June 2020, Vol. 247, No. 6


Pigging the Unpiggable: ‘Everything Is Possible’ Through Innovation

By Danielle C. Roberts, Energy Writer  

A pig used to clean large-diameter pipelines.

The notion of sending a robotic “pig” into a pipeline is no longer news. 

What is news is how the industry is revamping these pigs to make them smarter, more lightweight and more accurate in how they sniff out corrosion and other metal loss, cracks and defects in the vast network of onshore and offshore pipelines that drive our economic engines and our way of life.  

Today, estimates vary widely, but experts cite a range of between 30% to 60% of the world’s pipelines that remain unpiggable. Innovation is helping to close the gap. 

A Simple Solution

In 2016, TransCanada – now known as TC Energy – was two years into an aggressive plan to complete assessments of the unpigged portions of its pipeline infrastructure. In the province of Alberta – long recognized as a primary hub for Canada’s oil industry – much of its vintage system was built without permanent pigging facilities, and other large portions were determined unpiggable for a variety of reasons. 

In looking for solutions, its inspection team needed to weigh overall costs of traditional inspection, operating conditions and the ability to gather high-quality data such as pipe geometry and deformation.

While the idea is not entirely new, TC Energy determined that it would benefit from the development of a customized, bidirectional caliper tool that could dovetail with its current magnetic flux leakage (MFL) and internal mapping unit (IMU) inspections. 

TC Energy selected Onstream Pipeline Inspection (Onstream) as its partner to develop the tool under an aggressive timeline. Onstream came on board in July 2016, with a goal of using the tool for TC Energy’s 2017 inspection program and under the following specifications: 

  • Tools from 3 to 12 inches (76.2 to 304.8 mm) in diameter
  • Standard axial sampling of less than or equal to 0.12 inch (3.17 mm)
  • Minimal number of caliper arms at two times the nominal pipe diameter
  • Ability to detect a wall thickness change of 0.04 inch (1 mm)
  • Dent/ovality detection threshold of 1%
  • Dent/ovality sizing accuracy of +/-1% at 80% confidence

The company also wanted to be able to inspect shorter pipelines using a wireline inspection. All this would give TC Energy, said Dylan Davis, senior engineer, data strategy, “a greater flexibility in our inspection options when looking at the cost analysis of maintaining our gas system, while not sacrificing the high standard of data acquisition we expect from using inline inspection tools.”  

After the prototype passed testing, a field trial took place in snowy northern Alberta, where the tethered unit – including the caliper tool, an MFL tool and an inertial mapping unit – were blown out a distance of 2.6 miles (4,138 meters) and pulled back. The tool identified a number of dents, which were later verified in the field, and the remaining tool diameters were successfully developed over the next eight months. 

The solution would go on to allow the energy company to effectively inspect more than 300 pipelines in its Canadian gas system alone, leading to $50 million in cost savings. “The main lesson that can be taken away here is [that] if we step back from individual problems and look at the holistic benefit of pushing for new ideas, we often find simple solutions can achieve large benefits across a company and industry,” said Davis.  

If You Build It 

In the U.K., National Grid was facing similar challenges, with much of its gas transmission system laid in the 1960s and 1970s and needing to be regularly inspected.

Gas is a unique animal, traveling at high pressure and often in multidiameter pipes that don’t follow a straight line. According to Josh Blake, GRAID project engineer at National Grid, roughly 233 miles (375 km) of the company’s pipe is too complicated to be inspected by traditional methods, which would include costly excavation and venting of gas. 

But, “any pipeline is only unpiggable at this moment,” said Blake. “If you really want to inspect it, you can. It just requires new innovative ways of working. Everything is possible.”   

Innovation is a core part of National Grid’s business, he said. So, the company took, perhaps, an unusual step, with funding assistance from the Network Innovation Competition, which is governed by Ofgem, the government regulator for gas and electricity markets in Great Britain. It built its own robot.

Known as GRAID, or Gas Robotic Agile Inspection Device, the project took four and a half years, including 14 months of testing in a rig that National Grid built to mimic on-site conditions, as well as two live trials. Its initial design mimicked a dolphin but was tweaked to resemble a truck pulling a trailer.  

GRAID was built to travel in a 30-inch (762-mm) or greater working pipe to withstand forces of 1,450 psi (100 bar) – equal to being 3,280 feet (1,000 meters) underwater, which is about three times as deep as a submarine can travel. Its magnetic tracks were also designed to allow it to climb 45-degree angles.

During live trials at sites in north Yorkshire and at National Grid’s Bacton Gas Terminal, the tethered robot demonstrated its ability to travel under 1,015 psi (70 bar) of pressure and 16 feet/second (5 meters/second) of flow, gathering data through its monitoring arm, which uses electromagnetic acoustic technology to gather data on wall thickness. The robot also enables visual inspection through 10 live feeds. 

GRAID’s trials did uncover challenges, including the important process of withdrawing and cleaning the magnetic monitoring arm, which tended to attract debris as it gathered data. Another was time. Using the original sensor, the arm was only able to measure wall thickness at a localized point; algorithms would then be used to extrapolate the remaining data. But, to complete a full scan of 3.3 feet (1 meter) in a 36-inch (914-mm) pipe, the inspection would take 45 continuous hours – “which is not viable,” said Blake.

With the initial project complete, National Grid is already working on updating that sensor. Pending regulatory funding, it’s also looking at a 2.0 version, which could include refining the robot so it can inspect pipe diameters down to 12 inches and meet the needs of other conditions, which could include liquid pipelines. “That will require further testing and proving work in those conditions,” said Blake. “But there are a lot of eyes and ears on this.”   

The Next Wave 

In 2012, Halfwave was born out of a small technology group that had spun off of DNV-GL and was supported by Chevron and the private-equity firm Energy Ventures. That group had developed a “niche technology,” said CEO Paul Cooper, that would become the company’s patented ultrawide-band acoustic inspection technology, or its ART ScanTM tool. 

ART became commercially available in 2014, and its basic design and engineering has stood the test of time, said Cooper, with 20 tools based on that initial design now performing inspections globally both in onshore and offshore natural gas and liquid markets in the U.S., Canada, West Africa, Australia, the U.K. and Papua New Guinea. 

Acoustic resonance is a type of ultrasonic tool, but it has a different way of measuring and interpreting data than a traditional ultrasonic system, said Kimberly Ng, Halfwave commercial manager. 

The tool does not require liquid as a medium, inspects fully pressurized gas lines, navigates bends and can run in pipes measuring 12 to 48 inches (304.8 to 1,219 mm) and as long as 746 miles (1,200 km). It inspects wall thickness and corrosion both internally and externally, gauges ovality and can penetrate wax and rough surfaces – in a single run. High-resolution data identifies sizing defects at +/-0.008 inch (+/-0.2 mm). 

During a recent case study, Halfwave worked in the waters of the Norwegian North Sea to diagnose the specific cause of certain defects on a 50-foot (15-meter) bundle of four separate pipelines. Diagnosis was high priority since repair or replacement would be extremely expensive without understanding what or why was causing the corrosion. 

A typical inspection would have required four separate cleaning pigs to thoroughly remove wax from the pipeline, taking about 20 days. Halfwave’s ART ScanTM tool successfully completed the inspection to identify failure modes within just six.

Today, Halfwave is continuing to innovate, particularly as the company has recently been acquired by Eddyfi/NDT. Cooper sees huge potential in that range of pipelines that have long been considered unpiggable. 

In addition, during the last four years, the company has been working with TC Energy on a crack detection tool, and it’s now involved in National Grid’s GRAID project, applying its ART sensor to the GRAID robot to shorten the time for a full pipe scan of 3.3 feet to just minutes. 

“The market always wants increased accuracy and improved technical safety, so all the serious operators are looking to innovate their best available technology,” said Cooper. “As the technology moves forward, I think we will become more cost-effective and [have] more reliable reporting based on a complete inspection and integrity approach, reducing cost and improving technical safety. That’s the next step within pipeline integrity.”

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