Patent Number: 
Section: claims

1. A jet pump diffuser weld repair device operable on a jet pump diffuser including pockets formed in an exterior surface of the diffuser on opposite sides of a weld to be repaired, the weld repair device comprising:a lower ring section and an upper ring section respectively sized to fit entirely around a circumference of the diffuser on opposite sides of the weld to be repaired, the lower and upper ring sections including a plurality of aligned gripper slots formed in an inner circumference of the lower and upper ring sections;a corresponding plurality of grippers fit into the gripper slots and facing radially inward toward the diffuser, wherein the grippers comprise double-tapered cam surfaces respectively engaging the lower ring section and the upper ring section, the double-tapered cam surfaces being tapered radially outward from axially distal ends of the grippers toward a central apex to drive the grippers radially inward as the lower and upper ring sections are drawn toward each other; anda plurality of connector bolts secured between the lower ring section and the upper ring section, wherein tightening the connector bolts draws the lower and upper ring sections toward each other,wherein the grippers comprise engaging lugs shaped to fit in the pockets formed on the opposite sides of the weld. 2. A jet pump diffuser weld repair device according to claim 1, wherein the grippers comprise tapered surfaces as the cam surfaces on a side of the grippers facing the gripper slots. 3. A jet pump diffuser weld repair device according to claim 2, wherein the gripper slots comprise angled surfaces as the cam surfaces engaging the tapered surfaces of the grippers. 4. A jet pump diffuser weld repair device according to claim 1, wherein the lower ring section comprises a clamp half lower female part engageable with a clamp half lower male part, and wherein the upper ring section comprises a clamp half upper female part engageable with a clamp half upper male part. 5. A jet pump diffuser weld repair device according to claim 4, wherein the clamp half lower and upper female parts comprise T-slots that receive corresponding T connectors on the clamp half lower and upper male parts. 6. A jet pump diffuser weld repair device according to claim 1, wherein if the opposite sides of the weld in the diffuser exterior surface in which the pockets are formed are of different materials, a material of the grippers is selected such that its coefficient of thermal expansion falls between coefficients of thermal expansion of the different materials. 7. A weld repair device for a thin wall welded pipe comprising:a lower ring section and an upper ring section respectively sized to fit entirely around a circumference of the thin wall welded pipe on opposite sides of a weld to be repaired;a plurality of grippers fit into aligned gripper slots formed in an inner circumference of the lower and upper ring sections, the plurality of grippers facing radially inward toward the thin wall welded pipe, wherein the grippers include double-tapered cam surfaces respectively engaging the lower ring section and the upper ring section, the double-tapered cam surfaces being tapered radially outward from axially distal ends of the grippers toward a central apex to drive the grippers radially inward as the lower and upper ring sections are drawn toward each other; anda plurality of connector bolts secured between the lower ring section and the upper ring section, wherein tightening the connector bolts draws the lower and upper ring sections toward each other. 8. A weld repair device according to claim 7, wherein the opposite sides of the weld comprise different materials, and wherein a material of the grippers is selected such that its coefficient of thermal expansion falls between coefficients of thermal expansion of the different materials. 9. A weld repair device according to claim 7, wherein the pipe on one side of the weld is cylindrical and on an opposite side of the weld is conical constituting a shape change, the lower and upper ring sections and the grippers being configured accommodate the shape change. 10. A weld repair device according to claim 7, wherein the grippers comprise engaging lugs shaped to fit in pockets formed in an exterior surface of the thin wall welded pipe on the opposite sides of the weld.