Case studies

Robotic Crawlers Inspect and Locate SCC at Natural Gas Facilities

Problem
  • Gas pipeline operators had difficult to access pipes that required inspection
  • Most pipelines within the gas system were installed in the 1970’s and 1980’s and required inspection
  • The anticipated pipe flaws were difficult to inspect so high resolution sensor technology was required
Solution
  • In-line robotic crawler with bidirectional capabilities
  • Hand loaded tool easily deployed and retrieved
  • Advanced NDE EMAT technology for assessing corrosion and SCC
Results
  • Robotic ILI crawler successfully navigated unpiggable pipelines
  • NDE EMAT sensors provided high accuracy data on pipe wall condition and corrosion defects
  • Pipeline operators monitored findings within allowable operating and repaired critical anomalies before putting pipelines back into service

Diakont Advanced Technologies deploys robotic crawlers to inspect the condition of unpiggable gas pipelines at compressor stations and other gas industry facilities. These robotic crawlers use rugged track systems to inspect lines that are inaccessible to traditional inspection methods, including those with difficult geometries, buried sections, and/or only a single access point.

 

Self-Propelled Solution for Unpiggable Lines

For inspections of pipeline that include difficult geometries such as includes T-bends, crossings, and diameter reducers, buried pipeline, and lines accessible via just a single access point, the use of traditional “smart pigs” is often impossible. For cases such as these, Diakont has developed and frequently deploys robust robotic crawlers equipped with NDE sensor technology to perform in-line inspections.

Figure 1. Diakont ILI Crawler Hand Loaded into Pipe Opening

 

Each crawler employs three tank-like tracks—two at the bottom of the tool for primary propulsion, and a third upper track that extends out as necessary to stabilize the tool in difficult geometries such as bends and inclined or vertical pipes. As the crawler is self-propelled and bi-directional, its ability to be deployed and retrieved through the same access point for each line section to be inspected is often a crucial factor in its selection process.

 

High-Resolution Sensor for Precision Imaging

In addition to the challenge of accessing difficult-to-reach areas of pipeline, a secondary problem commonly posed in in-line inspection is the difficulty of actually locating and measuring stress corrosion cracking (SCC), a common cause of pipeline failure when left undetected and unrepaired. High-resolution sensor technology is required to thoroughly and accurately assess pipe wall integrity.

 

Diakont’s robotic crawlers are equipped with a suite of high-resolution NDE sensors, allowing for the selection of the right tool for the right part of each inspection job. Chief among the technologies utilized by the crawlers is the EMAT Ultrasonic Testing (UT) method. The main operating principle of EMAT testing is electromagnetic-acoustic transmission and receipt of ultrasonic shear waves (SH), with linear polarization. Diakont uses EMAT UT testing in conjunction with their robotic inspection crawlers to detect and measure the following:

  • Metal loss anomalies and remaining wall thickness
  • Internal pipe wall anomalies

Configured with an angle beam, the EMAT transducer sends a shear wave into the test material around the circumference of the pipe wall.  The shear wave signal travels through the test material and reflects back to the sensor when it encounters any cracking in the pipe wall.  See Figure 2 for a diagram of this operating principle.  

Figure 2. Diagram Angle Beam EMAT Signal Detecting Crack in Pipe Wall

 

Deployed via the robotic crawler, all EMAT sensor data feeds back to the inspection technicians in real time via an umbilical cable, and pipeline operators are given same-day assessment results. 

 

Inspection Results

Over the last decade of utilizing high-resolution EMAT technology to assess pipeline integrity, Diakont has located various pipe wall anomalies which were repaired by the operators before they caused pipeline failures.  Repairing these gas pipeline anomalies instead of blindly replacing the piping systems saved customers hundreds of millions of dollars.

 

Total
(2004-2015)

Number of inspected facilities

315

Scope of ILI

In-line Visual Examination, meters

300,408

Visual Measuring Inspection, number of girth welds

36,991

EMAT combined beam, meters

267,132

   

Repaired defects per ILI results

VMI, number of girth welds

2590

EMAT-DB (corrosion/lamination etc), defects

2313

EMAT-AB (SCC), defects

558

Table 1. Natural gas facility pipelines inspection by Diakont from 2004- 2015

 

The following images are actual corrosion and SCC detected in natural gas facility pipelines using EMAT NDE technology.

Figure 3: SCC 1.6 mm Deep    -   Figure 4: SCC 1.5 mm Deep   -    Figure 5: SCC 1.1 mm Deep

 

Learn more about Diakont's robotic in-line pipe inspection services