Dexon Challenging Pipeline Inspection Case Study Archive: Multiple Diameter Road Crossing Pipeline Inspection with Lateral Wye Launcher Receiver Fittings and Back-To-Back Bends.

The below case study comes from the Dexon challenging pipeline inspection archive. Dexon was faced with a challenging pipeline inspection that featured multiple pipe diameters, back-to-back bends, a lack of launchers and receivers, and the complete absence of prior inspection data of a pipeline crossing under a busy urban intersection. The combination of these pipeline configurations posed difficulties to the inspection team. To accomplish the inspection, specialists from Dexon’s RD&E (Research Development and Engineering) department were called in to design and develop modified pipeline integrity gauges (PIG’s). Inspection verification included complete pipeline configuration and testing at Dexon’s 6-acre test yard prior to inspection.

Multiple Diameter Pipelines

The inspection included multiple pipelines with multiple diameters including an 8” line with reduced sections down to 6” and a 12” line with reduced sections down to 10”. To accommodate the reduction in pipe diameter customized petal driving disks were developed that were able to maintain a seal in the larger diameters (12” and 10”) and then fold down and maintain a seal in the reduced sections.

Back-to-Back Bends

Back-to-back bends pose difficulties to inspection teams as they require higher operating pressures to propel the PIG through the bends. In addition to this as the tool’s modular bodies pass through a bend the transducers are moved out of the center of the pipe losing inspection data. Specialized spacing disks were used to ensure the tool remained in the center of the pipe while passing through bends.

Lack of Launchers and Receivers

The pipelines under inspection were required to be in operation during the inspection and could not be taken offline. Lateral Wye launchers and receivers were used to allow the flow of product to continue during the inspection. Lateral wye fittings pose difficulties to inspection teams as the seal is lost as the tool enters the wye and the tool can stall in the bend. To ensure the safe passage of the PIG through the line, an extended nose was developed that would push the nose around the bend and form a seal in the next pipe spool.

Absence of Prior Inspection Data

An absence of previous inspection data meant that the inspection team knew very little about the line under inspection. A lot of the time pipeline construction records can be incomplete and missing crucial data that could lead to issues during an inspection. High back welds, misaligned pipe spools, unbarred underground features, and high corrosion are only a few possibilities that can lead to a stalled PIG. As the pipeline was a road crossing under a busy urban intersection digging up the pipeline to retrieve a stalled PIG would not be possible. Special care was required during the cleaning and gauging process to ensure safe passage.

Contact a Dexon inspection engineer for more information on Dexon’s challenging pipeline inspection program.