Innovation is often achieved when one is confronted with a challenging problem. Imagine being approached with a job that called for a saw to cut through radioactive materials. And on top of that, imagine if the saw needed to be dismantled and passed through a small airlock and then reassembled in the workspace. Even the most confident machine builder gets the jitters when it’s time to deliver a new piece of equipment, but imagine the nerves that come with delivering a heavily customized saw to produce results in such an extreme situation.
That’s where engineers at HE&M Saw found themselves a few years ago when a company working on a decommissioned nuclear weapons plant reached out to them, seeking out a saw that could be broken down, transported and then reassembled to be used by operators wearing thick protective suits and gloves in a radiation-contaminated worksite.
The Nuclear Option
The project involves what was once the Rocky Flats Nuclear Weapons Plant, which was established by the Atomic Energy Commission (the U.S. Department of Energy today)
in 1951 and served as the facility where plutonium pits (the core of an implosion nuclear weapon) were made. Production was halted in 1989 following a series of environmental concerns and the plant completely shut down in 1991.
By 2006, the plant’s 800 buildings had been demolished and the contaminated material moved to Idaho where it was buried. Unfortunately, the barrels holding the radioactive materials were corroding, which is what led to HE&M getting the call in 2015 from Idaho National Labs, the organization working with the U.S. Department of Energy to clean up the nuclear waste.
A piece of equipment Idaho National needed was a saw that could cut through 55-gallon drums and the toxic materials within, all of which had been compressed to solid cubes for material handling purposes.
“We took a standard machine and heavily customized it so they could get it into their work area,” says Max Harris, chief engineer at HE&M. “They had to be able to break up the machine and package the pieces into small boxes. Their main requirement was that the machine could be broken up to fit through the airlock so no contamination left the cutting area.
“The saw had to be reassembled by workers in radiation-proof suits, so they had to more or less reassemble it in a space suit with thick gloves,” he continued. “They were only allowed to work in the area continuously for four hours. Anything longer would be dangerous.”
No HE&M employees were allowed at the worksite given the tight security, so the Idaho National crew went to the HE&M headquarters in Oklahoma to learn how to assemble and maintain the new saw.
Breaking It Down
To meet requirements, HE&M ended up splitting the saw head into two pieces and removing the electrical box off of the back of the machine so that the machine base could be moved in its own box. The saw’s electrical cabinets were transported through the airlock separately.
Harris says HE&M chose the VT140 bandsaw for the unique job because it can handle a variety of applications. The saw can cut left and right angles at 45 and 60 degrees, which wasn’t a major factor in choosing the saw, but gave the operators flexibility should they come upon material that they “didn’t anticipate being in the 55-gallon drums.”
Given that workers would be decked out in safety suits to protect them from radiation, including thick gloves, HE&M decided to use quick-release hydraulics, which are easier to manipulate while wearing gloves. HE&M also had to consider which saw blades would work best with this application, as well as configure a coolant system that wouldn’t cause radiation containment issues.
“We worked with a blade manufacturer to get the correct blade for the application,” Harris says.
Another challenge was the coolant system. “We ended up going with spray mist rather than flood coolant due to the exposure to radiation,” he says. “We wanted a minimum quantity system, so as little fluid as possible was exposed. Trying to contain radiated fluid is much more challenging because small leaks creates its own radiation contaminants. We ended up using a couple of spray heads to try to coat the blade heavily enough to allow for proper cutting.”
Another interesting project HE&M was brought into was through a contractor working with the U.S.
Air Force to determine how bombs degrade over time. Some of the details of the project involved sensitive information that Harris was unable to reveal, and even HE&M was kept out of the loop on some aspects. For example, choosing the right blade involves knowing what kind of material is being cut, but that information was kept close to the vest by the Air Force.
“They told us a little bit,” Harris says of the outer layer of material on the 400-lb. bombs, “enough that we could recommend blades for them as well as feed and speed rates.”
One of the reasons HE&M got the job is that other saw manufacturers weren’t willing to customize to the extent that Harris’ company does.
“Competitors offered to supply a standard piece of equipment and let the customer modify the machine to meet their application,” he says. “When the armament group reached out to us, we talked with them and said, ‘we can customize a piece of equipment to meet your requirements in terms of being able to meet all of the ATEX ratings (ATEX is short for atmospheric explosives and the ratings involve ensuring the safety of products being used in explosives) and minimize all friction points to generate a piece of equipment that is correct for their application.”
The right saw for the job was the highly customizable H160, which has a 25-in.by-25-in. capacity. Given that the saw would be used to cut through explosives, powdered bits
of the explosive would build up over time, which required some extensive customization.
“We had to minimize any point that had the potential to create a spark,” Harris says. “We had to limit metal on metal contact.”
Rather than utilize a full flood coolant or spray mist, which would create a gummy material, HE&M used an oil drip. This ensured all the material could be removed from the machine.
Another aspect of the project was to decommission old, out-of-date ordnance. Harris notes bombs aren’t designed to come apart unless they’re exploding. Because they don’t have any seams, there is no way to pull them apart, which is why the saw was used.
“As bombs get to a certain age, they can become unstable,” Harris says of what the project coordinators told him. “They needed a way to safely decommission them.”
The biggest challenge, Harris says, was keeping the temperature of the blade low during the cutting process. They were able to achieve this by introducing thermal cameras to monitor the heat and remotely control the blade speed rates from 400 ft. away, lowering the blade speed and limiting the fall rate of the saw head as needed.
An additional important step was eliminating spaces around the screws or bolts where explosive material could build up.
“Fine explosive powder could build up inside the threads of a bolt,” Harris explains. “If you broke the bolt loose, you transformed the bolt head into a projectile. Those threads would operate as rifling and actually shoot the bolt out. Therefore, every screw had to have a hole on the backside so it couldn’t operate as a bullet.”
Customizing saws is nothing new for HE&M, as “we pretty much have made our name over the years doing custom applications,” Harris says. “Even some of the first saws the company built had some degree of customization to them.
“A lot of the development we do, R&D-wise, for new projects and products stem from custom applications,” he concludes. “Some of the applications we’ve done include cutting exotic materials and designing giant material handling systems where we’re trying to handle material as fast as possible. We cover a wide range of products and applications.”