North Sea Daughter Craft Deployment and Diver Inspection

Our commercial diving team inspected 15 individual risers in the North Sea, utilizing our in-house dive intervention daughter craft.

As part of the client’s on-going preventative maintenance regime splash zone inspections of gas riser mains on various installations was required. The purpose of the inspections was to identify gross defects and areas which could benefit from early intervention. Inspections were to target the zone between +2m and -4m CD which could not be captured through ROV or drone surveys.

Project Details

A number of inspection types were specified depending on the Clients’ maintenance regime. The inspections carried out comprised of:

  • General visual inspection (GVI),
  • Close visual inspection (CVI), following removal of marine growth by Caviblaster
  • Pulsed Eddy Current (PEC)

Cathodic potential (CP) and ultrasonic thickness (UT) readings were undertaken on regular grid centers where a CVI was called fall. Opportunistic CP and UT readings were taken during GVI’s where marine growth coverage permitted.

All inspections were carried out by, as a minimum, a CSWIP 3.1U qualified inspection diver. Inspections were supervised by IMCA Dive Supervisors supported by CSWIP 3.4U Underwater Inspection Controllers.

Hughes Subsea mobilized their in-house dive intervention daughter craft, and dedicated G100 davit onto a suitable DP II dive support vessel.

Operating on the edge of installations 500m zone the mothership deployed the daughter craft to facilitate the delivery of the dive team to the risers in question. Supported by a fast response daughter craft that moored up to the installations to deploy the divers as close as practicable to the riser.

In total 15 No. individual risers were inspected over the course of the program. The works were completed safely, undertaken in accordance with the proposed program and reporting delivered to client satisfaction.

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