Induction heating

Induction Bolt Heating, is insertion of high temperatures by means of induction with the aim of prolonging the bolt. This method is especially used in steam turbines to disassemble and reassemble the different parts of the casing in a gas-tight way.

Induction Bolt Heating uses hollow bolts. An induction rod is placed in the hollow shaft of the bolt that allows a certain portion of the bolt to be heated up by a magnetic field (eddy current). The heated part of the bolt increases in length which allows the nut to be loosened in a relatively easy way. With the assembly the bolt is heated before the nut is hand tightened and then turned a pre-determined number of degrees. Cooling of the bolt will then ensure the proper clamp force.

Advantage

  • Complete control over the process
  • No damage to threaded Bolts
  • Bolts do not need to be replaced
  • The speed of work, short heat-up and cool-down times
  • No risk of broken bolts or studs
  • When using an angle instead of torque resistance is no factor
  • Limited spread in clamp force between bolts

Disadvantages

  • Use of specialized and expensive equipment is required
  • Only applicable to appropriate bolts or studs

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