Rack Phase Difference (RPD) is a difference in the elevation between rack teeth of the chords of any single leg of a jackup rig. This relative displacement creates an addition load on the leg members, which may results in failure of structure members in case RPD reaches more than the allowable value.[1]

Reasons

  1. Eccentricity of Spudcan centre due to uneven groud condition.
  2. Sliding of leg

Terminology

  • Spudcan - the foot on a leg of a jack-up type oil platform.

References

  1. http://www.hse.gov.uk/offshore/infosheets/is4-2007.pdf