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Daisy Chain Unit
Distribution Units

Daisy Chain Unit

Subsea Step-Out Hydraulic & Electrical Distribution Unit

Developed and designed to eliminate the procurement of additional expensive field umbilicals by offering the flexibility to hydraulically and electrically link (daisy chain) subsea step outs, removing the need for additional infield umbilicals and providing the ability to re-configure the field layout during field life.

Datasheet

The daisy chain distribution unit links two subsea trees, carrying hydraulic fluid supplies, methanol supplies and electrical connections between them for use in deep and shallow water applications. As a modularised, fabricated structure it is installed from a lift wire by a free-flying remotely operated vehicle, using a class 4 torque tool interface as described in API 17D and ISO 13628-8 for deployment on the subsea tree.

A unique guidance system, built around two fixed inboard junction plates (male stabplates) and an outboard junction plate (female stabplate), ensures repeatable mating even in poor visibility. A moving inner fabricated structure frame houses the hydraulic and methanol distribution lines, while generous vertical and lateral (±75mm) and angular (±10° on the X, Y and Z axes) tolerances accommodate as-built variation between adjacent trees.

Because the distribution unit and both hydraulic infield umbilical termination heads mate and de-mate under full system working pressure, the unit can be reconfigured on an operating field without a planned shutdown — a key advantage when step-out tie-backs are added after first oil. The assembly weighs 2200kg in air (1913kg in water) and measures 3413mm wide by 1600mm high.

Key Features

  • Unique guidance system for repeatable, low-risk mating
  • Two fixed inboard junction plates (male stabplates) and one outboard junction plate (female stabplate)
  • Moving inner fabricated structure frame housing the hydraulic and methanol distribution lines
  • Distribution unit and both hydraulic infield umbilical termination heads mate and de-mate under full system working pressure
  • Modularised fabricated structure installed from a lift wire by a free-flying ROV
  • Class 4 torque tool interface per API 17D and ISO 13628-8

Materials

UNS S31803Nitronic 50 HS

Applications

  • Distributes hydraulic fluid, methanol and electrical supplies from one subsea tree to a second subsea tree.
  • Suitable for deep and shallow water step-out tie-backs, removing the need for additional infield umbilicals.
  • Allows the field layout to be re-configured during field life.