Subsea Control System 

The Subsea Umbilical Termination Unit (SUTU) is the termination that mates with the umbilical flange for installation and pull-in of the umbilical to the required subsea structure. This unit is sometimes known as an Umbilical Termination Assembly (UTA) or Unit (UTU).

The SUTU terminates all of the elements (hoses, cables or tubes) of the umbilical and provides outputs for the jumpers which connect the SUTU to the SDU enabling the subsea distribution.

The SUTU is fabricated from carbon steel coated in accordance with a suitable subsea paint specification. The SUTU has a mounting flange for the umbilical armour flange termination, and mounting plates for the hydraulic, chemical and electrical connectors.

The hydraulic and chemical connections are mechanical connections to the back of male hydraulic connectors, and the electrical cables terminate in subsea mate able electrical connectors (which contain pressure balanced and oil filled housings for the connections themselves, with cable boot seals onto the outer sheath of the cable conductors).

The SUTU can be designed to be pulled into a subsea structure. To deploy this design needs special rigging and reaction with the ROV to pull into the subsea structure. This can be a slow task in Deepwater. Alternatively, the SUTU can be designed to be deployed vertically into a stab assembly on a structure. The stab has a hinge device, and when the SUTU is locked into the stab, the lay vessel starts to layaway and the hinge device will rotate to orientate the umbilical into the horizontal plane, and the umbilical can be laid away by the lay vessel.

With the umbilical in the horizontal plane, the SUTU connector plate is also in the horizontal plane. This allows the ROV access to make up the jumpers to the SDU.

A SUTU design that plugs directly into the SDU is feasible, although this may restrict the order in which the units must be deployed and may prevent the retrieval of the SDU without first removing the SUTU/umbilical. However design with a suction pile as foundation for the SDU (like on Moho 1Bis SDU) with dedicated porch on the foundation will allow disconnecting SUTU from SDU by disconnecting and stroking back the umbilical multi-bore connector that will rest on foundation porch making possible the retrieval of SDU unit (SDU pile left in place) without recovering SUTU/umbilical.

One other scenario is that the umbilical SUTU and the SDU are combined into one unit with a flange for termination of the umbilical and terminations for the hydraulic, chemical and electrical connections. This unit would retain the name of an SDU. The overall size and weight of such a unit, however, makes it difficult to store on an installation reel, forcing a first-end installation, or making a carousel necessary and is difficult to deploy in deepwater. The advantage is that the connection between the umbilical and SUTU is made (usually) at the factory and the whole can be tested as an assembly.

Neither of these allows the use of a protective weak-link device unless one is specially designed as part of the overall interface between the two items. In both this and the above cases, the units and their mounting structures must be designed to accommodate the maximum expected umbilical loads, making them considerably larger/heavier.