New Ulstein SX232: A subsea vessel for all markets

Ulstein SX232 configured for inter array cable laying

Seeing a “surge of optimism” in the offshore service vessel market, Ulstein has unveiled a design for a new subsea vessel, the Ulstein SX232, to serve both the fixed and floating offshore wind markets as well as offshore oil and gas.

Ulstein says that the offshore vessel market is currently benefiting from increasing CAPEX (capital cost) spending in both the oil and gas (O&G) and renewables sectors. The offshore O&G sector will reach its peak investment, of nearly $300 billion, in 2026. After that, offshore energy investment will shift towards offshore wind. Total investment in offshore energies will exceed $400 billion in 2028, almost double the amount in 2020.

With a length of 139.8 meters and beam of 28 meters, the Ulstein SX 232 is being launched at a time when subsea vessels originally built for offshore O&G operations, have become an integral part of the value chain in the offshore wind market.

“The smaller subsea vessels – light construction support vessels with cranes between 25 and 150 tonnes – depend largely on activity in the offshore wind and other markets (such as other renewables, defense, etc),” says Ulstein. “By 2023, 30% of their activity was outside the offshore O&G market. The larger subsea vessels – heavy construction support vessels with cranes between 200 and 400 tonnes – are more reliant on the O&G market, with less than 10% of their activity outside it.”

Ulstein says that its new Ulstein SX232 combines innovation, versatility, and emissions reduction and is based on three core principles

• an optimized hull design based on the Ulstein Twin X-stern,
  a smart power and propulsion system developed to minimize energy consumption during DP operations
• an integrated energy recovery system utilizing all the waste heat in the machinery systems (cooling water and exhaust).
• The design has been developed to include versatile fuel options and a battery energy storage system for peak shaving and spinning reserve purposes has been implemented.

The vessel’s forward section accommodates 130 people and includes two remotely operated vehicle (ROV) hangars. A moonpool is positioned at the rear of the accommodation block, complemented by an expansive flat deck spanning over 2,000 square meters. This flat deck design enhances the vessel’s adaptability, allowing multiple operational setups to suit diverse maritime tasks.

The basic platform has been configured with a 250-tonne offshore crane; however, the platform can also support a larger crane of 400 tonnes.

With the upgraded crane capacity, the vessel could support the installation of suction anchors, which are common for floating offshore energy.

An alternative use of the Ulstein SX232 platform is for inter-array cable laying operations.