Houlder worked with Global Marine, a market leader in subsea telecommunications cable installation and maintenance, to design and install a raised working deck onboard the OCV Normand Clipper.

The Normand Clipper, is currently on charter to Global Marine. Mobilised for inter array power cable installation, Global Marine identified the potential to multipurpose the vessel for fibre optic (FO) telecoms cable installation. They approached Houlder to provide the expertise to design, engineer and help install an additional working platform above the power cable carousel. The deck supports equipment for subsea FO cable installation work and makes use of the carousel below as a static cable tank. The deck utilises bolted deck connections which helps permit a rapid transition between power and FO modes.

Houlder has significant experience of designing and integrating new structures onto existing vessels.  The company used its in-depth knowledge and engineering experience to design the new deck for fabrication.  Features of the deck, typical with FO cable work include a bight slot, bight recess / access and equipment seatings. Houlder also designed access ways between the vessel and new deck as well as an additional cable way to route the cable to the vessel’s main deck.  Working with Global Marine, Houlder developed the vessel’s full mobilisation deck arrangement to ensure operational continuity between the new and main deck cable handling equipment.

A significant design challenge that Houlder faced was the large unsupported span of the new deck.  The engineering team undertook a detailed structural evaluation including lift analysis and weight optimisation studies to ensure the most efficient design was produced.  Integration of the new deck into the existing vessel and carousel structures was managed using 3D design packages.  The connection of the new deck to the vessel was designed to avoid the need for vessel strengthening and permit rapid installation.  Houlder worked with the classification society DNV to ensure full involvement at key stages of the design process.

Houlder acted as Global Marine’s representative whilst the deck was fabricated in NE England by Tolley Fabrications.  During the installation phase, Houlder were present to help supervise.

Bryce Harding, Engineering Manager, Houlder, commented: “Houlder prides itself on offering innovative and specialist expertise. For this project, our collaborative approach, working closely with Global Marine, ensured an efficient solution was produced whilst successfully navigating each challenge as it arose. As one example, early design reviews established a requirement to fabricate the deck remotely from the mobilisation port.  This highlighted a need to modularise the deck to ensure it was suitable for road transportation, followed by pre-assembly at the quayside.  An added benefit is the ability to stack the sections, reducing the space required for storage, when demobilised. Recognising each of our client’s requirements and undertaking regular design reviews with them, ensures Houlder offer the best solutions possible. Applying a ‘front end’’ approach to our design was paramount to success.  It is fantastic to see the vessel now in action and working as intended.”

Martyn Drye, Engineering Director, Global Marine, commented: “Having identified a possible way to easily and rapidly mobilise the Normand Clipper for FO cable work, we needed a pragmatic, comprehensive and rapid approach to the engineering design.  Houlder met these challenges as marine engineering experts and delivered as required.  The result is a vessel that is successfully installing FO cable but can be rapidly switched back to power cable mode if required.  Ultimately this improves vessel utilisation and enables us to offer the best support to our clients.

Houlder has previously worked with Global Marine’s sister company, Global Offshore – power cable installation and repair specialists and also part of the Global Marine Group, to design and deliver a new deck grillage system for the Q1400 Subsea Trencher system.