The current system, which requires six employees on the floor and two cranemen, is a compelling argument for automation. Workers guide the old rolls out and set them aside. The cranemen use a jig to carry the new rolls to each stand one at a time. Workers on both sides of the stand make hand signals to the craneman and help guide the rolls into the stand. When the new rolls are in place, the craneman swings the jig to gently bump the rolls into the stand a little more to ensure proper positioning.
Workers reattach the hydraulic hoses.
Then the old rolls are removed by looping cable attached to the cranes around both ends of each roll. On the day of New Steel's visit, the change takes 65 minutes. One of the rolls has to return to the roll shop because of a blown jack on one of its bearings. Pulpit operators will control the system, although someone will be on the floor to ensure that the change goes well. The hot-strip mill was designed in the 1960s to accommodate automated roll changers, Dinger says.