Difference between MC and MC-C Engines of MAN B&W
The last ‘C’ in MC-C stands for ‘COMPACT’. So all the improvements in the new design are targeted to achieve reduction in weight and cost of the engine, at the same time improving or maintaining the overall efficiency. Major design improvements of MC-C engines over MC engines are the following:
- Increased power to weight ratio.
- Increased mean effective pressure for same bore engines at same speed.
- All large diameter bearings are made of thin-walled bearings.
- A simple cross head pin structure with reduced size and weight.
- The introduction of reduced diameter twin tie bolts.
- Bottom end of the tie rods threaded to the transverse girder of bed plate and hence reduction in material.
- Reduced edge pressure of the main bearing.
- Simplified main bearing casting.
- High piston top land. It ensures the top piston ring is not exposed to high combustion chamber temperatures. Along with high top land, CPR (controlled pressure relief) piston rings are used to reduce the pressure drop across the ring and hence prevention of piston ring collapse.
- Reduced height of the cylinder block and the cylinder cam box.
- Due to the reduced mass of the moving parts the second-order moment decreased by about 8%, improving the vibration condition.
- A simplified frame structure makes it easier to weld.
- Holding down bolts in a sunken structure to make compact design.
Difference between MC and MC-C Engines of MAN B&W