Hydraulic External Tensioner (HET)

HET’s are tools that apply hydraulic preloads to studs by gripping the exposed threads above an existing nut. It does this by creating axial loads using hydraulic pressure to stretch the stud rather than torqueing the nut. The stud is hydraulically preloaded, the nut is tightened down by hand and the hydraulic preload is released.


  • Interchangeable puller screws allow you to use a single tensioner for similarly loaded studs
  • Puller screws can be made to fit any type, size and pitch thread
  • Any number of tensioners can be linked “daisy-chained” for simultaneous and even loading
  • HET can be customized for special applications

Full range of standard HET Tensioners:

  • 6 Frame Sizes
  • Thread Sizes: 3/4″ up to 4″
  • Can Produce Hydraulic Tensioning Loads Up to 890,000 LBF

External Tensioning Nut (ETN)

ETN’s are used with HET’s as a retrofit to existing hardware. When tensioning on the stud is not an option, ETN’s are used to replace the original nut and are externally threaded to allow tensioning. The HET is then threaded onto the ETN to apply hydraulic preload.


  • Retrofittable for joints not originally designed for hydraulic tensioning
  • Externally threaded nut eliminates the need for studs to be extended above the hex nut
  • Can reduce the radial footprint of the nut
  • Allows external tensioner to be used on nuts in counter-bored holes
  • Utilizes standard HET tensioning platform

HET’s and ETN’s are commonly used in many applications which include:

  • Steam Turbine Casings
  • Centrifugal Compressor Casing
  • Windmill Structure Base Bolts
  • Gas Turbine Compressor Tie Rods
  • Reciprocating Compressor Crosshead Connections


This blog was written by Shaun LaPolla in the Riverhawk Business Development group. If you have any questions, please contact Shaun or anyone in the Riverhawk Sales group for more information.

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