DEXON Technology specializes in the development of customized solutions for the inspection of challenging or “unpiggable” pipelines.  With the successful inspection of over 400 challenging pipelines, DEXON holds a 94% first-run success rate. DEXON’s headquarters feature extensive research development and engineering and testing facilities for the development of in-line inspection tools. The below case study is #327 in DEXON’s Challenging Inspection Archive.

S(P)BM Loading Line In-Line Inspection

Single Buoy Mooring lines (SBMs) allow large transport tankers to connect and unload raw hydrocarbons to onshore facilities via sub-sea pipelines, without the need for a jetty. Flexible hoses run from the Pipeline End Manifold (PLEM) on the sea floor up to the SBM on the surface. The absence of a launcher and receiver at the PLEM classifies the pipeline as challenging or “unpiggable” with no way to remove the PIG from the line once the inspection is complete. The majority of SBM configurations are different and for this reason, tailored procedures and inspection configurations are required to allow for in-line inspection. For example, multiple lines of varying diameters paired with PLEM valve configurations can further complicate an inspection. While in many cases valve and hose configurations can be used to allow for inspection without extensive modification or support vessels. If customized solutions are required, various solutions can be used to overcome these challenges. Inspections may require subsea diving teams and or support vessels to supply a pumping medium, storage tanks, and pumping equipment.  Support vessels and tankers can be costly with costs varying per region and dependent on requirements however, costs can regularly exceed USD 1.5 million. As a result, alternative solutions are used wherever possible.

The Challenge:

The SBM line under inspection consisted of a single pipeline running from the PLEM to an onshore facility. A traditional in-line inspection of this SBM line would require bi-directional inspection from the facility onshore out to the PLEM and then back to the facility. This process would require pumping units and product storage tanks at both ends of the pipeline in addition to a surface support vessel on the surface at the PLEM. A solution was required to allow for the inspection of the line without taking the pipeline offline and without the use of extensive support equipment.

• Standard inspection calls for Bi-directional inspection requiring extensive support equipment

  • Surface support vessel

  • Onshore and offshore pumping stations

  • Onshore pumping medium storage tank and offshore slop tank

  • Pumping medium treatment

• Single direction inspection required

• Online inspection required

The Solution:

• Subsea launcher installed at PLEM

  • The ability to attach a launcher to the PLEM is dependent on PLEM design

  • In the event that a launcher cannot be installed at the PLEM an Add On Gate Valve (AOGV) can be used instead. Key benefits to the use of the AOGV include.

    • Allows for isolation of individual pipe spools at the flange

    • Isolating both pipe openings without spillage

    • Allows for the installation of a launcher, receiver, or isolation valve regardless of PLEM design

  • Crane and diver-assisted launch

  • Delayed ILI tool start to conserve battery prior to launch

  • Inspection run performed in product on regular loading schedule