Field of Technology
The disclosure also relates to measuring the remnant thickness of the staves
having gradually bending cooling channels. Particularly the disclosure relates to
the specially designed ultrasonic measuring arrangement for measuring the stave
thickness.
Background
Blast furnaces in an iron and steel industry are used for smelting of iron from
iron ore. Maintaining a thermal barrier between the inside of the furnace and the
externa! steel shell is crucial to the operational efficiency and structural integrity
of blast furnace. Cooling staves in conjunction with the refractory linings are the
key elements to achieve this objective in most modem furnaces. Cooling staves
are designed, with internal channels for circulating water for protecting steel shell
from heat.
In this view each stave has inlet/outlet ports for the cooling water and these
openings provide for the access required for the sensors to be inserted for
measurement. In addition the staves employ a ribbed design (FIG, 1), that
provide slots for mounting refractory bricks which form the innermost lining of
the furnace, in addition to serving as fins which enhance heat extraction rate.
The flow of hot metal and gases subject the internal surfaces of the cooling
staves to wear especially the ribs. In the worst stave wear condition it can cause
massive water ingression, which can lead to catastrophic failure of the furnace
Hence, it is .crucial to monitor the thickness of the staves for preventing their
catastrophic failure.
Stave thickness measurement is quite difficult as staves are located inside a steel
shell. But this difficulty has been addressed in previous works where appropriate
fixture and ultrasonic probe were designed. Details of the previous works are
given below.

The patent application JP2012207270A claims a method of measuring residual
thickness of blast furnace stave. The objective of this work is 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 through the
water channel, when the probe contacted to inner side surface of the furnace of
water channel. The thickness of the stave wall towards inner side of the furnace
is measured with high precision by inserting resin-made soft probe through the
water channel. It claims that a residual thickness measuring method of the sheft
furnace stave along with the ultrasound soft probe made of resin.
The patent application JP202275515A claims a method for measuring thickness
of stave. The objective of this work is 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 was embedded into the stave main body where
the through holes were provided in the thickness direction of the stave main
body. The embedded rolled material is measured by the ultrasonic tbiek<>o$s
gauge. It claims that the embedded rolled stock made from copper or is alloy
and inserted into a stave which was having provided a through hole to a
thickness direction and a thickness measuring method using an ultrasonic board
thickness meter.
The patent application KR20120065119 claims a device and method for
measuring a thickness of a stave of a furnace. This method involves embedded
ultrasonic sensor in the cooling channel of the stave. Hence the thickness of the
stave can be periodically measured with the real-time and the attrition rate of the
stave can be measured.
The patent application 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
coling water channel surface in the stave. This technique also finds efficient to
measure remnant thickness of the staves.

In the patent application 1356/KOL/2013, a mechanism for measuring the stave
rib thickness is claimed. The mechanism includes ultrasonic probe, appropriate
fixture and guiding mechanism. This application addresses the issue of placing
the ultrasonic at the intended location. Also the application ensures the
measurement is from the rib section, and not from the thin section.
All the above patent applications are intended for thickness measurement of
stave system/ where cooling channels are parallel to rib face at the place where
ultrasonic sensor can be placed possibly using the fixtures (henceforth referred
as copper staves), as shown in FIG. 2. But these disclosures are not capable for
thickness measurement of staves which have bent cooling pipes as shown in
FIG. 3, because the bent in the cooling pipe is not only a hindrance for placing
sensor but it also adds difficulty by introducing mode conversion of ultrasonic
waves.
Objects
In view of the foregoing limitations inherent in the prior-art, it is an object of the
disclosure to measure thickness of staves with bent cooling channel.
Therefore, it is an object of the disclosure to design an ultrasonic measuring
arrangement which enables stave thickness measurement in staves with bent
cooling channel.
SUMMARY OF THE DISCLOSURE
In one aspect, the disclosure provides an ultrasonic measuring arrangement for
measuring thickness of a stave with a bent cooling channel is described. The
ultrasonic measuring arrangement is to be aligned and in contact with the bent
cooling channel while measuring thickness of the stave, the ultrasonic measuring
arrangement comprises an ultrasonic probe to be attached normally to a surface
of a shoe, the shoe is made up of the same material as that of the stave, the
ultrasonic probe is configured to send and receive ultrasonic wave so as to
measure thickness of the stave, the ultrasonic probe is attached normally to the
shoe so as to restrict mode conversion, the mode conversion arising on a
condition of the ultrasonic wave being transmitted from one medium to another
medium at an angle other than normal.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
FIG. 1 illustrates the sectional view of blast furnace and its different stages
where a copper staves are located.
FIG. 2 illustrates cross section of the copper stave along with ultrasonic based
thickness measurement system.
FIG. 3 illustrates a cross sectional view of a cast steel staves with a bent cooling
channel in accordance with an embodiment of the disclosure.
FIG. 4 illustrates mode conversion phenomena of ultrasonic waves.
FIG. 5 illustrates the inapplicability of a conventional ultrasonic probe for the
cast steel stave thickness measurement.
FIG. 6 illustrates alignment of an ultrasonic measuring arrangement in the cast
steel stave in accordance with an embodiment of the disclosure.
FIG. 6a illustrates design of the ultrasonic measuring arrangement in accordance
with an embodiment of the disclosure.
FIG. 7 illustrates simulated A-Scan for the ultrasonic measuring arrangement in
accordance with an embodiment of the disclosure.
FIG. 8 illustrates the experimental result of the ultrasonic measuring
arrangement in accordance with an embodiment of the disclosure.
Detailed Description
Various embodiments of the disclosure provide an ultrasonic measuring
arrangement for measuring thickness of a stave with a bent cooling channel, the
ultrasonic measuring arrangement being aligned and contacted with the bent
cooling channel while measuring thickness of the stave, the ultrasonic measuring
arrangement comprising: an ultrasonic probe, the ultrasonic probe being
attached normally to a surface of a shoe, the shoe being made up of the same
material as that of the stave, the ultrasonic probe being configured to send and
receive ultrasonic wave so as to measure thickness of the stave, the ultrasonic

probe being attached normally to the shoe so as to restrict mBde conversion,
the mode conversion arising on a condition of the ultrasonic wave being
transmitted from one medium to another medium at an angle other than normal.
Shown in FIG. 3 is a cast steel stave hereinafter ("stave (100a)") with a bent
cooling channel (104a) in a blast furnace made by casting process, in which the
whole stave is casted by keeping the cooling pipes in its place as per design.
Hence the stave (100a) has gradually bent cooling channel (104a), as shown in
FIG. 3. The gradually bending cooling channel (104a) is further continued by a
cooling pipe (108a) beyond the stave (100a). Rl, R2 and R3 are ribs of the stave
(100a). Tl is the thicknesses that need to be measured.
"L" is the location where an ultrasonic measuring arrangement is to be placed so
as to measure the thickness of the stave. In ultrasonic wave based thickness
measurement of cast steel staves with the bent cooling channel (104a) causes
mode conversion of ultrasonic waves and thereby refraction.
The following two conditions must co-exist for mode conversion of ultrasonic
wave:
Condition 1: Ultrasonic wave must propagate between two media having
different acoustic impedances (different materials).
Condition 2: Ultrasonic wave should incident at an angle to the normal at the
interface where change of material exists.
It is understood that in mode conversion, refraction happens (FIG. 4a)
simultaneously, except at normal incidence as shown in FIG. 4b.
Shown in FIG. 4a, is the incident wave (I) from medium (Mi) incident at an
angle (6i) to the normal at the interface of medium (M2). The Incident wave (I)
splits into longitudinal transmitted wave (TL) at angle (6L) and shear transmitted
wave (Ts) at angle (6S). Whereas, no such splitting occurs when the incident
angle is normal at the interface of medium (M2) from medium (Ml) shown in
FIG. 4b.

For the true thickness measurement of the stave, ultrasonic waves should be
generated perpendicular to hot face of the stave (100a). But as shown in FIG. 5,
inclined incident of ultrasound wave onto a cast steel stave (100b) from
conventional probe (P) causes mode conversion.
While longitudinal wave is intended for rib thickness measurement, the other
mode develops noise during measurement. Hence conventional ultrasonic probes
can lead to erroneous due to mode conversion. Rnite element studies also
confirmed the adverse effect of refraction and mode conversion on stave
thickness measurement.
Hence the challenge in stave thickness measurement is to generate ultrasonic
waves normal to the stave hot face without causing mode conversion.
Simultaneous existence of the conditions 1 and 2 should be eliminated to prevent
mode conversion. Due to accessibility issues it is not possible to achieve normal
incidence by any means. Also, since measuring arrangement used to measure
thickness exhibit best performance when the crystal is coupled with Plexiglas,
therefore, the ultrasonic wave must experience a change in material. Hence in
this application both conditions cannot be eliminated. But the new design can be
initiated to separate the conditions in time domain i.e. the design delaying the
condition 2 from condition 1 with a small known time delay.
For true thickness measurement of a cast steel stave (100c) with a bent cooling
channel (104c), an ultrasonic measuring arrangement (112) has been designed
in such a way that it prevents mode conversion as shown in FIGS. 6 and 6a.
The stave (100c) with the bent cooling channel (104c) along with the ultrasonic
measuring arrangement (112) is aligned and is in contact in the bent cooling
channel (104c) using a fixture (124) for measuring the thickness of the stave
(100). The bent cooling channel (104c) is further continued by a cooling pipe
(108c) beyond the stave (100c). Through the cooling pipe (108c) water is flown
in the stave (100c) via bent cooling channel (104c) for cooling.

The ultrasonic measuring arrangement (112) comprises an ultrasonic probe (116)
and a shoe (120) made up of cast steel as shown in FIG. 6a. A surface Se of the
shoe (120) Is curved to align in the bent cooling channel (104c). Other surface
(SA) opposite to the surface SB is flat. The ultrasonic probe (116) is attached
normally to the surface (SA) of the shoe (120). The ultrasonic probe (116) is
configured to send and receive ultrasonic waves so as to measure thickness of
the stave (100). The ultrasonic probe (116) comprises a transmitter (T) and a
receiver (R). The transmitter (J) is configured to transmit ultrasonic waves
towards the stave and the receiver (R) is configured to receive the ultrasonic
waves.
The ultrasonic measuring arrangement (112) further coupled to an ultrasonic
thickness gauge (128) by means of a cable (W). The ultrasonic thickness gauge
(128) is configured to manipulate the ultrasonic wave (as signal) from transmitter
and receiver to calculate the thickness of thestave (100c).
For exhibiting best performance, the ultrasonic probe (116) is made up of
Plexiglas.
It is to be noted that the ultrasonic measuring arrangement (112) is built on the
concept of delaying the second condition from first condition with a small known
time delay,
Separating the two conditions is achieved by using the shoe (120) made up of
die same material as that of the stave (100c). The shoe (120) is designed in
such way that it matches the contour of the bent cooling channel (104c). Surface
SA at one end provides a normal incidence to ultrasonic waves and SB at the
other end provides easy alignment of the ultrasonic measuring arrangement
(112) in the bent cooling channel (104c).

At the surface SA of the shoe (120), the ultrasonic wave is introduced from the
ultrasonic probe (116), made up of Plexiglas, at normal incidence and
subsequently to the surface SR, opposite to surface SA. Though the material is
changing, from Plexiglas to cast steel, but no mode conversion will occur as the
angle of incidence is normal due to the ultrasonic probe (116) being normal to
the SA.
While transmission of the ultrasonic wave from SA of the shoe (100) to the stave
(100c), though angle of incidence is not normal there is no mode conversion,
because the shoe (120) and the cast steel stave (100c) are made of the same
material.
Hence with the aid of the specially designed shoe, mode conversion is prevented.
In addition, design of the ultrasonic measuring arrangement (120) also avoids
cross talk issue by an acoustic isolation between transmitter and receiver.
Also the design of the ultrasonic measuring arrangement (120) is of great
flexibility as one can easily align it in the bent cooling channels of different
staves. One has to only design the shoe that matches with contour of the bent
cooling channel and the ultrasonic probe has to be fixed with the flat surface of
the shoe.
Effectiveness of the design of the measuring arrangement (120) can be validated
using Finite Element simulations. A simulated A-Scan for cast steel stave
thickness measurement using the shoe design is shown in FIG. 7. As found from
finite element simulation that this design of measuring arrangement is capable to
overcome the difficulties imposed by stave geometry for thickness measurement.
The developed ultrasonic measuring arrangement has been tested at lab and
found that it is capable to measure stave thickness. The experimental A-Scan
result shown in FIG. 8, not only validates that the above ultrasonic measuring
arrangement development concept is true, but also implies the viability of stave
thickness measurement using the above set up.

It should be appreciated that the ultrasonic measuring arrangement (120) can
also be used to measure thickness of staves made up of materials other than
steel. Similarly the shoe will also be made up of the same material as that of the
stave.
Advantages:
The disclosure is advantageous in measurement of thickness of staves with
gradually bent cooling channel. Also the design is helpful in avoiding cross talk
issue generated by an acoustic isolation between transmitter and receiver.

We claim:
1. An ultrasonic measuring arrangement (112) for measuring thickness of a
stave (100) with a bent cooling channel (104), the ultrasonic measuring
arrangement (112) being aligned and contacted with the bent cooling channel
(104) while measuring thickness of the stave (100), the ultrasonic measuring
arrangement (112) comprising:
an ultrasonic probe (116), the ultrasonic probe (116) being attached
normally to a surface (SA) of a shoe (120), the shoe (120) being made up of the
same material as that of the stave (100), the ultrasonic probe (116) being
configured to send and receive ultrasonic waves so as toirieasure thickness of
the stave (100), the ultrasonic probe (116) being attached normally to the shoe
(120) so as to restrict mode conversion, the mode conversion arising on a
condition of the ultrasonic wave being transmitted from one medium to another
medium at an angle other than normal.
2. The measuring arrangement (112) as claimed in daim 1, wherein the
stave (100) and the shoe (120) are made up of cast steel.
3. The measuring arrangement (112) as claimed in claim 1, wherein the
ultrasonic probe (116) comprises a transmitter (T) to transmit the
ultrasonic waves and receiver (R) to receive the ultrasonic waves.
4. The measuring arrangement (112) as claimed in daim 1, wherein the
measuring arrangement (112) is coupled to an ultrasonic thickness gauge
(128), wherein the ultrasonic thickness gauge (128) is configured to
calculate the thickness of the stave using ultrasonic waves.
5. The measuring arrangement (112) as claimed in claim 1, wherein the
ultrasonic probe (116) is made up of Plexiglas,

6. The measuring arrangement (112) as claimed in claim 1, wherein fte
ultrasonic measuring arrangement (112) is aligned in the bent cooling
channel (104) by means of a fixture (124).
7. The measuring arrangement (112) as claimed in claim 1, wherein a
surface Sa of the shoe (12G) being on opposite side to the surface (SA) is
curved in shape so as to align with the bent cooling channel (104).