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First introduced at the turn of the millennium, MAN PrimeServ - MAN Diesel & Turbo’s service division – recently retrofitted its 20,000th slide fuel valve [pictured].

Commenting on the landmark milestone, Christian Ludwig, Head of Retrofit & Upgrade, MAN Diesel & Turbo, said: "Slide fuel valves have proved to be very popular within the marine, two-stroke market. Really, it's a case of having introduced the right technology at the right time and the slide fuel valve's strong market performance is testimony to the fuel savings and increased environmental profile it brings to working vessels. It is important to note that slide fuel valves improve the low-load operating capability of engines."

Slide Fuel Valves

Slide fuel valves come as standard on all new MAN B&W engines, but can also be retrofitted on MC engines. The slide fuel valve eliminates the so-called 'sac volume', which reduces fuel oil consumption and also eliminates dripping from the fuel valve nozzle.

Compared to conventional valves, the slide fuel valve has NOx-reduction potential. The reduced sac volume leads, by nature, to an improved combustion process, resulting in fewer deposits throughout the gas ways and a reduction in overall emissions, such as HC, NOx and particulate matter. Furthermore, visible smoke conditions are said to be greatly reduced as a result of the improved combustion.

Conversely, engines fitted with slide fuel valves have, due to improved low-load performance with regard to soot formation, a significant advantage in an era where 'slow steaming' (sailing at part load) has become the industry norm. This reduces/eliminates the need to run at high revolutions in order to clean exhaust channels.

Retrofitting and benefits

The procedure for replacing standard valves with slide fuel valves is said to be straightforward and can be carried out by ship personnel after instruction or MAN PrimeServ as required.

The benefits of fitting the new valve type are described as follows:

- Improved low-load performance.
- Better combustion process.
- Reduced fouling of gas ways and exhaust-gas boiler.
- Reduced fouling of piston top land.
- No drips – no sac volume.
- Less visible smoke formation.
- Lower HC, NOx and particulate matter emission levels.