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Technology Report 2022 - Skipper NDT

Drone-Enabled, High-Precision Magnetic Mapping Technology for Buried Pipeline

Synopsis

Following several years of R&D supported by major utility and energy companies along with leading research labs, Skipper NDT has developed a technology to map buried metallic pipelines using a unmanned aerial vehicle (UAV). The innovation is based on the physical principle of magnetism combined with a powerful suite of patented algorithms to determine, within an inch precision, the 3D position of buried structures in addition to their depth of cover. Several proprietary patented algorithms process different parts of the magnetic spectrum on the right-of-way to provide a precise positioning of the pipeline.  It can be especially useful in environments where on-the-ground mobility is a challenge such as rivers, rocky and/or steep slopes.

  • Skipper NDT’s solution consists of a UAV-agnostic hardware system and software that filters noise from magnetic field data, automatically acquire and process magnetic information, and then utilizes an algorithm to deliver precise pipeline positioning information.
  • The pipeline geolocation technology is particularly helpful for troublesome environments, such as rivers and mountainous slopes, and in test cases was able to reveal an abandoned facility and compromised pipeline mechanical structures.
  • Field applications also include out-of-straightness assessment in case of geohazard events.
  • The Skipper NDT technology was validated by major operators under various configurations.  Facility diameters ranged from 3 to 47 inches and included bends and elbows, different soil types, and pipeline products (water, oil, gas).

 

 

 

Introduction

Utility and energy buried pipelines represent an extensive underground network covering much of a country’s territory. Their precise lateral, horizontal positioning along with their depth of cover is a critical element of any operator’s GIS. It enables to deploy more accurate pipeline predictive maintenance models and avoid third party interferences. The latter being identified as one of the main causes of pipeline failures. The 2020 CGA Dirt report indicates that 32% of reported excavation damages were due to poor locating practices with 38% of those being linked with locator’s error.

In addition to potential locating errors, specific areas can be challenging to inspect with a ground-based equipment such as:

  • Rural areas with cultivated fields or the presence of cattle
  • River crossings
  • Areas affected by weather and outside forces (WOF)
  • Difficult terrain, with steep slopes or the presence of obstacles (rocks, trees)

A fully automated unmanned aerial vehicle (UAV) system relying on mathematical models would enable to rapidly gather high precision data over large areas. It would also ensure field operators safety. Currently however, most existing technologies fitted on UAVs provide exclusively ground surface information enabled by sensors such as lidar, spectral, hyperspectral etc.

 

Technology Description

Following several years of R&D supported by major utility and energy companies along with leading research labs, Skipper NDT has developed a technology allowing to map buried metallic pipelines using a UAV. The innovation is based on the physical principle of magnetism combined with a powerful suit of patented algorithms to determine, within an inch precision, the lateral and horizontal positions of buried structures in addition to their depth of cover.

  • Skipper NDT drone
  • Skipper NDT payload
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Hardware:

The entire payload currently weighs 4kg and is composed of the following elements:

  • 5 triaxial fluxgate magnetometers
  • A GNSS RTK
  • Inertial Measurement Unit
  • Sensor to measure the distance to the ground
  • An automatic flight system allowing to allow for repeatable and reproductible measures
  • Proprietary electronic card allowing to integrate the data

The payload is UAV agnostic and can be fitted to any UAV with sufficient weight capacity. The case studies presented were acquired with a DJI M600 UAV.

Software:

A suit of algorithms were developed in order to filter any noise in the field magnetic data and to automatically process the information.

Noise filtering algorithms - Interferences can be of two sources:

  • Environment: the buried pipeline can cross various sources of interferences such as high voltage lines or ground based metallic elements
  • Vector: the UAV itself, with its various motors, creates a level of electromagnetic noise which needs to be compensated

Pipeline mapping algorithms:

  • Several proprietary patented algorithms will then process the high and low frequency magnetic signals in order to provide a precise positioning of the pipeline
 

Test Case: onshore pipeline mapping/tracking abandoned facilities

An operator was about to create a new connection to an existing pipeline. The objective was to precisely geolocate the pipeline and verify that no abandoned pipe was present at close proximity. Skipper NDT deployed its UAV based technology on the DN200 (8 inch) pipeline section of interest. The covered area was 387 feet long and 32 feet in width. The total data acquisition time was under 6 minutes.

The data collected allowed to create a magnetic map. The precise pipeline location was derived through Skipper NDT’s proprietary algorithms.

Magnetic map of the inspected area with its corresponding colorbar (in nanotesla) on the left

The results provided by Skipper NDT’s technology were compared to data from the operator’s GIS (gathered in an open ditch at the time of construction). The average difference was 5 inches in the lateral position and 1.6 inches in the vertical position. The histograms below illustrate the dispersion of the entire data set compared to the reference points.

Distance discrepancy between Skipper NDT’s predicted pipeline position and land surveyor reference  

In addition, Skipper NDT algorithms picked up high and low frequency magnetic anomalies on a specific section of the pipeline. It was identified as being a possible pipeline crossing. Subsequent field investigations confirmed that an abandoned pipeline, unknow to the operator, was lying underneath the pipeline under inspection.

This information proved valuable in order to avoid any potential incidents during excavation work to be carried out.

Low frequency magnetic map [left]; High frequency magnetic map [right]

 

Test Case: river crossing

Pipelines routes can cut across rivers making their geolocalisation particularly challenging in such environments. The pipeline will usually be buried under the river bed in order to protect it from third party interferences and movements due to strong water currents.

Traditionally, to determine  the pipeline position and  depth of cover a team of divers conducts manual measurements on the river bed. This operation can prove to be hazardous, with significant risks for the field operators given the potential harsh conditions and above water activity. In addition, the data sets gathered usually have a low density (1 point every 2 meters) and are highly dependent on the operator’s ability to perform such measurements (low repeatability / reproductability).

Traditional method: divers deployed

Skipper NDT technology: no divers required

Using a magnetic UAV based technology, data acquisition can be performed without having to deploy divers into the river. There are several advantages to such modus operandi:

  • Safety of field personnel : no diver needs to be deployed, the UAV collects the necessary data from the water surface
  • Speed: data will be gathered rapidly, in a matter of minutes depending on the length of the river crossing
  • Data reliability: all the information will be processed by algorithms avoiding any potential human error. Furthermore, a high density of points could be provided if necessary (1 point every 0.3 inch)
 

Test Case: Areas affected by weather and outside forces (WOF)

Certain geographical areas are particularly prone to ground movements or extreme weather conditions. These external surface factors can significantly impact a pipeline's integrity by deforming its structure. The most common consequence would either be a rupture or an abnormal bend compromising the mechanical integrity of the structure.

In such cases, a measure of mechanical deformation is performed either with a ground-based mobile equipment or with an invasive tool (in-line inspection). The latter being particularly demanding to deploy from logistical and cost standpoints.

A non-invasive tool allowing rapid bends measurements with a high level of accuracy would be useful for such situation. In addition, the UAV would ensure operators’ safety on unstable ground.

The Skipper NDT technology was compared with a data set from an in-line inspection tool over a specific pipeline section. The results showed a difference of 1° in planimetry (measurement of plane areas). This is sufficient to determine if a pipeline mechanical structure is compromised.

 

Conclusion

A precise pipeline geolocation is essential to ensure the safety of people and the environment in close proximity. This work needs to be performed under all field conditions while ensuring the safety of site operators. Skipper NDT has developed a patented technology with a comprehensive mapping solution for buried steel pipelines. It gathers data remotely and process it automatically. The solution was validated by major operators under various configurations, diameter range 3-47 inch, bends and elbows, different soil types and products (water, oil, gas).

The Skipper NDT technology is a solution for a safer, faster, cost-efficient and more reliable pipeline geolocation. 

 

 

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