For nearly four decades, an aging 230-meter-long carbon steel pipe buried in soil with high chloride levels was in need of replacement at Fermilab, America’s premier national laboratory for particle physics research.
Located 40 miles west of Chicago, Illinois, Fermilab operates large particle accelerators and is an R&D center for superconducting radio-frequency cavities. “The carbon steel pipe had been there 40 years and was experiencing vacuum problems,” says Ryan Schultz, Fermilab’s Accelerator Division Project Engineer. Video inspection of the carbon steel pipe suggested ground water leaks, which worsened during spring rains.
“I knew higher levels of chloride could be corrosive to 316 stainless. We had problems before with microbiologically induced corrosion and stress corrosion cracking. So I did some research to find an alternate material solution,” says Schultz.
His team had determined that inserting a slightly smaller, stainless steel pipe inside the berm pipe would be the best way to restore vacuum in the beamline. Excavating was ruled out because the pipe was buried amid electrical feeders, adjacent enclosures, and water and gas lines.
2205 bests 316
My research led me to Outokumpu,” Schultz recalls. After working with TMR Stainless (a consultant to Outokumpu in the Americas), Schultz specified 2205 stainless for the project. The steel was purchased through a service center from Outokumpu and formed into 12” pipe. He adds that 2205 is twice as strong and twice as corrosion-resistant than standard 316 stainless steel.
The pipe was welded at one end of the berm and pulled through from the opposite end. Twenty-two sections of 2205 stainless pipe, each 10 meters long, were welded and leak-tested on site. Subsequent inspections of the new 2205 pipe indicated a straight pipe for the proton beam pipe. The team sleeved the pipe in about eight weeks. Schultz quips: “Let’s hope the pipe will last forever, or at least until I retire!”