FIELD OF THE INVENTION
The invention relates to a device for uniform application of heat input to achieve
homogenous heating of coiled tube bundles during heat treatment. The invention
further relates to a process to apply uniform heat sources circumferentially
around tube bundles.
BACKGROUND OF THE INVENTION
In coiled bundles of Heat Exchangers, coiling of tubes are done by cold forming
process. To avoid spring back phenomenon and rewinding of the coils, the coil
ends are held firmly on a fixed frame.
To eliminate cold forming stresses and for retaining the bundle geometry, a
stress relieving heat treatment is provided to the coiled and locked bundle.
Heating of the tube bundle is done homogeneously from outermost surface to
inner-most surface, and temperatures at three sections from inner most, middle
and outer most surfaces are monitored. The temperature difference across
different sections is maintained with close tolerances. Achieving uniformity of the
heat treatment, temperatures within a close tolerance is not possible in
conventional furnaces. Conventional furnaces are not provided with heating
elements all round especially at the bottom portion on the surface bed which is
essential to achieve an uniform heating. Hence, an external heat source is
arranged to achieve the uniform temperatures at all cross sections of the
furnace.

OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a device which will house
additional heating coils and will hold the component during heat treatment which
aids uniform application of heat source to heat the component.
Further object of invention is to propose a method of applying heat input to the
component which produces acceptable, required consistent heat input and
uniform temperature during heat treatment.
SUMMARY OF THE INVENTION
According to the invention there is provided a device for uniform heat input to
component to achieve a homogeneous heating from outer surface to inner of the
component, the device comprising a shroud (2) which holds the component (1)
to be heat treated, a plurality of resistance coils (3) to heat the periphery of the
surface by increasing/decreasing current input, a coil holding shroud (4) houses
the resistance coil (3) in each segment of the periphery, a plurality of
thermocouple leads (7) connected to a multi point recorder (8) to measure the
temperature at various locations, a power source (6) provided for the adjustment
of heat inputs, and a furnace (5) for applying main heat source, wherein the
component is housed in shroud (2) without affecting geometry of the
component, and wherein the resistance heating coils (3) disposed around the
periphery of the component (1) to supply variable heat input to the selected
segment of periphery of the component corresponding to the thermocouple
reading of temperature at that point.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 schematically illustrated Heat treatment device according to the
invention.
DETAILED DERSCRIPTION OF THE PREFERRED EMBODIMENTS
As shown in figure 1, the heat treatment device comprises a shroud (2), a
plurality of heating coils (3), a coil holding shroud (4), a gross heat source-
Furnace (5), a fine heat power source (6) thermo couple leads (7), and a
multipoint temperature recorder (8).
A required number of thermocouple leads are fixed on the outer peripherals of
the component, and their terminals are connected to the Multipoint temperature
recorder (8).
The component to be heat-treated is housed in the shroud (2). The periphery of
the shroud (2) is divided into several segments, and the resistance coils (3) for
heating are placed in identified segments of the shroud (2). The resistance coils
(3) are also placed on front and rear end of the shroud (2).
All the resistance heating coils (3) held in position by the coil holding shroud (4).
The ends of the resistance heating coils (3) are connected to the power source
(6). The device accommodating a component (1) to be heat treated, the shroud
(2), the resistance heating coils (3), the coil holding shroud (4) are put inside the
gross heat source (5).

The Heating furnace (5) is put on and the temperature rise of the component (1)
is recorded in the Multi point recorder (8) via the thermocouple leads (7)
attached to component (1) and the multi point recorder (8). Identification of
location of the thermocouple leads (7) and the location of the heating coils (3)
are co-related. According to the temperature reading of the thermocouple point,
input current to the heating coil (3) is raised or lowered to maintain an uniform
temperature rise of coiled bundle (1). Gross heating is done through the furnace
(5).

WE CLAIM:
1. A device for uniform heat input to component to achieve a homogeneous
heating from outer surface to inner surface of the component, the device
comprising a shroud (2) which holds the component (1) to be heat
treated, a plurality of resistance coils (3) to heat the periphery of the
surface by increasing/decreasing current input, a coil holding shroud (4)
houses the resistance coil (3) in each segment of the periphery, a plurality
of thermocouple leads (7) connected to a recorder (8) and component (1)
to measure the temperature at various locations on component, a power
source (6) provided for fine adjustment of heat inputs, and a furnace (5)
for applying main heat source, wherein the component is housed in
shroud (2) without affecting geometry of the component, and wherein the
resistance heating coils (3) disposed around the periphery of the
component (1) to supply variable heat input to the selected segment of
periphery of the component corresponding to the thermocouple reading of
temperature at that point.
2. The device as claimed in claim 1, wherein the coil holding shroud (4)
rigidly maintains the resistance heating coil (3) in position without short
circuiting and being connected to the power source (6).

3. The device as claimed in claim 1, wherein in the furnace (5) provides main
heat source for heating the component (1).
4. The device as claimed in claim 1, wherein the power source (6) provides
additional heat input to the required heating coil (3) to impart heat to that
portion of peripheral segment of the component.
5. The device as claimed in claim 1, wherein the recorder (8) records the
temperature of periphery of the component at particular points.
6. A process for controlled heating of the periphery of component to impart
uniform heat radially to the inner surface of the component, wherein the
temperature of thermocouple readings of outer periphery of the
component is maintained within close tolerance, and wherein the
temperature of the thermocouple reading is constant throughout soaking
time of the heat treatment cycle.

7. The process as claimed in claim 6, wherein the component is heat treated
with nil distortion.

The invention relates to a device for homogeneous heating of coiled tube bundle
component (1) comprising a shroud (2) which holds the coiled bundle, at least
one resistance heating coil (3) which is used for adding finer heat input to the
coiled bundle from a power source (6), a coil holding shroud (4) used for
positioning and holding the resistance coils in corresponding segments, a gross
heat source (5) which provides main heating source treatment, a plurality of a
thermocouple leads (7) along with multi point recorder (8) which records the
temperature of heating at different sections of coiled tube bundle (1) enabling
the device to perform homogeneous heat treatment. The invention further
relates to a process of providing uniform input of heat during heat treatment of
components which require uniform temperature control at various locations using
external heat source in addition to main furnace heating.