Multi-angle Sludge Lance

Abstract

A lancing crawler or head crawls along a no-tube lane (NTL) on a floor defining a reference plane oriented transverse to tubes of a steam generator, and has nozzles that generate lancing fluid jets along at least two different angles in the reference plane spaced apart by at least 45.degree.. A rotational drive rotates the nozzles about an axis of rotation that may be offset from an axis of thrust imposed by the jets from the nozzles. An on-board sighting laser may be mounted with the nozzles, along with an on-board camera. A bladder expands to secure the lancing crawler or head between steam generator tubes adjacent the NTL. Each nozzle may include a taperlock seat. A nozzle tilt drive is configured to tilt the one or more nozzles respective to the reference plane.

Description

[0001] This application claims priority to U.S. Provisional Application Ser. No. 62/027,511, filed Jul. 22, 2014 entitled "Multi-Angle Sludge Lance". This application claims priority to U.S. Provisional Application Ser. No. 61/858,106, filed Jul. 24, 2013 entitled "Multi-Angle Sludge Lance".

[0002] U.S. Provisional Application Ser. No. 62/027,511, filed Jul. 22, 2014 entitled "Multi-Angle Sludge Lance" is incorporated by reference herein in its entirety. U.S. Provisional Application Ser. No. 61/858,106, filed Jul. 24, 2013 entitled "Multi-Angle Sludge Lance" is incorporated by reference herein in its entirety.

BACKGROUND

[0003] The following relates to the steam generator maintenance arts, sludge removal arts, sludge lancing arts, and related arts.

[0004] Sludge lancing is used in the commercial power industry to remove accumulations and deposits of debris and other matter, referred to as sludge, 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. 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.

[0005] Typically, sludge lancing is performed during a power plant outage or when particular equipment (e.g., 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.

[0006] 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 stream 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 stream of water as it travels through the tube sheet bundle, and manipulating the position of the nozzle until the stream of water exits the tube sheet bundle without disruption of the stream of water.

[0007] Because current methods rely on visual alignment of the nozzle, as described above, lancing sludge between tubes (i.e., sludge lancing) is generally performed with the nozzle positioned 90 degrees with respect to the tube sheet bundle, i.e., "head-on" to tube sheet bundle. In some cases, lancing is performed around an outer periphery of the tube sheet bundle. Such known methods are recognized as inefficient, time consuming, and having varying effectiveness.

BRIEF DESCRIPTION

[0008] In some illustrative embodiments disclosed herein, a sludge lancing apparatus comprises a lancing crawler or head configured to crawl along a no-tube lane (NTL) on a floor defining a reference plane oriented transverse to tubes of a steam generator, and one or more nozzles mounted on the lancing crawler or head and configured to generate lancing fluid jets along at least two different angles in the reference plane spaced apart by at least 45.degree.. In some embodiments the sludge lancing apparatus further comprises a rotational drive configured to rotate the one or more nozzles about an axis of rotation that is transverse to the reference plane over an angular range spanning the at least two different angles. Some embodiments further comprise a drive track configured to move the lancing crawler or head along the NTL, and a center slide separate from the drive track on which the one or more nozzles are mounted, the center slide providing translation of the one or more nozzles respective to the lancing crawler or head. In some embodiments with the aforementioned rotational drive, the axis of rotation is offset from an axis of thrust imposed by the jets from the nozzles. In some embodiments with the aforementioned rotational drive, an on-board sighting laser is mounted with the one or more nozzles and aligned to generate a laser beam parallel with a jet beam output by the nozzle. An on-board camera may be mounted with the one or more nozzles and aligned to view along a jet beam output by the nozzle. A bladder may be provided, which expands when filled with a fluid to secure the lancing crawler or head between tubes of the steam generator located adjacent the NTL. In some embodiments, each nozzle includes a taperlock seat comprising a conical seat of the nozzle that seats in a mating conical recess of a nozzle manifold. In some embodiments a nozzle tilt drive is configured to tilt the one or more nozzles respective to the reference plane.

[0009] In some illustrative embodiments disclosed herein, a sludge lancing method comprises moving one or more nozzles along a no-tube lane (NTL) on a floor defining a reference plane oriented transverse to tubes of a steam generator, and, using the one or more nozzles, generating lancing fluid jets along at least two different angles in the reference plane spaced apart by at least 45.degree.. The generating may comprise: positioning the one or more nozzles in a first position with the nozzles directed along a first angle of the at least two different angles; with the one or more nozzles in the first position, generating a lancing fluid jet along the first angle; positioning the one or more nozzles in a second position with the nozzles directed along a second angle of the at least two different angles that is at least 45.degree. away from the first angle in the reference plane; and, with the one or more nozzles in the second position, generating a lancing fluid jet along the second angle. The positioning operations may include rotating the one or more nozzles about an axis of rotation transverse to the reference plane to a first angle of the at least two different angles, and may further include translating the one or more nozzles using a translation mechanism that is separate from a mechanism for moving the one or more nozzles along the NTL. The positioning may employ sighting of the one or more nozzles along a tube lane to be lanced using a laser sight mounted with the one or more nozzles.

[0010] In some illustrative embodiments disclosed herein, a method comprises: positioning a nozzle assembly comprising a plurality of nozzles proximate a proximal end of a tube sheet bundle comprising a plurality of tubes; positioning a first sensor proximate a distal end of the tube sheet bundle; and aligning the nozzle assembly, wherein spray paths between each of the plurality of nozzles and the distal end of the tube sheet bundle are unobstructed by one or more of the plurality of tubes.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The following is a brief description of the drawings, which are presented for the purposes of illustrating embodiments disclosed herein and not for the purposes of limiting the same.

[0012] FIG. 1 diagrammatically shows a perspective sectional view of a sludge lancing system performing sludge lancing on a steam generator.

[0013] FIG. 2 diagrammatically shows sludge lancing suitably performed by the system of FIG. 1 along tube lanes at 90.degree. respective to the no-tube lane (NTL).

[0014] FIG. 3 diagrammatically shows sludge lancing suitably performed by the system of FIG. 1 along tube lanes at 90.degree. respective to the NT and at 30.degree. respective to the NTL.

[0015] FIG. 4 diagrammatically shows sludge lancing suitably performed by the system of FIG. 1 along tube lanes at 90.degree. respective to the NT and at 30.degree. respective to the NTL and at 150.degree. respective to the NTL.

[0016] FIG. 5 diagrammatically shows the effect of a misalignment of the lancing water jet respective to the tube lane being lanced.

[0017] FIG. 6 shows compact exit water jets in a case in which the water jets are precisely aligned with the tube lane being lanced.

[0018] FIG. 7 shows diffuse exit water jets in a case in which the water jets are misaligned with the tube lane being lanced.

[0019] FIGS. 8, 9, and 10 show perspective, side, and top views, respectively, of an illustrative lancing crawler or head.

[0020] FIG. 11 shows a perspective view of the spray head of the lancing crawler or head of FIGS. 8-10 showing the axis of rotation offset from the axis of thrust of the water jet nozzles.

[0021] FIG. 12 shows a perspective view of the lancing crawler or head of FIGS. 8-10 (bottom) highlighting the air bladder gripping system shown in Detail A.

[0022] FIG. 13 shows a perspective isolation view of one nozzle of the lancing crawler or head of FIGS. 8-10.

[0023] FIG. 14 shows a sectional view of the nozzle manifold of the lancing crawler or head of FIGS. 8-10 showing a taperlock seat configuration for mounting nozzles of the configuration of FIG. 13 in the nozzle manifold.

[0024] FIG. 15 shows a side view of the spray head of the lancing crawler or head of FIGS. 8-10 including an on-board sighting (alignment) laser diode, an on-board inspection camera also optionally used in the alignment, and an on-board fill light.

DETAILED DESCRIPTION

[0025] Disclosed herein are various improvements in sludge lancing for steam generator maintenance. In some illustrative embodiments, a plurality of nozzle assemblies is disposed about a tube sheet bundle at several different angles or positions with respect to the tube sheet bundle. For example, a first nozzle assembly can be positioned 90 degrees with respect to the tube sheet bundle. A second nozzle assembly can be positioned 30 degrees with respect to the tube sheet bundle, while a third nozzle assembly can be positioned 150 degrees with respect to the tube sheet bundle. Thus, sludge lancing can be performed at multiple angles with respect to the tube sheet bundle. Sludge lancing operations using multiple nozzles at multiple angles can result in increased amounts of sludge removal compared to known systems and methods.

[0026] Each nozzle assembly can comprise a plurality of nozzle manifolds and nozzles, which regulate water pressure, stream flow, and direction. In an embodiment, water pressure is about 3000 pounds per square inch (psi). Each nozzle assembly is coupled to a stationary structure for stability. Each nozzle can move or translate along the x, y, and z axes, and angularly. Thus, the nozzles can spray water along the height or longitudinal axis of the tube sheet bundle. Each nozzle assembly can also comprise at least one laser, which as will be described herein, can be used to align the nozzles.

[0027] The plurality of nozzle assemblies can be disposed or positioned near or proximate to a proximal end of the tube sheet bundle. The proximal end may also be referred to as an inlet end. Disposed or positioned near or proximate a distal end of the tube sheet bundle is a sensor. The distal end can alternately be referred to as an outlet end. In one embodiment, the sensor can determine whether the laser beam travels between the proximal and distal ends of the tube sheet bundle without interference from one or more tubes comprising the tube sheet bundle. In another embodiment, the sensor can comprise a camera. Thus, proper alignment can be determined prior to spraying water through the nozzle and the tube sheet bundle.

[0028] In one embodiment, a second sensor is disposed proximate the distal end of the tube sheet bundle to measure or monitor the effluent, that is, the water spray at the outlet end of the tube sheet bundle. The second sensor can identify whether and to what extent sludge is present in the effluent. Such monitoring can aid in determining whether the lancing operation is completed and/or whether the sludge lancing operation has been successful. In one embodiment, the sensor can comprise a conductivity meter.

[0029] With reference to FIG. 1, a sludge lancing system is illustrated in the context of a typical steam generator 10 which includes a vessel 12 through which tubes 14 pass so as to allow heat transfer between fluid contained in the vessel 12 and fluid flowing in the tubes 14. Depending upon the steam generator design, heated water, steam, or steam/water mixture (possibly superheated, subcooled or in another thermodynamic state) flows in the tubes 14 and feed water is fed into the vessel 12 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 (PWR) 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 10 where the primary coolant flows through the tubes 14. Secondary coolant flows outside the tubes and boils shell-side. The vessel 12 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. 1 diagrammatically illustrates a sectional perspective view of the steam generator 10 including portions of the vessel 12 and tubes 14. The tube configuration may be various, e.g. once-through steam generator (OTSG) tubing (optionally employing a counter-flow design in which primary coolant flows downward through the tubes 14 and secondary coolant flows generally upward in the vessel 12), U-shaped steam generator tubing, or so forth. The steam generator may also include various other components that are not illustrated in the diagrammatic partial sectional view of FIG. 1, such as (by way of non-limiting illustrative example) steam separator or dryer units, flow control features, etc.

[0030] The arrangement of the tubes 14 in the vessel 12 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 10, the tubes 14 are segregated (as viewed in a cross-sectional plane transverse to the tubes 14) into two hemispherical tube sections 16, 18 separated by a "no tube lane" or NTL 20 which provides the maintenance access. The tubes 14 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 NTL 20 at each planar tubesheet or other horizontal plate or surface intersecting the tubes 14. Without loss of generality, a "floor" 22 is denoted in FIG. 1, where it is to be understood that the floor 22 may be any upper surface oriented transverse to the tubes 14. For example, the floor 22 may be the upper surface of a lower tubesheet providing fluid communication to the bottom ends of the tubes 14, or the upper surface of a middle, upper, or other-elevation tubesheet. A vessel port, vessel penetration, or manway 24 can be opened (after depressurization and draining of the vessel 12, as in during a maintenance shutdown) to provide access to the space above the floor 22. Preferably, the manway 24 is aligned with the NTL 20 so that a lancing crawler or head 40 can be inserted and moved along the NTL 20 to perform lancing of the tubes 14. The floor 22 corresponds to a reference plane that includes the NTL 20 and is transverse to the tubes 14.

[0031] With continuing reference to FIG. 1 and with further reference to FIGS. 2-4, within each tube section 16, 18, the tubes 14 are arranged in a honeycomb or hexagonally symmetric pattern (see FIGS. 2-4). Without loss of generality, the direction of the NTL 20 is designated as reference 0.degree. as indicated in FIG. 1. The honeycomb or hexagonal layout of the tubes 14 then defines: a set of parallel tube lanes in the reference plane defined by the floor 22 at 30.degree. respective to the 0.degree. reference angle of the NTL 20; and a set of parallel tube lanes in the reference plane defined by the floor 22 at 90.degree. respective to the 0.degree. reference angle of the NTL 20; and a set of parallel tube lanes in the reference plane defined by the floor 22 at 150.degree. respective to the 0.degree. reference angle of the NTL 20. Each tube lane is a path (lane) in the reference plane defined by the floor 22 that does not intersect any of the tubes 14. The tube lanes are lines when referenced to the two-dimensional geometry (reference plane) of the floor 22. When referenced to three-dimensional space of the steam generator 10, the sets of tube lanes at 30.degree., 90.degree., and 150.degree. are sets of planes that are transverse to the floor 22 and oriented at angles of 30.degree., 90.degree. and 150.degree. respective to a "0.degree. plane" that is transverse to the floor 22 and contains the NTL 20.

[0032] It is to be appreciated that the geometry of the steam generator 10 shown in FIGS. 1-4 is illustrative, and other geometries are contemplated. In such other geometries, it will be advantageous to define a NTL (or possibly two or more NTLs, for example oriented at 90.degree. to each other) to provide access for maintenance, and to arrange the tubes on either side of the NTL in a pattern that defines tube lanes. The illustrative honeycomb or hexagonal pattern is advantageously a close packed lattice.

[0033] The sludge lancing systems 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 systems 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.

[0034] 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 the vessel 12) may generate buildup of deposits over time, which are commonly called "sludge". This sludge tends to accumulate at or near certain elevations in the vessel 12, 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 the tubes 14 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 Inconel 600, 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 the tubes 14 (either related to the sludge buildup or due to some other cause), failure modes of other components such as steam separators, etc.

[0035] Accordingly, the steam generator 10 is sometimes shut down for maintenance. A shutdown may be performed in response to a specific detected problem, or on a pre-determined schedule (such as when the nuclear reactor is shut down for maintenance). During a steam generator maintenance shutdown, coolant flow to the tubes 14 and the vessel 12 is terminated and the vessel 12 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.

[0036] Known approaches for sludge removal include chemical cleaning and lancing using a high-pressure water beam. Lancing using a 10 kpsi water beam or a 3 kpsi water beam are two conventional approaches. To this end, the lancing crawler or head 40 suitably includes one or more water ejection nozzles oriented horizontally. Preferably, the nozzle also can be tilted to a non-zero (that is, non-horizontal) tilt (or elevation angle). Such tilting reduces the effectiveness of the lancing since the path length increases with increasing tilt or elevation angle--however, since the sludge buildup is expected to be greatest near the floor 22 and is expected to decrease with increasing elevation above the floor 22, this reduced lancing effectiveness with increasing tilt is expected to be offset by the reduced amount of sludge at higher elevations.

[0037] With particular reference to FIG. 2, a conventional sludge lancing approach for honeycomb patterned tubes 14 orients the water beam at 90.degree. respective to the direction of the NTL 20. 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 lancing crawler or head 40 is moved along the NTL 20 to lance the various 90.degree. tube lanes. FIG. 2 shows the 90.degree. beams B.sub.90 passing along the 90.degree. tube lanes to remove sludge S. However, as illustrated in FIG. 2, this approach can leave large, typically hourglass-shaped, sludge remnants

[0038] With particular reference to FIG. 3, it is recognized herein that performing the sludge lancing along two tube lane angles, namely the 90.degree. and 30.degree. tube lanes in illustrative FIG. 3, provides some improvement in terms of reduced remnants. The lancing of FIG. 3 differs from that of FIG. 2 in that additional lancing is performed with successive 30.degree. beams B.sub.30 along with the 90.degree. beams B.sub.90. This leaves smaller, typically triangular or trapezoidal sludge remnants 44 as seen in FIG. 3.

[0039] With particular reference to FIG. 4, it is further recognized herein that performing the sludge lancing along three tube lane angles, namely the 90.degree., 30.degree., and 150.degree. tube lanes in illustrative FIG. 4, provides substantially more improvement in terms of reduced remnants. This approach uses lancing performed using 30.degree. beams B.sub.30, 90.degree. beams B.sub.90, and 150.degree. beams B.sub.150. This approach leaves only minor remnants 46. Note that disengaged sludge portions 48 are fully disengaged from the surrounding tubes 14 and hence are not likely to remain as remnants.

[0040] In test simulations using a test mock-up with 3/4-inch tubes on 1-inch tri-pitch, 0.100-inch lane width (typically 0.12-0.25-inch) with simulated sludge constructed with masonry cement (with 24 hour cure to simulate soft sludge with durometer 80A, or 72 hour cure to simulate hard sludge with durometer 100A+), and 90-inch long spray paths, and using 3 kpsi horizontal water beams with a 30 second active cut time for the lancing, it was found that the approach of FIG. 2 employing only the 90.degree. beams B.sub.90 achieved 38% to 60% sludge removal. Adding the 30.degree. beams B.sub.30 as shown in FIG. 3 achieved between 88% and 90% sludge removal. Further adding the 150.degree. beams B.sub.150 as shown in FIG. 4 achieved between 93% and 95% sludge removal.

[0041] For hard sludge, the approach of FIG. 2 employing only the 90.degree. beams B.sub.90 achieved 36% sludge removal. Adding the 30.degree. beams B.sub.30 as shown in FIG. 3 achieved 51% sludge removal. Further adding the 150.degree. beams B.sub.150 as shown in FIG. 4 achieved 71% sludge removal.

[0042] With reference to FIGS. 5-7, sludge lancing effectiveness was found to depend strongly on precise alignment of the lancing water beam with the tube lane. As indicated in the diagram at the left side of FIG. 5, precise alignment requires precise translational position and also precise rotational position. An angular misalignment of as small as 0.6 degrees was found to significantly degrade the sludge removal force of the water spray beams. FIG. 5 right side diagrammatically shows how angular misalignment can lead to a ricocheting of the beam that reduces its sludge-removing force. FIGS. 6 and 7 illustrate that the beam alignment can be observed visually. As seen in FIG. 6, precise beam alignment leads to a narrow beam exiting from the bundle of tubes 14. By contrast, as seen in FIG. 7 beam misalignment causes the beam exiting from the bundle of tubes 14 to be diffuse and scattered.

[0043] The illustrative embodiment employs the illustrative honeycomb or hexagonal tube pattern having tube lanes at 30.degree., 90.degree., and 150.degree. angles respective to the reference 0.degree. of the NTL 20, and lancing at two angles (illustrative 90.degree. and 30.degree. as per FIG. 3) or all three available angles (90.degree., 30.degree., and 150.degree. as per FIG. 4) provides improved sludge removal. More generally, lancing at two or more different angles is advantageous. Depending on the tube pattern, these different angles may be other than the illustrative 30.degree., 90.degree., and 150.degree. tube lane angles of the honeycomb pattern. Typically, the different angles will be at least 45.degree. apart, and in the illustrative embodiment the different angles are at least 60.degree. apart (i.e. the 30.degree. and 90.degree. different angles differ by a 60.degree. interval, the 90.degree. and 150.degree. different angles differ by a 60.degree. interval, and the 30.degree. and 150.degree. different angles differ by a 120.degree. interval).

[0044] The sludge lancing approach of FIGS. 1 and 4 can be achieved using a lancing crawler or head having water jet nozzles at different fixed angles, e.g. 30.degree., 90.degree., and 150.degree.. Optionally, the water jet nozzles at different fixed angles may have a small angular adjustment capability to precisely align with the respective tube lane angles. In another approach, a single water jet nozzle (or bank of water jet nozzles) may be oriented in a single direction that is rotatable. In this embodiment the lancing crawler or head is moved along the NTL 20 and the nozzles are rotated to each successive angle (e.g. 30.degree., 90.degree., 150.degree. for each tube lane). Thus, the same nozzles provide sludge lancing at each angle in time succession. In yet another contemplated approach, the nozzle (or nozzle bank) is repeatedly swept over the angular range (e.g. from 25.degree. to 155.degree. back to 25.degree., and repeat, for the illustrative embodiment). If the sweeping is fast enough compared with the movement of the lancing crawler or head along the NTL 20, then it is ensured that all tube lanes are lanced. However, this approach is inefficient since most of the time the water jet beam will not be along any tube lane.

[0045] With reference to FIGS. 8-16, an illustrative embodiment of the lancing crawler or head 40 is described, which employs a rotatable bank of nozzles to perform the lancing described with reference to FIGS. 1 and 4. The illustrative lancing crawler or head 40 includes a bank of nozzles 60 mounted on a precision center slide 62 and including a precision rotation drive 64 and a nozzle tilt drive 66. The rotation drive 64 rotates the nozzles 60 about an axis of rotation 90 (see FIG. 11) that is transverse to the reference plane defined by the floor 22. Water pressure is applied to the nozzles 60 via a water inlet 70 that is connected to a hose or tube that runs out the manway 24 (see FIG. 1) to a pressurized water source (water pump, etc., not shown) typically located outside of the steam generator 10. The lancing crawler or head 40 is moved with coarse precision along the NTL 20 via drive tracks 72, while the precision center slide 62 allows precise translational positioning (cf. FIG. 5). To rigidly position the lancing crawler or head 40 against the force imparted by the water jets output from the nozzles 60, the lancing crawler or head 40 includes brake pads, namely in the illustrative design a front break pad 80, a middle brake pad 82, and a rear brake pad 84. In a suitable approach, the brake pads 80, 82, 84 are inflatable bladders that are filled with air or water (optionally water from the inlet 70, or air from a separate compressed air inlet not shown) so as to compress against the tubes 14 adjacent the NTL 20. In this way the lancing crawler or head 40 is wedged into place during the lancing process between the adjacent tubes.

[0046] The illustrative lancing crawler or head 40 is designed to meet the following criteria. The center rotation 64 is of high precision, since testing has shown that only 0.6 degrees of misalignment can significantly degrade the sludge removal force of the water spray beams. The drive tracks 72 are of relatively low precision, which enables movement of the lancing crawler or head 40 down the NTL 20 without using the precise movement of the center stage slide 62 for that work. This enables the tracks 72 to be designed for speed, which makes the lancing process faster.

[0047] With particular reference to FIG. 11, the center rotation 64 is designed to have an offset axis-of-rotation 90 as compared with the axis of thrust 92 imposed by the water jets from the nozzles 60. As disclosed herein, if the center of the lancing head thrust is on the same axis as the rotation, it is difficult to prevent flutter or backlash related inaccuracies. The design shown in FIG. 11 in which the axis of rotation 90 is offset from the thrust axis 92 reduces backlash and flutter.

[0048] With particular reference to FIG. 12, and with particular focus on Detail A, an air bladder gripping system is disclosed which evens out load on the tubes 14 adjacent the NTL 20. Local support on the adjacent tubes to the lanes being cleaned holds the lancing crawler or head 40 steady so as to maintain accuracy. But supporting tubes with individual air cylinders may overload a few tubes. The illustrated integrated bladder 96 (for example, a bladder hose) ensures that the load is distributed uniformly over the tubes across the length of the crawler 40.

[0049] With particular reference to FIGS. 13 and 14, an illustrative nozzle alignment system includes a taperlock seat that helps straighten the waterjet beams. The taperlock seat includes a conical seat 100 and threaded connector 102 of the nozzle 60 (see FIG. 13). The threaded connector 102 is threaded into a mating connector 104 of a nozzle manifold 106, and this threaded connection draws the conical seat 100 to seat into a mating conical recess 108 of the nozzle manifold 106. In experiments reported here, it was found that even high-precision nozzles deviate from perpendicularity at 20-inches to 60-inches away from the nozzle 60. The taperlock seat of FIGS. 13 and 14 was found to provide improved perpendicularity sufficient to obtain the desired angular precision to maintain high lancing force.

[0050] With particular reference to FIG. 15, the illustrative lancing crawler or head 40 includes an on-board inspection camera 110 and a laser alignment system including an alignment laser diode 112. The camera 110 and the laser 112 are mounted with the bank of nozzles 60 so that the camera 110 and the laser 112 moves with the nozzles 60 in response to translation by the precision center slide 62, in response to rotation by the center rotation drive 64, and in response to tilting by the nozzle tilt drive 66. The laser beam generated by the laser diode 112 is pre-aligned parallel with the water jet produced by the nozzles 60, so that the laser beam serves as an optical sight for the water jet. The camera 110 is similarly aligned to view along the jet beam output by the nozzles 60. By turning the laser diode 112 on and viewing the laser spot generated by the laser beam using the on-board camera 110, the operator can see the laser dot imaged on the opposite shell or divider plate wall. The operator then uses the precision center slide 62 and the center rotation drive 64 to position the laser beam precisely down the tube lane to be lanced, viewing the laser dot via the camera 110. Thereafter, when the operator applies the water pressure to the nozzles 60 they precisely lance the tube lane aligned using the laser 112. Optionally, a fill light 114, such as a light emitting diode (LED) light or array of LEDs, provides illumination by which the operator can view the aligned tube lane before, during, and/or after the lancing. In a typical lancing sequence, the sludge buildup in the tube lane may prevent a clear line-of-sight through the entire tube lane, so that the laser alignment cannot be performed with maximum precision. After turning on the water jet some of this sludge is removed (lanced), thus permitting a longer line of sight. The operator can then turn off the water jet and repeat the laser alignment, or rely upon visual appearance of the water jet as viewed by the camera 110 under illumination of the fill light 114 to determine when the tube lane if sufficiently lanced. In the latter approach, the appearance of the exit beam of water (see FIGS. 6 and 7) can be utilized to perform beam angle and translation adjustment (in addition to or in place of the laser alignment). The fill light 114 and camera 110 can also be used to acquire representative photographs of the tube lanes before and after lancing so as to document the effectiveness of the lancing process (or to document any problems with the lancing that may call for further sludge cleanup processing by further lancing, chemical removal, or so forth).

[0051] It is also contemplated to use the laser diode 112 with the water jet on. In this case, a diffuse exit water jet (as in FIG. 7) will manifest as a blurred or obscured laser dot due to laser beam/diffuse water beam interaction. When the water beam (and the sighting laser) are precisely aligned with the tube lane, the exit water jet will be tight (as in FIG. 6) which reduces the laser beam/water beam interaction resulting in a sharper laser dot being observed via the camera 110.

[0052] Using approaches such as those just described, the illustrative lancing crawler or head 40 can efficiently achieve lancing of the tube lanes in all three angles: 30.degree., 90.degree., and 150.degree.. The illustrative lancing crawler or head 40 includes a single bank of nozzles 60 pointing in a single direction--in a contemplated alternative embodiment, a separate bank of nozzles can be provided for each angular direction (e.g. 30.degree., 90.degree., and) 150.degree. with each bank having separate precision slide and rotation drives, so that lancing along multiple directions can be precision-aligned and performed simultaneously.

[0053] The illustrative lancing crawler or head 40 moves along the NTL 20 by being driven across the floor 20 (for example, the upper surface of a tubesheet) using the drive tracks 72. Thus positioned, the illustrative lancing crawler or head 40 is near the floor 20, so that having the tilt drive 66 set to orient the nozzles 60 horizontally provides sludge lancing at or near the floor 20. To provide lancing at higher elevations, the tilt drive 66 is operated to tilt the water jets upward. If the tubes 14 are straight tubes (for example, as in a once-through steam generator, OTSG, or as in a U-tube design except near the "U" shaped upper turnaround) then this tilting may not require re-alignment of the water jet using the laser diode 112. Optionally, however, such re-alignment can be performed for the various tilt settings. Advantageously, the camera 110 and laser beam 112 (and also the fill light 114) tilt with the nozzles 60 so that alignment and visual inspection can be performed at any tilt angle.

[0054] With reference back to FIG. 1, in an alternative embodiment the alignment is performed using sensors 130 located proximate to the distal end of the tube sheet bundle, that is, distal from the nozzles 60, i.e. at the outlet end where the exit water jet discharges (as seen, for example, in FIGS. 6 and 7). Such sensors 130 can, for example, comprise optical sensors that detect the laser beam from the laser diode 112, or can comprise pressure sensors that directly detect the water pressure produced by the water jet, or can comprise a charge coupled display (CCD) imaging array that allows the operator to directly observe the exit water jet. A difficulty with this approach is that placement of the sensors 130 can be difficult as the periphery of the tube bundle is not readily accessible from the NTL 20.

[0055] In the illustrative embodiments, the nozzles 60 output a water jet as the lancing beam. In other embodiments, it is contemplated for the lancing beam to comprise a different fluid, for example a chemical (dissolved in water in some embodiments) that chemically attacks the sludge.

[0056] The present disclosure as been described with reference to exemplary embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the present disclosure be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

Claims

1. A sludge lancing apparatus comprising: a lancing crawler or head configured to crawl along a no-tube lane (NTL) on a floor defining a reference plane oriented transverse to tubes of a steam generator; and one or more nozzles mounted on the lancing crawler or head and configured to generate lancing fluid jets along at least two different angles in the reference plane spaced apart by at least 45.degree..

2. The sludge lancing apparatus of claim 1 further comprising: a rotational drive configured to rotate the one or more nozzles about an axis of rotation that is transverse to the reference plane over an angular range spanning the at least two different angles.

3. The sludge lancing apparatus of claim 2 wherein the at least two different angles in the reference plane spaced apart by at least 45.degree. include the angles 90.degree. and one of 30.degree. and 150.degree. respective to a 0.degree. reference along the NTL.

4. The sludge lancing apparatus of claim 2 wherein the at least two different angles in the reference plane spaced apart by at least 45.degree. include the angles 90.degree., 30.degree., and 150.degree. respective to a 0.degree. reference along the NTL.

5. The sludge lancing apparatus of claim 2 further comprising: a drive track configured to move the lancing crawler or head along the NTL; and a center slide separate from the drive track on which the one or more nozzles are mounted, the center slide providing translation of the one or more nozzles respective to the lancing crawler or head.

6. The sludge lancing apparatus of claim 2 wherein the axis of rotation is offset from an axis of thrust imposed by the jets from the nozzles.

7. The sludge lancing apparatus of claim 2 further comprising: an on-board sighting laser mounted with the one or more nozzles and aligned to generate a laser beam parallel with a jet beam output by the nozzle.

8. The sludge lancing apparatus of claim 7 further comprising: an on-board camera mounted with the one or more nozzles and aligned to view along a jet beam output by the nozzle.

9. The sludge lancing apparatus of claim 2 further comprising: an on-board camera mounted with the one or more nozzles and aligned to view along a jet beam output by the nozzle.

10. The sludge lancing apparatus of claim 1 further comprising: a bladder configured to expand when filled with a fluid to secure the lancing crawler or head between tubes of the steam generator located adjacent the NTL.

11. The sludge lancing apparatus of claim 1 wherein each nozzle includes a taperlock seat comprising a conical seat of the nozzle that seats in a mating conical recess of a nozzle manifold.

12. The sludge lancing apparatus of claim 1 further comprising: a nozzle tilt drive configured to tilt the one or more nozzles respective to the reference plane.

13. A sludge lancing method comprising: moving one or more nozzles along a no-tube lane (NTL) on a floor defining a reference plane oriented transverse to tubes of a steam generator; and using the one or more nozzles, generating lancing fluid jets along at least two different angles in the reference plane spaced apart by at least 45.degree..

14. The sludge lancing method of claim 13 wherein the tubes of the steam generator have a hexagonal pattern and the at least two different angles in the reference plane spaced apart by at least 45.degree. include the angle of 90.degree. respective to a 0.degree. reference oriented along the NTL and at least one of the angles 30.degree., 150.degree. respective to the 0.degree. reference oriented along the NTL.

15. The sludge lancing method of claim 13 wherein the tubes of the steam generator have a hexagonal pattern and the at least two different angles in the reference plane spaced apart by at least 45.degree. include the angles of 30.degree., 90.degree., and 150.degree. respective to a 0.degree. reference oriented along the NTL.

16. The sludge lancing method of claim 13 wherein the generating comprises: positioning the one or more nozzles in a first position with the nozzles directed along a first angle of the at least two different angles; with the one or more nozzles in the first position, generating a lancing fluid jet along the first angle; positioning the one or more nozzles in a second position with the nozzles directed along a second angle of the at least two different angles that is at least 45.degree. away from the first angle in the reference plane; and with the one or more nozzles in the second position, generating a lancing fluid jet along the second angle.

17. The sludge lancing method of claim 16 wherein the positioning operations each comprise: rotating the one or more nozzles about an axis of rotation transverse to the reference plane to a first angle of the at least two different angles.

18. The sludge lancing method of claim 17 wherein the positioning operations each further comprise: translating the one or more nozzles using a translation mechanism that is separate from a mechanism for moving the one or more nozzles along the NTL.

19. The sludge lancing method of claim 17 wherein the positioning operations each further comprise: sighting the one or more nozzles along a tube lane to be lanced using a laser sight mounted with the one or more nozzles.

20. A method comprising: positioning a nozzle assembly comprising a plurality of nozzles proximate a proximal end of a tube sheet bundle comprising a plurality of tubes; positioning a first sensor proximate a distal end of the tube sheet bundle; and aligning the nozzle assembly, wherein spray paths between each of the plurality of nozzles and the distal end of the tube sheet bundle are unobstructed by one or more of the plurality of tubes.

21. The method of claim 20, wherein the nozzle assembly is positioned 90 degrees with respect to the tube sheet bundle.

22. The method of claim 20 further comprising positioning an additional nozzle assembly at a second position with respect to the tube sheet bundle.

23. The method of claim 21, wherein the nozzle position is less than ninety degrees.

24. The method of claim 21, wherein the nozzle position is greater than ninety degrees.

25. The method of claim 20 further comprising spraying water through the nozzle assembly at a first pressure.

26. The method of claim 25 further comprising measuring conductivity of the spraying water.

27. The method of claim 25, wherein aligning the nozzle assembly is performed prior to spraying water through the nozzle assembly.

28. The method of claim 20, wherein the nozzle assembly comprises at least one laser.