MAN Engines selective catalytic reduction system successfully tested on pilot boat Luna
Pilot boats are essential for maritime navigation. They transport pilots to their destination in all winds and weathers so that incoming ships can be safely guided into harbour. To perform their duties, the boats must be equipped with powerful and reliable engines. For its latest pilot vessel, the Dutch Pilot Association (DPA) has entrusted this duty to two MAN D2862 LE469 engines. These power units are distinguished not only by their unequalled power/weight ratio, but also by their modular exhaust gas aftertreatment system (EAT) from MAN Engines. This is the first time the selective catalytic reduction (SCR) system, which enables working vessels to satisfy the IMO tier III emission standard, has been tested in the field.
The field test is based at the Port of Rotterdam, where since end of 2017 the Luna has been in operation for Loodswezen, known in English as the Dutch Pilot Association (DPA). This pilot boat is close to 23 metres in length and is driven by two MAN 12-cylinder engines. Tjeerd de Vos, fleet manager for the pilot service, explained: “For environmental reasons and to satisfy the tougher IMO tier III emission standards which come into effect in 2021 we decided to collaborate with MAN Engines and test the EAT system on the twin MAN type D2862 engines in one of our boats.”
Compact selective catalytic reduction system satisfies IMO tier III
An exhaust gas aftertreatment system is installed for each cylinder bank of each engine; this system introduces a metered amount of urea solution (AdBlue©) which reduces nitrogen oxide levels. The 32.5 percent aqueous urea solution is meted via the SCR mixer which is incorporated in the exhaust gas system immediately upstream of the catalytic converter. This generates a homogeneous mixture of AdBlue© fluid and exhaust gas, which in the downstream SCR catalytic converter reacts with the nitrogen oxides (NOx) to form water (H2O) and harmless nitrogen gas (N2).
“Our engineers at MAN Engines have succeeded in developing a modern and compact SCR-only system. We can dispense with bulky and heavy components such as diesel particulate filters and oxidation catalytic converters,” proudly explains Claus Benzler, head of marine sales, MAN Engines. De Vos also appreciates the system’s advantages: “The SCR system is very compact and lightweight, so it is ideal for our boats. A further advantage for us is that both the EAT and the engines come from a common source. That means we have one partner for both systems and an assurance that the systems are perfectly matched to each other.”
It is not just the EAT that is impressively lightweight, but also the two turbocharged engines. These lightweight engines weigh in at just 2,270 kg each. The D2862 offers the best power/weight ratio in its class, delivering 1,029 kW (1,400 hp) at 2,100 rpm. The pilot boats particularly need this power when transferring pilots. The pilot vessel must press itself hard against the hull of the incoming ship so that the pilots can climb aboard using a ladder. Thanks to the wide torque plateau of the MAN 12-cylinder engines the captain can keep the engine speed at its most efficient level without losing thrust. In addition, such a torque plateau permits smooth and powerful acceleration at the lowest specific fuel consumption.
Lightweight and powerful engines equal to any challenge
The light weight brings particular advantages when manoeuvring the pilot boat. “These engines are about 1,000 kilograms lighter than its competitors,” notes Peter Nieuwveld, project manager at MAN Rollo. The long-term agent and importer of MAN engines was responsible for the installation of the engines and is providing support throughout the entire project. But the installation of the selective catalytic reduction system was a step into the unknown. “The SCR system is highly compact. However, the installation was quite a challenge, because at that early stage in the development there was no detailed instruction manual available for such an installation. Together with MAN, we are learning as we go along.” MAN Rollo is available to the DPA at all times as an expert local support partner. The company’s offices in Zoetermeer are just half an hour by car from the Port of Rotterdam.
That is where the Luna is based as one of the DPA’s four pilot vessels. If the weather is too bad for the boats, there is also a helicopter available. “The DPA is a 24/7 organisation which has to provide a high level of service. Safety, availability and reliability are the principal requirements placed on us. The same is true of our boats. The Luna must be ready for service at all times and must operate under difficult conditions, such as a swell with waves up to three metres high,” explains de Vos. The boat’s power unit must measure up to such requirements. “The engines must perform reliably at high power for 3,000 operating hours a year,” he continues. Specifically, that means operation at full power for 50-60% of the duty cycle. The two engines each drive a Waterjet and can accelerate a pilot boat weighing more than 50 metric tonnes to speeds in excess of 30 knots (55.6 km/h).
Successful first year leads to renewal
The field trial was agreed initially for one year with an option for a further twelve months; this option has been taken up. De Vos draws a positive interim conclusion from this: “Overall we are pleased with the performance of the selective catalytic reduction system, as well as with the engines. The crew particularly appreciate the low noise level and smooth running of the engines.”
Benzler also expressed satisfaction with the experience to date: “The AdBlue© fluid needed is about what we had expected. We have reliably satisfied the new limit of 2 g/kWh for nitrogen oxides.” The previous IMO tier II exhaust emissions standard permitted 7.7 g/kW of nitrogen oxide emissions. From 2021, compliance with IMO tier III will be mandatory, requiring around a 70% reduction in nitrogen oxides, depending on the maximum rotational speed of the engine.
Loodswezen has ordered two new pilot vessels to help renew its fleet. The first of these is expected to come into service in 2020 and will also be equipped with the EAT system from MAN Engines.