FIELD OF THE INVENTION
The present invention relates to a process for in situ replacement of damaged
casing of emergency stop valve and control valve so as to be synchronizingly
operable with an existing HP-casing in a high pressure reaction steam turbine.
BACKGROUND OF THE INVENTION
According to the prior art, High pressure reaction steam turbine (HPT) comprises
emergency stop valve (ESV) and control valve (CS). The individual ESV & CV
casings and HP casing, are made to match each other during the final assembly.
While manufacturing these components their compatibility with respect to their
contact surfaces are ensured. They are assembled together and locked by
tightening of breech but which connects the ESV & CV casing at one end and the
High Pressure Casing at other end. In this fixed position, the dowel holes (half
portion of dowel holes in HP casing and half portion in Valve portion) are
configured through the holes available in the breech nut. Dowel pins are inserted
in these dowel holes. The purpose of the dowel pins is to properly locate the
assembly as well as to resist any tendency of relative movement between the
ESV & CV casing with respect to the HP casing. After completion of this trial
assembly, the components are dismantled and dispatched to Power Plant Site for
final assembly at site. In case of discrepancy or damage noticed in any of the
components i.e. ESV & CV casing and HP casing at site, the components are
brought back to the manufacturing shop for repair/replacement and further trial
assembly. Thus, the entire additional activities causing avoidable time and cost
implications.

According to the existing procedure, the ESV & CV casing is manufactured and a
trial assembly with the HP casing is done in the manufacturing plant. The
inspection process of these two assemblies involve colour matching of the inlet
insert part of ESV & CV casing with the inlet part of the HP casing. After perfect
colour matching of the mating surfaces a punch marking in the same orientation
is done on inlet insert part of ESV & CV body with respect to HP inlet part after
full tightening the Breech nut over it. Once full tightening of the breech nut is
done, dowel holes in the inlet insert and HP casing inlet part are made through
available holes of the Breech nut. Half portion of the holes are thus made in the
inlet insert portion and other half portion of dowel holes are made in the HP
casing inlet part. After making of the dowel holes, inlet insert of the ESV & CV
casing is dismantled/removed along with breech nut. After that final welding of
an inlet insert with the valve body is carried out as per the punch marked
orientation on inlet insert. Once the assembly requirements are achieved and
component's compatibility with each other is ensured, the ESV & CV casing and
HP Casing are dispatched in disassembled condition to site.
Accordingly, there exists a need to innovate an assembly process which avoids
the necessity of using a combination of shop-assembled ESV & CV casing.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to propose a process for in situ
replacement of damaged casings of emergency stop valve and control valve so
as to be synchronizingly operable with an existing HP casing in a high pressure
reaction steam turbine.

A further object of the invention is to propose a process for in situ replacement
of damaged casings of emergency stop valve and control valve so as to be
synchronizingly operable with an existing HP casing in a high pressure reaction
steam turbine, which saves time and cost on account of repair or replacement of
damaged components.
SUMMARY OF THE INVENTION
Accordingly, there is provided a process for in-situ replacement of damaged
casings of emergency stop valve and control valve to be synchronously operable
in combination with an existing casing of a high pressure reaction steam turbine,
the process comprising the steps of: (i) cleaning the contact surfaces of the inlet
insert of the ESV & CV casing and the HP casing inlet side; (ii)moving the breach
nut towards the extreme end of the ESV and removing the foreign
particles/dents from the breech nut; (iii) applying molykote on the threads of
breech nut, inlet insert and HP casing inlet side; (iv) applying blue on the inlet
insert face; (v)slowly moving the breach nut after proper alignment on the inlet
insert side and start normal tightening with the HP casing without U-seal ring;
(vi)after proper tightening of the breech nut checking through breach nut holes
between the HP casing inlet part and inlet insert surface of the ESV & CV casing
to ensure that no gap remains between the sealing; (vii) loosening the breech
nut and removing high spots on HP casing inlet face by fine emery oil stone;
(viii) repeating the steps (iii) to (v) to ensure proper colour contact; (ix)marking
location of dowel holes of the inlet inserts with respect to HP casing inlet holes.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 Shows an assembly of the casing of emergency stop valve, and
control valve with the casing of high pressure reaction steam
turbine of the invention.
Figure 2 Shows ESV casing and CV casing with inlet insert and breech nut of
the assembly of figure 1.
DETAIL DESCRIPTION OF THE INVENTION
The outer casing of the HPT is configured as a barrel type casing without any
axial joint. An axially split inner casing (2) is arranged in the barrel type HP outer
casing (1) (refer figure 1). The steam lines from the main stop and control valves
are connected to the inlet connection of the outer casing (1) by a plurality of
Breech nuts (3), through buttress threading arranged at both ends. Sealing is
achieved by U-seal ring (5) [refer fig-1], which each is forced against the outer
sealing surface by the inlet steam pressure. The annular space around the
sealing ring (5) is connected to the condenser through a steam leak off lime. A
plurality of cylindrical pin or dowel pin (6) are located at the joint flange to
prevent rotation of the inlet pipe with respect to the outer casing.
Assembly requirements of the casings (7) for ESV and CV (refer Fig-2) with the
HP casing (1) (refer Fig-l),warrants a surface contact between an Inlet Insert (4)
(refer Fig-1), of the ESV and the CV casing (7) (refer Fig-2), and inlet part of the
HP outer casing (1). This is ensured by proper machining and colour contact
between the mating surfaces during manufacturing and trial assembly at
manufacturing workshop.

Any mismatch or improper contacts between these two connecting surfaces will
result into steam leakage which is not permitted.
Also during assembly of the ESV & CV casing (7) with HP casing (1), after full
tightening of the Breech nut (3), dowel holes are made through the holes in the
Breech nut (3). These dowel holes are made in such a way that half of their
portion (semi circular cross section) are in the inlet insert body (4) and half of
their portion (semi circular cross section) in remains the HP casing inlet portion.
These dowel holes are used to hold cylindrical pins (6) which prevent rotational
movement of the ESV & CV casing (7) with respect to the HP casing (1) as well
as it locates the position of the ESV/CV casing (1) with respect to the HP casing
(1) for which the both surfaces are marked.
According to the inventive process, the following sequential steps are performed:
(i) cleaning the contact surfaces of the inlet insert of the ESV & CV casing
and the HP casing inlet side;
(ii) moving the breach nut towards the extreme end of the ESV and removing
the foreign particles/dents from the breech nut;
(iii) applying molykote on the threads of breech nut, inlet insert and HP casing
inlet side;
(iv) applying blue on the inlet insert face;
(v) slowly moving the breach nut after proper alignment on the inlet insert
side and start normal tightening with the HP casing without U-seal ring;

(vi) after proper tightening of the breech nut checking through breach nut
holes between the HP casing inlet part and inlet insert surface of the ESV
& CV casing to ensure that no gap remains between the sealing;
(vii) loosening the breech nut and removing high spots on HP casing inlet face
by fine every/oil stone;
(viii) repeating the steps (iii) to (v) to ensure proper colour contact;
(ix) marking location of dowel holes of the inlet inserts with respect to HP
casing inlet holes.
A) Dowel holes of HP casing and Inlet Insert of ESV & CV casing not
overlapping:-
making half/semi circular crossection stubs and place them in front of
breech nut holes from where the drilling is to be done;
making pilot drills at the corresponding locations;
carrying out final drilling and dowelling;
loosening the breech nut and moving the breech nut towards extreme end
of the ESV and removing the foreign particles/dents from breech nut; and
applying molykote on threads of breech nut, inlet insert and HP casing
inlet side and finishing the final assembly.

B. Dowel holes of HP casing and Inlet Insert of ESV & CV casing are
overlapping
making matching crossection stubs of casing dowel holes as well as inlet
insert dowel holes and place them in front of breech nut holes from where
the drilling is to be done;
making pilot drills at the corresponding locations; and
carrying out final drilling and dowelling; and
loosening the breech nut and moving the breech nut towards extreme end
of ESV and clean/remove the foreign particles/dents from breech nut; and
applying molykote on threads of breech nut, inlet insert and HP casing
inlet side and carrying out the final assembly .

WE CLAIM :
1. A process for in-situ replacement of damaged casings of emergency stop
valve and control valve to be synchronously operable in combination with
an existing casing of a high pressure reaction steam turbine, the process
comprising the steps of :
(i) cleaning the contact surfaces of the inlet insert of the ESV & CV casing
and the HP casing inlet side;
(ii) moving the breach nut towards the extreme end of the ESV and removing
the foreign particles/dents from the breech nut;
(iii) applying molykote on the threads of breech nut, inlet insert and HP casing
inlet side;
(iv) applying blue on the inlet insert face;
(v) slowly moving the breach nut after proper alignment on the inlet insert
side and start normal tightening with the HP casing without U-seal ring;
(vi) after proper tightening of the breech nut checking through breach nut
holes between the HP casing inlet part and inlet insert surface of the ESV
& CV casing to ensure that no gap remains between the sealing;
(vii) loosening the breech nut and removing high spots on HP casing inlet face
by fine every/oil stone;
(viii) repeating the steps (iii) to (v) to ensure proper colour contact;
(ix) marking location of dowel holes of the inlet inserts with respect to HP
casing inlet holes.
2. The process as claimed in claim 1, wherein when the dowel holes of the
HP-casing and that of the insert of the ESV and CS casings are not
overlapping, the process further comprising the proceeding steps of:

making half/semi circular crossection stubs and place them in front of
breech nut holes from where the drilling is to be done;
making pilot drills at the corresponding locations;
carrying out final drilling and dowelling;
3. The process as claimed in claim 1, wherein when the dowel holes of the HP-
casing and that of the insert of the ESV and CS casings are overlapping, the
process further comprising the proceeding steps of:
making matching crossection stubs of casing dowel holes as well as inlet
insert dowel holes and piace them in front of breech nut holes from where
the drilling is to be done;
making pilot drills at the corresponding locations; and
carrying out final drilling and dowelling;

ABSTRACT

The invention relates to a process for in-situ replacement of damaged casings of
emergency stop valve and control valve to be synchronously operable in
combination with an existing casing of a high pressure reaction steam turbine,
the process comprising the steps of: cleaning the contact surfaces of the inlet
insert of the ESV & CV casing and the HP casing inlet side; moving the breach
nut towards the extreme end of the ESV and removing the foreign
particles/dents from the breech nut; applying molykote on the threads of breech
nut, inlet insert and HP casing inlet side; applying blue on the inlet insert face;
slowly moving the breach nut after proper alignment on the inlet insert side and
start normal tightening with the HP casing without U-seal ring; after proper
tightening of the breech nut checking through breach nut holes between the HP
casing inlet part and inlet insert surface of the ESV & CV casing to ensure that no
gap remains between the sealing; loosening the breech nut and removing high
spots on HP casing inlet face by fine every/oil stone; repeating the steps (iii) to
(v) to ensure proper colour contact; marking location of dowel holes of the inlet
inserts with respect to HP casing inlet holes.