FIELD OF THE INVENTION
The present invention generally relates to manufacturing of non-return valves for
high temperature and high pressure steam generators. In particular, the invention
relates to an improved non-return valve without welding between body and stub as
well as stub and bonnet. More particularly the invention relates to a method of weld-
less manufacturing of forged high pressure non-return valve for high temperature
and high pressure applications.
BACKGROUND OF THE INVENTION
Normally, the check valve is used in the high pressure boilers, in the various system
like flow discharge line, feed water line (economizer inlet) and spray system in order
to allow the medium to flow in one direction only for the purpose of not mix the
water into steam and steam into water so as to prevent the flow in the opposite
direction.
Referring to the figure 1, the valve body (01) is machined for inlet and outlet. In the
middle of inlet and outlet boring operation is carried out centrally and stellite
deposition (05) is carried out followed by post weld heat treatment. The valve body
(01) is welded with stub (08) by means of conventional Tungsten Inert Gas (TIG)
welding for root and subsequently followed by manual arc welding process. The size
of valve ranging from 1/4" to 2" depends upon the pipeline where these valves are
used for high temperature and high pressure (1500 and 2500 class) applications. The

above welding process is limited for carbon steel and low alloy steels of grade F22
suited upto 525 deg C. For the temperature range more than 525 deg C, F91 alloy
steel materials are used for body and stub. The welding process is very stringent for
F91 alloy materials because of pre-heat, post heat and stress relieving requirements.
The machining operation is carried out internally on the stellite deposit portion of flat
contact seat (02) and externally on the stellite deposit portion of flat contact disk
(06) for desired finish.
In assembly, lapping operation is carried out on the flat contact seat (02) and flat
contact disk (03). After that, flat contact disk (03) is inserted in the bonnet (04) and
screwed with valve body (01), then the valve assembly is moved to hydro testing.
While hydro testing of valve, it is found that leakage occurred due to improper
matching of flat contact disk (02) and flat contact seat (03).The valve is dismantled
for correcting the surface of flat contact disk (02) and flat contact seat (03)for re-
lapping. Lot of time and skill is required for lapping the flat contact disk (03) and flat
contact seat (02). Again valve is assembled and re tested. The valve assembly is
moved to welding section for welding the bonnet (04) and stub (06).After that,
welding inspection is carried out in the stub and bonnet welded area (09).If the
defect is found in the welding, repairing takes more time for gouging, grinding,
welding and again testing. This leads to more lead time for the assembly.
Hence, there is a need to find out a new method of making the valve body (01) and
other components as one assembly, without involvement of welding. These problems
are to be addressed while developing a new method of manufacturing non return
valve for the above applications.

OBJECTS OF THE INVENTION
It is therefore, an object of the invention is to propose a new forged high non return
valve without welding of body, stub and bonnet.
Another object of the invention is to propose a method of making access for
repairing stellite deposition.
A still another object of the invention is to propose a new design of disk and seat
matching.
A further object of the invention is to propose a single casting valve body without
welding.
A still further object of the invention is to propose a method of weld-less
manufacturing of forged high pressure non-return valve, for high temperature and
high pressure applications.
SUMMARY OF THEINVENTION
Accordingly as shown in the figure 2, a new modified valve body is machined for inlet
and outlet. In the middle of inlet and outlet boring operation is carried out centrally
and stellite deposition is carried out in the angular contact seat followed by post weld
heat treatment. Then the modified valve body is moved to machine shop for

machining the stellite deposit portion of angular contact seat. Stellite deposition is
carried out externally in the angular contact disk followed by machining operation.
For ensuring line contact the degree of angular shape in the angular contact seat is
always maintained more than one degree given in the angular contact disk .After
that, the components are moved to assembly section.
In assembly, lapping operation is carried out in the angular contact disk and angular
contact seat. Spiral wound gasket is inserted in the modified valve body. After that,
angular contact disk is inserted into the modified bonnet and it is fully tightened with
the modified valve body by means of suitable spanner. Then the valve assembly is
moved to hydro testing. While hydro testing, it is found that no leakage occurred in
the new type non return valves and valve is completed with final inspection.
By means of the above assembly, the angular contact provides perfect seating and it
is found that there is no leakage during the hydro testing of non-return valves. The
whole welding process is eliminated and the drawbacks said in the background are
eliminated. Moreover, we introduce a spiral wound gasket which prevents the shell
leakage during hydro testing. This not only reduces the process time, but also
reduces the more rework and increases the productivity.
Now, this new method of manufacturing of forged high pressure non return valve
leads to increase the productivity to two times more than existing method of
manufacturing of non-return valve.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 shows the sectional views of existing assembly with all the part assembled.
Figure 2 shows the sectional view of the new forged high pressure non return valve
assembly with taper features introduced on disk and seat assembly and also with all
the part assembled with introduction of spiral wound gasket.
Figure 3 shows the isometric view of forged high pressure non return valve assembly
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE
INVENTION
Accordingly, as shown in the figure 2, the valve body and stub are integrated as a
single casting without welding and named as modified valve body (16) which is
machined for inlet and outlet. In the middle of inlet and outlet boring operation is
carried out centrally and stellite deposition (10) is carried out in the angular contact
seat (15) followed by post weld heat treatment. Then the modified valve body (16) is
moved to machine shop for machining the stellite deposit portion of angular contact
seat (15). Stellite deposition (14) is carried out externally in the angular contact disk
(13) followed by machining operation. For ensuring line contact the degree of
angular shape in the angular contact seat (15) is always maintained more than one
degree given in the angular contact disk (13). After that, the components are moved
to assembly section.

In assembly, lapping operation is carried out in the angular contact disk (13) and
angular contact seat (15). Spiral wound gasket (12) is inserted in the modified valve
body (16). After that, angular contact disk (13) is inserted into the modified bonnet
(11) and it is fully tightened with the modified valve body (16) by means of suitable
spanner. Then the valve assembly is moved to hydro testing. While hydro testing, it
is found that no leakage occurred in the new type non return valves and valve is
completed with final inspection.
By means of the above assembly, the angular contact provides perfect seating and it
is found that there is no leakage during the hydro testing of non-return valves. The
whole welding process is eliminated and the drawbacks said in the background are
eliminated. Moreover, we introduce a spiral wound gasket which prevents the shell
leakage during hydro testing. This not only reduces the process time, but also
increases productivity by reducing the rework and rejection rate.
Now, this new method of manufacturing of forged high pressure non return valve
leads to increase the productivity to two times more than existing method of
manufacturing of non-return valve.

WE CLAIM:
A method of weld-less manufacturing of forged high pressure non-return valve for
high temperature and high pressure applications, the method comprising the steps
of:
- integrating a valve body and stub as a single casting to form a modified
valve body (16) and machined for inlet and outlet;
- carrying-out a boring operation in the middle of the inlet and outlet and
conducting a stellite deposition (10) step in an angular contact seat (15)
followed by post weld heat treatment;
- machining the stellite deposit portion of the angular contact seat (15) and
carrying–out further a stellite deposition (14)) externally in the angular
contact disk (13) followed by machining operation to ensure that the line
contact of angular shape maintained at an angle of 45o in the angular
contact seat (15) which is more than at least one degree given in the
angular contact disk (13);
- carrying – out lapping operation in the angular contact disk (13) and
angular contact seat (15); and

- inserting a spiral wound gasket (12) in the modified valve body (16)
followed by insertion of the angular contact disk (13) into a modified
bonnet (11), the assembly being fully tightened with the modified valve
body (16) by means of a spanner, wherein the modified bonnet (11)
having a step to accommodate the spiral wound gasket (12) and thereby
allowing lamination of welded stub and bonnet.