Industrial consumables and engineering firm Bearing Man Group’s (BMG’s) Nord-Lock bolt securing system is used extensively in pumps and pumping equipment in the mining industry to enhance operation and reliability.
Divisional manager of BMG’s fasteners division Darryl Campbell states that the Nord-Lock bolt securing system uses tension instead of friction to ensure that joints holding sub- assemblies together remain secure.
“Bolts on pumps need to be easily removable during maintenance procedures, but must resist the loosening effects of vibrations and dynamic loads. Bolts that are locked conventionally by friction in the thread tend to lose most of their preload through vibrations, while those locked by the tension of this system present a minor loss of preload, which is caused mainly by settlement in the thread. Even after moderate tightening, the bolt is safely locked when using Nord-Lock,” he says.
Campbell adds that it is increasingly important to have good control of the torque-clamp load relationship when tightening a joint. To enhance the design of the joint and use as much of the capacity of each dimension as possible, it is important to know the required tightening torque.
“Nord-Lock washers, which are installed in pairs – cam face to cam face – have cams on one side, with a greater rise than the pitch of the bolt. When the bolt or nut is tightened, the radial teeth on the opposite side grip and seat the mating surfaces. The teeth also lock the washers in place, allowing movement only across the face of the cams. The resulting tension makes the bolt self-locking.
“These washers can be used on standard-grade as well as high-grade bolts, and there is no need for adhesives to lock the stud bolt. “This system is designed for use in tapped- and counterbored holes and for larger holes or on soft materials, while a flange nut or bolt should be used in combination with Nord-Lock washers with a larger outer diameter,” notes Campbell.
He further adds that the advantages of this reusable system include vastly improved safety when locking fasteners, easy assembly and disassembly, positive locking at low or high preload levels and minimum surface marring or scratching.
“This system, which has the same temperature characteristics as a standard bolt or nut, resists loosening caused by vibration and dynamic loads. “The locking function is not lost by lubrication.
“The bolted joints are subjected to a Junker-vibration test, where the preload bolt tension is measured by a load cell and vibrating motions are generated radially through the bolt. This method tests the bolts for security.
“BMG is able to provide almost any fastener required, within 24 hours, anywhere in the country. The fasteners division also offers a technical advisory and support service through BMG’s national network of over 100 branches,” he states.