Tri Tool Inc., Services Division has been involved since 1985 with T. V. A.'s Maintenance Partners to develop a process and perform weld removal on mainsteam-hot reheat and turbine main stop valve legs. The N.D.E. testing industry wide on all power piping created a need for quick, reliable excavation of cracks in each of these systems.

Scope of Work
The mainsteam piping machined ranged from 17.50" O.D. x 2.50" wall through 22.00" O.D. x 3.37" wall. The depth of the excavations came within .250" from the pipe's I.D. surface. The base of the excavation measured 1.50" to 2.00" wide and was beveled with a combination of 37.5º and 10º to ensure parent metal exposure. The hot reheat piping was 16.00" O.D. x .850" wall and was also excavated to within .250" from the pipes' I.D. surface. The weld bevel was similar in configuration. The turbine main stop valve legs required extensive linear machining due to past repairs that had been required due to cycle fatigue. The 12 x 8 reducer was restored after using this technique.

Tri Tool's Service Solution...
As the photos show, all of the welds that were repaired required that a three lug minimum by engineering to maintain position during repairs. Tri Tool's equipment operated within the space created underneath these lugs. No elaborate rigging or fixturing was required. The equipment used was the SB Series Split Frame Lathe System (clamshell) fitted with dual drive units. Stock tooling with slight modification to the tool holders resulted in a portable solution with minimal engineering costs, making this an effective and economic service project for the customer.