Using torque tools, such as nutrunners or hydraulic torque wrenches, you turn the nut. As the nut turns, it stretches the stud. The torque setting for the tool translates into load on the connection. When the tools are used following the appropriate specifications for lubrication, coating and other factors, a desired clamp force can be produced.
With tensioners, the action is not directly on the nut, rather tension is applied directly to the stud in order to produce stretch. Once the prestretch is achieved, the nut can be tightened. Once the pressure is released the nut holds the load on the bolt. This produces the clamp force. Multiple tensioners can be used together to provide even load when tightening. Hydraulic bolt tensioners have a footprint and thread height requirement.
We are one of the few tensioning companies in the world who offer custom tensioner tool solutions. If the standard ranges of tensioners are not suitable, contact us and we will design a custom tool to do the job. We use the latest 3D modeling software (Solidworks) and FEA analysis software (Solidworks Simulation) to design non standard tools. Once the custom solution has been designed we offer either 2D drawings of the proposed tool or if requested we can supply 3D step files which allows our customers to import the custom tool into their 3D assembly to check fit.
We recognised from the start that having the ability to rapidly design custom tensioner solutions was an important and necessary function of the company and we have invested heavily in its engineering department. We aim to provide special tensioner solutions within one week of receiving the enquiry. Special tensioner tools currently make up approximately 60% of the whole business.
The contract, to supply 4 massive custom design hydraulic nuts for a major forging press refurbishment project in the USA, was completed and delivered on time and on budget. The special hydraulic nuts required for the forging press had 25” Buttress thread forms and each hydraulic nut weighed 4 tonnes with an 8000 tonne bolt load capacity. Hydraulic nuts are a permanent form of bolt tensioning where the hydraulic nut replaces the conventional hexagon or round nut. With application of hydraulic pressure to the hydraulic nuts, bolt load is generated effortlessly and the user needs only to insert easily fitted shims to retain the bolt load. The hydraulic pressure is then released and an accurate bolt load is retained.