No abstract

The University of Tulsa, Citadel Technologies, and T.D. Williamson, Inc. were selected by The Oklahoma Center for the Advancement of Science & Technology (OCAST) for a program of research and testing a non-metallic structural pipeline repair composite sleeve. The name of this composite repair system is Diamond Wrap and the system is based on carbon fabric with an epoxy matrix wrapped around a damaged pipe. Baseline material coupon level testing has been completed on the repair system to compile data to fully define the engineering properties of the current primary product to which all changes and improvements can be compared. These properties include ultimate tensile strength and modulus in the longitudinal and transverse directions, lap shear strength, glass transition temperature, and coefficient of thermal expansion. Full scale fatigue and static rupture tests were also performed on pressure vessels to determine the effectiveness of repairs made using the overwrap repair system.

Rupture tests were performed on pressure vessels to determine the effectiveness of repairs made using a carbon/epoxy composite material system. The carbon/epoxy system is intended to repair externally damaged or corroded steel pipe. Rupture vessels were constructed from six inch nominal diameter, Schedule 40, A-106, Grade B steel pipes cut into 5 ft. (1.52 m) lengths with welded end-caps. To simulate external corrosion, defects were machined into the outer surface of each pressure vessel to determine limitations of the carbon/epoxy repair system. The test specimen geometries include: a six inch wide circumferential flaw, a patch removal of an area measuring 6 inches by 6 inches (15.2 cm by 15.2 cm), and no surface defect. For the defect geometries, vessels were prepared at wall losses of 50 and 80 percent. Results indicate the vessels repaired with the carbon/epoxy repair system performed significantly better than those vessels without the applied repair systems, approaching but not exceeding the virgin pipe strength with no defect.