FIELD OF INVENTION
The present invention relates to a probe holding device capable of removing
unnecessary overrun of probe during ultrasonic testing of rotor of a steam turbine.
More particularly, invention relates to a probe holding device which is capable of
removing unnecessary overrun of probe during ultrasonic testing of rotor of all kind in
which the surface is rough machined as the ultrasonic testing is done to check forging
defects.
BACKGROUND OF THE INVENTION
Metal forging is a metal forming process that involves applying compressive
forces to a work piece to deform it, and create a desired geometric change to the
material. The forging process is very important in industrial metal manufacture,
particularly in the extensive iron and steel manufacturing industry. A steel forge is often
a source of great output and productivity. Work stock is input to the forge, it may be
rolled, and it may also come directly from cast ingots or continuous castings. The forge
will then manufacture steel forgings of desired geometry and specific material
properties. These material properties are often greatly improved.

Inspection is an important aspect of metal forging manufacture. All parts should
be checked for defects after the manufacturing process is complete. Defects of metal
forged product include exterior cracking, interior cracking, laps, cold shuts, warping of
the part, improperly formed sections and dead zones. Cracking both interior and
exterior is caused by excessive stress, or improper stress distribution as the part is
being formed. Cracking of a forging can be the result of poorly designed forging die or
excess material in the work piece. Cracks can also be caused by disproportionate
temperature distributions during the manufacturing operation. High thermal gradients
can cause cracks in a forged part.
Metal forging is known to produce some of the strongest manufactured parts
compared to other metal manufacturing processes, and obviously, is not just limited to
iron and steel forging but to other metals as well.
A turbine rotor is at first just a forging and heavy rotor forgings for power
generation turbines and generators are inspected ultrasonically. Ultrasonic Testing (UT)
uses high frequency sound energy to conduct examinations and make measurements.
Ultrasonic inspection can be used for flaw detection/evaluation, dimensional
measurements, material characterization, and more.

A typical UT inspection system consists of several functional units, such as the
probe/receiver, transducer, and display devices. A probe/receiver is an electronic device
that can produce high voltage electrical pulses. Driven by the probe, the transducer
generates high frequency ultrasonic energy. The sound energy is introduced and
propagates through the materials in the form of waves. When there is a discontinuity
(such as a crack) in the wave path, part of the energy will be reflected back from the
flaw surface (Refer Figure 2). The reflected wave signal is transformed into an electrical
signal by the transducer and is displayed on a screen. Signal travel time can be directly
related to the distance that the signal traveled. From the signal, information about the
reflector location, size, orientation and other features can sometimes be gained. Forging
received from Foundry is tested for its material properties and cleared by Quality
department for further machining operation. Any defect recorded while testing may lead
to rejection of raw material. After rough machining of diameter (to make flat steps)
Non-destructive test is performed and test piece (rotor) is send for Destructive test.
After rough machining of diameter (to make flat steps) Ultrasonic testing (UT) is
performed by Non-destructive test (NDT) lab person manually on the machine. With the
help of Machine operator Shaft is rotated on machine and UT probe being held
manually is moved all around the shaft by NDT lab inspector. Graph is checked on
display for any recordable defect. Oil is applied and probe is moved over it, while any
defect is recorded on display unit. Shaft is rotated on machine and oil is applied
manually continuously and hand held probe is moved all over it. Display unit shows the

graph and any defect observed is recorded. 100% probe movement on shaft is ensured
for 100% UT.
This raises two major drawbacks of the present system:
1. Operator has to sustain high fatigue as the probe is handled manually. Also it
increases the work pressure on the operator, which can result in overlooking defect
recorded in the system.
2. Since hundred percent UT is mandatorily required, it involved overrunning of test
probe so as to ensure that 100% UT is done.
For customer, whether internal or external, the kind of UT method may not be
satisfactory as it should be whilst for manufacturer this leads in delay in other jobs,
accomplishment of targeted work, high power consumption and high cost of operation.
OBJECTS OF THE INVENTION
Therefore, it is an object of the invention to propose a probe holding device
capable of removing unnecessary overrun of probe during ultrasonic testing of rotor of
a steam turbine, which is capable of eliminating unnecessary time of over running of
test probe.
Another object of the invention is to propose a probe holding device capable of
removing unnecessary overrun of probe during ultrasonic testing of rotor of a steam

turbine which is able to avoid the handling of the test probe equipment manually,
thereby eliminating fatigue of the operator and minimizing human error.
A further object of the invention is to propose a probe holding device capable of
removing unnecessary overrun of probe during ultrasonic testing of rotor of a steam
turbine which is capable of adjusting itself to the surface irregularities.
A still another object of the invention is to propose a probe holding device
capable of removing unnecessary overrun of probe during ultrasonic testing of rotor of
a steam turbine which is capable of holding itself against the frictional force generated
while the probe touches the rotating rotor surface.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1: Shows ultrasonic testing methodology.
Fig. 2: Shows the developed probe holder.
Fig. 3: Shows the turbine rotor.
Fig. 4: Shows the ultrasonic testing on turbine rotor.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
The present invention of a probe holding device (P) as shown in Fig.2 and
capable of removing unnecessary overrun of probe during ultrasonic testing of rotor
consists of following Items.

Item-1: Socket Head Screw
Item-2: Threaded hole
Item-3: Upper Part
Item-4: Guide
Item-5: Guiding Rod (Main Body)
Item-6: Spring
Item-7: Lower part
a) As shown in Fig. 2. Item-7 works as the base of the probe holding device (P)
which fits into tool holder so that the whole device arrangement is fixed with the
carriage of the machine. The probe is fixed in Item-3 of the said device (P) using a
threaded joint between Item-1 and Item-2. For ultrasonic testing, the probe needs to
be in just touch condition with the surface of the rotor. Lubrication of surface is also
done so as to minimize the friction forces between the probe and the rotor surface.
b) Since the ultrasonic testing (UT) is done after rough machining so as to ensure
that the rotor is defect free for final machining, the surface of the rotor will be uneven
or wavy. This waviness will put stress on the probe, or even harm it when the rotator is
in rotating condition during UT. To keep the device free from harm through such
waviness of rotor surface, a spring (Item-6) is put inside Item- 5 whereas Item-4
touches Item-6 on its one end. The spring is put inside the guiding rod (5) for avoiding

stress on the probe during rotation of the rotor at the time of ultrasonic testing when a
guide (4) is in touch with the spring (6) on its one end.
c) The UT is automated in a way that the longitudinal distance covered by the
probe in one rotation of the (which is equal to the longitudinal distance covered by tool
holder) is equal to the width of the probe thereby completely eliminating the
overrunning of probe which sometimes consumes as much as 40% of the total UT time.
d) While this process of longitudinal traversing of the probe is happening, there is a
tendency that the probe may rotate due the resulting force of friction between the rotor
and probe surface. To avoid such rotation, a guide (Item-4) welded on Item-5 is
provided which forms kinematic pair of sliding type with Item-3. The guiding rod (5) is
connected to upper body (3) through a threaded joint.

WE CLAIM
1. A probe holding device capable of removing unnecessary overrun of probe during
ultrasonic testing of rotor of a steam turbine comprising;
a probe fixed on the upper part (3) of the device (P);
a base (7) of the probe holding device fixed in a tool holder, the said holder fixed
with the carriage of the machine;
a guiding rod (5) connected to upper body (3) through a threaded joint;
a spring (6) put inside the guiding rod (5) for avoiding stress on the probe during
rotation of the rotor at the time of ultrasonic testing when a guide (4) touches the
spring (6) on its one end;
wherein the ultrasonic testing is automated such that the probe covers the
longitudinal distance in one rotation of the rotor equal to the longitudinal distance
covered by tool holder and is equal to the width of the probe resulting elimination of
overrunning of the probe.
2. A probe holding device as claimed in claim 1, wherein the probe is fixed in the
upper part (3) by a socket head screw (1) and a threaded hole (2).
3. A probe holding device as claimed in claim 1, wherein the guide (4) is welded
with guiding rod (5) for arresting rotation of the probe due to the resulting force of
friction between the rotor and probe surface.