FIELD OF INVENTION
The present invention relates to a device for measuring cylindricity of 250 mw,
500 mw steam turbine high pressure (HP), intermediate (IP) and low pressure
(LP) shafts and turbogenerator rotor shafts and a method for the same. More
particularly, the invention relates to the measuring of cylindricity of steam
turbine, turbogenerator shafts independent of the machine.
BACKGROUND OF THE INVENTION
The circularity of cylindrical surfaces is an important criteria for various
components for their different applications. The requirement of circularity on
cylindrical surfaces is specified in all drawings.
The functional requirement of having uniform clearances all around the periphery
is the basis for this requirement. While circularity of cylindrical surfaces can be
easily measured on machine using a dial, the problem starts when the job is in
offloaded condition or where machine is not available especially at sites.
Even when a job has been measured on machine for cylindricity the results may
be erroneous. This may be because of the error that may creep in the machine
due to excessive or non uniform clearances in machine bearings caused due to
manufacturing fault or wear and tear occurring over a long period of time.
During erection / commissioning of HP and IP turbines at Bhilai site high runouts
were observed on journals of both HP and IP rotors. All efforts were made to
diagnose and rectify the problem but due to non availability of machine, the root
cause of the problem could not be identified and hence no correction could be
done. The rotors (both HP and IP) had to be brought back to haridwar plant for
necessary root cause analysis and corrective action. This resulted in long delay,
extra cost and a damage of the image of the organization. After inspection of
the rotors on machine, small local depressions at various locations across
journals were observed. After analysis it was concluded that it could have
happened due to damage during handling of the rotor at plant / site which was
subsequently smoothened.
So a need was felt to have a device which could measure circularity / local
depression in offloaded / site conditions. Keeping the above in view the device
has been designed.
OBJECTS OF THE INVENTION
Therefore it is an object of the invention to propose a device for measuring
cylindricity of 250 mw, 500 mw steam turbine high pressure (HP), intermediate
(IP) and low pressure (LP) shafts and turbogenerator rotor shafts and a method
for the same which can measure cylindricity of steam turbine, turbogenerator
shafts.
Another object of the invention is to propose a device for measuring cylindricity
of 250 mw, 500 mw steam turbine high pressure (HP), intermediate (IP) and low
pressure (LP) shafts and turbogenerator rotor shafts and a method for the same
which is capable of cross checking the cylindricity of rotors of steam turbine,
turbogenerators shafts, checked on machine.
Yet another object of the invention is to propose a device for measuring
cylindricity of 250 mw, 500 mw steam turbine high (HP), intermediate (IP) and
low pressure (LP) shafts and turbogenerator rotor shafts and a method for the
same which is able to measure cylindricity of steam turbine, turbogenerators
shafts at sites where machines are not available.
A further object of the present invention is to propose a device for measuring
cylindricity of 250 mw, 500 mw steam turbine high (HP), intermediate (IP) and
low pressure (LP) shafts and turbogenerator rotor shafts and a method for the
same which is capable of detecting local depressions which are not visible to
naked eye / micrometer.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The invention will now be described with the help of the accompanying drawings
where:
Figure 1(a) shows the device of the present invention.
Figure 1(b) shows the device assembled with dial gauge.
Figure 1(c) shows the application of the device.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
OF THE INVENTION
The device (D) consists of an inverted V shaped block (1) having two arms (3,
4) extending from the middle of the block (1). In the middle portion of the block
(1) there is a through hole (5) of 8 mm diameter for inserting a dial gauge (6)
which is mounted on the device tightened by a M8 screw (7) through a threaded
hole (2) provided on one side of the device, perpendicular to 8 mm hole (5).
The inner surfaces of arm touch the outer periphery of the shaft diameter. All
edges are rounded off to facilitate proper seating of the device on surfaces and
to avoid any damage to the shaft surface. The tip of the dial gauge (6) touches
the rotor surface and remains so when the cylindricity of the shaft is checked.
The two arms (3, 4) of the block (1) always remain in touch firmly with the
surface of the shaft when the tip of the dial gauge (6) touches the surface with
little pressure for showing the reading of error of cylindricity. The device is
moved around the periphery of the shaft whereby any defect or error in the
cylindricity is displayed by the reading of the dial indicator (6). The device is
moved along the length of the shaft to check the error at different periphery
section of the shaft. Figure 1(b) and 1(c) shows the device being used. The
whole operation is done manually.
WE CLAIM
1. A device (D) for measuring cylindricity of 250 MW, 500 MW steam turbine
high, intermediate and low pressure shaft and turbogenerator rotor shafts
comprising;
- an inverted 'V' shaped block (1) having two holes (5, 2) in the
middle of the block perpendicular to each other for holding a dial
gauge (6) tightly, characterized in that two arms (3, 4) extending
from the middle of the block (1) touches firmly the surface of the
shaft and moves manually around the periphery of the shaft
wherein the tip of the dial gauge (6) remains lightly pressed on the
surface for showing the reading of error of cylindricity.
2. A device for measuring cylindricity of steam turbine and turbogenerator
rotor shafts as claimed in claim 1, wherein the hole (2) in the block (1) is
a threaded hole for tightening the dial gauge (1) with a screw (7).
3. A method for measuring cylindricity of stem turbine and turbogenerator
rotor shafts comprising:
- resting the two arms (3, 4) of the inverted V shaped block (1) on
the surface of the shaft;
- placing the tip of the dial gauge (6) lightly pressed on the surface
of the shaft, wherein the device is manually moved over the
periphery of the shaft to obtain the readings of the dial gauge to
find the error in cylindricity of the shaft.

A device for measuring cylindricity of 250 mw, 500 mw steam turbine, high (HP),
intermediate (IP) and low pressure (LP) shafts and turbogenerator rotor shafts
consists of an inverted 'V' shaped block (1) having two holes (5, 2) in the middle
of the block perpendicular to each other for holding a dial gauge (6) tightly.
Hole (2) is a threaded hole for tightening the dial gauge. Two arms (3, 4)
extending from the middle of the block (1) touches firmly the surface of the shaft
and moves manually around the periphery of the shaft wherein the tip of the dial
gauge (6) remains lightly pressed on the surface for showing the reading of error
of cylindricity.