As part of an extensive upgrade, Houlder was contracted to deliver a guidance system for subsea Xmas trees onboard the Byford Dolphin. This allowed lateral restraint of packages whilst they were lowered and retrieved through the moon pool. Houlder’s designers overcame design challenges including only 400mm clearance from the bulkhead for stowage. The solution was a self-contained collapsible structure which, when not in use, took up the minimum possible space.

The system works in compression only and provides horizontal restraint in both lateral directions, leaving the subsea equipment free to be lifted and lowered vertically. It comprises guidance arms that are bolted onto the item being lowered, collapsible guidance frames (port & stbd), four sets of Hilman rollers, two sets of guidance buckets and two sets of guidance tracks constructed of I beams.   To ensure reliability and ease of operation these systems are mechanically operated manually rather than hydraulically.  

This bespoke system is utilised in combination with the Houlder designed 100te skidding trolley also installed on the Byford Dolphin. The combined system has recently been updated by Houlder to deploy the rig's Lower Riser Package (LRP) and Emergecy Disconnect Package (EDP).

You can see this new operation illustrated below.