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Technology and Innovation

Infographic illistrating how some of the technology works on-board the Partnership class vessels

Liquefied Natural Gas (LNG)

BP Shipping’s new Partnership LNG vessels boast the very latest in cutting-edge technology.

 

They are fitted with two,next-generation M-type, electronically-controlled, gas-injection (ME-GI) propulsion systems and a proprietary full reliquefaction system (FRS) designed by the Korean shipbuilders, Daewoo Shipbuilding & Marine Engineering.

 

The ‘slow speed’ tri-fuel engines, each of which has its own shaft, propeller and rudder, use compressed ‘boil-off’ gas from cargo tanks as fuel. The cargo on an LNG vessel will slowly warm up if gas vapour isn’t pulled off the top to keep the remaining liquid cool. It’s a bit like your body sweating and that evaporation keeping you cool. This gas vapour is called boil-off, and it becomes a useable lower carbon commodity to replace fuel oil.

 

Older LNG carriers would use this boil-off gas to power either steam turbine or dual fuel/diesel electric engines. But the Partnership vessels have a five-stage compressor that raises the pressure of the gas from just above atmospheric pressure to 300bar. It is then sent to the engines for fuel – or to the reliquefaction system.

 

When the re-liquefaction plant is in use, up to 70% of the gas discharged from the compressor is cooled to a temperature where it returns to liquid form. This is then pumped back to the cargo tanks, allowing the ships to deliver more LNG to the market.

 

It all adds up to an easy-to-operate system, which burns less cargo gas than its predecessors and improves fuel efficiency by around 25 per cent. It’s not just the engines that contribute to greater efficiency in the new Partnership class LNG tankers. Significant enhancements in hull design improve speed and manoeuvrability.

 

The ships environmental credentials are impressive too. Compared to the older vessels they replaced in the BP fleet, an exhaust gas recirculation system reduces nitrogen oxide emissions and the gas combustion system on board minimizes the potential for releasing methane to the atmosphere.

 

When it comes to waste management on all new build vessels, engine room sludges and waste water are processed to minimize the use of the incinerator and galley waste passes through a macerator and shredder, producing slurry that is retained in a tank until it can be safely discharged.  Dry waste is treated with high-duty shredders, glass crushers and a compactor for baling and landing ashore minimizing ship discharges.

 

Oil 

The British Cumulus sailing at sea

The mewis duct fitted to our new-build oil tankers delivered in 2016-17 reduces fuel consumption. Positioned just in front of the propeller, it straightens and accelerates the hull wake into the propeller, while also producing a net ahead thrust. The accompanying fin system generates a pre-swirl to the ship’s wake, which reduces losses in the propeller slipstream leading to an increase in propeller thrust at a given power. The greater efficiency translates into a saving of around $50,000 per ship per year. As it improves water flow into the propeller, an added advantage is that it reduces vibration
on board. 

 

Exhaust gas scrubbers cut emissions and save fuel costs. Using the natural alkalinity of seawater to remove and neutralise sulphur oxides - proven major cause of air pollution and related health problems - they simultaneously capture the sulphur content of emissions from all on-board combustion sources, including main engines, auxiliary engines and boilers. In doing so they enable ships to continue running on heavy fuel oil rather than the currently twice as expensive marine gas oil, while still comfortably exceeding the requirements of new environmental legislation introduced in 2015 by the International Maritime Organization. Those regulations restrict the maximum sulphur content in fuels to 0.1% while operating in Emission Controlled Areas (ECAs), such as those in Northern Europe, the Baltic, US, Canada and US Caribbean. By removing at least 98% of the sulphur from emissions, Clean and mean the scrubbers actually achieve around 0.03%.

 

The British Nimbus and British Stratus, will emit 25 tonnes less sulphur than others of a comparable size and with each ship consuming around 4,000 tonnes of fuel a year during their estimated 15-year lifetime, and taking into account the average price difference between heavy fuel oil and marine gas oil, it’s estimated that savings of US$4 million could be made per vessel.

 

Most oil tankers are fitted with manifolds on the side of the vessels as they usually dock alongside a terminal for loading and discharging. But stern manifolds allow vessels to dock  ’end on’ which
increases their trading flexibility giving them the capability for transporting distillates to key Turkish ports, where only stern discharging is possible. Three Cloud class vessels delivered between 2016 and 2017 were the first BP-operated vessels in more than 15 years to be fitted with stern manifolds for loading and discharging cargo in this way.

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