Technical solutions provider Bearing Man Group’s (BMG’s) extensive range of fasteners, tools and related equipment is used to enhance the reliability of equipment in diverse sectors, including light, medium and heavy industries, pulp and paper, construction, original- equipment manufacturers and agriculture.
These fasteners are enhanced by products that prevent the loss of joint clamp and, equally importantly, installation and disassembly tools that ensure each fastener is correctly installed and efficiently removed.
The selection of appropriate assembly and loosening tools, coupled with accessibility to the joints, is critical in overcoming factors that cause the loss of clamp and ensure ease of assembly and disassembly.
For a fastener to be effective, BMG manager Andrew Johns believes that key factors that require attention are the type of bolted joint design required and whether the joint should be serviceable or permanent.
He points out that there are two types of joints that have to be considered, namely tension joints and shear joints.
He explains that the name tension joints comes from the tension created on the bolt and clamped components of the joint, by stretching the fastener when torque is applied during tightening. This torque needs to be accurately calculated to ensure that the fastener’s limits are not exceeded. Equally, the application of insufficient torque and, thus, an ineffective clamp of components, could mean the joint will prematurely self-loosen.
The second type of bolted joint uses the shear strength of the bolt to transmit the load and often relies on a locking mechanism to retain the joint integrity as opposed to a high clamp force.
“If a serviceable joint is required, a number of factors need to be considered to ensure that bolt-securing elements are effective and that the joint tension is maintained over the life of the joint. These factors include thread size, clamp length ratio, preload, amplitude, lubrication and surface quality,” he comments.
Some of the products that BMG can provide include Nord-Lock wedge locking washers, which have a remaining joint clamp load of more than 80% after 2 000 cycles. Nord-Lock washers are available in standard, over-size and X-Series for softer materials or flexible joints, as well as stainless steel to combat corrosion.
BMG’s Nord-Lock bolt securing system uses tension instead of friction to ensure that joints holding subassemblies together remain secure. Bolts 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 between components 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 between contact surfaces. Even after moderate tightening, the bolt is safely locked when using Nord-Lock’s wedge-locking method.
Nord-Lock washers, which are installed in pairs, cam-face to cam-face, have cams between them, with a greater rise than the pitch of the bolt thread. When the bolt and/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. If the bolt or nut rotates loose in relation to the other, the resulting tension caused by a rise over the cams makes the bolt self-locking.
Advantages of this reusable system include maximum 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.
For a permanent, guaranteed clamp application, BMG recommends using Huck structural rivets and lock bolt solutions, which have been made for extreme temperatures and challenging environments. The Thome and Schwind ranges of specialised fasteners are recommended.
High strength challenges require the Nord-Lock Superbolt Multi-Jackbolt Tensioner system, which uses bolting technology that only requires simple mechanical torque tools for installation, eliminating the need for high-strength hydraulic torque tools.