FIELD OF INVENTION
The present invention relates to a method for accurate alignment of floating lever and
pilot valve in control valve servomotor casing of a steam turbine that controls the
opening and closing of valves and feedback linkages. More particularly, the present
invention relates to a device for accurate alignment of floating lever into the slots of
control valve servomotor casing with respect to position of pilot valve, feedback
linkages and top cover.
BACKGROUND OF THE INVENTION
The floating lever should be placed inside the Control Valve servomotor casing at a
defined location guided through pins with respect to position of both pilot valve and
feedback linkages. The floating lever should move smoothly inside the Control Valve
servomotor casing and return the pilot valve into centre position ensuring steady lifting
of valve otherwise it may result in improper functioning of turbine governing system.
Previously the alignment of floating lever and pilot valve inside the Control Valve
servomotor casing was done with hit and trial approach as there was no such device for
proper alignment.
As shown in Fig.2, floating lever is to be aligned inside the casing at a defined location
through guided pins of feedback linkages and pilot valve fittings. Then the assembly of
top cover is done with casing in such way that centre of threaded hole of bush (H8)
should exactly match with center of upper pin hole (H7) in floating lever. When centre
matches, the pinning of top cover is done with casing and its location is fixed. Many a
times it happens that while fitting the top cover the centre of bush did not match
exactly with pin hole centre in floating lever thus disturbing the position of pinning holes
of cover and casing because the floating lever and other items are not visible so the
chances of error are very high.
This whole process was done by hit and trial and there was no such device to ensure
the proper alignment of floating lever w.r.t. top cover and pilot valve. Thus the whole
assembly of top cover, pilot valve and floating lever was very time consuming. Any
disturbance in alignment of floating lever with respect to bore of bush with top cover,
pilot valve and feedback linkages will affect the movement of pilot valve which will
result in improper flow of oil inside the main steam control valve, hence the improper
functioning of steam turbine.
The flow of steam to the turbine is regulated by varying the lift of the control valve by
means of its servomotor. When the turbine is running and the valve is steady at any
particular value of lift, the pilot valve will be in the center position.
For proper functioning of the turbine, the floating lever needs to be properly aligned
with pilot valve and control valve servomotor casing. Hence, there is a need of a
suitable method for accurate alignment of floating lever and pilot valve in control valve
servomotor casing.
OBJECTS OF THE INVENTION
Therefore, it is an object of the invention to propose a method for accurate alignment
of floating lever and pilot valve in control valve servomotor casing of a steam turbine
which can eliminate the disadvantages of the prior art.
Another object of the invention is to propose a method for accurate alignment of
floating lever and pilot valve in control valve servomotor casing of a steam turbine
which can easily align the floating lever and pilot valve with control valve servomotor
casing.
Yet another object of the invention is to propose a method for accurate alignment of
floating lever and pilot valve in control valve servomotor casing of a steam turbine
which is capable of maintaining the desired movement of floating lever and pilot valve
inside the control valve servomotor casing.
A further object of the invention is to propose a method for accurate alignment of
floating lever and pilot valve in control valve servomotor casing of a steam turbine
which is able to reduce the assembly time of fitting of floating lever, pilot valve and top
cover with control valve servomotor casing.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig.1 (a) - shows device for accurate alignment of floating lever and pilot valve in
Control Valve servomotor casing.
Fig.1 (b) - shows Dummy pin cum pilot valve (1) according to an embodiment of the
present invention.
Fig.1 (c) - shows Special Guided screw (2) according to present invention having
threaded portion H6 and unthreaded portion H5.
Fig.2 - shows the layout of all items.
Fig.3 shows the assembly scheme of Control Valve servomotor casing in which items
floating lever, pilot valve, feedback linkages and top cover are shown.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
As shown in Fig.3, so far the floating lever (4) was being aligned with Pilot valve (7)
and feedback linkages (6) with the help of guided pins (8) by hit and trial method. The
task of this alignment is very clumsy and difficult.

In the present invention, the dummy pin (1) having a cylindrical portion (H2), a collar
(C) and a cylindrical portion (H1) which is guided to the hole (H4) of the floating lever
(4) outside the control valve servomotor casing (3). The floating lever (4) along with
dummy pin (1) assembled with it is placed inside the casing (3) in its proper position.
Upper portion (H1) of Dummy pin (1) is guided inside the lower pin hole (H4) of lever.
Dummy pin (1) having lower portion (H2) is guided inside the hole (H3) inside the
servomotor casing. Then the top cover and its bush is placed on casing together with
Special Guide screw (2) such that lower unthreaded potion (H5) of Special Guide screw
(2) gets guided inside the upper pin hole (H7) of lever. The threaded portion (H6) of
Special Guide screw (2) moves inside the threaded hole (H8) of bush to arrest the
movement of floating lever. After proper alignment of floating lever and pilot valve, top
cover (5) gets pinned with casing at proper pre-determined position when the dummy
pin (1) and guide screw (2) are removed. The floating lever (4) now being placed inside
the control valve servomotor casing (3) at a defined location with respect to position of
both pilot valve (7) and feedback linkages (6) are now guided through guide pins (8) as
shown in Fig.3.

WE CLAIM
1. A method for accurate alignment of floating lever and pilot valve in control valve
servomotor casing of a steam turbine comprising:
assembling the dummy pin (1) with the floating lever (4) outside the casing (3)
to guide pin diameter (H1) in the hole (H4) of the said floating lever;
disposing the floating lever inside the control valve servomotor casing (3);
characterized in that, the cylindrical portion (H2) of the dummy pin (1) is guided
inside the hole (H3) of the Pilot valve (7) when the unthreaded portion (H5) of
special guide screw (2) is guided inside the upper pin hole (H7) of the said lever
while the threaded portion (H6) of special guide screw (2) moves inside the
threaded hole (H8) of the bush to arrest the movement of the said lever (4) so
that the floating lever (4) and the pilot valve (7) is properly aligned when the top
cover (5) gets pinned with casing at proper predetermined position.
2. A method as claimed in claim 1, wherein the dummy pin (1) and the special
guide screw (2) are removed after the alignment of floating lever and pilot valve
being made.

A method for accurate alignment of floating lever and pilot valve in control valve
servomotor casing of a steam turbine comprising of assembling the dummy pin (1) with
the floating lever (4) outside the casing to guide pin diameter (H1) in the hole (H4) of
the floating lever and then the floating lever is disposed inside the control valve
servomotor casing (3). Then the cylindrical portion (H2) of the dummy pin (1) is guided
inside the hole (H3) of the pilot valve (7) when the unthreaded portion (H5) of special
guide screw (2) is guided inside the upper pin hole (H7) of the said lever while the
threaded portion (H6) of special guide screw (2) moves inside the threaded hole (H8) of
the bush to arrest the movement of the said lever (4) so that the floating lever (4) and
the pilot valve (7) is properly aligned when the top cover gets pinned with casing at
proper predetermined position.