New DNV GL class notation to boost LPG as marine fuel

New DNV GL class notation to boost LPG as marine fuel
In 2019, BW LPG announced plans to retrofit several vessels with LPG-propelled dual-fuel engines. Image courtesy of BW LPG

Classification society DNV GL has developed new class rules and a class notation “Gas Fuelled LPG” for using liquefied petroleum gas (LPG) as fuel in anticipation of growing industry interest.

The announcement was made at Marintec China trade fair held in Shanghai this week. DNV GL recognised that there is a growing demand for alternative fuels to meet IMO regulations and reduce shipping’s impact on the environment, but with the exception of LNG, international regulations for such fuels are absent.

Except for liquefied natural gas (LNG), currently all gases and low-flashpoint fuels are subject to the ‘alternative design approach’, which means that they may be used if their safety, reliability and dependability of the systems can be shown to be equivalent to those achieved by new and comparable conventionally fuelled main and auxiliary machinery. This can be a time-consuming and costly process and may impede the uptake and expansion of lower emission alternative fuels.

“With the new rules and class notation, we want to offer owners interested in LPG a straightforward path towards compliance with the alternative design approach mandated by the IGF Code,” said Geir Dugstad, director of ship classification & technical director at DNV GL – Maritime. “As the fuel environment within the maritime industry becomes more diverse, it is essential that we continue to broaden the enabling rules and regulation to support these new choices.”

The rules and notation are based on DNV GL’s rules for ships using LNG as fuel but account for the differences in properties and phases between LPG and LNG. The “Gas fuelled LPG” notation covers internal combustion engines, boilers and gas turbines for both gas-only and dual-fuel operations. It also includes requirements for the ship’s fuel supply, considering all aspects of the installation from the bunkering connection up to and including the LPG consumers (main and auxiliary engines, boilers, etc.).

LPG as a fuel can lower a vessel’s emissions to air, both in terms of greenhouse gases and other pollutants. It virtually eliminates sulphur emissions and reduces GHG output by approximately 17 per cent compared to burning HFO or MGO. LPG could also act as a bridging fuel to ammonia, as the materials used for LPG tanks and systems is, in most cases, suitable for ammonia. With advanced planning, the adjustments needed for a switch to ammonia from LPG could also be minimised.