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Wednesday Write-up: “Enhanced” Notations for retro-fit vessels

Several organizations have been exploring the opportunity to use “enhanced” notations to add value to retrofit upgrades of dynamic positioning systems.

Enhanced notations, such as DNVGL’s DYNPOS-ER, or ABS’s EHS provide vessel designers and owners with an opportunity to leverage modern technologies into dynamic positioning concepts. The “Enhanced” concept is designed to leverage modern technology improvements and improve reliability. While the design concept is complementary with traditional Dynamic Positioning rules, there are several variations between the notation philosophies.

DNVGL’s “enhanced” notations (DYNPOS-ER and DYNPOS-E) are held completely separate from the standard DYNPOS-AUTRO and DYNPOS-AUTR rules, and may have rules which do not align consistently, while ABS’s EHS notations are to be applied over and above existing DPS-2 and DPS-3 requirements.

The attractive aspect of the notations is the ability to provide a notation for closed bus operation without online spinning reserve: Enhanced reliability notations allow for the consideration of standby-start of generators, thereby improving the operational efficiency of the vessel.

The cost of the enhanced notations however is in the design. While there are different levels of notations available from each of the enhanced classes, the requirements may include all, any, or variations of the following:

  • Additional DP Controller on the bridge

  • 45-60 seconds to thrusters “DP Ready”

  • Additional segregation requirements

  • Additional generator protections

  • Fault ride through capability

A thorough gap analysis between the vessel’s current class certification and the proposed notation should be undertaken, including a “side-by-side” assessment of the current versus proposed rules, highlighting the variations should be considered.

The challenges of changing a vessel’s notation during a shipyard retrofit were highlighted in the presentation provided by DNVGL’s Richard Purser at MTS’s 2019 DP Conference last week. It’s not impossible, however early engagement and continuous communication with all stakeholders will be essential to the success of the project.

Purser’s presentation at the 2019 DP Conference highlighted some of the decision gates which must be considered for any dynamic positioning notation change. Source: MTS DP Committee 2019 Dynamic Positioning Conference Proceedings.

OneStep Power’s engineering team has experience with acceptance of enhanced notations, and we would be happy to help you assess the suitability of a specific vessel for a retrofit upgrade.

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