Industrial consumables and engineering firm Bearing Man Group’s (BMG’s) new range of Nord-Lock Superbolt multi-jackbolt tensioners has been well received by the market.

The Superbolt tensioners were introduced in February and were designed to reduce downtime and eliminate unsafe and laborious bolting methods for pumps. The tensioners were specifically designed for use on large slurry pumps and pumping equipment used in harsh mining conditions.

“These new Superbolt tensioners replace, or retrofit, nuts and bolts on pumps and only require hand or air tools for the installation and removal of any size tensioner,” says BMG fasteners division GM Darryl Campbell, adding that bolts on pumps and pumping equipment need to be easily removable during maintenance procedures, but must withstand the loosening effects of vibrations and dynamic loads.

Speaking to Mining Weekly, Campbell says the bolting method is based on a design that splits one big torque into several smaller ones.

He adds that the product has had good sales figures to date and will be exhibited at the company’s upcoming open days and cus- tomer days, the dates of which have yet to be confirmed.

“The Superbolt has numerous advantages over conventional bolting products, as it ensures that joints can be tightened with high accuracy, while eliminating the need for special- ist skills or heavy tooling. Tightening the bolt tension allows higher preloads on the same size bolt than those of conventional tightening methods,” asserts Campbell.

He adds that by generating a preload high enough above the separating forces, the bolting will not vibrate loose on properly designed joints, which eliminates costly downtime.

“The added elasticity increases fatigue life of the bolted joint and installations are safer, as only small hand tools are required. This means that there are no safety hazards from immense hydraulic pressures, no pinching hazards and no lifting of large tools or sockets breaking under high pressure,” explains Campbell.

He says Superbolt tensioners are easy to install, even in confined spaces and, although the applications have multiple jackpoints to tighten, which can be done using hand or power tools, installation times are faster than those of other bolting methods.

“A conventional bolting system, such as the sledgehammer, gives little control, is inconsistent and can cause injuries. Thermal tightening, crane and hydraulic wrenching and hydraulic tensioning are often costly, inaccurate, time consuming and generally unsafe,” warns Campbell.

Superbolt devices are threaded onto a new or existing bolt, stud, threaded rod or shaft. The main thread serves to position the tensioner on the bolt or stud against the hardened washer and the load-bearing surface. Once positioned, the actual tensioning of the bolt or stud is accomplished with simple hand tools by torquing the jackbolts, which encircle the main thread.

The jackbolts transfer the preload evenly into the main thread and, consequently, onto the joint. Jackbolts have a small friction diameter and can, therefore, create a high thrust force, with relatively little torque input.

“Superbolt tensioners are not available off the shelf in standard sizes from M16 to larger than M1450, and a large number of sales are for special nonstandard items,” notes Campbell.

This range is also custom-designed and manufactured in various materials to required specifications for diverse tightening applications.

These Superbolt tensioners are designed for demanding applications requiring a high clamping force, with limited space for tightening the bolts. They are also suitable for use in harsh underground mining conditions.

“Superbolt tensioners are used in diverse industries, including hydropower, wind turbines, gas and steam turbines, nuclear, steel, mining, shipbuilding, offshore, chemicals and transportation. Original-equipment manufacturers specify multijackbolts in their design to improve performance of their product,” states Campbell.

He adds that the high preload capacity and accuracy of this system have resulted in the design of smaller bolt sizes. The compact dimensions and reduction of tooling sizes allow for machinery sizes to be reduced, which, in turn, reduces material and machining costs.

“BMG also offers a technical advisory service to determine the dimensions and load conditions of existing or required bolted joints. Current tightening methods are evaluated and bolt preloads for absolute reliability and durability are calculated,” concludes Campbell.