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18001 Sheldon Road (Middleburg Heights, OH)

Main Facility
18001 Sheldon Road
Middleburg Heights, OH 44130
T: +

HydraNut® Bolt Tensioning System

Exclusive to Nova, a product and service brand of Curtiss-Wright Nuclear, the HydraNut® bolt tensioning system is a new and revolutionary product for tensioning and detensioning critical bolting applications. HydraNuts with metal seals are the ultimate system for joint integrity and reduce by 90% or more the time it presently takes to tension and detension the existing nuts.

The HydraNut eliminates the need for heavy wrenches, torque tools, heating, and hammering, and allows “hands free” tightening and loosening of nuts, which reduces the risk of common workplace injuries. HydraNuts also withstand service temperatures over 600°F and virtually eliminate stud and nut galling which results in joints seizing up.

HydraNut is exclusively manufactured by Nova Machine Products in the United States for commercial, ASME code Section III and safety-related applications under Nova’s Quality Assurance Program including our 10CFR50 Appendix B program.

Key Features and Benefits

  • 100% simultaneous tensioning
  • Eliminates star pattern torqueing process
  • Saves time and reduces the amount of shifts required to complete work
  • Reduces dose exposure
  • Eliminates heavy tensioning equipment
  • Eliminates dangerous reactive forces by eliminating torque wrenches
  • Increases worker safety
  • Even loading of the gasket
  • Eliminates risk of galling the stud, nut or flange

Principles of Operation

  • The Spherical Washer is placed and the HydraNuts are screwed down onto each stud.
  • Each HydraNut on the flange is pressurized at the same time using manifolds and hydraulic hoses.
  • As fluid enters the Hydraulic Area the pressure builds.

  • As the pressure builds the Nut Body is forced upwards thus stretching / tensioning the studs to the required load.
  • A small gap will appear between the Lock Ring and Piston. This is indication that the studs have been stretched / tensioned. The studs are now under hydraulic load.
  • The Lock Ring is screwed down until it touches the Piston.

  • The hydraulic pressure is released.
  • The studs are now under mechanical load that is being retained mechanically by the Lock Ring.
  • The hydraulic hoses are removed and the HydraNut remains on the flange during plant operation.

Plant Design


Typical Plant Applications

  • Steam Generators
  • Small and Large Valves
  • Heat Exchangers
  • Equipment Hatches
  • Safety Relief Valves
  • Steam Safety Valves
  • Reactor Coolant Pumps