Pressure Boundary Modifications
Specialty Machining and Code Repairs
BWXT has full capabilities for performing repairs to ASME Code pressure vessels. We have all required ASME and National Board certifications (N, NPT, NA, NS, and NR) for performance of design, modification and repair activities. In addition, we have the engineering analysis expertise, tooling, procedures and field personnel to deliver these services.
BWXT has designed, built and qualified portable tooling for manway/hand hole cover and gasket surface machining, addition of hand holes and instrument ports to steam generators (SG) and other pressure vessels, removal of stuck studs, and other specialty machining applications. BWXT utilizes both commercially available and custom designed tooling to perform machining processes.
For flange facing, our robust tooling design includes hardened slides and ball screws to eliminate backlash, while ensuring continuous depth of cut and removal of as little as 0.0005 inch of material, allowing the creation of a phonographic finish for ideal surface sealing. Additionally, the tooling is designed for quick set-up to increase efficiency and reduce dose. Custom shielding further reduces dose and serves as a foreign material exclusion (FME) barrier. Our machining specialists validate the process on realistic mock-ups prior to the job, to provide a quality repair.
For SG manway stuck stud removal, BWXT has designed a versatile system that works on steam generators for various manufactures and for different stud types and lengths. The machining system is a modular design that includes a base fixture, a feed rack, and a power unit. The variable output electric motor driver provides a wide range of speed and power necessary for drilling and tapping of various sizes of holes. The components are designed for ease of assembly at the manway, and incorporate a shield plug to reduce operator dose. Precision adjustments to tolerances of +/- 0.005 inch cleanly remove the stud without damage to the stud hole threads, permitting a return to service without helicoil or insert installation.
BWXT has an extensive library of registered weld procedure specifications available should welding repairs be required. Our engineered weld solutions include both portable manual equipment and customized automatic welding equipment. Our extensive knowledge of repair techniques to stainless steels, NiCr, modified Cr-Mo and numerous other steel alloys is vast. Our expertise in temper-bead welding allows us to perform repairs on material that typically requires post weld heat treatment when post weld heat treatment is not possible. Specialty welding applications performed by BWXT include SG tube-to-tubesheet seal weld repairs, small nozzle repairs and storage tank repairs. We have developed and deployed custom solutions for feeder tube repairs with as little as one inch working clearance around the piping in these high dose regions.
Key Features and Benefits:
- Experienced OEM and Engineering/Service provider with extensive code repair capability and expertise
- Routinely perform complex machining tasks such as flange face machining, installation of vessel inspection ports, and other specialty machining tasks
- Proven equipment and processes successfully deployed in challenging environments
- Digital controls with simple, intuitive operator interface
- Extensive mock-up facilities for custom tooling development and in-house training