FIELD OF INVENTION

The present invention relates to a method of manufacturing an improved “Y” type glove valve for a steam generator. More particularly the invention relates to the method for manufacturing an improved “Y” type globe value for high temperature and high pressure applications in the steam generator with modified components and with modified sitting arrangement of valve assembly.
BACKGROUND OF THE INVENTION
Normally, the “Y” type globe valve is used in the various systems like start up and economizer line, Boiler Re-circulating Centrifugal Pump (BRCP) discharge isolation line, BRCP motor drain isolation line and super heater spray water drain isolation line, in order to control the flow. The size of valve ranging from 1” to 2-1/5” depends upon the pipeline where these valves are used for high temperature and high pressure (1500 and 2500 Class rating) applications. Materials used for the valves are SA105 grade material (carbon steel) and F22 grade material (alloy steel).
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 then stellite deposition (02) is carried out on the surface of valve body (01) and stellite deposition (04) is carried out in the bottom of lower stem (06). The machining operation is carried out on the stellite deposit portion of valve body (01) and on the stellite deposit portion of lower stem (06). After that, flat contact seat (03) in valve body (01) and flat contact seat (05) in lower stem (06) are machined for required finishing. After that, the other components like yoke (10), bonnet (08), graphoil gasket (07), yoke bush (14), clamp (12), upper stem (15), packing cartridge (09), locking screw (11), handle (16) and collar (13) are collected for valve assembly.

In valve assembly, all components and tools are collected for assembly and lapping operation is carried out on flat contact seat (03) of valve body (01) and flat contact seat (05) of lower stem (06) for required surface finish (.8µ) by lapping tool. The lower stem (06) is placed in the middle of valve body (01) then bonnet (08) is screwed into valve body (01) along with graphoil gasket (07). Packing cartridges (09) are inserted into bonnet (08). After that, yoke bush (14) is screwed into yoke (10) then yoke assembly is screwed with bonnet (08). After that, upper stem (15) is assembled with yoke assembly. A collar (13) is placed in the middle of lower stem (06) and upper stem (15), then clamps (12) are fitted and tightened by means of locking screws (11). Handle (16) is fixed at the end of upper stem (15).
Then the valve assembly is moved to hydro testing. While hydro testing of valve, if it is observed seat leakage and/or shell leakage then valve assembly is dismantled for rectifying the problems. Again, lapping operation is carried out and high level surface finish is obtained in the flat contact seat (03) in valve body (01) and flat contact seat (05) in the lower stem (06). Here, one of main cause for seat leakage is due to poor surface finish in the flat contact seat (03) in the valve body and flat contact seat (05) in the lower stem (06). And another cause is flat seating arrangement between the valve body (01) and lower stem (06). Shell leakage occurs due to gasket broken during excess tightening of bonnet in shell testing. This leads to more lead time for rectification work. Particularly, seat leakage in the valves were repeated many times. Hence, due to high rate of rework because of seat leakage, this “Y” type globe valve manufacturing was discontinued and more than 1500 no of components were hold as non-moving items. This leads loss of costly resources and increase in inventory.
Hence, there is a need to modify the seating arrangement in the valve body (01) and lower stem (06). Hence, there is a need to improve the valve design. These problems are addressed while designing the “Y” type globe valve for the above applications.

OBJECT OF THE INVENTION
Therefore, it is an object of the invention to propose a method of manufacturing an improved “Y” type globe valve for a steam generator, which is capable of preventing seat leakage and shell leakage of the valve assembly.
Another object of the invention is to propose a method of manufacturing an improved “Y” type globe valve for a steam generator which is able to stop high rate of rework because of seat leakage.
A still another object of the invention is to propose a method of manufacturing an improved “Y” type globe valve for a steam generator which is able to provide a new seating arrangement in valve body and to provide a modified sealing arrangement between bonnet and valve body by incorporating a new designed steam and disk assembly.
SUMMARY OF THE INVENTION
Accordingly, as shown in the figure 4, the valve body is machined for inlet and outlet. In the middle of inlet and outlet boring operation is carried out centrally then stellite deposition is carried out on the surface of valve body and stellite deposition is carried out in the disk. The machining operation is carried out on the stellite deposit portion of valve body and on the stellite deposit portion of disk. After that, angular contact seat in valve body and angular contact seat in disk are machined for required finishing. After that, the other components like yoke, bonnet, spiral wound gasket, yoke bush, disk retainer, thrust plate, lock ring, stem and handle are collected for valve assembly.

In valve assembly, all components and tools are collected for assembly and lapping operation is carried out on the angular contact seat of valve body and angular contact seat of disk for required surface finish by lapping tool. Referring figure.6, new stem-disc assembly consists of the following process, Disk retainer and lock ring are inserted into slot provided in the stem and thrust plate is placed in the step provided in the disk then disk is screwed with disk retainer.
Now, this stem-disk assembly is located in the middle of the valve body. Bonnet is screwed in the valve body along with spiral wound gasket. Packing cartridges are inserted into bonnet. After that, yoke bush is screwed into yoke then yoke assembly is screwed with bonnet. Finally, handle is fixed at the end of stem. Then, the valve assembly is moved to hydro testing. While hydro testing of valve, it is found that no seat leakage occurred in the new “Y” type globe valve and valve is completed with final inspection.
Accordingly, the disk is manufactured with a tapered portion at the bottom side and corresponding matching taper is made in the valve body so that, while applying pressure on the disk, it won’t affect the alignment and hence seat leakage is totally avoided. Hence, rework due to seat leak is eliminated. Moreover, we introduce a spiral wound gasket which prevents the shell leakage during hydro testing. Thereby, substantial saving in time and money.
In addition to that, components in existing valve assembly like lower stem, upper stem, locking screw, clamp and collar are eliminated and new components like disk, disk retainer, thrust plate, lock ring and stem are introduced in the new type valve assembly. We manufactured more than 100 no of valves by this new design from non-moving items (as stated above) with approval of boiler inspector and supplied to different work orders successfully. Now, this new method of manufacturing of “Y”

type globe valve leads to increase the productivity by reducing the rework and rejection rate.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 shows the sectional view of existing valve assembly with all the part assembled
Figure 2 shows the sectional view of valve body having flat contact seat
Figure 3 shows the sectional view of existing stem-disk assembly
Figure 4 shows the sectional view of new valve assembly with all the part assembled
Figure 5 shows the sectional view of valve body having angular contact seat
Figure 6 shows the sectional view of new stem-disk assembly
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
Accordingly, as shown in the figure 4, the valve body (01) is machined for inlet and outlet. In the middle of inlet and outlet boring operation is carried out centrally then stellite deposition (02) is carried out on the surface of valve body (01) and stellite deposition (17N) is carried out in the disk (19N). The machining operation is carried out on the stellite deposit portion of valve body (01) and on the stellite deposit portion of disk (19N). After that, angular contact seat (03M) in valve body (01) and angular contact seat (18N) in disk (19N) are machined for required finishing. After that, the other components like yoke (10), bonnet (08), spiral wound gasket (07M), yoke bush (14), disk retainer (20N), Thrust plate (21N), lock ring (22N), stem (23N) and handle (16) are collected for valve assembly.
In valve assembly, all components and tools are collected for assembly and lapping operation is carried out on the angular contact seat (03M) of valve body (01)

and angular contact seat (18N) of disk (19N) for required surface finish by lapping tool. Referring figure.6, new stem-disc assembly consists of the following process, Disk retainer (20N) and lock ring (22N) are inserted into slot provided in the stem (23N) and thrust plate (21N) is placed in the step provided in the disk (19N) then disk (19N) is screwed with disk retainer (20N). Now, this stem-disk assembly is located in the middle of the valve body (01). Bonnet (08) is screwed in the valve body (01) along with spiral wound gasket (07M). Packing cartridges (09) are inserted into bonnet (08). After that, yoke bush (14) is screwed into yoke (10) then yoke assembly is screwed with bonnet (08). Finally, handle (16) is fixed at the end of stem (23N). Then, the valve assembly is moved to hydro testing. While hydro testing of valve, it is found that no seat leakage occurred in the new “Y” type globe valve and valve is completed with final inspection.
Accordingly, the disk (19N) is manufactured with a tapered portion (17N) at the bottom side and corresponding matching taper (03M) is made in the valve body (1) so that, while applying pressure on the disk (19N), it won’t affect the alignment and hence seat leakage is totally avoided. Hence, rework due to seat leak is eliminated. Moreover, we introduce a spiral wound gasket (07M) which prevents the shell leakage during hydro testing. Thereby, substantial saving in time and money.
In addition to that, components in existing valve assembly like lower stem (06), upper stem (15), locking screw (11), clamp (12) and collar (13) are eliminated and new components like disk (19N), disk retainer (20N), thrust plate (21N), lock ring (22N) and stem (23N) are introduced in the new type valve assembly. We manufactured more than 100 no of valves by this new design from non-moving items (as stated above) with approval of boiler inspector and supplied to different work orders. Now, this new method of manufacturing of “Y” type globe valve leads to increase the productivity by reducing the rework and rejection rate.

We Claim

1. A method for manufacturing an improved ‘Y’ type globe valve for a steam
generator, the said method comprising the steps of; machining inlet and outlet of a valve body (01).
carrying out a boring operation in the middle of inlet and outlet;
carrying out a stellite deposition (02) on the surface of the valve body (01) and in a disk (19N);
carrying out a machining operation of stellite deposited portion of valve body (01) and of the disk (19N);
machining of angular contact seat (03M) of valve body (01) and angular contact seat (18N) of the disk (19N) to obtain a taper surface on both (03M, 18N) totally matching each other;
carrying out lapping operation on the machined surface of angular contact seat (03M, 18N) of the valve body (01) and the disk (19) respectively; inserting a disk retainer (20N) and a lock ring (22N) into a slot provided in a stem (23N);
disposing a thrust plate (21N) in a step provided in the disk (19N) wherein, the disk (19N) is screwed with disk retainer (20N) to from a stem-disk assembly configured in the middle of the valve body (01) wherein, a bonnet (08) is screwed in the valve body (01) along with spiral wound gasket (07M) when packing cartridges (09) are inserted into the bonnet (08) wherein, a yoke bush (14) is screwed into a yoke (10) and the yoke assembly is screwed with bonnet (08) when a handle is fixed at the end of stem (23N) to obtain a complete valve assembly.