MRPC determined the steel plate lining the penstock delaminated from the concrete encasement and buckled within it, ultimately resulting in a partial flow blockage. MRPC needed a repair solution that would be:
A stand-alone system (i.e., not rely on any strength from the encasement),
Applied on the inside of the pipe and minimize loss of internal diameter,
Cost-effective and able to meet a design life of more than 50 yrs.
SGH investigated the condition of the penstock and designed a carbon fiber-reinforced polymer (CFRP) repair that accounted for all internal and external loads acting on the host pipe.
Based on our investigation, we determined that the variable geometry inside the penstock would require different design approaches for each area. We designed repairs for the circular cross-section, the flat top and bottom portions of the transition piece, and the circular sides of the transition piece. To accomplish the repair, we specified removal of the buckled steel plate, allowing the CFRP to be bonded directly to the concrete encasement.
SGH conducted on-site field engineering for the duration of the project and helped the project team address challenges, including water infiltration through the concrete and difficult laminate details.
After construction, SGH conducted three annual inspections to monitor the in-service performance of the repairs, particularly in areas of prior water infiltration and at locations with potential for abrasive flow.