Abstract
Trench breaker foaming systems are temporary or permanent barriers installed in pipe trenches at regular intervals to prevent trench collapse. The ability of the foaming systems to conduct or shield cathodic protection (CP) current has not been extensively studied. Investigations were conducted on trench breaker foams to understand the ability of the foaming systems to conduct CP current on an underground pipeline. Two different types of foams, open cell (low density) and closed cell (high density), were used. The testing was conducted on two FBE-coated pipelines buried in a trench with various foaming system combinations applied as breakers. Coating defects (holidays) were created at known locations on the pipeline by disrupting the coating; reference electrodes and electrical resistance (ER) probes were installed at the coating defect locations. Trench breaker foams were sprayed to embed the holidays, reference electrodes and ER probes with an intent to monitor CP current transfer activity through the foams. The CP current was applied using a sacrificial system and periodic data was recorded on reference electrodes and ER probes. The current densities occurring and polarized potentials achieved for effective CP of pipeline were investigated and compared. The results of the testing indicate that there is CP current transfer activity through the foam types, and the effect is more prominent when the foams are saturated with water.
