Semiautomatic weld crown contouring equipment. Final report
Pipe welds in nuclear plants are presently finished by tedious hand grinding for ultrasonic testing. A study has now been completed demonstrating that a semiautomatic machine for finishing weld crowns is quite feasible. Such a machine could produce more consistent contours than hand finishing as well as improved surface finishes; also it could virtually eliminate inadvertent undercutting of the weld crown and the need for subsequent repair before testing. The machine could reduce the time required to finish the welds by a factor of 10 on Class-1 welds, saving $31 million for plants being built and $21 million for reactors being planned. To determine feasibility and develop the concept, specialists of 30 utilities were surveyed to establish practical performance requirements for the machine including pipe materials, size of pipes, space restrictions, typical misalignments, offsets and out of roundness. The conceptual design is an external lathe that clamps over and encircles the pipe. The lathe tool bit is driven around the pipe by an electric motor. The radial position of the tool bit is real-time controlled by an on-board microprocessor to produce the smoothest blend across the area of the joint between the two pipes. The microprocessor program is set by making initial circumferential scans on both sides of the weld with an electronic stylus in place of the tool bit. This provides the microprocessor with initial and final coordinates from which to compute the cut. To test the general concept of an external lathe, a test machine was fabricated and set up to remove a 308 stainless steel weld crown on a 10-inch-diameter Schedule 40 pipe. The machine easily finished the welded area producing a surface finish of better than 100microinches RMS in one pass while simultaneously removing a weld crown 0.150 inches thick. Tests of the microprocessor-controlled cutting head and development of a field prototype design are planned.
- Research Organization:
- Sigma Research, Inc., Richland, WA (USA)
- OSTI ID:
- 6152605
- Report Number(s):
- EPRI-NP-1107; TRN: 79-017568
- Country of Publication:
- United States
- Language:
- English
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