Background / Challenge

  • Requirement to install a liner into an existing 98m long 24” OD caisson, to accommodate water discharge
  • Requirement to seal caisson / liner annulus space
  • The caisson could not be replaced due to worksite height and deck level restrictions
  • Caisson Liner required internal corrosion resistance
  • Caisson Liner must pass caisson bore restriction at waterline
  • Caisson Liner had to accommodate thermal expansion

24in Internal Caisson Liner
Caisson Liner during factory acceptance testing and offshore installation

Solution

  • Carbon Steel spools manufactured in suitable lengths to allow for space restrictions on installation deck
  • Overall finished length of liner 95 metres
  • Spools internally clad with Inconel 625 to address internal corrosion issues
  • Hydraulically operated dual seal and lock arrangement on base section of liner
  • Lower liner spools with reduced 14” OD slip-on flanges in order for spools to pass the bore restriction
  • Liner upper section allowed for thermal movement with a sliding sleeve arrangement
  • 8 off Inconel control, actuation and injection lines incorporated
  • In-house assembly of the whole liner to check for straightness and flexibility
  • Successful completion of the job safely and ahead of schedule

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