FIELD OF THE INVENTION:
The present invention relates to a refractory heat shield changing device which is adapted
to be a safe, faster and economic involving less manpower and complexity in changing of
heat shield. More particularly, the device of the invention is portable and adapted such as
to facilitate replacing the heat shield with precise positioning by controlled lowering/lifting
free of any jerk, normally experienced in conventional handling with EOT cranes. The
present heat shield changing device is further adapted to be connected to the VAD
chamber car through a car coupler for towing along track to desired location for simple
,easy and faster heat replacement. Advantageously, the device of the invention would
favour avoiding damage of the refractory bricks and thereby improving remarkably the
operating life of the heat shield. Moreover, the device of the invention adapted to change
heat shield for VAD by the operation of the hydraulic system/cylinders do not necessitate
taking out the electrodes completely before changing of the heat shield and thus favour
reducing the down time and also increasing the availability and productivity thus favoring
wide industrial application in related field in steel manufacturing industry.
BACKGROUND ART:
The Vacuum Arc Degassing (VAD) unit is conventionally used in steel industry for
secondary refining equipment used for treatment and refining of liquid steel during special
heat making comprising those for producing railway wheels and axles, special forgings etc.
The unit is mainly utilized for raising the liquid steel temperature by arcing under vacuum
and its refining is achieved by addition of Ferro alloys and degassing it under deep
vacuum.
The Vacuum Arc Degassing unit comprises mainly of VAD chamber car, Vacuum cover,
Heat shield, Vacuum pump unit, Ferro alloy system and electric arc heating system, and
transfer track for car conveying of heats.
Traditionally, in a VAD unit most of the sophisticated and sensitive equipments of arc
heating system are installed on the vacuum cover in a VAD unit. The vacuum cover as well
as, these delicate equipments need to be protected from the intense heat radiations
generated during arcing of the liquid steel, by favored disposition of a refractory heat
shield under the vacuum cover. The heat shield is a dome shaped refractory structure,
weighing approximately 15 T suspended under the cover. The refractory bricks for the
lining of the shield wears out in normal course of use over a period of time, depending

upon treatment duration, arcing duration and quality of steel etc. Hence, the heat shield is
required to be changed 2-3 times every month depending upon the production rate. The
conventional method and equipment for heat shield change over for VAD, is carried out
consuming much of time in the order of about 8 hrs involving a lot of resources and
manpower in a hazardous way. The conventional heat shield changing device and method
suffered from a number of limitations and disadvantages comprising using simultaneous
operation of EOT cranes and VAD hydraulic System, insufficient head room for lift of EOT
crane resulting in bypassing of limit switches, disconnection and connection of encoder for
auto T/S lance, disconnection and connection of hoses performed manually, standing
inside the chamber car with cover down in a risky position, operational limitation of the
EOT crane with respect to finer lifting/lowering resulting in accidents, occurrence of
sticking up of hanger rods in guide tubes during lifting/lowering of heat shield using EOT
cranes and thereby smooth operation is affected, unequal lifting of the heat shield corners
due to use of tackles of varied length, working of men required to be performed at three
different level during heat shield change over without proper communication, too much
reliance on EOT cranes and its operators involving risks of multiple risk of failure of
performance, usually a total of 8 men are required to complete the heat shield change
operation consuming at least 8hrs time.
In some steel plants, 3 number electrically operated linear actuators are provided on the
VAD cover for lowering/lifting of the heat shield at the time of change over. As these
drives are constantly exposed to heat and dust, their operation suffer from low reliability
and very much prone to frequent maintenance . Moreover, these electrical devices require
additional space for mounting on vacuum cover.
There has been therefore a continuous need for developing a device for safe, reliable and
fast changing of heat shield used in secondary refining operation of liquid steel in Vacuum
Arc Degassing Unit, eliminating the aforedescribed limitations in the related prior art and
also a method of using said device to ensure use of minimum use of resources including
skilled manpower and faster change over of shield, achieving reduced damage of firebricks
by favored smooth handling of the heavy weight heat shield during handling/lowering or
lifting, longer life of refractory shield, higher availability of the degasser unit and thus
improving productivity of the plant for secondary treatment and refining operation of liquid
steel.

OBJECTS OF THE INVENTION:
It is thus the basic object of the present invention to provide a simple, safe,
accurate/precise device for changing of refractory heat shield in VAD chamber, involving
less resources and manpower and at much lesser time than the existing method using EOT
cranes.
A further object of the present invention is directed to said device for changing of
refractory heat shield in VAD for secondary steel refining, wherein the lowering of old worn
out shield for dismantling and lifting the new shield inside the VAD chamber cover can be
precisely carried out involving required number of hydraulic jacks of requisite capacity and
a hydraulic system with adequate control to operate said jacks for the desired purpose
with desired accuracy and speed and free of any jerk or damage of lining.
A still further object of the present invention is directed to a device for changing of the
refractory heat shield of VAD wherein the requirement of manpower is reduced from 8 to 4
needing less skill and the total change over time is reduced from existing 8 hrs to about
2hrs.
A still further object of the present invention directed to a device for changing of the
refractory heat shield of VAD and a method using said device wherein by avoiding the jerk
free operation during the hydraulic cylinder/jack assisted change over of the refractory
shield of the VAD, increases heat shield life, avoids complete removal of electrodes used
for arc heating and thus reducing the down time and increasing the unit availability and
resultant improvement in productivity.
SUMMARY OF THE INVENTION:
Thus according to the basic aspect of the present invention there is provided a device for
changing heat radiation shield in VAD comprising:
a portable car having
(i) a hydraulic power pack ;

(ii) a main support means provided on hydraulic cylinders adapted to be lifted by a
hydraulic system;
(iii) means for controlling the old heat shield after dismantling and lifting of a new heat
shield ; and
(iv) means for balancing adapted to negotiate with inclination of the support ring with
respect to the said heat shield.
In the above device of the invention the said portable car comprise of four wheels which
can be placed on the transfer track involving an EOT crane.Advantageously, the said
portable car is adapted to be connected to the VAD chamber car through a car coupler for
towing along.
Importantly, in the above device the said hydraulic power pack is powered through a
quick connector cable. The said main support means comprise a main support ring
adapted to be fitted onto said hydraulic cylinders which can be lifted by said hydraulic
system.
In accordance with an aspect of the invention in the above device the said means for
controlling the old heat shield after dismantling and lifting of a new heat shield comprise a
pendant controller fitted with the car.
In accordance with another aspect of the invention the said means for balancing is
adapted to negotiate with inclination of the support ring with respect to the said heat
shield comprises valve block for balancing adapted to negotiate with inclination of the
support ring with the heat shield.

In accordance with yet further aspect the device for changing heat radiation shield in VAD
comprises control through multiple pendants from various locations, provision of
collapsible platform for hose removal.
Preferably , in the above device of the invention , the power pack is selectively placed over
the car in such a manner that there is no damage in case of falling bricks /slag jam in
course of heat shield changing.
The present invention and its advantages and objectives are described in greater details
with reference to the following non limiting illustrative figures.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES:
Figure 1: is the schematic illustration for the conventional process for changing heat shield
in VAD using EOT crane and lifting tackles.
Figure 2: is the schematic illustration of an embodiment of the portable 4-wheeled car
mounted device comprising three hydraulic cylinders operated by a hydraulic power pack
system on board, said car adapted to be hauled on track for safe, reliable and faster
changing of the refractory heat shield in VAD chamber, according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION WITH REFRENCE TO THE
ACCOMPANYING FIGURES :
The present invention relates to a heat shield changing device adapted to be used in
combination with the VAD chamber car for secondary treatment and refining of steel in
Vacuum Arc Degassing Unit. Importantly, the device of the invention is a portable car
having 4 wheels, having on-board hydraulic unit comprising 3 cylinders, operated by a
hydraulic system installed on the car and having a hydraulic power-pack capable to be

powered by a quick connector cable, facilitating replacing the heat shield with precise
positioning by controlled lowering/lifting free of any jerk, normally experienced in
conventional handling with EOT cranes. The present heat shield changing device
comprising a portable car having four wheels, can be placed on the transfer track using
EOT crane. Moreover, said wheel mounted heat shield changing device is adapted to be
connected to the VAD chamber car through a car coupler for towing along track to desired
location. A pendant controller, fitted with the car, controls the lowering and lifting of heat
shield during changing. Advantageously, the jerk free handling of the heat shield with
precise hydraulic control avoids damage of the refractory bricks and thereby improving
remarkably the operating life of the heat shield.
Reference is first invited to the accompanying Figure 1 that schematically illustrates the
conventional process for changing heat shield in VAD using EOT crane and lifting tackles.
The refractory heat shield used for secondary refining/treatment of liquid steel of special
grades protect the sensitive equipments of the arc heating system from the intense heat
radiation from molten steel during heating by arcing. Conventionally the heat shield is a
massive dome shaped refractory structure weighing about 15T, suspended under the
vacuum cover in a VAD unit and during changing of a heat shield a special tackle is used
which is operated with an EOT crane. It is appearing from the said Figure 1, that 3 slings
hung down from the tackle at regular spacing share the total load of the heat shield. The
EOT crane gradually lower the old/worn out heat shield on the platform of the VAD
chamber car. The process has been complex requiring lot of activities and co-ordination
among the operators at multiple levels of shop floor, making the communication difficult
and ineffective, making the conventional changing method of heat shield prone to
accidents or damages. There is also the possibility of unequal lifting of the heat shield at
its corners thus making the positioning of the shield inside the vacuum cover is difficult or
inaccurate. Further, the trial and error positioning of the shield inside the cover consume
more time, in the order of about 8 hrs involving usually eight persons at different
multilevel locations. Operators are forced to work under highly unsafe working conditions
such as insufficient lifting of EOT crane resulting in by passing of limit switches,
disconnection/reconnection of hoses for the vacuum system to the cover is performed
standing inside the chamber car with cover down and the like, working of people at three
different levels without proper communication, or too much reliance on functioning of EOT
crane and its operators etc. Thus the convention devices and means for changing of heat
shield in VAD is unsafe, inaccurate, unreliable and prone to accident of personnel and

damage of the shield or equipments and also consuming more time for shield replacement
and resultantly less availability of the VAD unit.
Reference is now invited to the accompanying Figure 2 that schematically illustrates the
system/device for safe, economic and faster changing of refractory heat shield in VAD Unit
at the secondary refining of liquid steel. As clearly apparent from the accompanying
Figure 2 that the present device comprises a four wheeled car that is provided with a
hydraulic device onboard operatively connected to three hydraulic cylinders (HCs) and a
Hydraulic Power Pack(HPP). The car of the invention for the heat shield change purpose
according to the invention is a portable car which can be placed on the transfer track using
EOT Cranes and can also be connected to the VAD Chamber car by means of a car coupler
for towing along the track for placing the car at desired position on track relative to the
vacuum cover of the VAD chamber for desired replacement of the refractory heat shield for
VAD Unit. The Hydraulic Power Pack (HPP) mounted on the car, adapted to be powered
through a quick connector cable favors synchronous operation of the three hydraulic
cylinders to horizontally lowering or lifting of a Support Ring (SR) attached to the
cylinders. The device according to a preferred embodiment of the present invention having
said main Support Ring (SR), fitted with said three hydraulic cylinders such as to favour
jerk free lowering and lifting of the support ring powered by a hydraulic system installed
on the car, said support ring in turn facilitates lowering of old heat shield after dismantling
and lifting of new heat shield in a controlled manner through a pendant controller fitted
with the car. The valve blocks are provided in said hydraulic system for balanced
movements of the heat shield along with the support ring, for favoring negotiating with
desired inclination of the support ring with the heat shield to suit fitment inside the
vacuum cover of the VAD chamber. The car is capable to jack up and down the heat shield
from below the chamber car cover. As the control is hydraulic and thus entire operation of
replacing the heat shield is precise, accurate, reliable and safe, avoiding time-consuming
trial and error approach. The power pack is placed over the car in such a manner that
there is no damage in case of falling bricks/slag jam in course of heat shield changing. The
level of walkway helps the crew to move around and removal of cooling hoses without any
obstacles. The device according to the present invention is further having optional features
like control through multiple pendants from various locations, provision of collapsible
platform for hose removal serve additional advantages during heat shield changing using
the new device and thus ensuring safety for the concerned operating personnel.

It is thus possible by way of the present invention to provide a device for the heat shield
removal/replacement in the VAD cover and a method for safe, accurate and manner of
replacing the heat shield free of any jerk/load on the refractory bricks and thus avoiding
any damage to the shield and at a much faster pace with less number of personnel
involved as compared to conventional EOT crane based change over operation of heat
shield in VAD unit. The life of the heat shield is also improved substantially following the
method of changing the heat shield using the device of the present invention by hydraulic
cylinder based operation for fixing of the heat shield. Resultantly, the availability of the
VAD unit is increased, lowering the downtime for replacement of heat shield and thus
increasing the productivity of the VAD unit.

WE CLAIM:
1. A device for changing heat radiation shield in VAD comprising:
a portable car having
(i) a hydraulic power pack ;
(ii) a main support means provided on hydraulic cylinders adapted to be lifted by a
hydraulic system;
(iii) means for controlling the old heat shield after dismantling and lifting of a new
heat shield ; and
(iv) means for balancing adapted to negotiate with inclination of the support ring
with respect to the said heat shield.
2. A device for changing heat radiation shield in VAD as claimed in claim 1 wherein said
portable car comprise of four wheels which can be placed on the transfer track
involving an EOT crane.
3. A device for changing heat radiation shield in VAD as claimed in anyone of claims 1 or
2 wherein said portable car is adapted to be connected to the VAD chamber car
through a car coupler for towing along.
4. A device for changing heat radiation shield in VAD as claimed in anyone of claims 1 to 3
wherein said hydraulic power pack is powered through a quick connector cable.

5. A device for changing heat radiation shield in VAD as claimed in anyone of claims 1 to 4
wherein said main support means comprise a main support ring adapted to be fitted
onto said hydraulic cylinders, which can be lifted by said hydraulic system.
6. A device for changing heat radiation shield in VAD as claimed in anyone of claims 1 to
5 wherein said means for controlling the old heat shield after dismantling and lifting of
a new heat shield comprise a pendant controller fitted with the car.
7. A device for changing heat radiation shield in VAD as claimed in anyone of claims 1 to
6 wherein said means for balancing adapted to negotiate with inclination of the support
ring with respect to the said heat shield comprises valve block for balancing adapted to
negotiate with inclination of the support ring with the heat shield.
8. A device for changing heat radiation shield in VAD as claimed in anyone of claims 1 to
7 comprising control through multiple pendants from various locations, provision of
collapsible platform for hose removal.
9. A device for changing heat radiation shield in VAD as claimed in anyone of claims 1 to
8 wherein the power pack is selectively placed over the car in such a manner that there
is no damage in case of falling bricks /slag jam in course of heat shield changing.
10. A device for changing heat radiation shield in VAD substantially as hereindescribed and
illustrated with reference to the accompanying figures.

The invention discloses a refractory heat shield changing device for changing of heat
radiation shield in VAD involving less manpower and complexity in a safe, faster and
economic manner. More particularly, the device of the invention is portable and adapted
for replacing the heat shield with precise positioning by controlled lowering/lifting free of any jerk. The device according to the invention is capable to be connected to the VAD
chamber car through a car coupler for towing along track to desired location for simple,
easy and faster heat replacement, avoiding damage of the refractory bricks, and thereby
enhancing the operating life of the heat shield. The changing of heat shield is operatively
achieved by the hydraulic system comprising cylinders and power pack on board such that
electrodes need not be taken out completely before changing of the heat shield and thus
favour reducing the down time and also favoring increasing the availability and
productivity in VAD in steel manufacturing industry.