Prior to Supergrip bolts, fitted bolts had to be 'slugged' into place with a sledgehammer. This followed time-consuming honing of the holes and grinding of the bolts. Even with improved technological methods for fitting bolts, it is hard to achieve an interference fit. After each assembly and surface restoration, a small gap remains, increasing the chance of misalignment and subsequent galling of standard studs. Eventually the bolts have to be replaced. With a gap, the risk of coupling slippage at an overload situation is increased, causing potential balancing problems.
The Supergrip bolt eliminates these problems. Supergrip bolts are a superior solution for connecting flange couplings. Compared with traditional bolt systems, Supergrip bolts are much easier to install and remove. The bolts are inserted and removed by hand and with a clearance, eliminating the risk of seizure. The bolt is hydraulically expanded and tightened into the coupling bolthole, using a set of portable tools. The need for an overhead crane and time-consuming slugging of bolts is eliminated. Once the holes have been line-bored for initial installation, there is no need for further reaming or boring of holes. Thus the use of Supergrip bolts eliminates uncertainty about the length of downtime needed for removing and installing bolts at outages. Costs are cut and the length of future outages is significantly decreased.
The oil-injection method used for removing the reusable bolts was pioneered by SKF. Originating in Sweden, this technology is based on nearly a half century of experience in the engineering and manufacture of couplings for the marine market, and since the late 1970s, for the utility industry also.