DNV launches new class notation for enhanced tailshaft condition monitoring and performance

With its TMON(Oil lubricated, +) notation, DNV becomes the world’s first classification society to provide a qualified notation that adds another dimension to propeller shaft and bearing condition monitoring, according to DNV's release.
 
The new notation serves to further minimize propulsion safety risk and prevent costly equipment failure, building on the benefits of the existing TMON class notation. Current DNV class notations TMON(Oil lubricated) and Shaft align are pre-requisites to meet the requirements for assignment of TMON(Oil lubricated, +).
 
The industry has been through a challenging decade with an increased number of propeller shaft bearing damages and with varying trends. DNV has been simultaneously implementing respective measures to mitigate the challenges. This is one of the latest steps towards enhanced monitoring and control.

In 2018, DNV introduced its Shaft align and Shaft align notations with prescriptive requirements for propeller shaft aft bearing design, installation and monitoring. Shaft align includes alarms for the rate of bearing temperature rise and incomplete propeller immersion, and facilitates enhanced aft bearing performance during normal and extreme turning operating conditions.
 
Many DNV-classed vessels in operation are eligible for the upgraded notation since they already carry the Shaft align and TMON(Oil lubricated) notations. DNV is already in discussion with a number of owners with a view to upgrading their vessels. More ships currently under construction with the above combination of class notations will be considered for the upgrade once they are delivered into the operational phase. The new notation will be offered for new contracts in the new building phase.
 
Sethumadhavan explained that TMON(Oil lubricated, +) is not just another ‘plus’ qualifier, but a monitoring and control dimension on one of most important components safeguarding the propulsion function. Operators have the possibility to achieve enhanced monitoring of their own vessel systems, preserving the lifetime of the asset through picking up early warning signs and preventing issues that can lead to damage.