Method and apparatus for hydraulically tightening threaded fasteners

An apparatus for tightening a threaded fastener, comprising:

• a hydraulically powered wrench;
• a source for supplying hydraulically under pressure to drive said wrench;
• a reservoir for receiving hydraulic fluid expelled from said wrench;
• means for determining an angle parameter from a measurement of the volume of fluid supplied to said wrench, said angle parameter being representative of an angle of rotation of said fastener by said wrench;
• means for determining a torque parameter from a measurement of the pressure of hydraulic fluid supplied to said wrench, said torque parameter being representative of a torque applied by said wrench to said fastener;
• means for terminating tightening of said fastener based on said torque and angle parameters;
• and
• a calibration fixture having means for determining the volumetric rate of angle advance for a given wrench.

A method of tightening a threaded fastener, comprising:

• engaging said fastener with a hydraulically powered wrench;
• supplying pressurized fluid to said wrench so as to rotate said fastener;
• measuring pressure applied to said wrench;
• determining a parameter representative of torque applied to said fastener from said pressure measurements;
• determining the angle of advance of said fastener corresponding to each said parameter representative of torque from a measurement of angular pump speed;
• and
• terminating tightening of said fastener in response to said parameters of torque and corresponding angle.