BRIEF DESCRIPTION OF THE DRAWINGS
Example embodiments of the methods that may be utilized in practicing the invention are addressed more fully below with reference to the attached drawings in which:
FIG. 1 illustrates a diffusing flow pattern exhibited by conventional nozzles;
FIG. 2 illustrates a coherent flow pattern exhibited by a an array of nozzles according to an example embodiment of the invention;
FIGS. 3A-3D illustrate several example configurations of the plurality of orifices provided in nozzles according to an example embodiment of the invention;
FIG. 4 illustrates an example configuration of the nozzles according to FIG. 3 in conjunction with a fluid distribution shuttle;
FIG. 5 illustrates general operation of an assembly including nozzles and a fluid distribution shuttle according to FIG. 4;
FIGS. 6A and 6B illustrate rotation of an assembly including nozzles and a fluid distribution shuttle according to FIG. 4 about a main longitudinal axis of the fluid distribution shuttle;
FIG. 7 illustrates an example positioning of an assembly including nozzles and a fluid distribution shuttle according to FIG. 4 along a no-tube lane provided within a tube bundle;
FIG. 8 illustrates an application of a cleaning apparatus according to an example embodiment of the invention configured to establish a circumferential flow that will tend to move the cleansing solution toward a vacuum extractor device;
FIG. 9 illustrates an example embodiment of a cleaning apparatus according to the invention in which the nozzles directed down opposing intertube lanes are provided on separate conduits;
FIGS. 10A and 10B illustrate a cross-sectional and a side view, respectively, of a nozzle arrangement on a single conduit wherein the nozzles are offset from adjacent nozzle(s) to direct the flow toward different portions of the adjacent intertube lanes; and
FIG. 11 illustrates a stacked configuration in which nozzles provided on two separate conduits are directed to different portions of a single intertube lane to provide both a primary and a secondary cleansing stream.
It should be noted that these figures are intended to illustrate the general characteristics of methods and materials with reference to certain example embodiments of the invention and thereby supplement the detailed written description provided below. These drawings are not, however, to scale and may not precisely reflect the characteristics of any given embodiment, and should not be interpreted as defining or limiting the range of values or properties of embodiments within the scope of this invention. In particular, the relative sizing and positioning of particular elements and structures may be reduced or exaggerated for clarity. The use of similar or identical reference numbers in the various drawings is intended to indicate the presence of a similar or identical element or feature.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
It was determined by the inventors that the high-pressure flows associated with conventional sludge lancing techniques were unnecessary and that sufficient cleaning could be achieved using lower pressure fluid jets providing a flow velocity of at least about 5-10 m/sec (16-33 ft/sec). Indeed, when flushing soft, highly mobile sludge to the periphery of the steam generator, increasing the pressure far beyond that which is required to produce the noted jet velocity of 5-10 m/sec actually tends to decrease the efficiency of conventional techniques intended for removing soft, highly mobile sludge. With this discovery in mind, the inventors developed a cleaning system and method that utilizes coherent low-pressure fluid jets (nominally no more than about 0.7 MPa, but pressures of up to about 2.1 MPa may be useful) (nominally no more than about 100 psi, but pressures of up to about 300 psi may be useful), rather than conventional high-pressure fluid jets, to flush soft, highly mobile sludge to the steam generator periphery.
The coherent low-pressure fluid jets utilized in this system and method are typically able to provide sufficient flow velocities for flushing soft, highly mobile sludge from within the tube bundle and can also provide a larger cross-sectional flow area than high-pressure fluid jets produced using conventional lancing techniques. Accordingly, these coherent low-pressure fluid jets may be configured to occupy a plurality of, a majority of, or even substantially all of, the intertube gaps whereby substantially the entire surface of the intertube gap can be washed in a single pass.
This system and method utilizing improved matching of the sizing of the fluid jet and the intertube gap(s) will tend to provide both more uniform surface area coverage on the tube sheet and higher sludge removal efficiency than can be achieved with conventional high-pressure lancing techniques. For example, a plurality of these low-pressure fluid jets may be operated simultaneously in a group of adjacent intertube lanes, thereby creating a cumulative “sweeping” flow pattern that greatly reduces lateral scattering of sludge into previously cleaned areas and thereby reduce the number of “passes” necessary to achieve the same degree of cleaning and/or reduce the time required to achieve such results when compared to the performance achieved with conventional high-pressure lancing techniques.
In theory, for a given target flowrate, one needs only to increase the nozzle diameter in order to decrease the required driving pressure of a fluid jet produced during the sludge removal techniques described above. However, as the nozzle diameter is increased (as the L/D ratio is decreased), the jet that is produced by the nozzle begins to disperse more quickly after exiting the nozzle. For example, as illustrated in FIG. 1, a cleaning system 10 applying a cleaning fluid through a conduit 12 to standard nozzles 14 will tend to produce rapidly widening stream 16, rather than a coherent fluid jet. As will be appreciated by those skilled in the art, as the width of the stream increases, the contact between the stream and the tubes adjacent the intertube gap also increases. This contact with adjacent tubes results in a rapid loss of the majority of the energy and volume of the flow, thereby reducing the ability of the stream to flush sludge from the intertube gaps and increasing the scattering of the sludge into adjacent intertube gaps. For reference, because the intertube gaps in typical steam generator designs are only about 2.5 to 10 mm (0.1 to 0.4 in.) wide, and the rapidly dispersing fluid streams produced by standard nozzles will contact and be scattered by adjacent tubes, thereby reducing the cleaning flow and increasing scattering of fluid and debris into adjacent areas.
Example embodiments of an apparatus 100 according to the current invention, as illustrated in FIG. 2, incorporate one or more nozzles 104 connected to a fluid conduit 102, each of which creates a coherent, high-volume fluid jet 106 that substantially maintains its exit width, We, over a distance corresponding to the maximum distance Lm between the no-tube lane and the outer perimeter of the tube bundle, i.e., the maximum length of the intertube gaps that will be cleaned with such an apparatus. For example, the width of the stream 106 at the maximum distance will typically represent no more than a 20% increase compared to the average exit width (W at Lm≦1.2 We), and will preferably exhibit no more than about a 10% increase compared to the average exit width (W at Lm≦1.1 We). In this way, energy and flow volume losses resulting from collisions between the stream(s) and the tubes lining the intertube gaps will be reduced, scattering of sludge into adjacent regions will be reduced and the efficiency of the sludge removal will be improved.
As illustrated in FIGS. 3A through 3D, the coherent jet nozzle elements 108 may be configured as a plurality of smaller holes/orifices 110, rather than one individual hole/orifice having a larger diameter/width. The coherent jet nozzles elements may be configured to provide a length to diameter (L/D) ratio that will produce a plurality of closely aligned coherent, fully-developed fluid jets. For example, it has been found that an L/D ratio of, for example, at least about 15 is sufficient to achieve the desired fluid flow profile of a plurality of aligned and coherent fluid jets. After exiting the nozzle, these individual jets coalesce to form one larger jet that remains substantially coherent over the treatment distance Lm. As will be appreciated by those skilled in the art, improved cleaning can be achieved when the treatment distance Lm approaches or surpasses, for example, the maximum distance between the no-tube lane in which the nozzles will be positioned and the steam generator shell, i.e., a distance approximately equal to the radius of a cylindrical steam generator with a no-tube lane provided across a diameter. As will also be appreciated by those skilled in the art, systems in which the treatment distance Lm is less than the maximum length of an intertube gap can still provide substantially improved cleaning relative to conventional sludge lancing or other systems that cannot produce substantially coherent streams by reducing the stream and sludge scattering.
As illustrated in FIG. 4, the fluid conduit 102 may be provided with a series of structures or fittings 112 for receiving the nozzle assemblies 108. The nozzle assemblies may be attached to the fittings 112 using an O-ring 114 or other structures to provide a substantially fluid-tight attachment and then held in place with a cap or fitting 116 configured to cooperate with the fittings 112 and/or the nozzle assembly to provide nozzles along a portion of the conduit 102.
As illustrated in FIG. 5, groups of nozzles may be provided on various portions of the conduit 102 to allow the resulting fluid streams 106 to be directed in different directions. As illustrated in FIG. 6A, the conduit 102, or a forward portion of the conduit which can be referred to as a shuttle, can be configured for at least partial rotation, thereby imparting a “sweeping” action to the fluid streams 106. As illustrated in FIG. 6B, corresponding nozzles provided in separate groups of nozzles may be spaced along the circumference of the shuttle by an angle Φ that may, of course, vary among the pairs of corresponding nozzles. As illustrated in FIG. 6B, rotation of the shuttle will alter the orientation of the fluid stream 106′ with respect to the cleaned surface 120 between first α1 and second α2 angles. As will be appreciated by those skilled in the art, these angles may be selected to provide for a “sweeping” action along all or at least some portion of the intertube lane along which the fluid stream is being directed.
As will also be appreciated by those skilled in the art and as illustrated in FIG. 6B, the conduit or shuttle portion of the apparatus may be associated with additional devices, for example, carriage 136, that provide the mechanical support for the conduit was well as additional mechanisms to provide for the indexing 138, positioning and rotating 140 functions as necessary to effect the cleaning method. The indexing mechanism 138 may include, for example, stepper motors, sensors and/or gearing that provides a sufficient degree of accuracy whereby the nozzles can be aligned with designated intertube lanes. The rotating mechanisms 140 may include, for example, belts, gears and sensors for controlling the rotation of the carriage and/or the rotation of the shuttle within the carriage, about one or more axes A, A′ to impart a “sweeping” motion to the cleansing fluid streams.
As those skilled in the art are expected to be familiar with the design and implementation of a range of mechanisms that can be used to achieve the desired functionality, these mechanisms are not illustrated in any particular detail. Indeed, the particular mechanisms utilized will be selected, at least in part, based on application-specific considerations including, for example, size, weight, available space, availability of utilities, cleanliness, radiation resistance of materials and design durability.
As illustrated in FIG. 7, the conduit or shuttle 102 may be indexed forward and backward through a no-tube lane in order to direct the fluid streams along the intertube (or intermember) lanes 127 defined by the arrangement of the obstructing tubes (or members) 126. As will be appreciated, particularly with respect to rotation, the forward portion of the conduit, the shuttle, may be configured in a manner substantially different than the rearward portion 124 with the two portions being attached through an appropriate fitting or fittings 122. As illustrated in FIGS. 9 and 11, the conduit or shuttle portion of the apparatus is not limited to a single tube configuration and may include two or more conduits, for example, 102a, 102b, arranged, for example, in a side-by-side (FIG. 9) or over-and-under (FIG. 11) or other configuration. As illustrated in FIG. 11, for example, the configuration allows two or more fluid streams to be applied simultaneously to different regions of a single intertube lane, thereby improving the cleaning process. As illustrated in FIGS. 10A and 10B, the nozzles within a single group, 118a, 118b, 118c, may have different circumferential positioning in order to apply the fluid streams to different portions of adjacent intertube lanes, thereby reducing the scattering and improving the cleaning process.
Example embodiments of cleaning apparatus according to the invention may also incorporate additional structures for establishing a peripheral flow system such as described in Hickman et al.'s U.S. Pat. No. 4,079,701, the contents of which are hereby incorporated, in its entirety, by reference, that will tend to direct the flow(s) exiting the tube bundle along the outer wall of the vessel toward an extraction point as illustrated, for example, in FIGS. 8 and 9. As illustrated in FIGS. 8 and/or 9, the cleaning apparatus may be inserted into the heat exchanger through an access port AP and advanced along a no-tube lane 130 and may provide additional nozzles 132 for establishing a circumferential flow along the outer wall 128 that will tend to sweep the removed debris toward an extraction point 134, for example, a drain or vacuum opening. As will be appreciated by those skilled in the art, however, the use of the low-pressure, high-volume (for example, 190 liters/min. (about 50 gal./min.) or more) cleaning jets removes many of the constraints imposed by the use of high pressure and allows the nozzles to be provided in a range of offset and adjustable configurations to better match the pitch of the nozzles to the pitch of the intertube lanes to be cleaned. Similarly, a plurality of nozzles may be provided with different arcuate offsets for use in combination with rotation of the distribution channel to provide a differential “sweeping” flow through a series of adjacent intertube lanes and thereby improve the effectiveness of the cleaning operation in removing sludge and silt.
For example, the apparatus can be configured so that two sets of nozzles operate simultaneously from opposing access holes in order to create a flow pattern directing the material toward associated extraction apparatus, typically suction equipment, as described in U.S. Pat. Nos. 4,492,186 to Helm and 4,848,278 to Theiss, the contents of which are hereby incorporated, in their entirety, by reference. The apparatus could also be used in conjunction with an adjustable suction device that can be appropriately positioned to maximize the removal of sludge flushed from the tube bundle by the primary fluid jets as described in U.S. Pat. No. 4,492,186. When used in conjunction with a peripheral flow system as described in U.S. Pat. No. 4,079,701 to Hickman, the coherent jet nozzles according to the example embodiments of the invention may be used both to produce the primary fluid jets and to enhance the efficiency of peripheral flow.
As will be appreciated by those skilled in the art, the cleaning apparatus may include an indexing mechanism by which the coherent nozzles provided on the cleaning apparatus may be aligned with the intertube lanes or gaps that are to be cleaned as illustrated, for example, in FIG. 7. This indexing mechanism may be integrated with one or more valves for interrupting the flow of the cleaning solution during movement of the cleaning apparatus. Similarly, the individual coherent nozzles may be provided with valves for interrupting the flow of the cleaning solution through a nozzle or a group of nozzles depending on the orientation of the nozzles (when, for example, as the nozzles approach a horizontal orientation or are otherwise not oriented for directing a stream of cleaning solution onto a horizontal surface in the intertube lane.
Those skilled in the art will also appreciate that although water may provide sufficient sludge removal efficiency, aqueous solutions of various chemical additives, for example, traditional chemical cleaning solvents, Advanced Scale Conditioning Agents (“ASCAs”), dispersants, surfactants, solvents, viscosity modifiers, and abrasives, may also be used as the fluid media with embodiments of the current invention in order to enhance removal effectiveness and efficiency. In particular, chemical treatments (e.g., traditional chemical cleaning solvents, ASCAs, etc.) may be utilized to flush sludge from intertube lanes, and also to dissolve sludge that is difficult to remove using mechanical cleaning techniques, including hard sludge, as well as “shadow” sludge that is shielded from mechanical removal by steam generator tubing.
Chemical treatments (e.g., dispersants, viscosity modifiers, etc.) may also by used to directly enhance the mechanical efficiency of sludge removal by increasing the time that loose sludge can be suspended in the fluid media. Note that the temperature of the fluid media may also be controlled in order to adjust the viscosity of the fluid media and/or the sludge dissolution rate (if chemical additives are used). As will also be appreciated, various combinations of water and aqueous chemical solutions can be sequentially ejected from the nozzles to, for example, remove the bulk of overlying loose sludge before chemically treating the underlying hard sludge, and then switching to a water rinse cycle to remove any additional loosened sludge or scale.
While the invention has been particularly shown and described with reference to certain example embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the following claims.
Patent Application
20080092924
