Magnetic particle inspection ensures that parts are free of fatigue stress, structural defects, or stress cracks. The technology, which can be applied to existing, in-use parts, or newly manufactured parts and components that require integrity testing, has been around for more than a century.

Because manufacturers are liable for the integrity of their products, magnetic particle inspection often ensures that such end-products will function as intended.

“In some cases, magnetic particle inspection (or MPI) is a matter of life or death,” says Bob Welsch, vice president, MQC Labs. “This type of testing is instrumental in making sure you are finding flaws in the raw materials before it goes into use. When you think about what goes into amusement rides, aerospace technology, and the locomotive industry, all of them use these materials, and they must be tested for safety. Anyone in the business, like Blue Origin, Space X, the military, Boeing, Lockheed, and Raytheon all rely on MPI to ensure their products are safe. And not just MPI, but all types of non-destructive testing (NDT) are used in almost all industries that we rely on.”

Defining MPI

Magnetic particle inspection is an approach to determining a part material’s integrity by studying magnetic flux leakage. The inspection particles are either in a wet fluorescent suspension or dry visible particles — black light versus visible light, says Welsch.

“It’s a type of nondestructive testing that uses magnetic fields to magnetize a test piece,” says Matt Parker, vice president, Parker Research Corp. “Once the product or material is magnetized, we use iron particles to adhere to areas of flux to test the strength and integrity of it.”

While magnetic particle inspection is the primary nondestructive test method used for confirming the integrity of most components in everything from steel to amusement parks to aerospace — essentially keeping these products safe — most people “have no idea what it is,” Parker adds.

Evolving equipment

While magnetic particle inspection techniques have stood the test of time, the equipment involved has seen updates to keep up with demand, experts say.

“Some companies might look for a smaller cheaper [unit], and they use it and burn through it, and some units last 20 years,” says Parker.

Some magnetic particle inspection equipment is designed for field testing with handheld yokes for refined work, and some are stationary machines for more advanced testing, says Welsch.

Part-specific magnetic particle techniques have changed in the last decade or so to include digital images of the component test setup, says George Hopman, president, NDE Solutions.

“These images are also annotated to document where either the AS5371 shim location or where the Hall effect gaussmeter measurement was taken,” he explains — two tools necessary to confirm that the proper magnetizing strength was used during the inspection. “Robotics has improved the efficiency of repetitive magnetic particle inspections on large numbers of the same part that are characteristic of the automotive industry,” he adds.

Welsch doesn’t predict much more near-term change for the field, however.

“I don’t think the industry is going to be changing a lot in the future,” he says. “It’s a very necessary field and touches almost every industry. MPI and NDT are the imperative forms of inspection, and it’s a proven and reliable process that’s used across the board.”

The pandemic’s impact

The pandemic has exacerbated the nationwide shortage of nondestructive testing personnel including magnetic particle inspection practitioners, Hopman says.

“The NDT industry is generally seeing a huge shortage of certified personnel,” Welsch says. “The average age of our inspectors is somewhere around 50, and it takes a lot of hours to get trained and certified in this industry. As the older generation moves on to retire, we are going to need to pass on this knowledge and need more inspectors to fill the void. It’s really a great career option.”

Because of the longtime shortage, Parker has partnered with training schools to help increase the pool of certified candidates.

“There are now a lot of schools for people to get training on the equipment. But you could have a PhD who comes out and does the testing, or other types of nondestructive testing (NDT), or one that heads up a program, or it could be someone just out of high school who goes straight to a training center to get certified,” he says.

Although Parker’s business ebbs and flows with the economy — more infrastructure development merits the production of raw materials — his company has remained busy throughout the pandemic. Supply and labor shortages have remained an issue.

Welsch has had a similar experience.

“Throughout the pandemic, our services were considered essential, so we worked right through it,” he says. “We didn’t shut down for one day because so many industries depend on magnetic particle inspection and nondestructive testing,” says Welsch. “Of course, we all had to adapt to the protocols issued by CDC, for workplace safety. And of course, there were workforce issues when people were getting sick and having to take time off and we had to adjust our workflows.”