Self-aligning turbine disc inspection apparatus

Measuring and testing – Vibration – By mechanical waves

Reexamination Certificate

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Details

C073S624000, C073S583000

Reexamination Certificate

active

06792809

ABSTRACT:

FIELD OF THE INVENTION
This invention relates generally to the field of turbine inspections, and more specifically to an apparatus for inspecting the discs of a turbine rotor assembly.
BACKGROUND OF THE INVENTION
High reliability of power generation equipment is an ongoing goal of the electric utility industry. Turbine parts are routinely inspected during planned plant outages in order to detect operationally induced discontinuities before they progress to a point where they may risk component failure. One portion of the turbine that is routinely inspected is the blade root area of the turbine rotor assembly.
A prior art steam turbine rotor assembly
10
is illustrated in cross-sectional view in FIG.
1
. The rotor assembly
10
includes a shaft
12
on which are mounted a plurality of wheels or discs
14
that are coaxial with the shaft
12
, with the shaft
12
extending through a bore formed at the center of each disc
14
. A plurality of blades
16
are mounted to the periphery of each disc
14
, generally by inserting a root portion of the blade (not shown) into a mating groove
18
formed along the circumference of the disc
14
, as shown in FIG.
2
. It is known to scan the disc web surface
20
with an ultrasonic transducer or other type of sensor in order to search for cracks in the region of the groove
18
. Such prior art inspections are normally conducted with the rotor assembly
10
removed from the turbine casing and supported on a test stand at an inspection location. The ultrasonic sensor is mounted on an elongated arm that is manually guided between adjacent blades
16
to position the sensor against the disc web surface
20
while the rotor assembly
10
is slowly rotated on the test stand. One may appreciate that such manual positioning of the sensor is strenuous and subject to the potential for positional inaccuracy. Accordingly, an improved scheme for positioning the sensor during a turbine rotor disc inspection is desired.
SUMMARY OF THE INVENTION
An apparatus for positioning a sensor proximate a surface of a disc of a turbine rotor assembly is described herein as including: a sensor assembly; and an alignment correction assembly supporting the sensor assembly from a support surface and providing passive freedom of movement there between.
An apparatus for positioning a sensor proximate a surface of a disc of a turbine rotor assembly as the rotor assembly is supported over a support surface is described herein as including: a means for supporting a sensor in a vertical direction; and a means for providing a passive freedom of movement between the sensor and the support surface about a horizontal plane.
A turbine rotor inspection apparatus is described herein as including: a base; a first sled supported vertically on the base and free to move in a first direction along a horizontal plane; a theta alignment assembly supported vertically on the first sled and free to rotate in the horizontal plane; a second sled supported vertically on the theta alignment assembly and free to move in a second direction perpendicular to the first direction in the horizontal plane; a vertical drive assembly supported by the second sled and having a selectable vertical length; a head assembly connected to the vertical drive assembly; and a sensor connected to the head assembly.


REFERENCES:
patent: 4304133 (1981-12-01), Feamster, III
patent: 4502331 (1985-03-01), Singh et al.
patent: 4586380 (1986-05-01), Patterson
patent: 4741203 (1988-05-01), Willaman et al.
patent: 5383355 (1995-01-01), Baleras et al.
patent: 5670879 (1997-09-01), Zombo et al.
patent: 5781007 (1998-07-01), Partika et al.
patent: 5959211 (1999-09-01), Wagner et al.
patent: 6065344 (2000-05-01), Nolan et al.
patent: 2002/0088282 (2002-07-01), Zayicek et al.

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