General Questions & Answers


When should hydraulic bolt tension be used for flange connections?


Hydraulic bolt tensioning involves axial stretching of bolts with hydraulic pressure to achieve the desired bolt preload and high integrity of flange connections.

According to BP logoBP-standards, bolt tensioning should be used under the following conditions..

  1. For all flange connections with a bolt diameter of 2 inches and above.
  2. For flange connections of Class 600 and above with a bolt diameter of 1.5 inches and above.
  3. For flange connections in hydrogen and toxic applications with a bolt diameter of 1.5 inches and above.
  4. For flange connections subject to high temperatures with a bolt diameter of 1 inch and above.
  5. For flange connections requiring high accuracy with a bolt diameter of 1 inch and above.

According to the Shell logoShell DEPs, bolt tension should be used in the following situations..

  1. For all flange connections with a bolt diameter of 2 inches and above.
  2. For flange connections of Class 1500 and above with a bolt diameter of 1.5 inches and above.
  3. For flange connections in hydrogen and toxic applications with a bolt diameter of 1.5 inches and above.
  4. For critical applications with a bolt diameter of 1 inch and above.

GENERAL TENSIONING PROCEDURE

  1. The bolt tensioner is fitted over the stud
  2. Hydraulic pressure is applied to the tensioner which then stretches the stud
  3. The stud's nut is wound down against the joint face
  4. Pressure is released and the tool removed

The bolt behaves like a spring, when the pressure is released the bolt is under tension and attempts to contract, creating the required clamping force across the joint.





Detailed Information

Bolt Tensioning
Bolt Tensioning
The article gives you a good impression of what is meant by Bolt Tensioning...





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