Cooling Tower Composite Pipe Repair
Nuclear Generating Station
A 54” diameter Cooling Tower Water Makeup line constructed of Reinforced Polymer Mortar Pipe (RPMP) had cracked approximately 180’ from an access point. The below grade pipe had severe damage near a 45 degree downward bend and the area was obstructed by a butterfly valve near the entry point.
To ensure adequate bond strength, Next experts performed adhesion tests on spare RPM pipe pieces. FRP repair materials were laminated to the surface. Once cure was achieved, elcometer adhesion pulls were completed in accordance with the ASTM standard.
The construction schedule required the installation to be complete, including the necessary cure time, in 72 hours. Next personnel were mobilized in two shifts and completed operations as follows:
- Installation of temporary power from panels at the entry point to approximately 200’ away.
- Moving fabric rolls and resin through butterfly valve to worksite.
- Surface preparation using powered sanding equipment to provide adequate profile.
- Removal of protruding pipe pieces via grinding.
- Filling of all voids in pipe where damage had occurred.
- Installation of 3 layers of bi-directional carbon fiber.
- Force curing to meet schedule.
Several alternative repair methods had been attempted – none lasted longer than 3 months. Next installation teams fully restored the surface of the pipe and it has been in service for 3 years.
Strengthening & Rehabilitation
The 60″D water main was approaching failure and required emergency repairs. Pre-stressing wire failure and internal cracks were noted in a 200′ section.
We teamed with a local contractor, the pipe repair was analyzed and an FRP based repair was engineered to meet the water system’s structural and regulatory requirements.
Following City review and approval, the pipe surface was water blasted and the pipe joints (every 20′) were repaired and reinforced with FRP.
Next, the pipe was wrapped internally with a 2-layer high strength carbon fiber system (FRP) to replace lost hoop strength in accordance with the engineering documents.
In the final step, an NSF topcoat was applied.
The FRP system restored the lost hoop strength without loss of pipe flow and pressure capacity. In addition, the work was completed using existing pipe access areas within the 10 day shutdown period.