Source: Biach Industries, Inc.
Biach Custom Tensioning For Bolting Problems
The bolting of any joint is a complex, dynamic series of interactions. High impact, heat and the wrenching application forces caused by conventional torquing can actually cause or compound fastener problems they are supposed to solve - with leakage, distortion, flange rotation, gasket, equipment damage and unscheduled downtime the costly result.
In critical applications where a high degree of uniformity is desired, or in dangerous or remote locations where crew safety is a concern, a Biach customer engineered tensioner can provide the safe, timesaving, cost-effective solution you require for your bolting problems.
What is stud tensioning?
Stud tensioning is a precise, automatic way to control stud tightening. Loading a fastener to a pre-determined level eliminates stress, distortion, flange rotation, gasket and equipment damage.
How does it work?
Tensioning provides a dependable direct axial loading without the use of torque or heat. Therefore, tensioning eliminates the distortion and damage caused by single point loading.
How can I ensure uniformity of load?
Tensioners are usually used in sets of at least three. Simultaneous tensioning of opposing studs assures parallel closure and balanced loading of flanges.
How are studs loaded?
Torquing - while torquing achieves axial stress, it also introduces an undesirable torsional stress, which often results in bolt fatigue and joint failure.
Heating - heating and cooling a bolt to leave desired residual load demands careful control of material, fabrication and temperature to obtain effective closure. This procedure is costly, time consuming and a potential safety threat.
Tensioning - Hydraulic stud tensioning pulls the stud in a straight line, thereby placing the stud in pure axial tension and eliminating torsion. The nut is then turned down to the flange surface and the hydraulic pressure is released to leave a predetermined residual stress in the stud.
Benefits of tensioning
- Fast, easy bolt tightening
- Reliable, accurate, even bolt load
- Lowered risk of load failures for enhanced worker safety
- Saves on equipment and labor downtime
- Reduces manpower cost
- Permits remote operation
- Adds life to equipment by eliminating joint distortion, gasket failure and galling
- Virtually eliminates noise associated with wrenching and torquing operations
- Eliminates the distortion, deformation and stress cracking which can result during torque applications.
- Simultaneous tensioning of opposing studs assures parallel closure and balanced loading of flanges especially suited for use in sets of three or more.
- Simultaneously tensions multiple bolts
- Greater durability of bolted connection
- When accurate, repeatable or even loading are required under critical conditions
- When the fasteners are designed to operate near yield, and the additional torsional stress inherent in torquing could cause failure
- When crew exposure time is critical, tensioning enables flanges to be closed fast and correctly the first time
- When actual loading of the fastener is dangerous, such as in high-pressure, high temperature reactor tube crimping operations. By tensioning, the loading can be done remotely with the crew operating from a safe distance
- When cramped spaces make long handled torque devices or large air powered tools awkward, if not impossible to use
- When replacement of fastener is expensive, galling and nut damage can be eliminated. Tensioners require no mechanical force to turn the nut
- When corroded fasteners are involved, tensioning may provide a means of removing the nut where torquing cannot since the nut is turned in a no-load condition
- When noise is undesirable, hydraulic tensioning is ideal, since no impacting elements are involved, and the hydraulic power source can be operated from a remote area
- When vibration is present, torsional loading of fasteners and uneven loading of flanges can cause loss of joint integrity. Tensioned flanges are evenly loaded, with no torsional stress in the fasteners.
Biach Industries, Inc., 75 Chestnut Street, P O Box 280, Cranford, NJ 07016. Tel: 908-276-3110; Fax: 908-276-0815.