FIELD OF INVENTION
The present invention relates to a new cross around pipe with new arrangement of
bellows, stiffener rod and pipe connections for 600 MW turbine with two LP cylinders.
More particularly, the invention relates to a new design and arrangement of cross
around pipe along with bellows, stiffener rods and pipe connections for four cylinder
machine having two cylinders of LP. without a conventional Push rod arrangement.
BACKGROUND OF THE INVENTION
BHEL is introducing new rating steam turbines of 600 MW by combining their well
proven existing modules. This configuration comprises of one HP (High Pressure)
cylinder, one IP (Intermediate Pressure) cylinder and two LP (Low Pressure) cylinders
connected in series with Turbo generator.
Cross Around Pipe is a critical component of Steam Turbine. It carries steam exhaust
from IP cylinder to LP cylinder for further expansion and power production. The Cross
Around Pipe is rigidly connected to outlet of IP cylinder at one end and to inlet of LP
cylinders at other end.
Generally for four cylinder machines having two cylinders of LP, a push rod
arrangement is used by manufacturer's world over to contain differential thermal
expansions between LP casings and LP rotors.
BHEL has designed four cylinder machine of 600 MW without push-rod, so that it can
use its existing well proven modules only by combining them differently. For such
arrangement controlling thermal strains in cross around pipe having steam inlet into
two LP cylinders is a bit difficult and required a new combination of bellows, stiffener
rods and intermediate pipes to keep the design safe on operation.
Hence, there was a need to design a new Cross Around Pipe with different arrangement
of bellows, stiffener rods and pipe connections for this new module combination of 600
MW steam turbine.
OBJECTS OF THE INVENTION
Therefore it is an object of the invention to propose a new cross around pipe with new
arrangement of bellows, stiffener rods and pipe connections for 600 MW turbine with
two LP cylinders which is capable of carrying steam from one IP cylinder exhaust to
inlet connections of two LP cylinders in series with I.P. turbine.
Another object of the invention is to propose a new cross around pipe with new
arrangement of bellows, stiffener rods and pipe connections for 600 MW turbine with
two LP cylinders which can optimize the thermal strains to least value by suitably
locating different bellows and pipe segments of cross around pipe.
A still another object of the invention is to propose a new cross around pipe with new
arrangement of bellows, stiffener rods and pipe connections for 600 MW turbine with
two LP cylinders which optimizes the number of convolutions in each bellow so that
thermal strains in all the bellows are within limits.
Yet another object of the invention is to propose a new cross around pipe with new
arrangement of bellows, stiffener rods and pipe connections for 600 MW turbine with
two LP cylinders which is capable of effectively distribute thermal strains among bellows
to keep them within limits by suitably arranging stiffener rods connecting bellows.
A further object of the invention is to propose a new cross around pipe with new
arrangement of bellows, stiffener rods and pipe connections for 600 MW turbine with
two LP cylinders which can maintain low stresses in the newly designed stiffener rods.
A still further object of the invention is to propose a new cross around pipe with new
arrangement of bellows, stiffener rods and pipe connections for 600 MW turbine with
two LP cylinders where newly designed spring supports can carry the weight of the
cross around pipe assembly without causing any loading of IP and LP turbine
connections with the cross around pipe.
Yet another object of the invention is to propose a new cross around pipe with new
arrangement of bellows, stiffener rods and pipe connections for 600 MW turbine with
two LP cylinders which is capable of making easy access to areas near IP and LP
turbine connections by suitably designing and locating the manhole in the cross around
pipe.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig.l - Detailed Description of invented design of Cross Around Pipe assembly
Fig.2 - Details of slider support arrangements
Fig.3 - Details of Spring Support Arrangements
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
Three bellows (1,2,3) are located in the segment of pipe carrying steam from IP
exhaust towards both the LP cylinders before the pipe segment branch of inlet to the
LP-1 cylinder. The number of convolutions in each of the bellows is 10. Two bellows
(1,2) are connected directly with each other very near to elbow end of the Cross
Around Pipe segment coming from IP connection. One bellow (3) of 10 convolutions is
connected in the pipe near to the branch pipe segment of LP-1 inlet connection. A small
pipe segment is put in between the bellow (3) and the branch pipe ofLP-1 inlet
connection. A long pipe segment is put between the bellow (3) and bellow (4) before
the reducer pipe segment (10). Two stiffener rods (8) are connected between all the
bellows. The stiffener rods (8) are provided with two pin type hinged joints (17) and
two slider supports (15) for each stiffener rod (8) arrangement. These hinged joints
(17) are provided to further redistribute the thermal strains between bellows (1,2,3,4)
by allowing the transverse movement of pipe segments and for relieving the stress at
the welded ends of stiffener rods (8) with the stiffening box (16).
The slider support of (15) are provided to support the weight of stiffener rods (8),so
that they don't sag causing excessive stresses at the weld joint of the stiffener rods
with the stiffening box (18). At the same time they help in constraining the expansion
of stiffener rods in axial and transverse direction only and avoiding angular movement.
After the reducer (10) two bellows (5,6) of 10 convolutions each are placed after
welding them together. They are placed near the bend of pipe segment of inlet of LP-2
cylinder. After the inlet branch of LP-2 cylinder one pipe segment (12) along with one
bellow (7) is provided for pressure balancing. Two stiffener rods (9) are provided
connecting bellows (5,6) after the reducer (10) and the bellow (7) after pressure
balancing arrangement. Slider supports (16) are provided to these stiffener rods (9)
also for supporting them against sagging due to own weight. This pressure balancing
arrangement eases out the thermal strains in all the affected bellows (5,6,7).
Three man-holes (11) are provided near the connection of the Cross Around Pipe with
IP, LP-1 and LP-2 cylinders. These man-holes (11) provide opportunity to inspect the
exhaust area of IP turbine and inlet area of respective LP turbine by allowing man to
creep in through the hole and inspect. Without dismantling the turbine, these holes can
be useful for monitoring the condition of turbine blades by visually inspecting turbines
through them.
Thermocouples (19) are provided at the exhaust pipe segment of IP turbine and before
bellow (4). These thermocouples (19) can be used for monitoring the temperature of
steam inside the Cross Around Pipe at identified critical locations.
Spring support arrangement (13, 14) having helical spring between two supporting
plates is provided at identified locations for supporting the weight of the whole Cross
Around Pipe assembly. They help in reducing the reaction force at the weld point of the
Cross Around Pipe with the IP and LP1/2 cylinders and hence reducing the stresses at
the weld connection of the pipe with the IP turbine casing and turbine casings of LP-1
and LP-2 cylinders. Two kinds of spring support arrangements (13, 14) are used. One
(13), which is connected to the pipe directly and another (14), which is located below
the stiffening box (18).
These supports (13, 14) are fixed at turbine-generator (TG) deck and the weight of the
Cross around Pipe assembly is transferred through the supporting plates (21) and
spring (20) to the TG deck. Four numbers of such supports (14) are provided below the
stiffening box (18) and one number of support (13) is provided below the pipe segment
at the IP exhaust end.
WE CLAIM
1. A new cross around pipe with new arrangement of bellows, stiffener rods and
pipe connections for 600 MW turbine with two LP cylinders comprising:
cross around pipe (20) segment for carrying steam from IP exhaust to a plurality
of LP cylinders;
a plurality of bellows (1,2,3) disposed in the segment of pipe carrying steam
when two bellows (1,2) connected directly with each other very near to elbow
end of the cross around pipe segment (20) coming from IP connection;
one bellow connected in the pipe (20) near to the branch pipe segment of LP-1
inlet connection;
a long pipe segment put between the bellow (3) and bellow (4) before the
reducer pipe segment (10);
a plurality of stiffener rods (8) connected between these bellows (1,2,3,4) for
uniform distribution of thermal strains among all the bellows;
the said stiffener rods provided with a plurality of pin type hinged joint (17);
a plurality of bellows (5,6) welded together placed near the bend of pipe
segment of inlet of LP-2 cylinder;
one pipe segment (12) along with one elbow (7) disposed after the inlet branch
of LP-2 cylinder for pressure balancing;
a plurality of stiffener rods (9) connecting bellows (5,6) after the reducer (10)
and the bellow (7);
a plurality of man-holes (11) disposed near the connection of the cross around
pipe (20) with IP, LP-1 and LP-2 cylinders; characterized in that,
a plurality of thermocouples (19) are provided at the exhaust pipe segment of IP
turbine and before bellow (4) for monitoring the temperature of steam inside the
cross around pipe (20) at identified critical locations wherein spring support
arrangement (13,14) having helical spring between two supporting plates at
identified locations for supporting the weight of the whole cross around pipe (20)
assembly, when the slider arrangements (15,16) are provided to support the
weight of stiffener rods and in constraining the movement of stiffener rods in
the transverse and axial directions only.
2. A new cross around pipe with new arrangement of bellows, stiffener rods and
pipe connections as claimed in claim 1, wherein the number of convolutions in
each of the bellows (1,2,3) is 10.
3. A new cross around pipe with new arrangement of bellows, stiffener rods and
pipe connections as claimed in claim 1 and 2, wherein the two bellows (5, 6) are
of 10 convolutions.
4. A new cross around pipe with new arrangement of bellows, stiffener rods and
pipe connections as claimed in claim 1 to 3, wherein spring support arrangement
(13, 14) has helical spring between two supporting plates.
5. A new cross around pipe with new arrangement of bellows, stiffener rods and
pipe connections as claimed in claim 1 to 4, wherein one spring support
arrangement (13) is connected to the pipe directly and another (14) is located
below the stiffening box (18) when the said both support arrangement are fixed
at turbine-generator deck.

A new cross around pipe (20) with new arrangement of bellows, stiffener rods and pipe
connections consists of a plurality of bellows (1,2,3,4,5,6,7) of 10 convolutions each
arranged between different pipe segments and reducer (10). Stiffener rods (8,9) are
connected between bellows with the help of stiffener boxes (18) for uniform distribution
of strains among bellows. In the LP-1 branch hinged joints (17) are provided in the
stiffener rods. Slider arrangements (15, 16) are disposed to support the stiffener rods
(8, 9). A plurality of man holes are provided near the connection of the cross around
pipe with IP, LP-1 and LP-2 cylinders for inspection of exhaust area of IP turbine and
inlet area of respective LP turbine. Thermocouples (19) are provided at the critical
locations to monitor the temperature of the steam inside the pipe. The whole assembly
of Cross Around pipe (20) is supported on springs support arrangements (13, 14).