Articulated Sludge Lance

The present invention relates, in general, to equipment for cleaning steam generators and, in particular, to an articulated fluid lance for cleaning sludge from the lower portions of steam generator tubes.

In nuclear power stations, steam generators, such as recirculating steam generators and once-through steam generators, are used for heat exchange purposes in the generation of steam to drive the turbines. Primary fluid which is heated by the core of the nuclear reactor passes through a bundle of tubes in the steam generator. Secondary fluid, generally water, which is fed into the space surrounding the tubes receives heat from the tubes and is converted into steam for driving the turbines. After cooling and condensation has occurred, the secondary fluid is directed back into the space around the tubes to provide a continuous steam generation cycle. Due to the constant high temperature and severe operating conditions, sludge accumulates on the lower portions of the tubes and on the tubesheet which supports same. The sludge which is mainly comprised of an iron oxide, such as magnetite, reduces the heat transfer efficiency of the tubes and can cause corrosion. Thus, the tubes must be cleaned periodically to remove the sludge and various types of apparatus and methods are available to accomplish this task.

U.S. Pat. No. 4,566,406 entitled "Sludge Removing Apparatus for a Steam Generator" discloses a manifold which is rigidly attached to the tubesheet and remains in place during conventional operation of the steam generator. A plurality of nozzles on the manifold emits streams of water to break up sludge on the upper surface of the tubesheet. Openings are provided in the walls of the steam generator to remove the slurry.

U.S. Pat. No. 4,079,701 entitled "Steam Generator Sludge Removal System" discloses an arrangement of headers at the elevation of the sludge to be removed from around the tubes in order to establish a circumferential fluid stream at that elevation. A fluid lance moved along a line between the headers emits a fluid jet perpendicular to the line of movement of the fluid lance. The lance may also be rotated as it is moved.

U.S. Pat. No. 4,700,662 entitled "Sludge Lance Wand" discloses a lance for cleaning once-through steam generator tubes. The lance has a fixed radius of curvature thus necessitating manual manipulation of same in order to insert the lance between tubes within the tube bundle in the steam generator.

All of the foregoing apparatus have some inherent disadvantages which prevent them from efficiently removing the sludge which accumulates around the tubes within the tube bundle. Because of this, it has become desirable to develop a sludge lance which can be manipulated so as to easily pass through the openings between adjacent tubes within the tube bundle.

The present invention solves the problems associated with the prior art and other problems by providing a sludge lance having an adjustable articulated portion permitting easy insertion of the lance between the tubes within a tube bundle in a steam generator. The lance includes a manipulator member whose outer end is attached to a plurality of radius blocks arranged in an abutting relationship. The radius blocks are movable through the actuation of a cam assembly causing the radius blocks to form an arc having an adjustable radius of curvature. A fluid distribution member having a split manifold at its outer end is affixed to the manipulator member and the radius blocks and positioned so that the split manifold is positioned outwardly from the end of the radius block assembly. A spring backing plate is attached to the manipulator member and the radius blocks so as to cover a portion of the fluid distribution member, and is used to bias the manipulator member and the radius blocks into the same plane upon deactuation of the cam assembly. A plurality of orifices in the split manifold located at the end of the fluid distribution member permit the passage of fluid therethrough for impingement upon the sludge between the tubes within the tube bundle to dissolve same.

FIG. 1 is a front elevational view of the articulated sludge lance of the present invention.

FIG. 2 is a top plan view of the articulated sludge lance shown in FIG. 1.

FIG. 3 is a top plan view of the fluid distribution member utilized by the articulated sludge lance of the present invention.

FIG. 4 is a top plan view of the articulated sludge lance of the present invention in use in a steam generator.

Referring now to the drawings where the illustrations are for the purpose of describing the preferred embodiment of the present invention and are not intended to limit the invention described herein, FIG. 1 is a front elevational view of the articulated sludge lance 10 of the present invention. The sludge lance 10 is comprised of a manipulator member 12, a cam assembly 14 attached to one end of the manipulator member 12, a spring backing plate 16 attached to the underside of the manipulator member 12 adjacent the opposite end thereof, and a water distribution member 18 positioned so that a portion thereof is interposed between the bottom surface of the manipulator member 12 and the top surface of the spring backing plate 16.

The manipulator member 12 is formed from a high impact strength plastic, is elongated and typically has a substantially rectangular cross-section. As previously stated, the cam assembly 14 is attached to one end of the manipulator member 12. A plurality of radius blocks 20, each having a substantially rectangular cross-section of approximately the same size as the manipulator member 12, is attached to the opposite end of the manipulator member 12 so as to be aligned therewith. Attachment is effected by means of the spring backing plate 16 which is attached to the bottom of the manipulator member 12 and to the bottom of each of the radius blocks 20 by fasteners 22. The radius blocks 20 are positioned in an abutting relationship to one another and to the end of the manipulator member 12. As shown in FIG. 2, a wire cable 24 traverses through the length of the manipulator member 12 and through each of the radius blocks 20. One end of the cable 24 is connected to the outer most radius block 20 and the other end of the cable 24 is connected to a pin 26 (shown in phantom) within the cam assembly 14. A cam lever 28 is attached to the cam assembly 14 permitting rotation thereof. Rotation of the cam lever 28 in the clockwise direction causes the wire cable 24 to move to the left causing the radius blocks to be drawn into an arc with respect to the manipulator member 12, as illustrated in FIG. 1. Subsequent rotation of the cam lever 28 back to its original position causes the wire cable 24 to move to the right resulting in the radius blocks 20 returning to their original position so as to be in the same plane as manipulator member 12. The spring backing plate 16 urges the radius blocks 20 to return to their original position.

The water distribution member 18 is elongated and has a substantially rectangular cross-section which is similar to, but smaller, than the rectangular cross-section of the manipulator member 12 and the radius blocks 20. The water distribution member 18 is received within a recess provided in the bottom of the manipulator member 12 and is attached thereto by a mounting block 30. The water distribution member 18 is similarly received within a recess provided within the bottom of each radius block 20 so as to be interposed between the sprig backing plate 16 and the radius blocks 20. The length of the water distribution member 18 is greater than the combined length of the manipulator member 12 and the radius blocks 20 attached thereto causing the outer end of the water distribution member 18 to be exposed. The rear manifold portion 32 of the water distribution member 18 includes a water inlet 34 which communicates with a plurality of longitudinally extending spaced apart water tubes 36 within the water distribution member 18. Approximately 8 water tubes having an outside diameter of 0.084 inches and a wall thickness of 0.008 inches are provided. The water tubes 36 terminate in a transverse passageway 38 located in a split manifold 40 at the outer end of the water distribution member 18. The split manifold 40 is positioned so as to be located adjacent the outermost radius block 20. Each of the ends of the transverse passageway 38 and the center thereof is provided with an outlet orifice 42. Each outlet orifice 42 is provided with a sapphire jewel therein to minimize wear thereof.

Referring now to FIG. 4, in operation, the sludge lance 10 is inserted through a handhole 50 provided in a steam generator shell 52 and into a lane or space between tubes in a tube bundle 54. As shown, a space provided in shroud 56 surrounding the tube bundle 54 allows easy access thereto. The manipulator member 12 is supported by the lower tubesheet and fluid pressure is supplied to the lance from a fluid source (not shown). By rotation of the cam lever 28, the angular deflection of the radius blocks 20 can be adjusted permitting the sludge lance 10 to enter between tubes within the tube bundle 54. As the sludge lance 10 is moved through the tube bundle 54, fluid flow from the outlet orifices 42 in the water distribution member 18 loosens and removes sludge from the tubes which is then removed from the generator by a suction system. The fluid/sludge mixture is filtered to remove the solids and the fluid is recirculated. Manipulation of the sludge lance 10 by rotation of the cam lever 28 during operation permits entry of the lance 10 between the tubes within the tube bundle 54 and the foregoing manipulation can be done manually or remotely while being monitored by a video system.

Certain modifications and improvements will occur to those skilled in the art upon reading the foregoing. It should be understood that all such modifications and improvements have been deleted herein for the sake of conciseness and readability, but are properly within the scope of the following claims.