FIELD OF THE INVENTION
The present invention generally relates to manufacturing of check valves for high
temperature and medium pressure applications. Particularly, the invention relates to
manufacturing of check valve for high pressure steam generators. More particularly
the invention relates to an improved disk and seat ring in the check valves.
BACKGROUND OF THE INVENTION
Normally, the check valve is used in the high pressure boilers, in the various systems
like evaporating system, startup system (re-circulating line) and superheated system
in order to allow the medium to flow in one direction only for the purpose of not
mixing the water with steam and steam with water so as to prevent the flow in the
opposite direction. The size of valve ranging from 1/4" to 2" depends upon the
pipeline where these valves are used for high temperature and medium pressure
(800 class) applications.
Referring to the figure 1, the valve body (02) is a casting with machined inlet and
outlet. In the middle of inlet and outlet, boring and threading operations are carried
out centrally for screwing the flat contact seat ring (01). Stellite deposition (07) is
carried out internally in the flat contact seat ring (01) and also stellite deposition (08)
is carried out in the flat contact disk (03) followed by machining operation. Welding
inspection is carried out in the machined surface of flat contact disk (03) and flat
contact seat ring (01). If any defect is observed in the stellite deposit portion of flat
contact disk (03) or flat contact seat ring (01), then the component will be re-
welded, re-machined and re-inspected. Finally the components required for valve
assembly is moved to assembly section.

In assembly, the lapping operation is carried out in the flat contact seat ring (01) and
flat contact disk (03) for desired finish by lapping machine. After that, flat surface
seat ring (01) is screwed with valve body (02) and a spiral gasket (04) is inserted in
the valve body (02). Flat surface disk (03) is inserted in the cover plate (05) and it is
assembled with valve body (02) by means of tightening the four numbers of
hexagonal bolt (06).After that, 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 (03) and flat contact seat ring (01).Then the valve is dismantled for
correcting the surface of flat contact disk (03) and flat contact seat ring (01) for re-
lapping. Lot of time and skill is required for lapping the flat contact disk (03) and flat
contact seat ring (01). Again Valve is assembled and re tested for zero leakage
before final inspection.
We are manufacturing more than 500 no of check valves per year and huge quantum
of valves are being booked for every year to be manufactured and delivered timely.
Hence, we need to find out an alternate method of manufacturing and assembling of
the check valves to eliminate the rework.
OBJECTS OF THE INVENTION
It is therefore, an object of the invention is to propose a new design of disk and seat
matching in the manufacturing of the check valves.
Another object of the invention is to propose a perfect seating of the disk and seat
ring.
A further object of the invention is to modify the shape of the disk and seat ring to
match perfect seat of disk with seat ring. A still further object of the invention is to
propose an angular contact between disk and seat ring.

SUMMARY OF THE INVENTION
Accordingly as shown in the figure 2, the valve body is a casting with machined inlet
and outlet. In the middle of inlet and outlet, boring and threading operations are
carried out centrally for screwing the angular contact seat ring. Stellite deposition is
carried out internally in the angular contact seat ring followed by machining
operation. Stellite deposition is carried out externally in the angular contact disk
followed by machining operation. Welding inspection is carried out in the machined
surface of angular contact disk and angular contact seat ring. If the defect is found
in the stellite deposit portion of angular contact disk and angular contact seat ring,
then re-welding, re-machining and re-inspection is carried out for repairing the
defects. Finally the components required for valve assembly is moved to assembly
section.
In assembly, lapping operation is carried out in the angular contact disk and angular
contact seat ring. After that, angular contact seat ring is screwed centrally with valve
body. Spiral gasket is inserted in the body. After that, angular contact disk is inserted
in the cover plate which is fully tightened with the valve body by means of tightening
the four numbers of hexagonal bolt. Then the valve assembly is moved to hydro
testing. While hydro testing, it is found that no leakage occurred in the new type
check valve and valve is completed with final inspection.
This not only reduces the process time, but also reduces the lot of reworks and
increases the productivity. 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 check valves. Now, this new method of manufacturing of forged high
medium pressure check valve leads to increase the productivity to two times more
than existing method of manufacturing check valve.

Accordingly, the disk is manufactured with a tapered portion at the bottom side and
corresponding matching taper is made in the seat ring so that, while applying
pressure on the disk, it won’t affect the alignment and hence leakage is totally
avoided. Hence, rework due to seat leak is eliminated. Thereby, substantial saving in
time and money.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS.
Figure 1 shows the sectional views of a prior art check valve assembly with all the
part assembled.
Figure 2 shows the sectional view of a forged medium pressure check valve assembly
with all the part assembled according to the invention.
Figure 3 shows the isometric view of forged medium pressure check valve assembly
according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE
INVENTION
Accordingly as shown in the figure 2, the valve body (02) is a casting with machined
inlet and outlet. In the middle of inlet and outlet, boring and threading operations
are carried out centrally for screwing the angular contact seat ring (09). Stellite
deposition (12) is carried out internally in the angular contact seat ring (09) followed
by machining operation. Stellite deposition (11) is carried out externally in the
angular contact disk (10) followed by machining operation. Welding inspection is
carried out in the machined surface of angular contact disk (10) and angular contact
seat ring (09). If the defect is found in the stellite deposit portion of angular contact
disk (10) and angular contact seat ring (09), then re-welding, re-machining and re-
inspection is carried out for repairing the defects. Finally the components required for
valve assembly is moved to assembly section.

In assembly, lapping operation is carried out in the angular contact disk (10) and
angular contact seat ring 09). After that, angular contact seat ring is screwed
centrally with valve body (02). Spiral gasket (04) is inserted in the body. After that,
angular contact disk (10) is inserted in the cover plate (05) which is fully tightened
with the valve body (02) by means of tightening the four numbers of hexagonal bolt
(06). Then the valve assembly is moved to hydro testing. While hydro testing, it is
found that no leakage occurred in the new type check valve and valve is completed
with final inspection.
This not only reduces the process time, but also reduces the lot of reworks and
increases the productivity. 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 check valves. Now, this new method of manufacturing of forged high
medium pressure check valve leads to increase the productivity to two times more
than existing method of manufacturing check valve.
Description of Parts:
1- Flat contact seat ring 07-Stellite deposition on the flat contact seat ring
2- Valve body 08- Stellite deposition on the flat contact disk
03-Flat contact disk 09- Angular contact seat ring
04-Spiral gasket 10-Angular contact disk
05-cover Plate 11- Stellite deposition on the angular contact disk
06-Hexagonal bolt 12- Stellite deposition on the angular contact seat ring

WE CLAIM:
1. A method of manufacturing forged medium check valve with angular contact
disk and seat ring for high temperature and medium-pressure applications,
the method comprising the steps of;
- casting a valve body (02) with machined inlet and outlet and carrying out in
the middle of the inlet and outlet a boring including threading operations
centrally for screwing an angular contact seat ring (09);
- internally carrying out a stellite deposition (12) in the angular contact seat ring
(09) followed by machining operation and stellite deposition (11) externally in
an angular contact disk (10), further followed by machining operation;
- subsequently carried out welding inspection in the machined surface of the
angular contact disk (10) and the angular contact seat ring (09) to detect any
defect in the stellite deposit portion of said angular contact disk (10) and
angular contact seat ring (09), if any defect noticed through the welding
inspection, carrying-out re-welding, re-machining and re-inspection for
repairing the defects;
- moving the inspected valve assembly components to assembly section for
carrying out lapping operation in the angular contact disk (10) and angular
contact seat ring 09), followed by centrally screwing the seat ring (09) with
the valve body (02);

- inserting spiral gasket (04) in the body (02), and further inserting the angular
contact disk (10) in the cover plate (05) which is fully tightened with the valve
body (02) by means of tightening at least four numbers of hexagonal bolt
(06), and hydro testing of the manufactured check valve for leakage.