FIELD OF THE INVENTION:
The invention relates to removal of deposits on metal parts. A particularly
important application of this invention is the removal of heat scale or oxide scale
formed at high temperatures, from metal parts such as iron and steel. This
invention is concerned with novel method and means for the removal of such
deposits.
The device for descaling metal part shall hereinafter referred as 'device'.
Turbines used in coal or gas or nuclear fuel based thermal power plants shall
hereinafter referred as ‘turbine’ and also, rotors used in such turbine shall
hereinafter referred as ‘rotor’.
BACKGROUND AND PRIOR ART:
One important application of this invention is for turbine rotors of coal or gas or
nuclear fuel based thermal power plants, which are constructed from special heat
resistant alloys and super-alloys. During service the various component parts are
exposed to high operating temperatures in the vicinity of 550-800°C or even
higher. At these elevated temperatures the metal alloys are exposed to both

reducing and oxidizing atmospheres at various times and, as a result, very tightly
adherent scale deposits are formed on turbine rotor.
The chief alloys used for turbine rotors on which the above-noted scales or
deposits are formed include alloy steels, e.g., of the straight chrome type
(martensitic or ferritic), austenitic stainless steels, stainless steels of the chromium
or chromium-nickel type, and heat resistant alloys and super-alloys including nickel
base and cobalt base alloys, iron-chromium-nickel alloys, and cobalt-nickel-
chromium alloys. These belong to the general classification of heat resistant alloys.
The aforementioned deposits may also be formed on other types of alloys. These
deposits, the heat scale or obdurate oxide deposits, are thus different and
distinguished from ordinary rust produced by corrosion of mild steel and iron in
their physical and chemical nature and are much more refractory and difficult to
remove by alkaline reagents. For example, in the case of Inconel (a nickel base
alloy) it appears most probable that the heat scale is largely a mixture of oxides
with nickel oxide the major component. On stainless steels, the initial scale formed
may be of the nature of an iron oxide-chromic oxide spinel. These hot scale
deposits are fused oxide layers of refractory nature and highly resistant to
chemical and mechanical attack.
For old turbine sets, rusted and scaled bladed rotors are often sent back for any
critical service or repair or in some instances for carrying out a particular research

activity. For proper maintenance of the turbine rotors, overhaul procedures must
be applied during which the rotor is completely and safely cleaned of heat scale
deposits and any other contamination which may be present. One of the most
important reasons for removing the foreign matter and scale deposits is to provide
clean metal surfaces which are suitable for inspection for flaws. Inspection is
especially important for checking rotor run-out and other surface flaws.
A large steam turbine rotor must run with low vibration levels during operation and
when going through critical speeds. Rotors must be straight and true within a tight
run-out tolerance, typically within 0.02 microns.
Prior art descaling method includes arrangements whereby the rotor is placed on
bearings and coupled with rotating means and emery belt is manually or
mechanically held against slow rotating turbine rotor. Such descaling methods are
both exceedingly time consuming and therefore expensive, for not only descaling
the rotor, but also an operational threat to the operator performing such descaling
operations.
OBJECTS OF THE INVENTION:
An object of the invention is to descale metal parts of, particularly, but not
exclusively, turbine rotors.

Another object of the invention is to execute a procedure for efficient removal of
oxide deposits in the form of scale from metal parts carrying the same to enable
suitable inspection of the parts by production-line methods, utilizing penetrant
dyes or fluorescent materials.
Still another object of the invention of a method and means for descaling metal
parts is the provision of a method for accomplishing such descaling without
producing, during the cleaning or descaling cycle, any substantial or significant
weight loss or dimensional change of the metal or alloy of which the rotor is
formed.
Further object of the invention of a method and means for descaling metal parts
is accomplishing such descaling through which intricate profiles such as stepped
surface, contours etc.
SUMMARY OF THE INVENTION:
In present invention, a device and a method of metal parts are described using a
device that uses pneumatic sanding wheel 10 being attached to a pneumatic gun
8. The holding device 1, pneumatic gun 8 and pneumatic pipe 7assembles as one
unit. This unit is attached to a tool holder 11 at one end of the tool holder 11 and
the other end of tool holder is mounted in carriage of a tool post. The tool holder

is long enough to reach intricate approached and scale removal can be done at all
surfaces viz. flat, tapered, counters, profile sections etc.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
These together with other objects and advantages which will become subsequently
apparent reside in the details of construction and operation as more fully
hereinafter described and claimed, reference being had to the accompanying
drawings forming a part hereof, wherein like numerals refer to like parts
throughout, and in which:
Figure 1: shows an holding device 1 having provision of holding pneumatic gun
8 Figure 2: shows pneumatic pipe 7 having in it threaded connection 9ˋ
Figure 3: shows pneumatic gun 8 having in it threaded connection 9
Figure 4: shows sanding wheel 10 having plurality of grit flaps 17
Figure 5: shows Allen bolt 14, 15
Figure 6: shows assembly of pneumatic pipe 7, pneumatic gun 8, holding
device 1 and sanding wheel 10
Figure 7: shown illustration of sanding wheel 10 and grit flap 17
Figure 8: shows tool holder 11 having on it plurality of threaded hole 13
Figure 9: shows tool holder 11 having on it plurality of threaded hole 13
Figure 10: shows descaling process using L-shape shaft 16

Figure 11: shows descaling process using coaxial shaft 16
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT:
For better understanding of the proposed method and means of descaling metal
parts, reference numerals for important features are being linked with like parts in
relevant drawings wherein:
Item-1 is a holding device
Item-2 is a slot in holding device 1 towards pneumatic gun 8
Item-3 is a counter hole in holding device 1 starting from pneumatic gun 8
side
Item-4 is plurality of threaded holes in holding device 1
Item-5 is a through hole in holding device 1 towards pneumatic pipe 7 side
Item-6 is switch through which pneumatic gun 8 is operated
Item-7 is pneumatic pipe carrying compressed air at high pressure
Item-8 is pneumatic gun to which pneumatic pipe 7 is connected through
threaded connection
Item-9 is threaded connection male part in pneumatic gun 8
Item-9' is threaded connection female part in pneumatic pipe 7
Item-10 is sanding wheel connected to pneumatic gun 8
Item-11 is tool holder to which holding device 1 will be mounted for intricate
profiles, if required

Item-12 is slot in tool holder 11 to accommodate holding device 1
Item-13 is plurality of threaded holes in tool holder 11
Item-14 is plurality of Allen bolt corresponding to threaded holes 13
Item-15 is plurality of Allen bolt corresponding to threaded holes 4
Item-16 is shaft attached to pneumatic gun 8
Item-17 is plurality of grit flap of sanding wheel 10
Item-18 is rear end of holding device 1
Description of the present invention, i.e., method and means for descaling metal
parts is as per below:
The device for performing descaling in a way to meet the objects of the invention
is broadly divided into four assemblies or four major parts viz. pneumatic pipe 7,
pneumatic gun 8, holding device 1 and tool holder 11 arranged in a sequence to
work and deliver output as intended.
The first of which is a pneumatic pipe 7 carrying high pressure compressed air
connected to compressed air source at one end and a threaded connection female
part 9ˋ (Refer figure 2). The pneumatic pipe 7 is selected as per the compressed
air pressure requirements. This pneumatic pipe 7 completely passes through hole 5
of holding device 1 and connects to standard pneumatic gun 8 through a screw
kinematic pair comprising threaded connection female part 9ˋ and threaded

connection male part 9 (Refer figure 3) provided at one end of pneumatic gun 8
assembly. (Refer figure 6).
The pneumatic pipe 7 and pneumatic gun 8 assembly resides inside hole 3 in such
a way that the gun takes a position in a manner through which the switch6, to
operate the pneumatic gun, locates itself in a slot 2 in a poka-yoke manner.
Pneumatic gun 8 is held rigidly against fluctuating operational loads by plurality of
threaded hole 4 and plurality of Allen bolt 15 pressing the gun laterally. The
number and size of these threaded hole 4 and corresponding Allen bolt 15 are to
be determined on the basis of fluctuating machining load calculations. (refer figure
5)
This pneumatic pipe 7 connects at one end of the standard pneumatic gun 8 and
the other end of this standard pneumatic gun 8 have a shaft 16 on which a
sanding wheel 10 is mounted (Refer fig 4, 6, 7). The sanding wheel rating depends
on operational load parameters such as wheel-work piece interaction, abrasive
machining force, heat and energy, required machined surface quality, sanding
wheel life etc. It is apparent that the compressed air source rating, pneumatic pipe
7 as well pneumatic gun 8 are to be selected on the basis of aforementioned
operational load factor.

The sanding wheel 10 can be mounted on a shaft 16 in one way that the
longitudinal axis of pneumatic gun 8 and sanding wheel 10 are on same axis for
abrasive machining on sides or intricate profiles such as stepped surface, contours
etc. on sides (refer fig. 11) and in other way that the longitudinal axis of
pneumatic gun 8 and sanding wheel 10 are at an angle (refer fig. 10).
The sanding wheel 10 rotates at a high velocity and brushes against scaling and
performs the necessary ploughing action to descale the deposits and upon
repeated brushing descales the entire surface area of the rotor perpetually.
In case of intricate profiles and complex out-of-reach geometric locations such as
between blade stages, holding device 1 (assembled with pneumatic gun 8) is
attached to tool holder 11 through its rear end 18 and through plurality of
threaded holes 13 and plurality of corresponding Allen bolt 14 on tool holder.(Refer
figure 8, 9)
The tool holder 11 is mounted on of standard tool carriage of a machine through
so as to provide manual or automatic feed to the entire mechanism for performing
descaling. For descaling flat diameters such as journal area the descaling process
shall not require tool holder 11 and in this case holding device 1 shall be clamped
with carriage. Stiffeners 12 are provided in order to strengthen tool holder. (Refer
figure 8)

Thus it is apparent that the proposed method and means of descaling metal part
will provide an extremely critical fixture to descale metal parts and a method
thereof to completely descale metal parts in significantly less time and eliminating
the operational threats of descaling as per prior art.
Since, the foregoing is considered as illustrative only of the principles of the
invention. Further, since numerous modifications and changes will readily occur by
those skilled in the art, it is not desired to limit the invention to the exact
construction and operation shown and described, and accordingly all suitable
modifications and equivalents may be resorted to, falling within the scope of the
invention as claimed.

WE CLAIM
1) A pneumatic descaling device 19 for removal of oxide deposits from metal parts
comprising of :
• Pneumatic pipe 7 having threaded female part 9' at one end to connect the
pneumatic gun and the other end connected to the compressed air source,
characterized to carry high pressure compressed air
• Pneumatic gun 8 having threaded male part 9 at one end to be connected
to the female part 9'of the pneumatic pipe 7, and a bend shaft 16 at the
other end to connect sanding wheel 10
• Holding device 1 to hold the assembly of pneumatic pipe 7 and pneumatic
gun 8, having a slot 2 towards pneumatic gun 8, counter hole 3 starting
from the pneumatic gun side, plurality of threaded holes 4 and plurality of
Allen bolts 15 corresponding to holes 4, a through hole 5 towards
pneumatic pipe 7 along with the rear end 18
• Tool holder 11, wherein holding device 1 is mounted for de scaling of an
intricate profile through plurality of threaded holes 13 & plurality of Allen
bolts 14 corresponding to holes 13 and stiffeners 12 provided to strengthen
tool holder 11
• Plurality of grit flap 17 for sanding wheel 10

2) The pneumatic pipe 7 as claimed in claim 1, characterized to carry high
pressure compressed air, one end of which connected to high pressure
pneumatic source, the other end connects the pneumatic gun 8 through the
threaded female part 9’.
3) The pneumatic gun 8 as claimed in claim 1, characterized by its disposition in
the slot 2 in a poka-yoke manner, having threaded male part 9 connected to
the female part 9’ of the pneumatic pipe 7, bend shaft 16 at the other end
connecting sanding wheel 10.
4) The holding device 1 as claimed in claim 1, characterized to hold the assembly
of pneumatic pipe 7 and pneumatic gun 8 securely through plurality of
threaded holes 4 and allen bolts 15, having slot 2, counter hole 3, through hole
5 for easy access of the pneumatic pipe and the gun assembly.
5) The tool holder 11 having stiffener slot 12 with tools as claimed in claim 1,
mounted on tool carriage, clamped with the holding device 1, through plurality
of threaded holes 13, allen bolts 14, carrying out descaling intricate profiles
and out-of reach geometric locations of a job.

6) The grit flap 17 as claimed in claim 1, to be fitted on the sanding wheel 10 for
de scaling and cleaning.
7) A method of de scaling oxide deposits from metal parts comprising,

• Selection of shaft 16 according to the profile or surface to be descaled.
• Selection and mounting of sanding wheel 10 and grit flap 17 on shaft 16
based on operational load parameters such as wheel work piece interaction,
abrasive machining force, heat and energy, machine surface quality,
sanding wheel life so that longitudinal axis of pneumatic gun 8 and sanding
wheel 10 are on the same axis for abrasive machining or mounting sanding
wheel 10 at an angle for abrasive machining on faces or intricate profiles.
• Selection and holding pneumatic gun 8 by alien bolt 15 against fluctuating
operational load by pressing the gun laterally on holding device 1, wherein
the nos. of bolts are selected based on the load calculations.
• Selection of pneumatic pipe 7 as per compressed air pressure requirements.
8) The method as claimed in claim 7, wherein the holding device 1, pneumatic
gun 8 along with shaft 16, and pneumatic pipe 7 are assembled as one single
unit.

9) The method as claimed in claim 8, wherein the said unit is attached to one end
of the tool holder 11, and the other end of tool holder is mounted in carriage of
a tool post, and the tool holder is long enough to reach intricate approach to
remove scale.