.
Identification of the optional feature and their relevance: -
1) 4-20 mA can be fed PC in case required.
2) Less no. of plug in type relay are used.
3) Similar system can be developed for any other process load sensing
system.
Illustration of the best workable Embedment of the Invention
System is working satisfactorily since installation.
Highlights of the Invention Step: -
o User Friendly
o Customer can go for quality productivity
o Auto zero facilities when input zero.
o External reference voltage with adjustment range to calibrate the A/D
conversion and the system requirement results.
o 4½ digit A/D conversion for better accuracy,
o Single chip & easy to replace
ADVANCEMENT OF THE NEW SYSTEM
o The system was very simple to handle (Fig 6)
o The system is less in weight, size and handy, Fig 5 , (New)
o Fault diagnosis and troubleshooting became simpler

o Trouble free system setup where no maintenance was required for months
together.
o Cost is much less than the earlier system
o Reliability is greater then the original system
o Better cost control through optimum utilization of developed circuit
o System can be prepared with local available components (proprietary
items are not required)
HIGHLIGHTS OF THE INVENTION
o Components available in local markets are used.
o Better customer satisfaction
o Better system stability and repeatability
o Similar systems can be tailored to meet other site requirements
ABBREVIATIONS USED

Table. 1

Table. 2

Symbols
Description
R
Relay
S
Switch
L
Lamp
DWI
Digital Weight Indicator
Although the foregoing description of the present invention has been shown and
described with reference to particular embodiments and applications thereof, it
has been presented for purposes of illustration and description and is not
intended to be exhaustive or to limit the invention to the particular embodiments
and applications disclosed. It will be apparent to those having ordinary skill in the
art that a number of changes, modifications, variations, or alterations to the
invention as described herein may be made, none of which depart from the spirit
or scope of the present invention. The particular embodiments and applications
were chosen and described to provide the best illustration of the principles of the
invention and its practical application to thereby enable one of ordinary skill in the
art to utilize the invention in various embodiments and with various modifications
as are suited to the particular use contemplated. All such changes, modifications,
variations, and alterations should therefore be seen as being within the scope of
the present invention as determined by the appended claims when interpreted in
accordance with the breadth to which they are fairly, legally, and equitably
entitled.

WE CLAIM:
1. An improved hopper weighing and control system for LD convenors in
steel plants comprising of:
a power supply circuit comprising four different supplies;
a load cell excitation unit;
a signal processing and tarring network;
a comparator configured for comparing the outputs;
a set the required weight circuit configured for measuring the current
output; and
a display configured for displaying the weights.
2. An improved hopper weighing and control system as claimed in claim 1,
wherein the power supply unit is configured for outputting +/- 15 V :1 amp for
load cell excitation, + 12 V unregulated supplies for Min. & Max. relay operation
and use of potential free contacts and for controller network, +/- 5 V for A/D &
Display Circuits and +/- 9 V for analog supplies & other associated circuits.
3. An improved hopper weighing and control system as claimed in claim 1,
wherein the load cell output is directly fed to a instrumentation amplifier through a
driver network and further the output of the said amp is fed to the buffer
amplifier to A/D conversion circuit to display the weight value of the hopper
4. An improved hopper weighing and control system as claimed in claim 1,
wherein the external manual tarring network is configured to make the Display
system to zero when required.
5. An improved hopper weighing and control system as claimed in claim 1,
wherein set the required weight circuit is associated with the comparator circuit.

6. An improved hopper weighing and control system as claimed in claim 1,
wherein the set the required weight is further configured for the minimum relay
operation with indication of minimum weight in the hopper and potential free
contacts are used for both Min and Max relays to set the value for Hopper
loading.
7. An improved hopper weighing and control system as claimed in claim 1,
wherein the display comprising with seven segment display chip is achieved with
the buffer output from the Instrumentation amplifier wherein the analog output is
converted into digital output and drives the display directly.
8. An improved hopper weighing and control system as claimed in claim 1,
wherein the output weight is determined by a current loop circuit wherein the
current output is proportional and linear to weight display in the Hopper.
9. An improved hopper weighing and control system as claimed in any of the
preceding claims wherein the system comprises 2 sets of potential free relay
contacts (No- Nc) with seven no of plug in type relays for the complete process
requirement function.
10. An improved hopper weighing and control system for LD convenors in
steel plants substantially as herein described with particular reference to
accompanying drawings.

The present invention relates to An improved hopper weighing and control
system for LD converters in steel plants comprising of a power supply circuit
comprising four different supplies; a load cell excitation unit; a signal processing
and tarring network; a comparator configured for comparing the outputs; a set the
required weight circuit configured for measuring the current output; and a display
configured for displaying the weights.