by Tim Wilson
When Non-destructive Testing, or NDT, came of age over fifty years ago, it required technicians for most tasks. Over the decades there have been major technological advances, most notably the adoption of digital technology and advanced computing. However, the human element remains an essential component.
“Both ultrasonic and eddy current inspection relied on technicians manually looking at signals on an instrument,” says Walter Weber, CEO of UTEX Scientific Instruments in Toronto. “The resulting manual inspection procedures never foresaw automation, and that is why they remain labour intensive today.”
Explicitly, this is a shift from looking at signals to taking measurements and automatically making decisions. But getting the industry to accept that a machine can do what a human has always done can be a challenge.
“Many people want to remain in control,” says Weber. “However, the reality is that NDT has not kept up with the rest of factory automation, which has the motivation to automate. By contrast, inefficient manual work in NDT often brings overtime, which acts as a motivation to resist change.”
But inspection automation is by no means a slam dunk. Though robots routinely weld, grind, trim, paint, pack and move, there are issues with regard to NDT that argue for human involvement.
“We are trying, but automation is very difficult for basic methods,” says David Craig, manager NDT at Pratt and Whitney Canada in Longueuil, QC. “Manual manipulation can deliver 100 per cent inspection coverage of external surfaces, and to use a robot is difficult.”
Nonetheless, many NDT groups are under continual pressure to remove the human factor. Important advances in computer science, combined with a desire to do things faster, more precisely, and at reduced cost, make for a compelling argument.
“Machines work faster and don’t get tired,” says Weber. “The human ego can also get in the way.”
An automated NDT system can be configured to self-report its own errors, whereas over-tired or distracted NDT techs might not want to draw attention to their failings. But this is not a one-size-fits-all argument.
“I am not advocating the complete removal of humans,” says Weber. “Some jobs are better done by people, but there are also more examples of human failure than automation failure. There have been cases of entire batches of parts being signed off without proper inspection, simply because flaws are extremely rare events in well run manufacturing processes.”
Access is also an issue. Though there are some areas where humans are nimble and best suited for testing, there are also numerous examples where a machine–and only a machine–can do a test.
“Humans have limitations due to the length of their arms,” says Dr. John Baron of the CANDU Owners Group. “There was a recent situation in a US nuclear plant where the inspection was poorly conceived –if the folks had access to automated equipment they would have been way ahead.”
In the example of the US nuclear plant, there were five significant flaws missed by inspectors, with one of the issues being restricted access. But the value of human involvement is more complex than whether or not an arm can access a space: it has a lot to do with the unique characteristics of the human mind.
“Automated systems are not innovative like human beings,” says Baron. “We have inquiring minds. If a well-trained inspector sees something that is not familiar he’ll chase things down. You won’t necessarily get that with software.”
Interestingly, advocates of increased automation make a similar argument when they claim that productivity increases are only part of the reason for embracing technology. Their bigger concern is accuracy and consistency.
“Every NDT department knows that person A will always get better results that person B on the night shift,” says Weber. “What does that then suggest in terms of the quality of what you are doing?”
It may suggest that humans are the problem, or it may suggest that person B is not doing such a terrible job, and that person A is doing a job above and beyond the requirements.
“Visual inspection is still as important as any technology,” says Mr. Roy O. Christensen, Factory Acceptance Testing (FAT) coordinator at AMEC Oil Sands in Calgary. “Many inspectors come from a trades’ background. They know how tools work and they can see the process for welds.”
The problem then becomes that NDT remains a labour cost centre, even as some of the traditional processes themselves are not that pricey.
“The simplest methods–liquid penetration, magnetic particle inspection–for these the materials and the apparatus can be relatively inexpensive,” says Edward Ginzel of the Materials Research Institute in Waterloo, ON. “But they require qualified technicians, and that adds to the cost.”
Dealing with the added cost of NDT technicians can be a challenge, with smaller shops having to rely on third parties to provide the service. This is a must for those companies active in the nuclear and aerospace industries, where NDT requirements are at their highest due to the incredible risk associated with structural failure
“In aerospace allowable flaw sizes are far smaller,” says Eric Sjerve of IRIS NDT Corp in Edmonton, which provides NDT services. “An aircraft skin might be 1/16th of an inch aluminum, or 1.5 mm, and you can’t have a crack in that. But a half inch carbon steel pipe on muskeg is over-designed, and far less sensitive to critical defects. Same with bridges; you can have fairly big defects and it’s not a huge problem.”
Aerospace in particular tends to design a lot closer to engineering tolerance, because it costs money to fly. As a result, NDT specialists in aerospace are embracing cutting-edge technologies in thermography and laser-based inspections. And for a big company that means keeping track of a lot of shops.
“My group is responsible for approving hundreds of suppliers worldwide,” says Craig from Pratt and Whitney Canada. “In Canada we have authority over NDT lines in Montreal, Mississauga, Halifax, and Lethbridge.”
Whether in house or offered as part of a service provided by a company like IRIS NDT Corp, the squeeze is on to get more qualified NDT technicians, even though training facilities in Ontario and Alberta are working hard to deliver more qualified personnel.
“We are having difficulty recruiting all over–out of Houston and even England,” says Sjerve at IRIS NDT. “Customers are willing to pay top dollar to get someone out.”
Clearly, the future of NDT is going to be a mixed bag of computing technologies for data capture and analysis, along with a cohort of highly trained individuals. These individuals will continue to prove their worth at least partly in regard to their ability to leverage the latest technology–assuming you can find them.