2 Answers

0 votes
answered Apr 15, 2016 by jakangaru (2,010 points)

Consider the following steps:

  • The Catenary Riser can be installed as either the first-end or second-end connection of the pipelaying operation, using the J-lay, S-lay, or tow methods.  For each of these methods, the maximum allowable strain analysis (Fatigue Analysis) should be satisfied. 
  • The pipe reeling method may be an acceptable alternative method of installation, provided that the high strain levels caused by the pipe reeling and unreeling operations are adequately addressed during design.
  • A principal requirement during Catenary Riser installation is that the correct Catenary Riser hang-off angle (and hence tension) at the top support point is achieved.
0 votes
answered Apr 16, 2016 by antonjoh (2,870 points)

Further to what already posted,

  • An installation analysis should also be performed prior to the actual installation using proven and industry-accepted methods and software.  The objective of the analysis should be checked that the installation stresses in the Catenary Riser are within the allowable limits for the proposed installation equipment, methods, and the maximum sea state.  Any fatigue damage due to the installation activities should be evaluated and appropriately included in the Catenary Riser fatigue analysis.
  • The installation analysis should consider the following:
    • Installation methods
    • Installation equipment
    • Water depth
    • The maximum sea states under which installation may proceed
  • The analysis should include all phases of the installation, including:
    • Pipelay initiation
    • Bottom tie-in (if appropriate)
    • Tie-in to the floating facility
    • Pipeline abandonment and recovery
    • Pipeline and riser lay down
    • Commissioning/testing
  • Spectral analyses should be used for the installation analyses.  The riser should be evaluated for a number of different deployment depths.  The potential for riser contact should be evaluated using the same techniques described for the riser interference analysis above.  Both storm induced and current induced interference analyses should be evaluated.
  • The installation analysis results should include the followings:
    • Definition of the limiting sea state for installation of each of the riser components
    • Definition of “limiting vessel motions and offsets” and “controlling factors for the components”
    • Estimated relative displacements between the riser and any nearby structure (e.g. installed risers)
    • Maximum compressive load permitted at touch down