FIELD OF THE INVENTION:
The present invention relates to steam blowing device for HP control valve for 660 MW supercritical steam turbine function of which is to a device to prevent the leaked steam from going into the turbine through HP control valve.
BACKGROUND OF THE INVENTION:
Steam blowing of Main steam pipe lines of steam turbine is carried out in order to remove welding slag, grease, loose foreign materials, iron pieces, rust etc. from the system, generated during manufacturing, transportation and erection. Steam blowing operation of the pipe lines is of great importance to ensure satisfactory operation of steam turbines as impurities in the steam can deposit on the turbine blades, imbalance the rotor chain and damage the valve and turbine components.
During steam blowing operation, steam of high pressure (50 bar) and temperature (540°C) is blown in the pipelines. This steam is bypassed upstream of turbines with the help of steam blowing devices to prevent ingress of impurity in turbines during steam blowing operation as per arrangement shown in figure-1. As per normal practice Steam blowing device is installed in HP stop valve. Steam enters on HP stop valve from inlet connection and blown out from outlet connection (shown in figure-1). During the operation steam flow to HP control valve is blocked by steam blowing of HP stop valve at its valve seat area.

To prevent any risk of ingress of impurities to HP control valve side and in turn to turbine due to the leakage in steam blowing device of HP stop valve, steam blowing device for HP control valve has been invented for 660MW supercritical steam turbines which shall further seal the valve seat surface of HP control valve and shall prevent ingress of steam in turbine. Before installing steam blowing device of HP control valve, HP control valve internal components are taken out from valve body.
OBJECTS OF THE INVENTION:
Object of invention is to develop a steam blowing device for HP control valve for 660MW supercritical steam turbines to prevent ingress of steam in the turbine if some leakage occurs in the existing steam blowing device of HP stop valve.
SUMMARY OF THE INVENTION:
A device for HP control valve of steam turbine comprising a spindle (2), one end of which abuts with the central portion of plug (1) having circular cross section, whereas the other end of the said spindle (2) having external thread (E) for passing through the cover plate (5) also having matching internal thread; an intermediate ring (3) provided along with sealing ring (4) for holding against the sealing surface (B) of HP control valve with the help of existing threaded ring (C); wherein a pipe (8) is welded on the inner surface and centre of plug (1) for aligning the spindle (1) on the central axis such that when the spindle (2) is tightened in cover plate (5), it creates push force on the inner surface of plug

(1) thus abutting its inclined surface ( F ) with the valve seat face (A) of HP control valve.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1: Cross-section view of HP stop cum control valve indicating major components of Steam blowing device for HP control valve;
Figure 2: Front view of the steam blowing device assembly indicating different components;
Figure 3: Top view of the steam blowing device assembly indicating different components;
Figure 4: Side view of the steam blowing device assembly indicating different components.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION:
Steam blowing device for HP control valve consists of a cone shaped item Plug (1) which seats on valve seat (A) of HP control valve. The Plug is having very fine surface finish to make a steam tight surface contact with valve seat (A) of HP control valve. 4 no. special plates (7) having rectangular cross-section are welded on valve seat side surface of Plug (1), 90 degree apart from each other which gets inserted in the inner dia. of valve seat so as to hold the Plug (1). Spindle (2) pushes the Plug (1) towards the valve seat. Outer end of Spindle (2) is having external thread which joins with Cover plate (5) having matching

internal threads. Tightening of spindle (2) with Cover plate (5) provides push force to Plug (1). Inner end of spindle (2) is aligned with the centre of Plug (1) with the help of pipe (8) which is welded on the plug (1).
To prevent damage of sealing surface (B) of HP control valve from impurities in steam during steam blowing operation, Intermediate ring (3) is provided which rests on sealing surface of HP control valve with sealing ring (4) in between. Intermediate ring (3) is held against sealing surface with the help of existing threaded ring (C). Cover plate (5) is mounted on the existing valve casing (D) with the help of fasteners (6). As complete valve casing is not covered by Cover plate (5) and HP control valve seating surface area is blocked by Plug (1), steam leaked from HP stop valve shall come out from cover plate side.

WE CLAIM:
1. A device for HP control valve of steam turbine comprising:
a spindle (2), one end of which abuts with the central portion of plug (1) having circular cross section, whereas the other end of the said spindle (2) having external thread (E) for passing through the cover plate (5) also having matching internal thread;
an intermediate ring (3) with sealing ring (4) for holding against the sealing surface (B) of HP control valve with the help of existing threaded ring (C);
wherein a pipe (8) is welded on the inner surface and centre of plug (1) for aligning the spindle (1) on the central axis such that when the spindle (2) is tightened in cover plate (5), it creates push force on the inner surface of plug (1) thus abutting its inclined surface (F) with the valve seat face (A) of HP control valve.
2. The device as claimed in claim 1, wherein four numbers of plates (7) having rectangular cross-section are positioned on the outer surface of plug (1) at 90° apart and welded therein.
3. The device as claimed in claim 1, wherein when the push force applied on the plug (1) by the spindle (2), the inclined surface (F) of plug (1) abut with the surface of valve seat (A) of the HP control valve.

4. The device as claimed in claim 1, wherein a sealing ring (4) placed between the sealing surface (B) of HP control valve and intermediate ring (3) for prevention the damage of sealing surface (B) HP control valve from impurities of steam during steam blowing operation.
5. The device as claimed in claim 1, wherein the intermediate ring (3) is held against the sealing surface (B) with the help of existing thread ring (C).
6. The device as claimed in claim 1, wherein the cover plate (5) is mounted on the existing valve casing (D) with the help of fasteners (6).