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Locating Underground PE Gas Main Butt Fusion Welds

Project Overview

Utility companies that operate and maintain PE gas distribution mains have a growing need to accurately locate and inspect specific pipeline features such as fusions and tees. While PE is a highly reliable material, it can pose a unique set of challenges such as improper installations, manufacturer defects or operator errors.

Because some utilities do not have accurate records of features or cannot accurately locate them, the process of locating features can result in excessive excavation, guesswork and extended project durations. To help overcome these challenges, ULC Robotics works with utility companies in the US and UK to identify, inspect and accurately mark out the main and features within the main for more efficient excavations and maintenance operations.

Industry: Natural Gas Networks

Location: California

Business Areas Addressed:

  • Field Operations and Maintenance
  • QA/QC
  • Contractor Oversight

Solution Improved:

  • Community and Worker Safety
  • Project Cost and Duration
  • Project Efficiency


  • Enhance Field Operations
  • Highly Accurate Mark Out Pinpointed Excavation Locations
  • Remove Guesswork and Excessive Excavation


A California-based utility had recently installed a gas network of 2” MDPE coiled pipeline with each segment joined together through butt fusion processes. After identifying a problematic fusion, the utility wanted to conduct testing on several additional fusions carried out in the same area to ensure public safety and system reliability, but the locations of the fusions were not included in utility mapping.

ULC Robotics was contracted to identify and accurately mark out the location of each butt fusion so the utility could efficiently excavate over fusions.



ULC’s operator qualified crews conducted inspection along 2,700ft. of PE main through 5 excavations which enabled them to identify, locate and mark out a total of 9 butt fusions.

  • ULC identified and marked out each butt fusion on the street surface and was able to identify more fusions than the utility accounted for initially.
  • Mark outs on the street provided pinpoint accurate locations of each fusion so contractors could safely and accurately dig above each fusion for destructive testing.
  • Visuals inside the pipe enabled the utility to visually assess each fusion for defects prior to destructive testing.

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