Steam generator dual head sludge lance
View Patent ↗A moveable sludge lance ( 76 ) said moveable sludge lance having duel lance heads ( 77, 79 ) passed through handholes ( 62 ) in the side of a nuclear steam generator and into a central tube lane ( 60 ) having a central stay rod ( 61 ) which cleans with high pressure fluid through the row 1 tubes ( 85 ) in the tube lane, where the distance ( 200 ) between the dual lance heads ( 77, 79 ) is wide enough to allow the dual lance heads to extend beyond the central stay rod ( 61 ).
1. A method of sludge lancing a tube bundle in a tubular steam generator having a plurality of entry handholes allowing access to a center tube lane, the bundle having a hot leg side and a cold leg side separated by the center tube lane which lane at its midpoint has a central stay rod, which extends from a tube sheet to an elevation above at least one of the plurality of entry handholes, comprising the steps of:
1) opening at least one of the plurality of entry handholes providing access into the center tube lane;
2) introducing a moveable sludge lance having dual lance heads into the center tube lane, with the dual lance heads extending in parallel along a length of the center tube lane and laterally separated from each other a distance greater than the diameter of the central stay rod so the central stay rod can fit into an opening between the dual lance heads; and
3) moving the dual lance heads along the center tube lane while sludge lancing the tube bundle with the moveable sludge lance, so that the dual lance heads traverse a first portion of the central tube lane to extend on either side of the central stay rod wherein the dual heads simultaneously sludge lance a tube lane transverse to the center tube lane on the hot leg side and on the cold leg side and in line with the central stay rod before or upon reaching a limit of movement of the dual lance heads along the central tube lane, wherein the dual lance heads have axial compliance allowing alignment with any adjacent misdrilled tubes.
2. The method of claim 1 , wherein the step of moving the dual lance heads comprises moving the dual lance heads along a rail that extends between the at least one handhole opening and the central stay rod, including the step of registering a jaw, located and supported at one end of the rail, on the central stay rod to center the rail within the center tube lane.
3. The method of claim 2 , including the step of supporting a second rail between a second handhole, substantially opposite the at least one handhole, and the central stay rod and moving a second sludge lance along the second rail between the second handhole and the central stay rod.
4. The method of claim 3 including the step of operating the dual lance heads and the second sludge lance simultaneously.
5. The method of claim 1 , including the step of oscillating the dual lance heads as they move.
6. The method of claim 1 , wherein the dual lance heads transverse the center tube lane to extend beyond an end point of the central stay rod.