Plasma Technology

River run

By Michelle Avila

Above: The Hypertherm HyPerformance HPR400XD system cuts any shape in heavy gauge material.

Plasma cutting system makes quick, accurate work of assembling modular barge components

April 2017 - Building bridges, constructing wharfs and piers in a shallow river, excavating and drilling underwater, and traversing sensitive wetlands with heavy equipment aren’t exactly easy jobs in the best of circumstances. Add in obstacles like contaminated soil on a river bottom, high-voltage power lines directly over a work site, a narrow river channel, or a deadline that encompasses mere hours instead of days or weeks, and now the toughest jobs are decidedly tougher. 

It’s precisely those types of jobs that the team at Robishaw Engineering Inc. in Houston lives for. The team designs and manufactures modular steel pontoons, or barges, called Flexifloats. Flexifloats move  on water and then are anchored on site, allowing construction crews to get the job done without disturbing the surrounding environment.

The Flexifloats are unique in that each pontoon includes a locking system. This system allows engineers at this 60-year-old company to design vessels small enough to transport using a standard tractor-trailer, yet when connected, expand to hold heavy equipment like a 400-ton construction crane. 

Clients can quickly connect the Flexifloats in shapes that configure to the shape of the job site using just three items—a pry bar, rope and sledgehammer. 

FFJ 0417 plasma image1

Robishaw Engineering Inc. makes Flexifloats. The platforms here float cranes for American Bridge, a Missouri-based heavy construction contractor.

Though built in Houston, the floating pontoons have found their way to just about every continent on the globe. The Flexifloats are made from carbon steel. Until recently that steel was cut using an oxyfuel cutting system. Using a table equipped with four oxy torches, a machine operator would cut 5-ft. by 20-ft. plates down to size two at a time. The operator would then cut out holes for tube turns used to add a variety of attachments to the finished platforms. Provided all the cutting turned out as planned, Robishaw would have 476 completed plates by the end of 11 work days. 

Back in the 1980s, when the oxyfuel cutting setups were new technology, it served Robishaw well. But as its line aged and the cut quality of plasma systems improved, oxyfuel started looking less and less attractive.

“We really kept the table up and running forever,” said Hayden Smith, a manufacturing manager for Robishaw. “We knew that, at some point, we wouldn’t be able to fix it anymore and that plasma was the way we were going to go.”

Though the company knew it needed a new system, Robishaw continued to use oxyfuel because it dreaded the cost and downtime required to make the switch to plasma. “It was hard for us to think of shutting down completely for two weeks to install a new machine,” Smith says. 


Eventually, increasing maintenance requirements and diminishing cut quality reached an unsustainable level. Smith and his team just couldn’t get the system to cut straight anymore. Now, instead of cutting the round holes Robishaw needed, the oxy torches were cutting ovals.

Frustrated, Robishaw contacted Rick Keeton at Houston-based Plasma Systems Inc., a table and system manufacturer. Keeton was happy to take the call, as he’d been trying to convince Robishaw to move to plasma for years. “I asked the owner to bring four full plates to our facility and we would cut his parts as a demo.”

Keeton placed the plates on a Plasma Systems table equipped with a Hypertherm HyPerformance plasma system. He then proceeded to cut the plates at a speed of 200 in. per minute with a set of 200 amp consumables.

That’s all it took. Robishaw Engineering ordered a new table on the spot. The company selected a 15-ft. by 45-ft. Plasma Systems CuttingEdge II 2014-XH water table equipped with a Hypertherm HyPerformance HPR400XD system. 

FFJ 0417 plasma image2

Flexifloat sections can be transported by semi-trailer, then are connected on site to reach tight spots.

Now, work that used to take 11 days to complete is done in half that time.“They’re only using it a few days a week. They used to run the oxy table hard—one, sometimes two, shifts a day. A part that took 45 minutes to cut with oxyfuel is cut in less than five minutes with the plasma,” Keeton says. 

In five or six days, Robishaw will cut 1⁄4-in.-thick, 5-ft. by 20-ft. sheets, up to 476 of them. Cutting speed is one major reason for the increased productivity since Robishaw went from cutting 18 in. to 20 in. per minute on a good day to 200 in. per minute with plasma. But Keeton says that’s only part of the story. 

Pierce time

“Most people who compare plasma with oxyfuel just look at the cutting speed, but it’s not just the cutting speed. You need to look at the pierce time. If you’re cutting a 1-in.-thick plate with six pierces, the oxy is going to take about 30 seconds per pierce, whereas the plasma will take three-tenths of a second. That’s the secret. I can cut an entire part with plasma before an oxy operator’s even pierced the first hole.”

In addition to the significant time savings brought on by a speedier cutting process, Robishaw is saving on labor. Smith no longer needs two people at the cutting table. He used to have one person running the table and a second loading and unloading parts. That second person is now working downstream at a welding station helping to fabricate the increased number of plates coming off the table. 

Cut quality is also improved. “We’re getting a more accurate cut. The straighter edge on the cut makes the fit-up process much easier and faster,” Smith says. 

Holes are also more consistent thanks to Robishaw’s use of Hypertherm’s True Hole technology. Smith estimates that technology alone is saving Robishaw a few days of production time every couple of weeks since his crew doesn’t have to go back and perform clean-up work on each pierced plate.

As Keeton sums up, “Robishaw’s accuracy is 100 times better, and holes are 100 times better.” FFJ



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