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Hydraulic twin-cylinder high-strength bolt tensioning tensioning method Fastening Technology
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The 1 hydraulic twin-cylinder high-strength bolts tension Rafah Fastening Technology

The tower of the wind turbine installation the use of hydraulic torque wrench forged flange bolts fastening. Its major shortcomings: Bolt torsional the composite force so the bolt strength required reduction, the discrete nature of the torque coefficient caused by the bolt pre-tension is difficult to accurately applied, hydraulic torque wrench size determines bolts to be far away from the cylinder wall resulting in the flange material amount of the increase.
The pre-tension is applied to the high-strength bolts using a torque wrench is applying pre-tension bolts indirect method. The design of steel structures (GB50017-2003) "the provisions of Article 7.2.2 Description Pre-Rally. Where 1.2 grounds pull, shear (torque caused by) the composite stress-induced strength reduction; bolt strength tensile strength prevail, the introduction of additional safety factor of 0.9. This shows that the torque applied to the bolt pre-tension the bolt strength decreases.
"Steel Construction Quality Acceptance provides high strength bolts connecting the vice end of screw torque values​​. Bolt Nominal Diameter standard value for the construction of pre-tension values ​​for the torque coefficient, for the final screw torque values​​. The average torque coefficient is 0.110 to 0.150, and the standard deviation is less than or equal to 0.010. Construction acceptance of the torque coefficient relative error of about ± 15%. The error of the torque coefficient bolt pre-tension must exist a certain degree of error. In addition, the high-strength bolts must be timely determination torque coefficient failed torque coefficient can not be used more than six months need to retest. The measured torque coefficient takes a fee and may result in bolt scrapped due to the torque coefficient single unqualified. Visible using traditional fastening bolt torque method, there is a certain lack of.
Hydraulic twin-cylinder high-strength bolts the tension can be directly applied to the bolt pre-tension the butt nut (sets pulled the bolts at the top of one end of the other end of the double-headed screw end sets in tension), through the oil pump on the tension is pressurized, in order to achieve the purpose of the tensioning bolt. Using two-cylinder tension can be reduced to the size of the tension, the tension and the bolt closer to the cylinder wall.

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