Patent Description:
Sludge lancing operations are used in the commercial power industry to remove accumulations and deposits of debris and other matter, referred to as sludge, from between individual tubes in an arrangement of a group of tubes, i.e., a tube sheet bundle, in various power plant components, such as steam generators and heat exchangers of the shell-and-tube variety. The accumulation of sludge in between individual tubes in tube sheet bundles may result in reduced efficiencies of power plant components. Sludge accumulation can also result in mechanical impingement or damage to tubes and chemical degradation or corrosion of tube walls in such components. Failure of one or multiple tubes can result in a power plant being taken out of service to repair or replace damaged tubes.

Typically, sludge lancing is performed during a power plant outage or when particular equipment (e.g., a steam generator) is placed out of service. Sludge lancing involves directing a high pressure stream of water through a tube sheet bundle to remove accumulated sludge from between individual tubes.

In a conventional system, a nozzle is mounted or secured to a pipe or other structure to provide stability and to allow the nozzle to translate along a horizontal axis. The nozzle can translate along a vertical axis by raising or lowering the pipe on which the nozzle is mounted. Aligning the nozzle prior to initiating the lancing operation is typically attempted by spraying a stream of water through a tube sheet bundle and visually observing the steam of water as it exits the bundle. Once the nozzle is aligned, there is no disruption to the water stream itself. Aligning the nozzle is an iterative and time consuming process that involves spraying water through the nozzle, visually observing the the stream of water exits the tube sheet bundle without disruption of the stream of water. As well, because the nozzles are typically oriented so that their spray patterns are in a horizontal plane, numerous passes are typically made with the vertical position of the nozzle changed on each pass.

Because current methods rely on visual alignment of the nozzle, as described above, lancing sludge from between tubes (i.e., sludge lancing) is generally performed with the nozzle positioned <NUM>° with respect to the tube sheet bundle, i.e., "head-on" to tube sheet bundle. However, it is often desirable to direct the stream of water from the nozzles at angles other than <NUM>° in order to remove additional sludge that cannot be reached at <NUM>°.

The present invention recognizes and addresses the foregoing considerations, and others, of prior art constructions and methods.

<CIT> discloses a cleaning apparatus and an associated method of using the disclosed apparatus.

<CIT> discloses a sludge lancing system according to the preamble of claim <NUM>.

One embodiment of the present disclosure provides a sludge lancing system for use in a steam according to claim <NUM>.

The sludge lancing system may further comprise a second nozzle that is mounted to the manifold and defines a conduit that generates a lancing fluid jet, wherein the first nozzle and the second nozzle define an acute angle therebetween and a longitudinal center axis of the conduit of the second nozzle lies in the first vertical plane that is transverse to the longitudinal center axis of the rail so that the lancing fluid jet of the second nozzle is disposed in the first vertical plane when the manifold is pivoted about the axis of rotation.

The sludge lancing system may further comprise:.

The sludge lancing system may further comprise a shaft that connects the motor to the manifold.

A cross-sectional shape defined by the elongated groovein the first vertical plane may be the same as a cross-sectional shape of the head portion in the first vertical plane.

The at least one flow conduit may further comprise a plurality of parallel flow conduits.

The flow conduit of the first nozzle may include a frustoconical portion disposed adjacent the flow straightener and a conical portion that extends from the frustoconical portion to a distal end of the first nozzle.

Another embodiment of the present disclosure provides a sludge lancing system for use in a steam generator including a no tube lane disposed between a first bank of tubes and a second bank of tubes that are transverse to a horizontal reference plane, the system including a rail that extends through the no tube lane and includes a longitudinal center axis that is parallel to the reference plane, and a first lancing head. The first landing head includes a body having a manifold defining a conduit, and a nozzle assembly that is mounted to the manifold of the body, the nozzle assembly including a first nozzle housing that is mounted to the manifold and defines a bore that is in fluid communication with the conduit of the manifold, a first nozzle that is mounted to the first nozzle housing and defines a conduit that generates a lancing fluid jet, a second nozzle housing that is mounted to the manifold and defines a bore that is in fluid communication with the conduit of the manifold, and a second nozzle that is mounted to the second nozzle housing and defines a conduit that generates a lancing fluid jet. A longitudinal center axis of the conduit of the first nozzle lies in a first vertical plane that is transverse to both the horizontal reference plane and a first horizontal plane that is parallel to the horizontal reference plane and contains a longitudinal center axis of the conduit of the manifold, and the longitudinal center axis of the conduit of the first nozzle and an intersection line of the first vertical plane and the first horizontal plane define a first acute angle therebetween. A longitudinal center axis of the conduit of the second nozzle lies in a second vertical plane that is transverse to both the horizontal reference plane and the first horizontal plane that is parallel to the horizontal reference plane and contains a longitudinal center axis of the conduit of the manifold, and the longitudinal center axis of the conduit of the second nozzle and an intersection line of the second vertical plane and the first horizontal plane define a second acute angle therebetween, and the first acute angle is larger than the second acute angle.

A sludge lancing system for use in a steam generator including a no tube lane disposed between a first bank of tubes and a second bank of tubes that are transverse to a horizontal reference plane, comprising:.

The rail may define an elongated groove that is parallel to its longitudinal center axis; and
the first lancing head may include a head portion that is slidably received in the elongated groove.

A cross-sectional shape defined by the elongated groove in a vertical plane that is both transverse to the horizontal reference plane and the longitudinal center axis of the rail may be the same as a cross-sectional shape of the head portion in that same vertical plane.

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments of the invention and, together with the description, serve to explain the principles of the invention.

A full and enabling disclosure of the present invention, including the best mode thereof to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, which makes reference to the accompanying figures, in which:.

Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the invention.

Reference will now be made in detail to presently preferred embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment.

As used herein, terms referring to a direction or a position relative to the orientation of the water heater, such as but not limited to "vertical," "horizontal," "upper," "lower," "above," or "below," refer to directions and relative positions with respect to the heat exchanger's orientation in its normal intended operation, as indicated in <FIG> and <FIG> herein. Thus, for instance, the terms "vertical" and "upper" refer to the vertical direction and relative upper position in the views of <FIG> and <FIG> and should be understood in that context, even with respect to a heat exchanger that may be disposed in a different orientation.

Further, the term "or" as used in this disclosure and the appended claims is intended to mean an inclusive "or" rather than an exclusive "or. Throughout the specification and claims, the following terms take at least the meanings explicitly associated herein, unless the context dictates otherwise. The meanings identified below do not necessarily limit the terms, but merely provided illustrative examples for the terms. The meaning of "a," "an," and "the" may include plural references, and the meaning of "in" may include "in" and "on. " The phrase "in one embodiment" as used herein does not necessarily refer to the same embodiment, although it may.

With reference to <FIG>, a sludge lancing system <NUM> is illustrated in the context of a typical steam generator <NUM> which is constructed similarly to that described in <CIT>. As shown in the partial cut-away view of <FIG>, steam generator <NUM> includes a vessel <NUM> through which tubes <NUM> pass so as to allow heat transfer between fluid contained in vessel <NUM> and fluid flowing in tubes <NUM>. Depending upon the steam generator design, heated water, steam, or steam/water mixture (possibly superheated, subcooled or in another thermodynamic state) flows in tubes <NUM> and feed water is fed into vessel <NUM> and converted to steam (an arrangement known as shell-side boiling since the feedwater that boils is outside the tubes); or vice versa (tube-side boiling). In a typical steam generator used in conjunction with a nuclear reactor of the pressurized water reactor variety, coolant in the nuclear reactor (called "primary" coolant) is heated by the nuclear reactor core to an elevated temperature and pressure (e.g. a sub-cooled or other thermodynamic state), and is piped from the nuclear reactor to the steam generator <NUM> where the primary coolant flows through tubes <NUM>. Secondary coolant flows outside the tubes and boils shell-side. Vessel <NUM> is a pressure vessel which contains the pressurized steam (that is, boiled secondary coolant), which is piped out of the steam generator to drive a turbine that in turn drives an electrical generator (in a nuclear power plant), or the secondary coolant steam may be used to perform other useful work. <FIG> diagrammatically illustrates a sectional perspective view of steam generator <NUM> including portions of vessel <NUM> and tubes <NUM>. The tube configuration may vary, e.g., once-through steam generator (OTSG) tubing (optionally employing a counter-flow design in which primary coolant flows downward through tubes <NUM> and secondary coolant flows generally upward in vessel <NUM>), U-shaped steam generator tubing, or so forth. The steam generator may also include various other components that are not illustrated in the partial sectional view of <FIG>, such as (by way of non-limiting illustrative example) steam separator or dryer units, flow control features, etc..

The arrangement of tubes <NUM> in vessel <NUM> is designed to facilitate both operation and maintenance. In general, it is desirable to have a high packing density of tubes to provide a large total heat transfer surface area, but provision is also made to provide access to tubes for maintenance. In the illustrative steam generator <NUM>, tubes <NUM> are segregated (as viewed in a cross-sectional plane transverse to the tubes) into two hemispherical tube sections <NUM> and <NUM> separated by a "no tube lane" <NUM> which provides the maintenance access. Tubes <NUM> are typically straight and mutually parallel (although some tube bends are contemplated to accommodate components or so forth, and other variants may exist such as an upper "U"-shaped turn in the case of "U"-shaped tubing or so forth), and so this arrangement defines an "instance" of the no tube lane <NUM> at each planar tubesheet or other horizontal plate or surface intersecting tubes <NUM>. Without loss of generality, a "floor" <NUM> is denoted in <FIG>, where it is to be understood that the floor <NUM> may be any upper surface oriented transverse to tubes <NUM>. For example, floor <NUM> may be the upper surface of a lower tubesheet providing fluid communication to the bottom ends of tubes <NUM>, or the upper surface of a middle, upper, or other-elevation tubesheet. A vessel port, vessel penetration, or manway <NUM> can be opened (after depressurization and draining of vessel <NUM>, as in during a maintenance shutdown) to provide access to the space above floor <NUM>. Preferably, manway <NUM> is aligned with no tube lane <NUM> so that a first lancing head <NUM> (<FIG>) and/or a second lancing head <NUM> (<FIG>) can be inserted and moved along no tube lane <NUM> to perform lancing of tubes <NUM>. First and second lancing heads <NUM> and <NUM> are moved along a rail <NUM> that is inserted into vessel <NUM> through manway <NUM> so that it extends along no tube lane <NUM>. Floor <NUM> corresponds to a reference plane that includes no tube lane <NUM> and is transverse to tubes <NUM>.

Referring additionally to <FIG>, within each tube section <NUM>, <NUM> of the present embodiment, tubes <NUM> are arranged in a honeycomb or hexagonally symmetric pattern. Without loss of generality, the direction of no tube lane <NUM> is designated as reference <NUM>°, as shown in <FIG>. The honeycomb or hexagonal layout of tubes <NUM> then defines a set of parallel tube lanes in the reference plane defined by floor <NUM> at <NUM>° respective to the <NUM>° reference angle of no tube lane <NUM>, a set of parallel tube lanes in the reference plane defined by floor <NUM> at <NUM>° respective to the <NUM>° reference angle of no tube lane <NUM>, and a set of parallel tube lanes in the reference plane defined by floor <NUM> at <NUM>° respective to the <NUM>° reference angle of no tube lane <NUM>. Each tube lane is a path (lane) in the reference plane defined by floor <NUM> that does not intersect any of tubes <NUM>. The tube lanes are lines when referenced to the two-dimensional geometry (reference plane) of floor <NUM>. When referenced to three-dimensional space of steam generator <NUM>, the sets of tube lanes at <NUM>°, <NUM>°, and <NUM>° are sets of planes that are transverse to floor <NUM> and oriented at angles of <NUM>°, <NUM>° and <NUM>° respective to a "<NUM>° plane" that is transverse to floor <NUM> and contains no tube lane <NUM>.

It is to be appreciated that the geometry of steam generator <NUM> shown in <FIG> is illustrative, and other geometries are contemplated. For example, alternate embodiments of the disclosed sludge lancing system <NUM> may be used for lancing operations in steam generators having tube geometries such as, but not limited to, triangular, square, rotated square, rotated triangular, and rectangular. In such other geometries, it may be advantageous to define a no tube lane (or possibly two or more no tube lanes, for example oriented at <NUM>° to each other) to provide access for maintenance, and to arrange the tubes on either side of the no tube lane in a pattern that defines tube lanes. As well, for lancing operations of steam generators having various tube geometries, lancing heads can be provided in which the nozzles are angled accordingly with regard to the no tube lane along which the corresponding lancing head travels. The illustrative honeycomb or hexagonal pattern is advantageously a close packed lattice.

The sludge lancing system and techniques are described herein in conjunction with the maintenance of a steam generator for a nuclear reactor. However, this is merely an illustrative example, and it will be appreciated that the disclosed sludge lancing system and techniques may more generally be employed in the maintenance of other types of steam generators which may for example be used in conjunction with a fossil fuel boiler or the like.

The primary and secondary coolants typically comprise purified water, either one or both of which may contain additives. For example, the primary coolant of a nuclear reactor may contain a soluble boron additive acting as a neutron poison to control the nuclear chain reaction. Furthermore, although purified, the primary and secondary coolant may include some contaminants. The secondary coolant does not contact the nuclear reactor core and (absent any tube leakage in the steam generator) should be free of radioactive contaminants. The secondary coolant may have a lower purification level as compared with the primary coolant. Contaminants and/or additives in the secondary coolant (or other coolant flowing shell-side or in vessel <NUM>) may generate buildup of deposits over time, which are commonly called "sludge". This sludge tends to accumulate at or near certain elevations in vessel <NUM>, such as at the upper surface of a tubesheet. Sludge may collect on (or precipitate out onto, or react with, or so forth) the outsides of tubes <NUM> and/or on the tubesheets or other structures. Sludge buildup can produce various problems. For example, sludge comprising chemical formation of deposits can initiate stress corrosion cracking in the tubes or other steam generator components, and can cause denting in other materials due to its growth. Other maintenance issues besides sludge buildup can arise, such as degradation of some of tubes <NUM> (either related to the sludge buildup or due to some other cause), failure modes of other components such as steam separators, etc..

Accordingly, steam generator <NUM> is sometimes shut down for maintenance. A shutdown may be performed in response to a specific detected problem, or on a predetermined schedule (such as when the nuclear reactor is shut down for maintenance). During a steam generator maintenance shutdown, coolant flow to tubes <NUM> and vessel <NUM> is terminated and vessel <NUM> is drained. Various maintenance operations are typically performed such as tube inspection, plugging of any tubes found to be defective (so as to remove the plugged tubes from service), inspection of ancillary components such as cyclonic steam dryers, and so forth. One common maintenance operation is sludge removal.

Known approaches for sludge removal include chemical cleaning and lancing using a high-pressure water beam. Lancing using a <NUM> kpsi water beam or a <NUM> kpsi water beam are two conventional approaches. With particular reference to <FIG>, a conventional sludge lancing approach for honeycomb patterned tubes <NUM> orients the water beam at <NUM>° respective to the direction of no tube lane <NUM>. This orientation is suitably determined visually, by rotating the water ejection nozzle until a strong beam is observed exiting from the tube bundle. Then, the beam is locked into this angle and the corresponding lancing head is moved along no tube lane <NUM> to lance the various <NUM>° tube lanes. <FIG> shows the <NUM>° beams B<NUM> passing along the <NUM>° tube lanes to remove sludge from the space between tubes <NUM>. However, as illustrated in <FIG>, this approach can leave large, typically hourglass-shaped, sludge remnants <NUM>.

Referring now to <FIG>, it is recognized herein that performing sludge lancing along two tube lane angles, namely the <NUM>° and <NUM>°, provides improvement in terms of reduced remnants. The lancing shown in <FIG> differs from that shown in <FIG> in that additional lancing is performed with successive <NUM>° beams B<NUM> along with the <NUM>° beams B<NUM>. This leaves smaller, typically triangular or trapezoidal sludge remnants <NUM>, as shown.

Referring now to <FIG>, it is further recognized herein that performing sludge lancing along three tube lane angles, namely the <NUM>°, <NUM>°, and <NUM>° tube lanes, provides substantial improvement in terms of reduced remnants. This approach uses lancing performed using <NUM>° beams B<NUM>, <NUM>° beams B<NUM>, and <NUM>° beams B<NUM>. This approach leaves only minor remnants <NUM>. Note that disengaged sludge portions <NUM> are fully disengaged from the surrounding tubes <NUM> and hence are not likely to remain as remnants.

With reference to <FIG>, sludge lancing effectiveness depends strongly on precise alignment of the lancing water beam with the tube lane. As indicated in the diagram at the left side of <FIG>, angular misalignment can significantly degrade the sludge removal force of the water spray beams. The right side of <FIG> diagrammatically shows how angular misalignment can lead to a ricocheting of the beam that reduces its sludge-removing force. <FIG> and <FIG> illustrate that beam alignment can be observed visually. As seen in <FIG>, precise beam alignment leads to a narrow beam exiting from the bundle of tubes <NUM>. By contrast, as seen in <FIG> beam misalignment causes the beam exiting from the bundle of tubes <NUM> to be diffuse and scattered.

The illustrative embodiment employs the illustrative honeycomb or hexagonal tube pattern having tube lanes at <NUM>°, <NUM>°, and <NUM>° angles respective to the reference <NUM>° of no tube lane <NUM>, and lancing at two angles (illustrative <NUM>° and <NUM>° as per <FIG>) or all three available angles (<NUM>°, <NUM>°, and <NUM>° as per <FIG>) provides improved sludge removal. More generally, lancing at two or more different angles is advantageous. Depending on the tube pattern (triangular, square, etc.), these different angles may be other than the illustrative <NUM>°, <NUM>°, and <NUM>° tube lane angles of the honeycomb pattern. Typically, the different angles will be at least <NUM>° apart, such as with the triangular and rotated square tube geometries, and in the illustrative embodiment the different angles are at least <NUM>° apart (i.e. the <NUM>° and <NUM>° different angles differ by a <NUM>° interval, the <NUM>° and <NUM>° different angles differ by a <NUM>° interval, and the <NUM>° and <NUM>° different angles differ by a <NUM>° interval).

Referring now to <FIG>, a first lancing head <NUM> of the disclosed sludge lancing system <NUM> is shown which provides for lancing along the <NUM>° tube lanes (<FIG>). Preferably, first lancing head <NUM> includes a body <NUM>, a nozzle assembly <NUM> pivotably mounted thereto, and a housing <NUM> in which a motor (not shown) for rotating nozzle assembly <NUM> is disposed. Referring additionally to <FIG>, during lancing operations, first lancing head <NUM> is configured to be both supported by, and slidably moved along, an elongated rail <NUM> of the system. As previously noted, when in use rail <NUM> is mounted inside a vessel <NUM> of a steam generator <NUM> so that it extends along the generator's no tube lane <NUM>, as shown in <FIG>. When positioned for lancing operations, a longitudinal center axis <NUM> of an elongated groove <NUM> that is defined along the length of rail <NUM> is parallel to floor <NUM> (horizontal reference plane) of the steam generator. Body <NUM> of first lancing head <NUM> includes a head portion <NUM> that is slidably received in elongated groove <NUM> to support first lancing head <NUM> on rail <NUM>. Specifically, as best seen in <FIG>, the cross-sectional shapes of elongated groove <NUM> and head portion <NUM> are the same when taken in a vertical plane that is transverse to longitudinal center axis <NUM> of the rail's groove <NUM>. As shown, the cross-sectional shapes are circular, but other cross-sectional shapes may be used in alternate embodiments. Body <NUM> also includes a fluid inlet <NUM> for attachment of a high pressure fluid hose (not shown) to a "U"-shaped conduit <NUM> defined with body <NUM> of the lancing head. Preferably, as discussed in greater detail below, the high pressure water hose is used to move first lancing head <NUM> along rail <NUM> is sized such that it is retained within groove <NUM> during lancing operations.

As best seen in <FIG> and <FIG>, nozzle assembly <NUM> of first lancing head <NUM> includes a pivotable nozzle manifold <NUM>, and a first bank of nozzles <NUM> and a second bank of nozzles <NUM> disposed on opposite sides thereof. Preferably, each of first and second banks of nozzles <NUM> and <NUM> includes a plurality of nozzles <NUM>, each of which is removably secured to nozzle manifold <NUM>. Each nozzle <NUM> preferably includes a frustoconical seat <NUM> and a threaded base <NUM> or its proximal end. Each frustoconical seat <NUM> is configured to be matingly received in a corresponding frustoconical recess <NUM> defined in nozzle manifold <NUM> as threaded base <NUM> of each nozzle <NUM> is rotatably received in a corresponding threaded recess <NUM> of the nozzle manifold. Frustoconical seats <NUM> and recesses <NUM> are configured to facilitate proper alignment of nozzles <NUM> and, therefore, the lancing fluid jets during lancing operations. As shown, each nozzle <NUM> of nozzle assembly <NUM> is configured to produce a lancing fluid jet that radiates outwardly from first lancing head <NUM> at a <NUM>° angle with respect to longitudinal center axis <NUM> of the elongated rail. Note, as best seen in <FIG>, first and second banks of nozzles <NUM> and <NUM> are configured to produce corresponding fluid lancing jets that form an acute angle therebetween. In the embodiment shown, the angle formed between the fluid lancing jets of the two of the respective banks is <NUM>°, although in other embodiments the angle may differ.

As shown in <FIG> and <FIG>, nozzle manifold <NUM> defines a main conduit <NUM> that extends axially along its length. Main conduit <NUM> of nozzle manifold <NUM> is in fluid communication with U-shaped conduit <NUM> of body <NUM>. Conduit <NUM> is shown in dotted reference lines in <FIG>. Additionally, nozzle manifold <NUM> defines a plurality of cylindrical bores <NUM> that extend radially-outwardly from its main conduit <NUM>. Each bore <NUM> is configured to receive a flow straightener <NUM> therein for each corresponding nozzle <NUM>. Each flow straightener <NUM> includes a cylindrical body <NUM> and a plurality of longitudinal conduits extending between its end faces. One end face is disposed adjacent main conduit <NUM> whereas the other end face is disposed adjacent a threaded base <NUM> of a corresponding nozzle <NUM>. Further, each nozzle <NUM> includes a conduit extending along its longitudinal center axis that is defined by a frustoconical portion <NUM> that is adjacent a corresponding flow straightener <NUM> and a cylindrical portion <NUM> that extends from frustoconical portion <NUM> to a distal end of the nozzle. Each flow straightener <NUM> is configured to enhance laminar flow within the fluid that is provided to the corresponding nozzle <NUM>. Enhancing the laminar flow entering each nozzle <NUM> improves the performance of the nozzle, as compared to known lancing systems, in that the laminar flow improves the ability of each nozzle to produce a more cohesive fluid lancing jet.

As best seen in <FIG>, first lancing head <NUM> preferably includes an on-board inspection camera <NUM> and one or more light emitting diodes <NUM>. As shown, camera <NUM> and light emitting diodes <NUM> are mounted on one side of nozzle manifold <NUM> adjacent a bank of nozzles, in this case first bank of nozzles <NUM>. As such, camera <NUM> and light emitting diodes <NUM> move with the nozzles as nozzle manifold <NUM> is pivoted about its longitudinal center axis during lancing operations. Light emitting diodes <NUM> provide illumination by which an operator can view the tube lanes of the corresponding steam generator before, during, and/or after lancing operations. As such, inspection camera <NUM> may be utilized to determine the state of sludge buildup prior to lancing, align first lancing head <NUM> with the desired tube lanes prior to lancing, and determine the effectiveness of sludge removal both during and after the lancing operations. In alternate embodiments, a laser alignment system utilizing an alignment laser diode (not shown) may also be provided. In such an embodiment, the laser diode is mounted to nozzle manifold <NUM> so that the laser being generated by the laser diode is pre-aligned parallel with a lancing fluid jet of one of the plurality of nozzles <NUM>. As such, the laser beam serves as an optical sight for the lancing fluid jet and is visible to camera <NUM> for alignment of the lancing head prior to operations. Note, in alternate embodiments, an inspection camera <NUM> and light emitting diodes <NUM> may be provided on both sides of nozzle manifold <NUM>.

Referring now to <FIG>, a second lancing head <NUM> of the disclosed sludge lancing system <NUM> is shown. Whereas first lancing head <NUM> allows for lancing along the <NUM>° tube lanes (<FIG>), second lancing head <NUM> allows for lancing along both the <NUM>° and <NUM>° tube lanes (<FIG> and <FIG>). Preferably, second lancing head <NUM> includes a body <NUM> having a nozzle manifold <NUM>, a first nozzle bank <NUM>, a second nozzle bank <NUM>, and a housing <NUM> in which electronics are enclosed. Referring additionally to <FIG>, during lancing operations, second lancing head <NUM> is configured to be both supported by, and slidably moved along, elongated rail <NUM> of the system in a manner similar to that of first lancing head <NUM>. As previously noted, when positioned for lancing operations, longitudinal center axis <NUM> of elongated groove <NUM> is parallel to floor <NUM> (horizontal reference plane) of the steam generator. In addition to nozzle manifold <NUM>, body <NUM> of second lancing head <NUM> includes a head portion <NUM> that is slidably received in elongated groove <NUM> to support second lancing head <NUM> on rail <NUM>. Similarly to first lancing head <NUM>, the cross-sectional shape of head portion <NUM> is circular, but other cross-sectional shapes may be used in alternate embodiments. Body <NUM> also includes a fluid inlet <NUM> for attachment of the high pressure fluid hose to a "U"-shaped conduit (not shown) defined within body <NUM> of the lancing head. As described before, the high pressure water hose is used to move second lancing head <NUM> along rail <NUM> during lancing operations.

As shown, first bank of nozzles <NUM> and a second bank of nozzles <NUM> are disposed on opposite sides of nozzle manifold <NUM>. Preferably, each of first and second banks of nozzles <NUM> and <NUM> includes a plurality of nozzles <NUM>, each of which is removably secured to nozzle manifold <NUM> by way of a corresponding nozzle housing <NUM>. Each nozzle <NUM> of second lancing head <NUM> is similar to the previously discussed nozzles <NUM> (<FIG> and <FIG>), so that discussion is not repeated here. Note, however, each frustoconical recess <NUM> (<FIG>) and corresponding threaded recess <NUM> (<FIG>) for receiving a nozzle <NUM> are now defined with a corresponding nozzle housing <NUM> rather than directly in the nozzle manifold. Similarly, each nozzle housing <NUM> also include a cylindrical bore for receiving one of the previously discussed flow straighteners <NUM> (<FIG>).

As shown, each nozzle <NUM> of first and second nozzle banks <NUM> and <NUM> is configured to produce a lancing fluid jet that radiates outwardly from second lancing head <NUM> at a <NUM>° angle with respect to longitudinal center axis <NUM> of the elongated rail. However, as best seen in <FIG>, each nozzle <NUM> within each bank of nozzles preferably produces a lancing fluid jet that varies angularly with respect to the lancing jets of the receiving nozzles with reference to a horizontal plane <NUM> in which a longitudinal center axis of the nozzle manifold <NUM> lies. For example, as shown in <FIG>, the angle defined between a fluid lancing jet from nozzle 242a and the noted horizontal plane <NUM> is greater than the angle defined between a fluid lancing jet from nozzle 242b and horizontal plane <NUM>. As such, as second lancing head <NUM> is moved along rail <NUM>, the fluid lancing jet of each subsequent nozzle <NUM> within a given nozzle bank will impact a different portion of the sludge disposed within the tube lanes. This feature allows for enhanced sludge removal along the <NUM>° and <NUM>° tube lanes although first and second nozzle banks <NUM> and <NUM> are not rotated during lancing operations. Note, also, as best seen in <FIG>, second lancing head <NUM> includes a pair of inspection cameras <NUM>, or for each bank of nozzles, and multiple light emitting diodes <NUM>. As shown, each inspection camera <NUM> is angularly aligned with nozzles <NUM> of its corresponding bank of nozzles.

Referring now to <FIG> and <FIG>, a sludge lancing operation utilizing the previously disclosed sludge lancing system <NUM> is discussed. First, vessel <NUM> of steam generator <NUM> is accessed by way of manways <NUM> so that elongated rail <NUM> can be positioned along the steam generator's no tube lane <NUM>. As previously noted, rail <NUM> is mounted to vessel <NUM> such that its longitudinal center axis <NUM> is parallel to floor <NUM>, or the horizontal reference plane, of the steam generator. Once a high pressure fluid hose (not shown) and a power cable (not shown) are connected to first lancing head <NUM> (<FIG>) by way of fluid inlet <NUM> and threaded stem <NUM>, respectively, head portion <NUM> of first lancing head <NUM> is slidably disposed within elongated groove <NUM> of rail <NUM>, as shown in <FIG>. Preferably, the fluid hose is used to urge first lancing head <NUM> along rail <NUM> to its opposite end. Once first lancing head <NUM> is positioned at the distal end of rail <NUM>, the operator utilizes light emitting diodes <NUM> and inspection camera <NUM> to properly align the fluid lancing jets produced by first and second banks of nozzles <NUM> and <NUM> with the <NUM>° tube lanes, as shown in <FIG>. Specifically, inspection camera <NUM> allows an operator to observe the alignment of the fluid lancing jets in real time. Preferably, first lancing head <NUM> remains in the first lancing position on rail <NUM> for approximately three to four minutes as nozzle manifold <NUM> pivots the fluid lancing jets of the nozzle banks through a desirable degree range. The fluid lancing jets remain within vertical planes that are transverse to longitudinal center axis <NUM> of rail <NUM>.

After lancing is complete in the first position, first lancing head <NUM> is moved incrementally the distance between adjacent parallel <NUM>° tube lanes, and a second interval of the lancing operation is performed in the second position. This incremental movement of first lancing head <NUM> is continued until first lancing head <NUM> has been moved the length of rail <NUM> and is positioned at the rail's proximal end, as shown in <FIG>. First lancing head <NUM> is now removed from rail <NUM> so that second lancing head <NUM> may be disposed thereon.

After second lancing head <NUM> (<FIG>) is connected to the high pressure fluid hose and the power cable, second landing head <NUM> is positioned on rail <NUM> with its head portion <NUM> being disposed in elongated groove <NUM>. As with first lancing head <NUM>, second lancing head <NUM> is urged along rail <NUM> by the fluid hose until it reaches the distal end of the rail. Once second lancing head <NUM> is in position, light emitting diodes <NUM> and inspection cameras <NUM> are used to align the fluid lancing jets produced by first and second banks of nozzles <NUM> and <NUM> with the <NUM>° tube lanes within the steam generator, as shown in <FIG>. When aligned, a first interval of fluid lancing is performed for a pre-selected amount of time, which is variable and determined based on the requirements of the sludge lacing plan. Upon completion of the first lancing interval, second lancing head <NUM> is moved incrementally along rail <NUM> a distance corresponding to the distance between adjacent, parallel <NUM>° tube lanes. When positioned, a second interval of fluid lancing is performed in the second position. Note, the intervals of fluid lancing need not be identical for each position of the lancing head. For example, increased time intervals may be desired at positions where sludge concentrations are expected to be the highest, such as in the middle region of the tubesheet. This process is continued until second lancing head <NUM> has been moved incrementally along the entire length of rail <NUM>.

Next, the operator positions second lancing head <NUM> on the opposite end of rail <NUM> by way of the opposite manway <NUM>. The same process discussed above for second lancing head <NUM> is repeated, but from the opposite end of rail <NUM>. As such, second lancing head <NUM> can be used to lance both the <NUM>° tube lanes and <NUM>° tube lanes, as shown in <FIG>.

Claim 1:
A sludge lancing system (<NUM>) for use in a steam generator (<NUM>) including a no tube lane (<NUM>) disposed between a first bank of tubes and a second bank of tubes that are transverse to a horizontal reference plane, comprising:
a rail (<NUM>) that extends through the no tube lane (<NUM>) and includes an elongated groove (<NUM>) having a longitudinal center axis (<NUM>) that is parallel to the reference plane; and
a first lancing head (<NUM>), comprising:
a body (<NUM>) including a head portion (<NUM>), a fluid inlet and defining a conduit, the head portion (<NUM>) being slidably received in the elongated groove (<NUM>);
a high pressure hose attached to the fluid inlet (<NUM>), the high pressure hose being configured to move the head portion (<NUM>) along the rail (<NUM>); and
a nozzle assembly (<NUM>) that is mounted to the body (<NUM>) and is pivotable with respect to the body (<NUM>) about an axis of rotation, the nozzle assembly (<NUM>) including a manifold defining a conduit that is in fluid communication with the conduit of the body (<NUM>), and at least a first nozzle that is mounted to the manifold and defines a conduit that generates a lancing fluid jet,
wherein a longitudinal center axis of the conduit of the first nozzle lies in a first vertical plane that is transverse to the longitudinal center axis of the rail (<NUM>) so that the lancing fluid jet of the first nozzle is disposed in the first vertical plane when the manifold is pivoted about the axis of rotation,
the sludge lancing system being characterised in that the high pressure hose is retained within the elongated groove (<NUM>) of the rail (<NUM>).