Marine engines DI09, DI13, DI16
The type of engine suspension that is appropriate varies for different engine installations. In general, the following applies:
- The engine suspension should be designed for the forces it is exposed to, both continuously and momentarily during operation. Such forces are reaction forces from the transmitted torque and in some cases longitudinal acceleration, retardation and reaction forces in the engine.
- For engines with marine transmission, Scania recommends a 6-point suspension or common rear suspension for pipes, transmission and engine.
- Both the engine suspension and the engine bed should be designed so that there are no resonant oscillations within the engine speed range. They should also be designed so that annoying vibrations from the engine are not transmitted to the surroundings.
- The engine suspension and engine bed should be designed in a manner which allows access for maintenance and repair work.
- The engine bed location and the engine suspension must be designed so that the permissible angles of inclination for the engine are not exceeded. See the table Permissible installation and operating angles.
Marine engines DI09, DI13, DI16 Flexible engine suspension
Flexible engine suspension dampens vibrations more effectively than rigid engine suspension. It prevents extreme movement between engine and engine bed during violent ship movement. Flexible engine suspension can also absorb some level of reaction force from the propeller. Flexible engine suspension does not require such careful alignment of the engine as rigid engine suspension. However, flexible engine suspension does not absorb longitudinal and lateral forces in the engine to the same extent as rigid engine suspension, scania trucks,trucks scania,scania trucking,scania cars,scania car,scania truck usa.
Rigid engine suspension
A rigid engine suspension can absorb greater forces in all directions than flexible engine suspension. It requires highly accurate alignment of the engine in relation to the driven unit. On the other hand, it requires no special flexibility in the hoses, pipes and controls connected to the engine.
A rigid engine suspension can be used in engine installations where vibration causes no significant problems and where other characteristics make it desirable. Even with a rigid engine suspension, the transmission of vibration to the engine bed can be kept low if the masses of the engine bed and connected parts are large in relation to the mass of the engine. It is also possible to construct flexible engine suspension between the frame and the engine bed to reduce the transmission of vibration to the engine bed.
Scania Permissible installation and operating angles
Maximum permissible installation angle means maximum permissible installation angle for an engine relative to the horizontal plane. The angle indicates the limit for engine inclination during continuous operation. Maximum operating angle means maximum permissible angle of inclination for an engine in operation and with minimum oil level. The angle may only be used for short periods. The maximum forward or rearward operating angles are not applicable to their full extent if the engine is inclined laterally at the same time.
Flywheel housings
Silumin housings are supplied as standard on most marine engines, except on certain 16 litre engines. The maximum permissible bending torque for a silumin housing is 10,000 Nm. This presumes that there are no axial loads from, for example, the propeller shaft, abnormal G forces or vibration.
However, nodular iron flywheel housing can also be chosen. Nodular iron housings can dampen vibrations at certain engine speeds but increase vibrations at other engine speeds. Nodular iron is stronger than silumin and can therefore tolerate greater bending and torsional forces. Certain 16 litre engines have nodular iron casing as standard.
The stronger nodular iron housings are recommended in installations where the flywheel housing is exposed to serious stress, e.g. with high reverse gear ratios and when heavy components without support are attached to the rear of the engine (e.g.hydraulic pump). Nodular iron housings are also recommended for generator sets with high outputs. The propeller installation without separate thrust bearing can be approved if the following requirements are met:
- Max. pressure load from the propeller must not exceed 40,000 N.
- Reverse gear ratio must not exceed 2:1.
- The suspension must be on the front engine bracket and the common bracket for the rear edge of the engine and the reverse gear.
- The displacement between the input and output shaft of the reverse gear must not exceed 250 mm.
- Most of the propeller force must be taken up by the rear suspension.
- The support points of the brackets must be aligned with the propeller shaft as much as possible.
Scania Marine engines DI09, DI13, DI16 Engine alignment
The alignment of the engine in relation to the driven unit is very important in order to prevent malfunctions. Otherwise there is a risk of vibration and serious stress to the crankshaft, engine brackets, drive shaft and coupling, causing damage which is costly to repair. For propeller installations, a first alignment is made before the ship is launched. Alignment must then be checked after the ship is launched and has been placed under load. The ship should also be laden and equipped with filled tanks. Since there can be some settling in the hull after the first hours of operation, further checks on the alignment should be made after a period in service.
Alignment should be checked regularly on certain vibration-sensitive engine installations. If flexible engine suspension is part of the system, this should be placed under load before alignment. Otherwise, it will quickly settle by several millimeters. Poor alignment between engine and propeller shaft can cause damaging vibration in the hull, damage to the reverse gear and accelerated wear of the shaft and propeller bearings.
Flexible coupling
The alignment requirements are reduced if a flexible coupling is installed between the engine and the driven unit. Refer to the data on the flexible coupling concerned for permissible deviations.
Flexible coupling allows a certain angular displacement towards the output shaft. It also has an effect of evening out irregularities in torque and therefore counteracts the tendency towards torsional oscillation. The correct choice of rubber hardness reduces the stress on the driven units.
Relatively large deviations are permissible with flexible couplings. However, alignment should be as accurate as possible to achieve low vibration and a long service life on the coupling.
Connection of sensors for external monitoring systems
External monitoring systems for classed engines require in some cases that extra sensors are connected so that the following operating conditions can be monitored:
- coolant pressure
- coolant temperature
- oil pressure
- oil temperature
- fuel pressure
- engine speed
- charge air pressure (DI16 only)
- charge air temperature (DI16 only)
The following pages show suitable positions for installing such sensors. Scania offer a classified electrical system for monitoring of coolant pressure, coolant temperature, oil pressure, fuel pressure and engine speed. How to connect the Scania monitoring system is described in the installation manual 03:03 – Instrumentation 2.0.