AIDAprima cruise ships count on KSPG large pistons

Jumbo pistons from Neckarsulm are popular with makers of heavy four-stroke engines

Pistons in car engines weigh on average 200 grams. By contrast, KSPG’s jumbo variants weigh in at half a tonne or more. These large pistons, intended exclusively for four-stroke engines, are used primarily in ships, power plants and locomotives.

“The latest example of a maritime application is the AIDAprima”, declares Wolfgang Hartmann, 59, head of KSPG’s Large Pistons unit, noting that “this is the first cruise ship anywhere that features an environmentally friendly dual-fuel engine which, along with the ship’s three diesel generators, is equipped with our pistons”.

In October 2015, the new flagship of Rostocker Reederei Aida Cruises will set out on its maiden voyage from Yokohama to Dubai. On board the 300-metre-long luxury liner will be more than 3,000 passengers enjoying the trip of a lifetime. More than a floating resort, however, the ship also sets new standards for environmental friendliness. Contributing to this is the newly developed dual fuel engine that can be used to power the AIDAprima in port, using either conventional fuel or liquefied petroleum gas (LPG), which produces virtually no emissions.

When diesel is used, the pistons are subject to high temperatures of up to 500° C. Conversely, anti-knock resistance is the most important characteristic during gas operation. As Hartmann explains, “knocking results from uncontrolled firing, which can’t always be avoided completely, since the engines are always kept running as close to their performance limit as possible.”

The pistons consist of two parts connected by four space bolts. The upper part is made of forged steel, the lower part of spheroidal graphite iron. “This way, the pistons can handle high temperatures as well as high firing pressures,” declares Hartmann. The pistons for the three diesel generators have a diameter of 430 millimetres and weigh 219 kilos. The diameter of the pistons for the dual-fuel engine is thirty millimetres larger. “Otherwise the engine wouldn’t achieve the same output during gas operation as the diesel generators do.”

The four drives, which have a combined output of 48,000 kilowatts (approx. 65,000 HP), come from a Caterpillar subsidiary in Kiel. “In the western world today, there are only five makers of heavy engines: Wärtsilä, Rolls Royce and MAN in Europe, and the two American companies Caterpillar and General Electric”, notes Hartmann. KSPG supplies all of them, and is far and away the top supplier for three.

A centrepiece of the Large Pistons unit’s strategy is its new plant in Kunshan, a suburb of Shanghai. KSPG’s customers are increasingly building engines in China, and expect their suppliers to follow suit. The investment is already paying off: “We’ve already booked ten projects that we probably wouldn’t have otherwise”, says Hartmann.

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