Safety, Quality, and Productivity Since its founding in 1990, Rockwood operates through  its wholly owned subsidiaries of Acuren, Sperry Rail,  RAT and Hellier.  These operations are worldwide  leaders in their served markets. Acuren / TEI © 2012-13 Rockwood Service Corporation Overview Rockwood Group of Companies Rockwood Service Corporation is the largest and fastest growing non-destructive testing (NDT) and inspection firm in the  world.  NDT is the application of non-invasive technologies (such as Utrasonics or Radiography) to inspect the structural  integrity of materials and structures.  We invite you to explore the array of services offered through our subsidiaries.