Waterwall Quench Crack Inspection Without Cleaning or Scaffolding

The Mutual Inductance Bridge (MIB) system scans waterwalls for multiple defect types. Already used successfully to detect fireside corrosion and erosion, the capability has been expanded to quench cracking. The MIB electromagnetic approach uses in-phase and quadrature information to detect defects well before potential breakouts might cause plant outages. Fireside corrosion, scale and clinker deposits as large as 0.5” do not interfere with measurement accuracy or speed. Although quench crack defects alone do not change the mass of ferromagnetic material, the magnetic field perturbations caused by their presence provide a unique signature. The robotic MIB deployment containing a position measuring laser, video cameras and proprietary electronics scans 400 ft² per hour; the handheld unit scans 125 ft²/hr. Scan results include color-coded maps that describe the condition of scanned areas, and individual tube profiles. Results of several applications are presented.