When DNV GL introduced the BMON class notation in 2012, it aimed to improve boilers' performance. It also wanted to establish an efficient and flexible survey approach. With this notation, operators are able to reduce vessels’ downtime in port, while also maintaining their boilers optimally.


Since the launch of the notation, over 150 vessels have been granted it. It is interesting that DNV GL reported zero findings regarding boiler condition in service.

Analyzing its findings, DNV GL noted the following:

Better focus on water treatment

By using prescriptive methods to achieve a passive magnetite layer on steel surfaces, as well as by enhancing the frequency of monitoring the water condition, the risk of corrosion is reduced. Furthermore, if the heat transfer surfaces are in their best condition, the heat transfer barriers are reduced as well. This improves the fuel efficiency.

Maintenance of the boiler plant

By focusing on maintenance, the danger of a defect is limited.

Improvement of feed water system design

By improving the feed water system design, the hazard of water side contamination is minimal.

Flexible class survey

Ships that use the BMON class notation carry out an improved approach on managing the boiler condition. A part of the scope can then be credited according to the chief engineer’s inspection report. This is documented for review and final acceptance.

This could lead to better flexibility regarding the location and the time of internal inspections. The remaining scope of the survey must still be conducted by a DNV GL surveyor. Then, the survey will be officially credited.

Based on these findings, DNV GL suggested operators to reduce common boiler problems, by focusing on boiler water condition management and monitoring.

Experience demonstrates that the BMON class notation leads to better boiler performance, with an accompanying benefit of flexibility of the intermediate boiler survey

DNV GL concluded.