FIELD OF THE INVENTION:
The present invention relates to a novel hair pin type heat exchangers in general or
more particularly an exchanger where the gasket can easily be replaced when the
flange connections are dismantled without complete removal of whole U-tube bundle
assembly out of the shell.
BACKGROUND OF THE INVENTION:
Hair-pin type heat exchangers are employed in petro-chemical industries and in
establishments such as high pressure boilers with oil firing in thermal power projects
where heat transfer is to be effected between two fluids which are at different
temperatures. Gaskets are used in heat exchangers to ensure leak tightness of flanged
joints. Due to the limitation in the service life of gaskets, they are prone to warp and
hence is required to be replaced.
It is required to replace the gaskets whenever flange connections are dismantled for
one cause or the other. Replacement of shell-side-gasket is done by removing the U-
tube bundle assembly completely out of the shell.
Fig. 3 discloses the conventional hair pin type exchangers, which comprises a cylindrical
shell (11) with shell-flange (12), plurality of channel assembly having the channel-

flange (13), plurality of U-tube bundle assembly (14) having the tube-sheet (15), shell-
side-gasket (16) and the channel-side-gasket (17). The shell-side gasket (16) is placed
between the shell-flange (12) and the tube-sheet (15). The channel-side gasket (16) is
placed between the tube-sheet (15) and the channel-flange (13).
Replacement of shell-side-gasket (16) is done by removing the U-tube bundle assembly
(14) completely out of the shell (11).
But this complete removalof U-tube bundle assembly (14) enhances the effort and time
required considerably and also makes it quite expensive. Hence, there is always a need
to develop an innovative hair pin exchanger where the complete removal of gasket
would not be necessary.
The present invention meets the long felt need by providing a heat-exchanger and
process associated with it which would be more easy and economic yet effective.
OBJECTS OF THE INVENTION:
It is therefore the principle object of the present invention to provide a heat exchanger
as in Fig. 1, where the gasket (7) can easily be replaced without the complete removal
of U-tube bundle assembly (5) out of the shell (1).
Another object of the present invention is to provide a heat exchanger, which employs
substantially less man power with simple tricks for replacing the gasket.

Yet another object of the present invention is to provide a heat exchanger, which
employs very less effort, time and it is cost effective as well.
Further object of the present invention is to provide a heat exchanger, where the minor
axis of tube-sheet (6) is smaller than the major axis of shell-side gasket (7) so that the
gasket can be slipped easily over the tube sheet (6).
Another object of the present invention is to provide a heat exchanger, where the shell
side gasket (7) is suitably rotated over the tube sheet (6) for its placement.
SUMMARY OF THE INVENTION:
A hair-pin type heat exchanger for replacing gasket easily without complete removal of
U-tube bundle assembly (5) comprises a cylindrical shell (1) with shell flange (2), at
least plurality of channel assembly (3) which also having channel flange (4), at least
plurality of U-tube bundle assembly (5) which hold tube sheets (6) which are flattened
suitably; a shell-side gasket (7); a channel-side-gasket (8); heat transfer tubes (5)
which are situated in the tube-sheet (6); characterized in that the shell-side gasket (7),
and tube sheet (6), are elliptical in shape with suitable eccentricity, so that the shell-
side gasket (7) can be slipped over the tube-sheet (6) smoothly.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure-1 illustrates the present art of tube-sheet (6) design and the arrangement of U

tube bundle (5) for Hair-pin type heat exchanger.
Figure-2 illustrates the present art of shell-side-gasket (7) replacement in Hair pin type
heat exchanger.
Figure-3 shows the prior art of tube-sheet (15) design for Hair-pin type heat exchanger.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF
THE INVENTION:
The present subject matter relates to a novel hair-pin type of heat exchangers, wherein
the U-tube bundle assembly (5) does not require to be completely taken out while
replacing of the gaskets (7).
In accordance with embodiment of the present subject matter, there is provided hair-
pin type heat exchangers, where the replacement of shell-side gasket (7) takes place by
slight movement of U-tube bundle assembly (5) out of the shell.
The tube-sheet (6), flanges and the shell-side gasket (7) are of elliptical in shape with
suitable eccentricity.The shell-side gasket (7) is an elliptical ring whose outer side is
accommodated in the elliptical recess provided in the tube-sheet (6). The opening in
the shell-side-gasket (7) is also elliptical. Tube sheet (6), shell-side gasket (7) and shell
flange (2) are of elliptical shape. Replacement of shell-side gasket (7) can be completed
by suitably manuaring the shell side gasket (7) over the Tube sheet (6). The heat-

transfer tubes (5) are so organized in the tube-sheet (6) to enable the gliding of the
shell-side gasket (7) over the tube-sheet (6). Shell and Channel flanges are provided
with elliptical grooves to accommodate and confine the gasket.
Fig. 1 illustrates the hair-pin type heat exchanger as per the present invention.
The heat exchanger comprisesa cylindrical shell (1) with shell-flange (2), plurality of
channel assembly (3) having channel-flange (4), plurality of U-tube bundle assembly (5)
which further includes the tube-sheet (6).Further, the head exchanger also includes a
shell-side-gasket (7) and a channel-side-gasket (8) is also provided therein. In
accordance to the another embodiment of the present invention, the tube-sheet (6) and
the shell-side gasket (7) are elliptical in shape. The shell-flange (2) further comprises
Elliptical groove for confinement of shell-side gasket (7). The shell-side gasket (7) is
placed between the shell-flange (2) and the tube-sheet (6). The channel-side gasket (8)
is provided between the tube-sheet (6) and the channel-flange (4). The plurality of U-
tube bundle assembly (5) is placed inside the cylindrical shell (1) by holding the tube-
sheet (6) between the shell-flange (2) and the channel-flange (4) by means of a set of
fasteners (9 and 10). The shell side gasket (7) and channel-side gaskets (8) are used
for checking of the leak and thereby ensuring leak tightness of flanged joints.
Fig. 2 illustrates the whole method for replacing the shell-side gasket (7) by slight
withdrawal of U-tube bundle assembly (5) out of the cylindrical shell (1).

The shell-side gasket (7) is rotated so that its major axis is perpendicular to the minor
axis of the tube-sheet (6). As the minor axis of tube-sheet (6) is smaller than the
major axis of the shell-side gasket (7), hence the shell-side gasket (7) can be slipped
over the tube-sheet (6). Shell-side gasket (7) is suitably rotated over the tube-sheet
(6).
The shell-side gasket (7) is suitably rotated over the tube-sheet (6) and the
replacement of shell side gasket (7) is completed by its free rotation over the U-tube
bundle (5) and placing the shell-side gasket (7) on the elliptical groove in the shell-
flange (2).
Revised arrangement of the heat-transfer tubes (5) in the tube sheet (6) finds its use in
increasing the smoothness of gliding the shell-side gasket (7) over the tube-sheet (6).
Further, there is provided recess on shell-side flange (2), tube-sheet (6), channel side
flange.
Further, the shell-side flange is also of elliptical shape and hence the shell-side gasket
(7) can be slipped easily because of their elliptical shape.
The shell-side flange (2) has suitable raised face or recess for accommodating the
shell-side-gasket (7).

The dimensional features of the shell-side gasket (7) can be arrived through Finite
Element Analysis (FEA) or through iteration and conducting hydro-test for the required
working pressure.
The tube-sheet (6) and the shell-side gasket (7) are elliptical in shape. The tube-sheet
(6) is flattened suitably. The elliptical opening in the shell-side-gasket (7) and the
flatness on the tube-sheet (6) ease the gliding of the shell-side gasket (7) over the
tube-sheet (6).

WE CLAIM:
1. A hair-pin type heat exchanger as per Fig. 1, for replacing gasket easily without
complete removal of U-tube bundle assembly (5) comprises:
a cylindrical shell (1) with shell flange (2);
at least plurality of channel assembly (3) whichis also having channel flange (4);
at least plurality of U-tube bundle assembly (5) for holding tube sheets(6);
a shell-side gasket (7);
a channel-side-gasket (8);
heat transfer tubes (5), which are situated in the tube-sheet (6);
characterized in that the shell-side gasket (7), and tube sheet (6), are elliptical inshape
with suitable eccentricity, so that the shell-side gasket (7) can be slipped over the
tube-sheet (6) smoothly.
2. The hair-pin type heat exchanger as claimed in claim 1, wherein the channel-side
gasket (8) is placed between tube sheet (6) and the channel-flange (4).
3. The hair-pin type heat exchanger as claimed in claim 1, wherein U-tube bundle
assembly (5) is inside in the cylindrical shell(1) by keeping the tube-sheet (6)
between shell-flange (2) and channel-flange (4).
4. The hair-pin type heat exchanger as claimed in claim 1, wherein the U-tube
bundle assembly (5) is attached between shell-flange (2) and channel-flange (4)

by means of a set of fasteners (9 and 10).
5. The hair-pin type heat exchanger as claimed in claim 1, wherein the tube-sheet
(6) is flattened and the shell side gasket is an elliptical ring so that the gasket
can easily glide over the tube sheet (6).
6. The hair-pin type heat exchanger as claimed in claim 1, wherein the minor axis
of tube sheet (6) is smaller than the major axis of shell side gasket (7).
7. The hair-pin type heat exchanger as claimed in claim 1, wherein to replace the
shell-side gasket (7), it is rotated over the tube sheet (6) so that the major axis
of gasket is perpendicular to the minor axis of the tube sheet (6).
8. The hair-pin type heat exchanger as claimed in claim 1, wherein the shell-side
flange, tube-sheet (6) and channel side flange (4) further comprises recess or
raised faces facilitates accommodation of shell-side gasket (7) through the outer
side of its elliptical ring.
9. The hair-pin type heat exchanger as claimed in claim 1, wherein shell-side flange
(2) and channel side flanges (4) have elliptical grooves for accommodating and
confining the shell-side gasket (7).

10. The hair-pin type heat exchanger as claimed in claim 1, wherein the tubes in
tube bundle assy (5) are arranged in tube sheet (6) so as to enable smooth
gliding of the shell side gasket over the tube sheet (6).
11. The hair-pin type heat exchanger as claimed in claim 1, wherein the dimensional
features of the shell-side gasket (7) is achieved through Finite Element analysis
(FEA) or through iteration.