MAN B&W Auxiliary Propulsion System. Alpha Clutcher characteristics
The MAN B&W AP System is based on the “Power Take-in” principle including the Alpha Clutcher, for the clutching out the main engine from the propeller shaft in PTI-mode.
The prototype of the Alpha Clutcher was produced in the spring of ’99. The clutch function is controlled by hydraulic oil added through an oil distributor ring similar to that of the CP Propellers.
No foundation required
The propeller shaft is connected to an intermediate shaft passing through the tunnel gear. The alpha clutcher is installed on this intermediate shaft.
A short intermediate shaft is installed between the clutcher and the main engine. The tunnel gear is connected to the clutcher via a flexible coupling. A single bearing supports the shaftline and the tunnel gear has a normal foundation seating in the ship.
The Alpha Clutcher has internal bearings and does therefore not need an expensive thrust transmitting foundation.
The cone bolt connection instead of gearwheels is chosen in order to avoid clearance problems and hence hammering in-between the load transmitting surfaces. It may be critical to use gearwheels in the shaftline of a two-stroke engine because of torsional vibrations.
The principle consist of two radially split shaft flanges with a number of cone holes, a part of each in the inner flange. When the cones are pressed into the holes, the flanges are locked together. When the cones are out of the holes, the flanges are free of rotate independently of each other.
Perfect fit connection
To align the two flange parts for a perfect fit between the cone holes and the cones, a ring is pressed against the flanges opposite the cones. This ring is controlled by studs and tightened by nuts on these to the backside of the cones. Tension in the studs presses the cones into the cone holes and ensures alignment of the flanges. This ensures a perfect fit connection, which prevents hammering in-between the connection surfaces like an ordinary fitted bolt.
When the nuts are loosened, the cones and the ring are free to move and the flanges are free to rotate because the studs are placed outside the split diameter.
In Alpha Clutcher the stay bolts do not pass inside the cones, but in-between them. The cones and the studs are moved by servo pistons to enable hydraulic remote control.
Patented locking principle
Instead of tightening a nut on each stud, a locking ring locks all cone bolts at one time. When hydraulic pressure is added, the studs are stretched and the ring is turned into locked position. The pressure is then released and the cone bolts are mechanically locked. To unlock the cone bolt connection, ‘Clutch-in pressure’ has to be added to be able to turn the locking ring, and after this pressure is added for clutching out.