Patent Description:
Cooling plates for metallurgical furnaces, also called "staves", are well known in the art. They are used to cover the inner wall of the outer shell of the metallurgical furnace, as e.g. a blast furnace or electric arc furnace, to provide:.

Originally, the cooling plates were cast iron plates with cooling pipes cast therein. As an alternative to cast iron staves, copper staves have been developed. Nowadays, most cooling plates for a metallurgical furnace are made of copper, a copper alloy or, more recently, of steel.

The refractory brick lining, the refractory guniting material or the process generated accretion layer forms a protective layer arranged in front of the hot face of the panel-like body. This protecting layer is useful to protect the cooling plate from deterioration caused by the harsh environment reigning inside the furnace. In practice, the furnace is however also occasionally operated without this protective layer, resulting in erosion of the lamellar ribs of the hot face.

While the blast furnace may be initially provided, in some cases, with a refractory brick lining on the front side of the staves, this lining may wear out during the campaign depending on the operating conditions. In particular, it has been observed that, in the bosh section, the refractory lining may disappear relatively rapidly. While an accretion layer of slag and burdening then typically forms on the hot side of the cooling plates, it actually continuously builds-up and wears out, so that during certain periods of time the cooling plates are directly exposed to the harsh conditions inside the blast furnace, conducting to the wear of the cooling plate body.

The principal causes of wear to the accretion layer, and of course to the lining and cooling plate, are the upward flow of hot gases and the rubbing of the sinking burden (coal, ore, etc.). Regarding the flow of hot gases, the wear is not only due to a thermal load, but also to abrasion by particles carried in the ascending gases.

Ultimately, therefore, the presence of a good accretion layer is strictly connected to good conduction of the blast furnace, with all the complications that the process itself requires, and to a good condition of ribs of the staves.

The state of consumption of the cooling plate ribs is particularly critical; if not sufficiently "sharpened", they cannot allow sufficient adhesion of the accretion layer itself, even in the case of good conduction of the blast furnace.

For this reason, the periodic check of the thickness of the cooling plates is of utmost importance, in particular of the ribs. Non-invasive systems like ultrasound testing technology is preferred to minimize the impact on the plant operation, avoiding to stop the plant and disturb the production.

Document <CIT> discloses a cooling stave comprising a wear detection system using an ultrasonic probe in contact with the rear face of the stave body in order to detect erosion thereof. This system allows measuring the residual body thickness between the front and rear faces.

Document <CIT> discloses a thickness measurement system, wherein an ultrasonic probe is mounted at the end of a flexible extension member, which permits inserting the ultrasonic probe in the inlet and outlet regions of the coolant channel. It is thus possible to actually measure the thickness of the body between the cooling plate front side and the coolant channel. This information is of interest since it gives the residual body thickness to the coolant channel, which is critical for safe operation of the blast furnace, as introduction of water into the blast furnace must be avoided. However, this system only permits a local measurement (at the beginning and/or at the end of the coolant channel) and is today considered insufficient for a proper assessment of the condition of the cooling plate. Indeed, experience shows that often, the cooling plate is more worn in the middle body than at the extremities. Assessments based on this system thus leads to an incorrect analysis in reference to the actual general wear of the cooling plate, and therefore to an incorrect forecast of its residual life time.

<CIT> discloses a stave thickness measuring apparatus wherein an ultrasonic sensor unit is connected to a driving unit, which permits inserting the ultrasonic sensor in a stave and moving the sensor inside the stave. It is thus possible to perform thickness measurements along the whole length of a stave. However, the operating principle requires installation of the ultrasonic sensor unit at each measuring point, e.g. contact legs being deployed or a balloon being inflated, to ensure close contact between the ultrasonic probe and the inner surface of the stave, which complicates the whole measuring process.

Other systems for thickness measurement of staves are disclosed in documents <CIT> and <CIT>.

<CIT> discloses a thickness measurement device with an expandable structure comprising pivotable levers.

The object of the present invention is to provide an alternative and reliable way of monitoring the wear status of cooling plates.

This object is achieved by a system and method of measuring the thickness of a cooling plate as claimed in claims <NUM> and <NUM>.

The present invention proposes a system for measuring a thickness of a cooling plate comprising:.

The inventive ultrasound testing system provides a number of advantages. The probe holder unit, with its spring biased rear housing part, allows for self-adaptation to the cooling channel diameter. This ensures a continuous contact of the ultrasound probe to the side to be measured. The use of a chain, forming a flexible but torsionally stiff guide member, allows for a precise guiding of the probe unit in the cooling channel. Furthermore, the chain can be coupled to an encoder gear, allowing to measure the position of the probe unit inside the coolant channel without any slipping or the like.

The 'length" of the coolant channel is the greatest dimension of the coolant channel. Since the cooling plate is, in use, substantially vertical, the length may also be referred to as the 'height'.

In embodiment, the housing comprises a main housing part defining the sensor side, the ultrasonic probe being arranged in a recess opening in the sensor side. The main housing part may be formed of a generally semi-cylindrical wall extending between the two ends; and the rear housing part may be configured as a wall portion having a rounded outer side and an inner side complementary to a facing side of said the housing part.

In embodiments, the rear housing part comprises at least one, preferably two, pins engaged in a respective cavity in the main housing part, each pin being surrounded by a spring biasing the rear housing part away from the main housing part.

In embodiments, the rear housing part comprises lateral branches that cooperate with guide means on the main housing part, for guiding the rear housing part. The branches may comprise fingers that are engaged into grooves in the guide means, the grooves defining a sliding axis parallel to the axis of said pins.

The probe holder unit may be fixed to the drive chain by any appropriate means. Fixing means may be provided at the first side of the housing for connecting said drive chain, in particular coupling links pivotally affixed to the housing and comprising an orifice for connecting the drive chain.

Advantageously, an articulated stabilizer member is pivotally connected to the housing. The stabilizer member comprises a set of elements that are articulated on one another and are configured to form a guide housing for the cable assembly. The elements of the stabilizer member may be shaped as hollow cuboid- or parallelepiped-shape pivotally and serially connected to one another and defining a central passage for the cable assembly. Preferably, the elements of the stabilizer member are configured such that pivoting is mainly possible towards the rear side of the housing.

The use of such stabilizer member forms a protection for the cable assembly and is of particular interest to protect the cables in the angled portions of the coolant channel.

In embodiments, the encoder arrangement includes a mounting frame adapted for mounting to an outer periphery of a connection pipe or pipe coupler in communication with the cooling channel and supporting the first gear and the encoder. The first gear is located, when the mounting frame is in place on the cooling pipe or pipe coupler, such that at least part of its periphery is in axial continuity of the cooling pipe or pipe coupler. The chain may thus be discharged from the first gear in direct alignment with the connection pipe. Preferably, the second gear is provided proximate the first gear for tensioning the drive chain, the second gear being pivotally mounted on a pivotable arm fixed to said mounting frame.

The cable assembly may conveniently include a flexible hose for supplying a coupling fluid to the probe holder unit. The housing may comprise an inlet port for the fluid coupling medium and a spray orifice in the sensor side (the latter connected by an internal duct).

For protection, the wires/hose of the cable assembly are arranged in a flexible steel socket.

Advantageously, drive chain is a multi-row chain connected to the probe housing to extend longitudinally in the coolant channel, hence showing longitudinal flexibility and torsional stiffness.

These and other embodiments of the present device and method are described in the appended dependent claims.

The present invention thus provides an improved system for measuring/monitoring the thickness of cooling plates. The inventive system can use commercial ultrasound testing equipment. The combination of the ultrasound probe and encoder arrangement allows for accurate thickness measurements in relationship to the precise position (length/height) of the probe, thanks to the encoder. The UT measurements can be done continuously along the length of the coolant channel, or in a spot by spot manner, at a plurality of predefined positions.

The system, in particular the probe holder unit, is preferably periodically submitted to certification, ensuring that the system is <NUM>% reliable for the measurements.

According to another aspect, the invention relates to a method as claimed in claim <NUM>.

The present invention will now be described, by way of examples, with reference to the accompanying drawings, in which:.

The present invention relates to a system and method for measuring the thickness of cooling plates. The system includes a probe holder unit <NUM> designed to be inserted into coolant/cooling channels of cooling plates <NUM>, to measure the body and ribs thickness remaining to the front side of the cooling panel. The probe holder unit <NUM> is driven through the cooling channel by means of a drive chain <NUM>. An encoder arrangement <NUM> allows determining the position of the probe holder unit <NUM> inside the cooling channel. The principle of the present system is illustrated in <FIG>.

As it is known, cooling plates <NUM> are used in the iron making industry for cooling the wall of furnaces such as e.g. shaft furnaces, blast furnaces or electric arc furnaces. A cooling plate comprises a body that is typically formed from a slab e.g. a cast or forged body of copper, copper alloy or steel. Furthermore, the body has at least one conventional coolant channel embedded therein. The coolant channels may be formed by cast-in pipes or by drilling through the body.

<FIG>, shows a conventional cooling plate <NUM> comprising a slab-shaped cast body <NUM> of copper alloy comprising a plurality of coolant channels <NUM> (only one is seen in the Figure). The coolant channels <NUM> have been obtained by drilling through the shaped body from one longitudinal end to the other; then drilling top and bottom access holes <NUM> at the extremities of the coolant channel <NUM>. The axial extremities of the coolant channel <NUM> are closed by plugs (not visible), whereas connection pipes <NUM> are welded to the access holes <NUM>. In the blast furnace, such cooling plates <NUM> provide a heat evacuating protection screen between the interior of the furnace and the outer furnace shell <NUM> (or armour).

In the blast furnace, the cooling plate <NUM> is mounted onto the furnace shell. The body <NUM> has a front face generally indicated <NUM>, also referred to as hot face, which is turned towards the furnace interior, and an opposite rear face <NUM>, also referred to as cold face, which in use faces the inner surface of the furnace shell.

As is known in the art, the front face <NUM> of body <NUM> advantageously has a structured surface, in particular with alternating ribs <NUM> and grooves <NUM>. When the cooling plate <NUM> is mounted in the furnace, the grooves <NUM> and lamellar ribs <NUM> are generally arranged horizontally in order to provide an anchoring means for a refractory brick lining (not shown).

As it is known, depending on the operating conditions of the blast furnace, the protection formed by the refractory brick lining or the accretion layer produced by process may be subject to erosion due to the descending burden material, leading to the fact that the cooling plates are unprotected - at least for a period of their life time - and have to face the harsh environment inside the blast furnace. As a result, abrasion of the cooling plates occurs too, and it is desirable to know the wear status of the cooling plates.

Referring to <FIG>, the probe holder unit <NUM> comprises a housing <NUM> in which an ultrasonic probe is arranged to be able to transmit and receive ultrasonic waves. The housing <NUM> is generally made from metal, e.g. aluminum alloy. As will be understood from the drawings, the housing <NUM> has a generally cylindrical or tubular outer shape (however not necessarily circular in cross-section), adapted to fit inside a coolant channel <NUM> of a cooling panel <NUM>.

The housing <NUM> extends along a longitudinal axis L, from a first end <NUM> to a second end <NUM>. The housing <NUM> has a lateral, sensor side <NUM> and an opposite back side <NUM>. An ultrasonic probe <NUM> is arranged in the housing <NUM> to be able to transmit and receive ultrasonic waves from the sensor side <NUM>.

Direction L is the direction in which the probe <NUM> is used in practice.

In the shown embodiment, the housing <NUM> comprises two parts or shells. The first housing part comprises a lateral housing wall <NUM> extending between the two ends <NUM>, <NUM> and having a rounded outer surface. This housing part <NUM> defines the sensor side, which appears here generally as a cylinder half. The ultrasonic probe <NUM> is arranged in a cylindrical recess <NUM> in wall/part <NUM>.

Opposite the sensor side <NUM>, at the rear side <NUM>, is the second housing part <NUM>, which is moveable with respect to the first housing part <NUM> to allow the probe holder unit <NUM> to adapt to the internal diameter of the coolant channel, as will be explained below. The second housing part <NUM> is formed as a wall portion, which is assembled to the first housing part <NUM> in such a way as to be moveable with respect to the latter, transversally to the length axis L, typically perpendicularly thereto. The moveable second housing part <NUM> has a cylindrically shaped outer surface. In order for the probe holder unit <NUM> to self-accommodate to the internal diameter of the cooling channel <NUM>, the second housing part <NUM> is spring biased away from the first part <NUM>.

In the shown embodiment, the second housing part <NUM> comprises two lateral branches <NUM>, by which it is slideably guided on the first housing part <NUM>. With these branches <NUM>, the moveable wall <NUM> has a kind of U-shaped cross-section.

Reference sign <NUM> indicates a core element that is positioned in the first housing part <NUM> in an internal section, preferably in alignment with the recess <NUM>. Core element <NUM> may have a prismatic shape and protrudes from the first housing part <NUM> toward moveable wall <NUM>. It comprises a couple of blind bores (not visible) that receives a respective pin <NUM> integral with the moveable wall <NUM> (see <FIG>). Each pin <NUM> extends from the inner side of moveable wall <NUM>, substantially perpendicularly to length axis L, and is surrounded by a compression spring <NUM>, which bears at one end against the inner side of wall <NUM> and at the other end against the bottom of the blind bore in core <NUM>. The springs <NUM> thus exerts an outward biasing force, which pushes the moveable wall <NUM> away from the first housing part <NUM>.

The movable wall <NUM> forms an expandable structure, which deploys / adapts automatically such that device <NUM> expands over the whole inner diameter of the coolant channel <NUM>, this deployment ensuring intimate contact between the inner surface of the coolant channel <NUM> and the probe holder sensor side <NUM>.

<FIG> shows the rest position, the moveable wall <NUM> being in the outermost position. This is basically the configuration when the probe holder unit <NUM> is outside the cooling channel or in a large diameter connection pipe. In this configuration, the maximum cross-section dimension is Dmax.

<FIG> in turn shows the compact configuration of the probe holder unit <NUM>, where the moveable wall <NUM> rests against the first housing part <NUM>. The distance Dmin is here the minimum dimension of the probe unit <NUM>.

In the embodiment, the branches <NUM> of the moveable wall <NUM> comprise outwardly protruding fingers <NUM> that fit into guide elements <NUM> provided with grooves <NUM> extending parallel to the pins <NUM>.

Fixing means are provided at the first end <NUM> of the probe holder unit, to attach the drive chain <NUM>. The fixing means here comprise a pair of connecting links <NUM> affixed to the first housing part <NUM>. In <FIG>, the links <NUM> have a first hole <NUM> by which they are pivotally fixed to the first housing part <NUM> by a screw or the like. The second hole <NUM> is for connection to the drive chain <NUM>.

The connecting links <NUM>, by way of the holes <NUM> and <NUM>, define a pivoting direction P which corresponds to the centers of the holes. The pivoting direction P is perpendicular to direction L and perpendicular to the direction the pins <NUM>.

In use, the drive chain <NUM> provides the desired bending capacity along the length direction L (by way of its articulated structure) while being rather stiff in the transversal direction, i.e. it is torsion resistant. The flexibility of the chain <NUM> together with the articulated structure of the probe holder makes it easy to take the <NUM>° bend after the inner end of pipe. The torsional stiffness of the drive chain <NUM> permits controlling its orientation.

In particular, for increased strength and stiffness, the chain <NUM> may be a multi-row chain, e.g. duplex-type roller chain having two rows of side links.

At the second side <NUM>, the probe holder unit <NUM> is linked to an articulated stabilizer member <NUM>. The stabilizer member <NUM> comprises a set of elements <NUM>, <NUM>, <NUM> that are articulated on one another and are configured to form a guide housing for a cable assembly <NUM>. The elements <NUM>. i may be formed as hollow cuboid elements that define a central passage <NUM> in length direction L from a rear side <NUM> to a front side <NUM> adjacent second end <NUM> of housing <NUM>. The elements 52i are pivotally connected to one another so that they can pivot about respective transverse axes A parallel to axe P. However, the articulation of the stabilizer member <NUM> is carried out with offset axes - towards the bottom on <FIG>- such that the stabilizer member <NUM> may only be bent downward, i.e. on the side of rear side <NUM> and as indicated by arrow <NUM> in <FIG>.

Reference sign <NUM> designates a fitting nut screwed on a cylindrical sleeve defining the inlet of internal passage <NUM> through stabilizer member <NUM>. Fitting nut <NUM> is adapted to attach the cable assembly <NUM> to stabilizer member <NUM>. Cable assembly is thus connected to the housing <NUM> through inner channel <NUM> inside stabilizer member <NUM>, which it enters through an inlet defined by sleeve <NUM> at the rear <NUM>.

A pair of orifices, not shown, are provided on the end side <NUM> for the input and output wires. Additionally, an inlet of an internal fluid duct (for a coupling fluid; necessary for US testing measurements) that opens at spray hole <NUM> in the sensor side <NUM>. The cable assembly <NUM>, which is guided inside stabilizer member <NUM>, may thus include a pair of wires for the sensor signal as well as a flexible fluid duct, which are connected to the probe holder unit <NUM> through the second end <NUM>. These wires and fluid ducts are advantageously arranged inside a flexible steel sock <NUM>.

In use, these signal cable of the cable assembly are connected at the other end to a control unit <NUM>, shown in <FIG>, that is configured to operate reflection-type ultrasonic thickness measurements. Here control unit <NUM> also receives the signal from the encoder arrangement <NUM>. Control unit <NUM> can be any appropriate commercial ultrasound testing controller.

Turning to <FIG>, a variant of the encoder arrangement <NUM> will now be described. Conventionally, connection pipe <NUM> crosses through the furnace outer wall <NUM> via opening <NUM> and is surrounded by a sealing box <NUM> comprising an annular <NUM> flange surrounding the opening <NUM> and welded to the outer wall surface. A metal bellows seal <NUM> surrounds connection pipe <NUM> and is attached at one end to the annular flange <NUM> and at the opposite end to a collar <NUM> fitted over the connection pipe <NUM> and welded thereto. The bellows seal <NUM> is protected by a surrounding metal sleeve <NUM> affixed to the annular flange <NUM>.

Reference sign <NUM> indicates a pipe coupler fitted over the end of the connection pipe <NUM>, for coupling to cooling fluid distribution piping (not shown).

The encoder arrangement <NUM> comprises a mounting frame <NUM> that is mounted on the pipe coupler <NUM> (but could be directly on the end of the connection pipe <NUM> where such pipe coupler <NUM> is absent). Mounting frame is shaped as an open annular member supporting an encoder <NUM> and encoder gear <NUM> (or first gear) coupled thereto. In use, the drive chain <NUM> meshes with the encoder gear <NUM>, whereby forward or rearward movement of the drive chain <NUM> causes rotation of the encoder gear <NUM>, such that the first gear rotation can be measured/detected by the encoder, and a corresponding positions/distances computed based on the encoder signal.

In the shown embodiment, the mounting frame <NUM> includes an inner ring <NUM> surrounded by an outer, cover ring <NUM> attached thereto, both of which are formed as open rings. The cover ring <NUM> has a wider opening than the inner ring <NUM>.

The inner ring <NUM> includes three radially extending threaded bores <NUM> that receive three radially extending rods <NUM>. The rods have an outer threaded surface and bear at one end on the pipe coupler <NUM> and are provided at the other end with a butterfly. Rotating the rods <NUM> within bores <NUM> allows fixing the mounting frame <NUM> on the coupler <NUM> in an appropriate position, preferably centered. Locking nuts <NUM> are provided on the rods <NUM> to block them in the desired radial position.

The mounting frame <NUM> supports various elements. Reference sign <NUM> designates a first angle bracket integral with the inner ring <NUM> and extending axially outside of the mounting frame circumference. Encoder gear <NUM> is rotatably supported on a shaft <NUM> protruding from first angle bracket <NUM>. Reference sign <NUM> designates a second, tensioner gear that is rotatably supported on a shaft <NUM> extending from a pivoting arm <NUM>. Pivoting arm is L-shaped and mounted by a pivot <NUM> at the free end of first angle bracket <NUM>.

In <FIG> pivoting arm <NUM> is represented in solid lines in the operating position, where it is proximate the encoder gear <NUM> to ensure that the drive chain <NUM> remains in meshing engagement with the encoder gear <NUM>. The arm <NUM> is however also represented in dashed lines in a position remote from the encoder gear <NUM>; this corresponds to a rest configuration, where the drive chain and probe unit can be conveniently positioned. The arm <NUM> can be locked in the operating position by a pin <NUM> that engages respective aligned holes in the bracket and arm. Reference sign <NUM> indicates a second angle bracket that is also fixed at one end to inner ring <NUM> and fixedly supports at the other end the encoder <NUM>. The encoder <NUM> has an input axis <NUM> that is substantially aligned with the shaft <NUM> of the encoder gear <NUM> and coupled thereto via an encoder coupling <NUM>. Encoder coupling <NUM> conventionally takes the form of a tubular member with annular grooves that is mounted on the encoder axis <NUM> and encoder gear shaft <NUM> and provides a torsionally adaptive coupling between parts.

It may be noted that in order perform thickness measurements by means of the probe holder unit <NUM>, the cooling plate <NUM> is beforehand disconnected from the furnace coolant circuit and emptied from coolant water.

In general, the drive chain <NUM> alone is first inserted from the upper connection pipe <NUM>, visible in <FIG>, and lowered through the cooling channel down to the bottom and further through the lower connection pipe, so as to exit therefrom. Then the probe holder unit <NUM>, with the stabilizer <NUM> and cable assembly <NUM>, is connected to housing <NUM> by means of the links <NUM>.

Next, the chain is withdrawn to bring the probe unit <NUM> towards the top of the coolant channel, as illustrated in <FIG>. The chain <NUM> is then properly coupled to the encoder gear <NUM>, by bringing tensioning gear in the operating position of <FIG>. From there, measurements can start. The probe unit will be moved inside the cooling channel <NUM> by moving / escorting forward the drive chain <NUM> and pulling the iron cables sock <NUM> from bottom.

Inside the coolant channel <NUM>, probe holder <NUM> is progressively lowered to perform thickness measurements at a plurality of positions along the length of the coolant channel <NUM>. The present probe unit <NUM> allows measuring the body thickness not only at the inlet and outlet regions of the body, but also at a plurality of positions along the length of the body and ribs, including in the central regions. In practice, the probe unit <NUM> is moved to a plurality of positions, and a thickness measurement is performed for each position over the entire length of coolant channel. In other words, the measurement could be done at spot (local defined positions) in at any desired length/height of coolant channel. During the thickness measurement, the sensor side <NUM> is maintained substantially perpendicular to the front side <NUM>. The angular orientation of the probe unit <NUM> in the coolant channel <NUM> is known thanks to the configuration of the chain <NUM>, which has a flattened cross section.

Water is preferably used as coupling medium, however any appropriate couling fluid/medium may be used (in particular cases of presence of rusting inside the channel). The coupling fluid is supplied through the cable assembly <NUM>, enters into the housing <NUM> and is sprayed against the inner surface of the coolant channel <NUM> by spray orifice <NUM>.

As it will be understood, since the probe unit <NUM> is inserted inside the coolant channel <NUM>, it measures a body thickness that corresponds to the distance from the inner side of the coolant channel <NUM> (facing the front side) to the foremost body or end rib portion on the front face, at the level of the probe holder <NUM> (i.e. perpendicular to the front side).

That is, when the probe is at the level of a rib <NUM>, the body thickness corresponds to the distance between the inner surface of the channel to the tip of the rib <NUM>. When the probe is at the level of a groove <NUM>, the body thickness corresponds to the distance between the inner surface of the channel to the tip of the rib <NUM>.

Claim 1:
A system for measuring a thickness of a cooling plate, said system comprising:
a probe holder unit (<NUM>) designed to fit inside a coolant channel (<NUM>) of the cooling plate (<NUM>) in order to perform thickness measurements, the probe holder unit comprising a housing (<NUM>) extending along a length axis (L) from a first end (<NUM>) to a second end (<NUM>), a lateral, sensor side (<NUM>) and an opposite rear side (<NUM>), an ultrasonic probe (<NUM>) being arranged in said housing to be able to transmit and receive ultrasonic waves from said sensor side;
a rear housing part (<NUM>) being moveably arranged at the rear side, transversally to the length axis, and elastically biased away from the sensor side, thereby permitting the probe holder unit to adapt to the cooling channel size by ensuring intimate contact between the inner surface of the coolant channel (<NUM>) and the probe holder sensor side (<NUM>);
a drive chain (<NUM>) to assist the progression of said probe holder unit (<NUM>) through the length of the coolant channel, said drive chain linked to first connecting means (<NUM>) at said first end of said housing;
a cable assembly (<NUM>) comprising electric wires connecting the ultrasound probe;
an encoder arrangement (<NUM>) configured to cooperate with the drive chain such as to measure a length of drive chain passing along it, the encoder arrangement comprising a first gear (<NUM>) meshing with said drive chain and coupled to an encoder.