B&W Alpha division of B&W Diesel A/S is a company in the MAN-B&W Diesel group that designs, manufactures, markets, and services complete ship propulsion systems consisting of diesel engines in the power range of 475 to 4,770 bhp. Alpha Diesel has been producing these propulsion packages, which include controllable-pitch propellers, since 1903. Current production is about 180,000 bhp annually, equal to 1,000 cylinders for ship propulsion, mainly to types T/V23L-VO and S/U28L-VO.
The T23L-KVO in-line engine and the V-built V23L-VO have a bore of 225 mm, stroke of 300 mm, and output of 155 bhp per cylinder at 825 rpm. The S28L-VO in-line and U28L-VO Vee engine have a bore of 280 mm, stroke of 320 mm, and output of 265 bhp per cylinder at 775 rpm.
These engines were designed and developed to meet the demand for using lower grade fuels. The initial experience with intermediate fuel was based on B&W service results with the two-stroke, direct-coupled diesel engines for ship propulsion and auxiliary four-stroke engines, of which the first were in service before 1960. Extensive tests have been carried out with different lube oils and fuels of up to 3500 Sec. Redwood.
Since 1974 Alpha Diesel has tested different components to suit the demand for heavy fuel operation. For the past five years it has also followed up on service experience with its parent company B&W Diesel to find the best solution to obtain the highest benefit by using poorer quality fuel.
Today there are about 600 Alpha Diesel 4-stroke engines in service for main propulsion. Of these, some 135 are running on fuel of 250 to 1500 Sec. Redwood with good results.
More than 90 percent of the Alpha propulsion systems have been delivered with controllable-pitch propellers of the company's own design — a rugged construction that features a heavy mechanical linkage that has proved extremely reliable over the past 75 years.