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NSK is a worldwide leader in the engineering and manufacture of bearings, including those used in critical steelmaking processes. When NSK bearings are installed in applications related to melting steel, the company prefers that their customers use SPC4® Load Indicating Fasteners from Valley Forge & Bolt to secure the bearings in place.
“We know that using a high-quality, load indicating fastener from Valley Forge will give our customers the best result,” said Paul Brda, strategic segment manager for NSK. “SPC4® assures proper bolt tensioning at installation, promotes maximum bearing service life, makes maintenance faster and more effective, and enhances safety of the application.”
One such application is an electric arc furnace (EAF), which uses electrodes to melt scrap metal at the beginning of the steelmaking process. A massive 12-foot NSK cylindrical roller bearing is used in the mast that controls the roof of the EAF, which seals the chamber as the melt occurs. Because melting steel requires heat in excess of 2500° F (1370° C), closing the roof is vital to the safety of surrounding workers as well as integral to a successful melt.
The roof’s mast is installed alongside the lower bowl of the EAF. It pushes the roof, which weighs several tons, upward and rotates it 90 degrees so the EAF can be filled with scrap metal, then rotates 90 degrees in the opposite direction and closes the roof before the melt begins. The NSK three-row cylindrical bearing is installed at the base of mast to aid the 90-degree rotation.
Because of the bearing’s 12-foot diameter, it takes 150 bolts to secure it in place. SPC4® fasteners make installation more reliable because they measure elongation from within the bolt, information that is read as a percentage of yield using an external meter. This direct tension monitoring is accurate to within +/-5% of minimum yield.
Bolts tend to relax after installation. If bolts come loose, the bearing can begin pulling and distorting. SPC4® fasteners avoid this issue two ways. First, by indicating load at installation, bolts can be accurately tensioned from the outset. This reduces the likelihood and severity of bolts loosening. Second, the easy readability of tension within the SPC4® bolt after installation makes regular maintenance faster and easier, promoting ongoing accurate tensioning.
“In addition to increased accuracy and improved performance, SPC4® fasteners also speed up maintenance and reduce the manpower needed,” said Brda. “With the SPC4® system, one technician can check all the bolts in just a couple of hours because, by using an SPC4® external meter, they will know in seconds whether a bolt requires retorquing. If the tension is still within specifications, they can move on to the next bolt.” Brda adds there have been instances where no SPC4® bolt needs retorquing when checked at a service interval.
Conversely, checking traditional bolts is typically a three-person job that takes upward of eight hours. One person holds a hydraulic torquing wrench, another operates the pump, and a third person has a backup wrench. SPC4® also reduces injury risk by requiring only the bolts that need it to be retorqued, limiting a worker’s exposure to pinching and other injuries caused by torque wrenches.
“For these reasons, we highly recommend that NSK customers use SPC4® Load Indicating Fasteners to install bearings for EAF and LMF (ladle melt furnace) applications,” said Brda.
About Valley Forge & Bolt
Valley Forge & Bolt Mfg. Co. is a domestic manufacturer of patented bolting products for critical applications. These bolts and studs are widely trusted for their unrivaled quality, extraordinary performance, and enduring reliability. Call: (602) 269-5748. On the web: www.vfbolts.com.
