24” Caisson Liner 95m Long | Piper Bravo, North Sea, UK

Caisson Liner during factory acceptance testing and offshore installation

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

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