American Machinist

Where the chips fall. (handling of oily chips from Northrop Corp.'s machine-tool operation)


Prior to June 1989, chip handling at Northrop was little more than loading up roll-off bins and getting rid of the containment to whoever would take it.

The system in place at the company's plant in Hawthorne, Calif was typical of large companies handling large volumes of chips. After a shift, machine-tool operators would clean each of the 22 three-spindle gantry profile mills in the manufacturing area by shovelling chips into strategically situated holes in the floor. From there, a vacuum system powered by a 150-hp fan would push the chips at 60 mph through underground plumbing (18- to 21-in.-dia duct pipe), out of the facility, over a roadway, and into one of two cyclones, or separators, which would exhaust the conveyed air out of its top through a filtration system and drop the chips out of its bottom.

According to Al Krane, manager of plant engineering and energy management at Northrop, the chips, laden with coolant, would overflow two bins ("who knew when they were full?" he queried), creating a mess on the floor. The chips would then be stored for a period of time, often leaking, and finally transported off-site by a vendor whose containers leaked onto the roadways in the area.

Having a messy problem with chips on-site was one thing, but because there were leaks on the highways, it became an entirely different snag. To alleviate this problem, Krane purchased and modified new roll-off bins. "We had to build them in such a way that they would be as water-tight as possible and also covered to stop chips from becoming airborne during transit," he says.

Problem solved? Not quite

Because Northrop generates hazardous waste and also treats it, it issued a federal Resource Conservation and Recovery Act (RCRA) permit. …

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