FIELD OF THE INVENTION
The present invention relates to development of Hot Reheat Steam Strainer
Housing which is placed between Hot Reheat Pipe from boiler and IVCV Valves
for 306MW rating. More particularly, the invention relates to an improved process
for manufacturing a Hot Reheat Steam Strainer Housing to hold a steam strainer
for carrying steam from boiler is IP Turbine.
BACKGROUND OF THE INVENTION
The configuration of 306MW rating steam turbines generally comprises one HP
(High Pressure) cylinder, one IP (Intermediate Pressure) cylinder and one LP
(Low Pressure) cylinder connected in series with a Turbo generator.
HRH Steam Strainer Housing is a critical component of steam turbines, in a
steam strainer housing a steam strainer is placed to clean the steam coming
from Boiler and supply the steam to IP (Intermediate Pressure) turbine for power
production. At least two Steam strainer housing are disposed in hot reheat (HRH)
pipelines coming from the boiler to supply steam to the IP (Intermediate
Pressure) cylinder.
The temperature of the IP (Intermediate Pressure) turbine 306MW rating , is set
around 565°C which helps in achieving better heat rate .

Three cylinder machine of 306MW can be constructed by increasing the
parameters of its IP (Intermediate Pressure) for which design of Steam strainer
housings has been carried out. However, designing steam strainer housings to
match the increased parameters is a bit difficult, for which material selection,
design and analysis has been carried out for operating condition.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a new design for
manufacturing of Hot Reheat Steam Strainer Housing to hold a steam strainer for
cleaning the steam coming from boiler to IP Turbine.
Another object of the invention is to propose an improved design for Hot Reheat
Steam Strainer Housing to hold a steam strainer for cleaning steam coming from
boiler to IP Turbine which can be manufactured by casting process.
A still another object of the invention is to propose an improved design for
manufacturing a Hot Reheat Steam Strainer Housing to hold a steam strainer for
cleaning steam coming from boiler to IP Turbine in which the end diameters of
the housing matches with Hot Reheat pipe diameter and maintain the stresses to
allowable values.

Yet another object of the invention is to propose an improved design for
manufacturing a Hot Reheat Steam Strainer Housing to hold a steam strainer for
cleaning steam coming from boiler to IP Turbine, wherein the fillet in neck
contour including locations of changes in the Housing is optimized to ensure
minimization of stress developed.
A further object of the invention is to propose an improved design for
manufacturing a Hot Reheat Steam Strainer Housing to hold a steam strainer for
cleaning steam coming from boiler to IP Turbine, in which the inner contour of
the strainer housing allows easy removal of the strainer element during overhaul.
SUMMARY OF THE INVENTION
Accordingly, there is provided an improved design for manufacturing a Hot
Reheat Steam Strainer Housing to hold a steam strainer for carrying steam
coming from boiler to IP Turbine, the strainer housing disposed on the hot
reheat steam lines exiting from the boiler and connected to an interceptor valve
to prevent admission of foreign objects into the intermediate pressure turbine,
the process comprising the steps of casting a blanking means corresponding to
dimension of an inlet of the housing and constructing an internal slot;

fixing a steam strainer in the blanking means and fixing the subassembly
internally at an inlet of the housing; inserting a graphite gasket into the housing
followed by a protective ring; locating a segmental split ring on the slot of the
housing; a cover plate releasably attached to the housing via fastening means;
and a drain stub projecting from the housing for drainage of collected condensed
steam.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Figure 1 shows an improved Hot Reheat Steam strainer Housing assembly in first
angle projection according to the invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
A Steam Strainer is installed in the hot reheat line exiting from a boiler. The
strainer prevents admission of foreign objects into the IP turbine. This steam
strainer is located inside a strainer housing.
As shown in figure 1, a HRH steam strainer housing (1) is connected between
HRH steam pipes and an interceptor valve. HRH steam strainer (10) is welded
over a blanking device (2) of the housing (1), and then it is uplifted and located

inside the strainer housing. When the strainer (10) gets fixed inside the housing,
a graphite gasket (3) is inserted into the housing (1) followed by insertion of a
protective ring (4) and a segmental split ring (5) in a slot available in the
housing. This segmental split ring (5) protects the elements (2, 3 and 4) from
falling. A tightening cover (6) is inserted into which studs (7), washer (8) and
nuts (9) are tighten for final assembly.
A drain stub (11) welded with the blanking device (2) protrudes from the bottom
of the housing (1) which further connects a drain pipe. This drain stub (11) is for
drainage of collected condensed steam, if any.
HRH steam comes from the boiler through the HRH pipe via the strainer housing
(1), and the filtered steam goes to the IP turbine through IVCV valves.

WE CLAIM :
1. An improved process for manufacturing a Hot Reheat Steam Strainer
Housing to hold a steam strainer from carrying steam from boiler to IP
Turbine, the strainer housing disposed on the hot reheat steam lines
exiting from the boiler and connected to an interceptor vale to prevent
admission of foreign objects into the boiler via the intermediate pressure
turbine, the process comprising the steps of:
- forming a blanking means corresponding to dimension of an inlet of the
housing and constructing an internal slot;
- welding a steam strainer over the blanking means and fixing the sub-
assembly internally at an inlet of the housing;
- inserting a graphite gasket into the housing followed by a protective ring;
- locating a segmental split ring on the slot of the housing;
- a cover plate releasably attached at the inlet of the housing via fastening
means; and
- a drain stub projecting from the inlet of the housing for drainage of
collected condensed steam.

2. The process as claimed in claim 1, wherein the housing is formed of
casting material.
3. The process as claimed in claim 1 or 2, wherein the housing is formed
with a contour such that the end diameters of the housing matches that
of hot reheat pipes.
4. The process as claimed in claim 1, wherein the housing comprises
changed contours, and wherein the location of the changed contours are
optimized to maintain minimum stress application.