FIELD OF INVENTION
This invention relates to a probe fixture and guiding mechanism for measuring
thickness of rib portion of copper staves in a blast furnace by ultrasonic testing techniques
and a method for the same. More particularly, the invention relates to measuring the
remnant thickness of the stave by creating proper contact of sensing unit with object to
introduce ultrasonic waves into the material.
BACKGROUND OF THE INVENTION
Blast furnace is the core of iron and steel industry where smelting of iron is carried
out, shown in Fig. 1. Copper stave is an integral part of a blast furnace to increase its
campaign life. Copper staves is critical part whose role is to enhance the cooling in order to
protect the external steel shell from heat as well as to maintain the inner profile of the
blast furnace. Copper staves are provided with inlet and outlet ports to circulate water
through them. Water that enters through inlet is guided to flow in vertical cooling channel
and as it is passing, it takes away heat from the copper stave, which is exposed to elevated
temperature. Based on the blast furnace design, copper staves will be installed in a
particular orientation to the molten liquid flow direction at different elevations. Copper
stave orientation and the molten metal temperature highly influence the wearing in the
copper stave. Inner face of the copper stave has ribs like structure as shown in Fig. 2.
These thicker portions (rib) are vulnerable to wearing, since they are exposed to sliding
molten metal before the thinner portion. Thickness of copper stave should be tracked on a
continuous basis to pre-empt end of life to prevent unexpected catastrophic failure.

Measuring copper stave thickness of the rib portion involves two challenges; direct
accessibility from the outside and its inherent intricate geometry. These two challenges
have to be tackled to measure the remnant thickness of the copper stave and also to
monitor the damage level of the same.
The patent JP2012207270A claims a method of measuring residual thickness
of blast furnace stave. The objective of this work was to provide a method of measuring
the residual thickness of a blast furnace stave, which accurately measures the wear
damage of a stave fixed on a blast furnace shell. This method involves a resin-made soft
probe which was inserted in the water channel, when the probe contacted to inner side
surface of the furnace of water channel. The thickness of the surface of the furnace inner
side of the water channel and the back surface of the stave unit is measured. The wear
and tear of the stave fixed to the case of blast furnace can be measured at high precision
by inserting resin-made soft probe in the water channel. It claims a residual thickness
measuring method of the shaft furnace stave along with the ultrasound soft probe made of
resin.
The patent JP202275515A claims a method for measuring thickness of stave.
The objective of this work was to provide a method of measuring the residual thickness of
a blast furnace stave. This method involves a copper or a copper alloy-made rolled material
embedded into the stave's main body where the through holes were provided in the
thickness direction of the stave's main body. The embedded rolled material is measured by
the ultrasonic thickness gauge. It claims an embedded rolled stock made from copper or its
alloy and inserted into a stave which was provided with through holes in the thickness
direction. The patent further discusses about a thickness measuring method using an
ultrasonic board thickness meter.
The patent KR1220798B1 (KR20120065119) claims a device and method for
measuring thickness of stave of a furnace. This method involves an ultrasonic sensor

embedded in the bottom portion of the cooling channel of stave and not at the rib portion
and the ultrasound was transmitted to the stave and reflected to measure the thickness of
the stave. Since it was embedded into the cooling channel of the stave, the thickness of
the stave can be periodically measured with the real-time and the attrition rate of the
stave. The patent KR2012067786A claims a device and a method for measuring a thickness
of a stave of a furnace. This method involves an ultrasonic based technique comprising a
special probe made straight to get access with cooling water channel in the stave.
All the above patents except KR1220798B1 claims that their probe fixtures
are straight and they make contact with the portion of the copper stave which is located in
same level either with the inlet or outlet pipe. But in actual blast furnace (shown in Fig. 1),
the copper staves are fixed according to the distinctive shape of the blast furnace. Hence,
the copper stave is not normal to the inlet/outlet pipe at all the elevations, the usage of the
straight probe may not make proper contact as it is required in ultrasonic testing. And also
the straight probe fixture will not reach the rib portion which is intended. KR1220798B1
employs embedded probe for continuous monitoring of thickness of the stave, in which
embedding should be done before erection of the staves. This work is not applicable for
staves are already erected.
It is evident from the said prior art that proper contact of the fixture with
copper stave is essential for measuring the remnant thickness of the staves precisely.
Further, there is need of a mechanism or arrangement which ensures proper contact of the
fixture with the copper staves so that precision can be improved.

OBJECTS OF THE INVENTION
The object of the present invention is to propose a probe fixture for
measuring thickness of rib portion of the copper staves, which is inclined at different angles
with respect to inlet and outlet cooling ports at different elevation.
Another object of the invention is to propose a probe fixture to predict the
inside damage level of copper staves in a blast furnace.
Further, object of the invention is to propose a probe fixture and guiding
mechanism for measuring thickness of rib portion of copper staves in blast furnace by
ultrasonic testing techniques and the method for the same, which is capable of measuring
thickness of rib portion of the copper staves inclined in different angles with respect to inlet
and outlet cooling ports at different elevation.
Another object of the invention is to propose a probe fixture and guiding
mechanism for measuring thickness of rib portion of copper staves in blast furnace by
ultrasonic testing techniques and the method for the same, which is capable of predicting
the inside damage level of copper staves.
A further object of the invention is to propose a mechanism for making
proper contact of probe fixture with rib portion of copper staves in a blast furnace.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1 - Illustrates the sectional view of blast furnace and its different locations where the
copper staves are located.
Fig. 2 - Illustrates the end view of the copper staves where the rib (thicker) and thinner
portion are shown.
Fig. 3 - Explains the measurement setup along with probe fixtures and guiding mechanism.
Fig. 4, 5, 6, 7 and 8 shows the sectional view of copper staves with different orientations
according to its located level in blast furnace.

Fig. 9, 10, 11, 12 and 13 shows the two dimensional view of probe fixtures for the
respective staves shown in Fig. 4 - 8.
Fig. 14, 15 and 16 illustrates the different guide blocks for guiding the probe fixtures.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
Copper staves are used for protecting steel shell from high temperature
molten metal condition in blast furnace and whose thickness needs to be measured for
ensuring safety operation of blast furnaces. Ultrasonic based thickness measurement is one
of the most appropriate techniques. But the difficulties involved in measuring copper stave
thickness, are direct access to it and its intricate shape. The prior work to measure copper
stave thickness was done by a long straight fixture, which holds ultrasonic probe in its end
and it makes accessibility with copper stave through the inlet and outlet pipe. The proper
contact of the probe with test surface is essential since even air passage would affect the
preciseness of the measurement. So ultrasonic based thickness measurement demands not
mere contact of probe, rather it demands proper contact. Since copper staves are kept at
different orientations according to blast furnace design, straight probe fixture will result in
poor contact. And also the vulnerable portion of the staves (rib) not necessarily to be in
level with inlet/outlet pipes, so that always straight probe measures thickness at rib
portion. By considering these short comings of the prior works in measuring copper stave,
the current invention has devised a probe fixture with bent portion with preferred
orientation as it is described in detailed description of the invention.
In addition guiding mechanism has been designed with guide block as shown
in Fig. 14. Function of guiding mechanism along with probe fixture is described in detailed
description of invention. Guide block serves two purposes; it prevents probe fixture getting
tilted while measuring thickness and ensuring the exact measurement location (rib portion
or thin portion) by employing three different guide blocks (70) as shown in Fig 14 - 16.
Thus the probe fixture and guiding mechanism serves the purpose of measuring the
thickness.

Method to measure remnant thickness:
In case of objects where one face of it is not accessible, measurement can be
done by different non-destructive techniques. Ultrasonic based thickness measurement is
one of the most appropriate techniques. In ultrasonic testing (UT) technique, the material
is tested by the tendency of sound wave to get reflected at places where it experiences the
change in acoustic impedance.
UT based thickness measurement requires contact of sensing unit with object
to introduce ultrasonic waves into the material. Rather than Normal beam mode,
Transmitter - receiver (TR) mode, is used in which two crystals of sensing unit which are
acoustically and electrically separated from each other in the same probe housing are
deployed. TR probe reacts considerably less sensitive to coupling variations which may be
caused by rough or curved material surfaces. This characteristic explains why TR sensing
unit play a valuable part in industries. Velocity of ultrasonic waves in any medium is a
constant dependent of materials' young's modulus. Hence, time of flight of ultrasonic
waves can be transformed into distance scale. Ultrasonic wave flight distance, before it is
getting reflected, holds details of remnant thickness. On this principle ultrasonic based
thickness measurement is carried out using ultrasonic flaw detector (50). As discussed in
background section, two critical challenges involved in this work needs to be sorted out.
For that special probe fixture which can bring accessibility of copper stave perfectly and tip
of the probe itself has to have curvature as that of the cooling channel of copper stave.
Probe fixture and guiding mechanism:
As shown in Fig. 3 the function of probe fixture (10) is to accommodate the
transmitter-receiver transducer firmly and also to access the copper stave portion rib
portion (30) properly. Cross sectional view of copper stave Al is shown in Fig. 4. In Fig.4,
"X" is the inner diameter of the pipe (100) provided for water circulation. "Y" is the length
that is needed to reach cooling channel's wall and "Z" is the distance down from the centre
axis of the pipe (100) to the centre of the immediate rib. R is the diameter of the cooling
channel.

Probe fixture is longer than Y mm, so that it could be handled from outside. In an
embodiment of the invention, 'Y' is 700 mm. However, length of the Y can be varied
depending upon dimensions of the pipe (100) and copper stave. Since the rib portion of
the stave is away from pipe center axis by "Z" mm, so the probe fixture is having a bent
portion at least "Z" mm to reach the centre of the rib portion. In an embodiment of the
current invention, the bent portion is Z+ dz. The dimensions of the Z1, Z2, Z3, Z4 and Z5 are
35 mm, 30 mm, 40 mm, 30 mm, and 35 mm. The dimensions of the Z can be varied
depending upon the dimensions of copper staves.
Ultrasonic probe (30) should be seated properly such that there will be no air
film between probe and the surface of the cooling channel (40). While handling the probe
fixture from outside, there are possibilities for the fixture to get tilted. If the fixture is tilted
then the probing unit may not contact with the inner surface of the cooling channel
perfectly which will give erroneous results. To avoid this misalignment, a special guide
block has been designed as shown in Fig. 14. As per the design, the guide block will make
sliding pair with probe fixture and it will arrest the rotational movement of the fixture. The
outside diameter of the guide block matches with inner diameter of the inlet or outlet pipe,
and V groove in the guide block restricts the fixtures movement in circumferential direction.
W and T are the width and height of the V groove, respectively and V projection in the
probe fixture also has the same dimensions.
As shown in Fig. 7, 8, 9, 10 and 11 "V" projection in the fixture is designed to seat
on the groove made in the guide block. Length of the fixture is "Y" + dY mm, dY was given
to make it extend outside the pipe to hold properly during measurement. Degree of
inclination at bent portion is equivalent to the angle of the stave that it makes with
horizontal plane. Bent portion of the fixture is less than "Z" + dZ mm, here dZ was chosen
based on the condition, "Z" + dZ < "X", so that the fixture can be inserted freely.
As shown in Fig. 14, 15 & 16, guide blocks have been made in three heights,
they are H, H - 0.6S and H + 0.6S, Where H and S are the radius of the inlet pipe and

width of the rib, respectively, to assure the readings were indicating the thickness at rib
portion. For instance, while the fixture with guide block of H makes the probe to measure
the thickness of rib portion at the center, then the fixture with other two heights H - 0.6S
and H + 0.6S will measure from less thickness portion, because height variation in the
guide block moves the fixture away from the rib. Total height variation in the guide block
is 1.2 times of S that is greater than the width of the rib portion. In an embodiment of the
invention, H is 27.5 mm and 'S' is 30 mm. Further, H and S are dependent upon the
dimensions of inlet pipe and dimensions of the copper stave. Greatest thickness measured
by this method with different guide blocks, will represent the thickness of the rib portion.
"Z" and angle of inclination varies stave to stave. In the same methodology, other special
fixtures for staves A2, A3, A4 and A5 also designed based on their inclination with
horizontal pipe. Stave drawings and fixture details are given in Fig. 4, 5, 6, 7, and 8, and
Fig. 9, 10, 11, 12 and 13, respectively. Probe fixture was made of Aluminium (Al) because
it is cheap and light in weight. However, other material can also be used to construct probe
fixture depending upon the requirements and suitability to the operations.
The current invention overcomes the disadvantages of the invention from the perspective
of ensuring proper contact with the surface of the rib portion of the stave whose thickness
needs to be measured. Further, the current invention provides a mechanism that restricts
tilting of the probe fixture during the measurement.

WE CLAIM
1. A probe fixture for measuring thickness of rib portion of copper staves in blast
furnace by ultrasonic testing techniques, the probe fixture comprising;
a fixture (10) equipped with an ultrasonic probe (30);
said fixture (10) having a predetermined length more than Y needed to reach
cooling channel's wall (40) and to facilitate handling from outside; a bent portion
(80) inclined at an angle equivalent to the angle of the copper stave with the
horizontal plane (0), the bent portion is less than Z + dZ where Z is the distance
down from the centre axis of the pipe (100) to the centre of the immediate rib
(K) wherein the ultrasonic probe (30) seats properly on the rib portion so that
there is no air film between the ultrasonic probe (30) and surface of the cooling
channel wall (40) exists when the fixture (10) is held in position by a guide block
(G).
2. The probe fixture as claimed in claim 1, wherein the fixture (10) is made of
Aluminium.
3. The probe fixture as claimed in claim 1, wherein the dimensions 'y' , Z and θ vary
depending upon dimensions of the copper staves.
4. The probe fixture as claimed in claim 1 and claim 3, wherein length of 'Y' is 700
mm.
5. The probe fixture as claimed in claim 1 and claim 3, wherein Z1, Z2, Z3, Z4 and Z5
and angle of inclination (θ1 θ2 θ3 θ4 and θ5) are 35 mm, 30 mm, 40 mm, 30 mm,
35 mm and 93 degree, 99 degree, 90 degree, 81 degree, 99 degree respectively
for staves A1 to A5.
6. The probe fixture as claimed in claim 1, wherein the fixture (10) is having a 'V'
shaped projection for seating on the groove in the guide block (G).

7. The probe fixture as claimed in claim 1, wherein Z + dZ is less than X where X is
the diameter of pipe (100).
8. The probe fixture as claimed in claim 1, wherein the guide block (G) is disposed
at different heights to position probe (30) along the width of rib portion (Z) of the
copper stave.
9. The probe fixture as claimed in claim 1 and claim 8, wherein the guide block (G)
is preferably disposed at three heights H, H - 0.6S and H + 0.6S where H is the
radius of the inlet pipe and S is the width of the rib.
10.The probe fixture as claimed in claim 9, wherein 'H' is 27.5 mm and 'S' is 30 mm.
11. Method for measuring thickness of rib portion of copper staves (C) by the probe
fixture and the guiding block (G) claimed in claim 1, comprising;
arranging a probe fixture (10) of length more than Y mm to reach the wall of
cooling channel (40) and to handle it from outside;
deploying Transmitter - Receiver mode having two crystals of sensing unit
acoustically and electrically separated from each other in the probe housing;
accommodating the transmitter - receiver transducer firmly on the probe fixture
(10) to access the copper stave (20) portion;
arranging a probe fixture (30) to seat firmly on the rib portion so that no air film
exists between the ultrasonic probe (30) and surface of the cooling channel (40);
and disposing a guide block (G) with 'V' groove to restrict the movement of the
probe fixture (10) in circumferential direction wherein ultrasonic based thickness
measurement is carried out deploying a ultrasonic flaw detector (50).

12.The method as claimed in claim 1 and claim 11 further comprising the step of
disposing guide blocks (G) in three heights H, H - 0.6S and H + 0.6S where H is
the radius of the inlet pipe and S is the width of the rib.
13. The probe fixture as claimed in claim 12, wherein 'H' is 27.5 mm and 'S' is 30
mm.

ABSTRACT

The present invention relates to a method of measurement of thickness of copper
staves (20) used in a blast furnace by special probe fixture (10) and guiding mechanism
(G). The system works by transmitter - receiver method of sound wave technique. A probe
fixture (10) is arranged with predetermined length that can reach the wall of cooling
channel (40) and which can be handled from outside. An ultrasonic probe (30) seats
properly on the probe such that no air film between probe (10) and the surface of the
cooling channel (40) exists. The probe has curvature as that of the cooling channel of
copper stave (20). Transmitter - Receiver mode having two crystals of sensing unit
acoustically and electrically separated from each other in the same probe housing. A guide
block with 'V' groove is disposed to restrict the movement of the probe fixture (10) in
circumferential direction wherein ultrasonic based thickness measurement is carried out
deploying a ultrasonic flaw detector (50).