The invention relates to a methodology for stave thickness measurement. Particularly, the invention relates to a flexible fixture for measuring thickness of staves with ribs significantly deep from cooling pipes. Particularly the invention relates to a flexible fixture which enables to have a longer bent portion in the fixture.
BACKGROUND OF THE INVENTION
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 external steel shell is crucial to the operational efficiency and structural integrity of the blast furnace. Refractory linings in conjunction with the cooling staves are the key elements to achieve this objective in most modern furnaces. Cooling staves are designed with internal channels for circulating water to protect steel shell from heat. As the staves are located inside of steel shell like a liner, they are prone to wear due to the relative motion of hot gases and metal inside the furnace. Severe wear condition of staves may lead to catastrophic failure of blast furnaces, hence it is of high importance to measure the remnant thickness of the staves frequently for safe operation of the furnace. Generally staves are designed with rib structures as shown in FIG. 1. As the rib sections of the staves are projected towards the flow of hot metal and gases, they are more vulnerable to wear than the thin section. So stave thickness measurement often refers to the measurement from the rib section.
Prior Art:
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 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 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 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 rod 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 thickness gauge. It claims for the embedded rolled stock made from copper or its alloy and inserted into a stave in its thickness direction. The patent also claims the thickness measurement technique using ultrasound.
The patent KR1220798B1 (KR20120065119) claims a methodology for measuring stave thickness measurement. 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 KR2012067786A claims a device and a method for measuring a thickness of a stave. This method involves an ultrasonic based technique comprising a special probe made straight to get access with cooling water channel surface in the stave. This technique also finds efficient to measure remnant thickness of the staves.
In the patent 1356/KOL/2013, a mechanism for measuring the stave rib thickness was claimed. The mechanism includes ultrasonic probe, appropriate

fixture and guiding mechanism. The above patent addresses the issue of placing the ultrasonic at the intended location. Also the patent ensures the measurement is from the rib section, and not from the thin section.
All the above patents are intended for thickness measurement of stave system where ultrasonic sensor can be placed at the rib section using the fixtures, as shown in FIG. 2. It must be noted that in these inventions, the height of the end section of fixture where the sensor is mounted must be less than the diameter of inlet/outlet pipe. If the height of the end section is more, the fixture will simply not be able to enter through the pipe as shown in FIG. 3. But there are staves with rib sections much below the cooling pipe, and because of the above constraint these previous fixture designs cannot help in thickness measurement of those staves.
Further in the cast steel staves, the region accessible through cooling pipe for stave thickness measurement is non-planar curved surface, which causes refraction and mode conversion of ultrasonic waves during generating it in the stave. Refraction is the phenomena, which describes the change in wave propagation direction at the interface of two medium. In sound wave propagation, refraction happens except normal incidence as shown in FIG. 4.
Mode conversion is the phenomena of splitting of ultrasound into shear and longitudinal modes at the interface. Mode conversion happens along with refraction. For stave thickness measurement ultrasound should be generated perpendicular to the rib section without mode conversion and refraction so as to make unambiguous measurement. But curved surface in the stave creates oblique positioning of the sensor which eventually will result in erroneous readings. Hence to reach the straight portion of the cooling channel in cast steel staves, the length of the end section of the fixture should be close to radius of inner curvature of the bend. But generally the radius of inner curvature is more than the cooling pipe diameter. So the rigid design proposed in previous works cannot help for casts steel stave thickness measurement.

OBJECTS OF THE INVENTION
In view of the foregoing limitations inherent in the prior-art, it is an object of the invention to measure thickness of staves where the rib section is at a deeper distance and much larger than the diameter of inlet/outlet pipe diameter.
Another object of the invention is a flexible fixture which provides flexibility at the time of insertion through the curved inlet/outlet pipes and the same can provide rigidity while taking measurement so as to apply pressure against the stave surface.
SUMMARY OF THE INVENTION
In one aspect, the invention provides a flexible fixture for measuring staves thickness in bend cooling channel used in blast furnace comprising a guide rod flexibly joined with a bend section, the guide rod being configured to rest at a horizontal section of a bend cooling channel, the bend section being configured to rest at a curve section and further down of the bend cooling channel, an ultrasonic probe being fixed at the bend section, the ultrasonic probe being configured to send and receive ultrasonic signals for measurement of the stave thickness, the bend section comprising one or more link, each of the link being detachable and hinged to each other, and an adjustable stopper coupled at the guide rod to bend the bend section for various angles to accommodate the next subsequent link after the guide rod to rest at the curve section.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
FIG. 1 illustrates cross section of a typical cooling stave.
FIG. 2 shows copper stave cross section and ultrasonic thickness measuring fixture.
FIG. 3 shows schematic showing curved cross section of a typical cooling stave.

FIGS. 4a and 4b show transmission of ultrasound in solid media in normal incidence and oblique incidence.
FIG. 5a shows a design of a flexible fixture in accordance with an embodiment of the invention.
FIG. 5b shows critical dimensions of the stave relevant to stave thickness measurement in accordance with an embodiment of the invention.
FIGS. 6a, 6b and 6c show the flexible fixture inserted in straight orientation through cooling channel, fixture gradually bends as it approaches the curved portion and bending of flexible fixture restricted to certain angle to match the angle of cooling channel respectively in accordance with an embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Various embodiments of the invention provide a process for manufacturing a flexible fixture for measuring stave thickness in bend cooling channel used in blast furnace, the flexible fixture comprising: a guide rod flexibly joined with a bend section, the guide rod being configured to rest at a horizontal section of a bend cooling channel, the bend section being configured to rest at a curve section and further down of the bend cooling channel; an ultrasonic probe being fixed at the bend section, the ultrasonic probe being configured to send and receive ultrasonic signals for measurement of the stave thickness; the bend section comprising one or more link, each of the link being detachable and hinged to each other, and an adjustable stopper coupled at the guide rod to bend the bend section for various angles to accommodate the next subsequent link after the guide rod to rest at the curve section.
Shown in FIG. 5a is a flexible fixture (500) for measuring stave thickness in a bend cooling channel (504) (shown in FIG. 5b). The cooling channel (504) is mainly comprised of a horizontal section (508) and a curve section (512). The

flexible fixture (500) comprises of a guide rod (516) and a bend section (520) flexibly joined together. The guide rod (516) is configured to rest at the horizontal section (508) and the bend section (520) rests at the curve section (512) and further down of the bend cooling channel (504) while measuring staves remnant thickness. Since the guide rod (516) and the bend section (520) are flexibly joined, the bend section (520) has the tendency to bend as it encounters curve and gravity.
An ultrasonic probe (524) is fixed at the bend section (520) to send and receive the ultrasonic signals. The ultrasonic probe (524) is fixed at such location of the bend section (520) from where the bend section can reach and the stave thickness can be measured. The ultrasonic probe (524) is further electrically coupled to the ultrasonic equipment (not shown) which converts the signal into stave thickness.
The bend section (520) is comprised of one or more links (528). The number of links depends on the depth of the point from the horizontal section (508) where the stave thickness is to be measured. Each of the link/links (528) is detachable and hinged to each other. The links are hinged in such a manner that they bend on curve surface and gravity, but the maximum they can bend is 90 deg. (clockwise) from the horizontal section (508).
In various other embodiments the links can be made to bend at angle other than 90 deg. as per the requirement.
The links can be in various sizes. But the maximum length of the any link can be 2 √D (2R-D), where “D” is the diameter of the cooling channel and “R” is the radius of the curve section. Else the link may not be able to move in the curve section.
An adjustable stopper (532) is coupled to the guide rod (516). The adjustable stopper (532) is configured to bend the bend section (532) at for various angles as desired. This is to accommodate the next subsequent link after the guide rod (516) to rest at the curve section (512). Since the bend section comprises of one or plurality of the link/links (528) and also the bending is

required and hence affected only to the link subsequent to the guide rod and not to the other links.
The adjustable stopper (532) comprises of a nut like structure (536) joined to the guide rod (516), through which a bolt like structure (540) is passed (nut bolt mechanism). Various other mechanisms can be used in place of nut bolt mechanism.
Shown again in the FIG. 5a are ref. line “link 2” and angle θ between “link 2” and the guide rod (516). The maximum bend angle of the bend section (520) is fixed as “θ” (clockwise). Generally the bend angle of the bend section (520) is already known to the operators hence the angles are set initially using the stopper while measuring stave thickness. This angle can be changed for various other bend sections having different angles.
Through the adjustable stopper (532), various angles can be adjusted between the guide rod (516) and the bend section (520). It should be noted that when the bent section attains its maximum angle (set initially) it becomes rigid/locked if the angle is decreased by pushing the guide rod (516). This locking can be sensed by the operator. This sense signifies the operator that ultrasonic probe (514) is well contacted with the stave and now the readings can be taken accurately.
FIGS. 6a-6c shows different states of the flexible fixture (500) during stave thickness measurement. For brevity purpose, the bend section (520) of the said fixture is shown with a single link. The angle (θ) between the bend section and the horizontal section is set initially.
The fixture is inserted in a straight orientation through the bend cooling channel (504) as depicted in FIG. 6a. As the fixture (500) is pushed into the cooling channel (504), the bend section (520) of the fixture with the probe (524) gradually bends as it approaches the curve section (512) of the cooling channel (504) as shown in FIG. 6b. Then the fixture (500) obtains the desired angle θ, as the fixture is pushed horizontally against the cooling channel and the stopper (532) restricts the rotation. As shown in FIG. 6c, the fixture becomes rigid at this

orientation so that measurement can be carried out. After completion of measurement, the fixture can be retrieved out of the cooling channel in a reverse fashion.
The angle (θ) can be varied by adjusting the bolt’s (540) effective length (L). So the same fixture can be applied for staves at different orientations.
Advantages:
The flexible fixture can easily measure the thickness of staves where the rib section is at a deeper distance and much larger than the diameter of inlet/outlet pipe diameter.
The flexible fixture provides flexibility at the time of insertion through the curved inlet/outlet pipes and the same can provide rigidity while taking measurement so as to apply pressure against the stave surface. Hence the stave thickness can be measured accurately.

WE CLAIM
1. A flexible fixture (500) for measuring stave thickness in bend cooling
channel used in blast furnace, the flexible fixture (500) comprising:
a guide rod (516) flexibly joined with a bend section (520), the guide rod (516) being configured to rest at a horizontal section (508) of a bend cooling channel (504), the bend section (520) being configured to rest at a curve section (512) and further down of the bend cooling channel (504);
an ultrasonic probe (524) being fixed at the bend section (520), the ultrasonic probe (524) being configured to send and receive ultrasonic signals for measurement of the stave thickness; and
the bend section (520) comprising one or more link (528), each of the link (528) being detachable and hinged to each other, and an adjustable stopper (532) coupled at the guide rod (516) to bend the bend section (520) for various angles to accommodate the next subsequent link after the guide rod (516) to rest at the curve section (512).
2. The flexible fixture (500) as claimed in claim 1, wherein maximum length of each of the link is 2 √D(2R-D), wherein D is the diameter of the cooling channel and R is the radius of the curve section.
3. The flexible fixture (500) as claimed in claim 1, wherein the ultrasonic probe (524) is coupled to an ultrasonic equipment for data conversion.
4. The flexible fixture (500) as claimed in claim 1, wherein the adjustable stopper (532) comprises a nut bolt mechanism for bending various angles.

5. The flexible fixture (500) as claimed in claims 1 and 4, a nut like structure (536) is joined to the guide rod (516).