Engineering these days has a tendency to cross disciplines more than ever. Decades ago, companies started using medical technologies (radiography to be exact) to inspect solid structures and mechanical parts. Since bringing an entire pipeline system into a lab for inspection is impossible, engineers have combined the know-how of GE Healthcare, GE Oil & Gas, BP, and the applied marine technology company, Oceaneering International to safely inspect miles of underwater pipeline that sits under more than 4,400 pounds of pressure.
Much like traditional radiology that can be used to identify cancer, these engineers have created a robust X-ray system that can detect leaks and weaknesses in a pipeline before a detrimental leak or breakage occurs.
“This project started as an idea to solve a customer problem. We know how important radiographic inspection is to help the oil and gas industry evaluate critical welds and piping corrosion,” explains Rajashekar Venkatachalam, GE X-ray detector lead engineer. “The major oil and gas companies have comprehensive asset integrity programs in place to regularly inspect critical components and repair or replace them proactively before they fail.”
Making the Delicate Robust
In order to create an X-ray system that can operate underwater, the team had to design a housing for an incredibly expensive and delicate piece of glass. As the team deconstructed the detector and reassembled it to work properly at subsea levels, breakthroughs were bound to occur. “The first [breakthrough] was our proof of concept research, which we literally did in a plastic storage bin full of liquid in our office," explains Venkatachalam. “We were taking bets among ourselves as to whether it would work. Once we passed this first hurdle, we knew we had a viable idea.”
“The key challenge we had to solve was how to take an extremely delicate technical instrument and design a housing and delivery mechanism that could function at extremely low temperatures and extremely high pressures,” Venkatachalam says. “Optimizing image quality under these difficult conditions was another major challenge.”
For the equipment to function at extreme depths, the team needed a way to equalize the pressure in the housing with the extremely high subsea pressures, which required a redesign of the detector. To help the pressure equalization process, a new housing was also developed, which the team filled with liquid. “Identifying a fluid with the right physical and chemical properties that would not distort the radiographic image was the major hurdle to overcome,” says Venkatachalam.
“Our radiography devices are enabled by a delicate piece of glass the thickness of a quarter, and we’re operating at temperatures close to zero degrees Celsius and at pressures approaching 4,500 PSI,” explains Shana Telesz, GE radiography product manager. “Operations are performed remotely from more than a mile away while surrounded by moving water.”
“We broke six X-ray detectors during the product development process. Every time we failed, we would say, ‘Now we know how to do it right,’ but it took multiple attempts to finalize a functioning design," Venkatachalam adds.
A Drop in the Ocean
Aside from the operation of the radiological equipment itself, the team also had to confront the challenge of deploying the sensitive device. “Working with Oceaneering we developed the equipment and procedures to take the equipment into the field for subsea operation with remote access,” Telesz explains.
The equipment is deployed with a diver, and operated remotely from the surface. Digital X-ray technology allows instant transmission of images to the surface so operators can make immediate decisions about their equipment. “That’s what inspection technology is ultimately about – helping industry make better decisions about asset health,” Telesz adds.
According to the team, a 12-inch pipe can be inspected with a total X-ray on-time of close to two minutes. Currently, the Subsea X-ray is commercially available and performs reliably at 2,000 feet. “Further product development is underway to enable subsea X-ray at greater depth and under more extreme and unconventional applications,” Venkatachalam says.
“This technology and this environment require a completely different way of thinking. While the underlying technology is the same, a number of times we had to go back and completely rethink our approach to the technology, the housing, the application,” Telesz explains. “This is where partnering with Oceaneering really paid off – with their understanding of the subsea environment and how the product would be used.”
The project was a collaboration between GE Healthcare, which has a deep understanding of the radiography detector technology; GE Inspection Technologies, which has expertise in design and application for industry; and Oceaneering, an oil and gas products and service company with expertise in subsea environments and extensive experience in asset integrity.
The team knew that if they could enable industrial radiography in a subsea environment, customers could improve equipment reliability and reduce downtime. “In some cases parts that were previously taken out of service and brought to the surface for inspection can now be inspected in place, which is a major improvement,” Telesz says. “We can help operators pinpoint an area of concern on their equipment.
In the future the team hopes to be able to help customers measure and quantify defects and track conditions over time. “We also hope to enable remote collaboration so operators can get an immediate second opinion from experts onshore,” Venkatachalam says.
According to the team, this equipment pays for itself with the first day of production downtime avoided by a subsea installation, or the first time an operator reduces the time of a maintenance outage by a day.
“We are planning future developments that will help operators better analyze the data gathered to make better predictive decisions about their assets," Venkatachalam says. Ideally, GE will eventually have data for every pipeline in the water, making the system safer and more economic.