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Marine Diesel Engines (2 - Stroke)

MARINE DIESEL ENGINE STRUCTURE THE BEDPLATE : The Bedplate is the foundation on which the 2 stroke engine is built. It must be rigid enough to support the weight of the rest of the engine, and maintain the crankshaft, which sits in the bearing housings in the transverse girders, in alignment. At the same time it must be flexible enough to hog and sag with the foundation plate to which it is attached and which forms part of the ships structure. If the bedplate was too rigid, then as the hull flexed, the holding down bolts, which secure the engine into the ship would be likely to break, and there would be a danger of the bedplate cracking. Basically the bedplate consists of two longitudinal girders which run the length of the engine. Connecting these longitudinal girders are the transverse girders which are positioned  between each crankshaft throw, and either side of the thrust collar. Built into the transverse girders are the main bearing pockets for the cranksh...
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4 - Stroke Marine Diesel Engine Construction

THE ENGINE FRAME: The engine frame of a modern 4 stroke medium speed diesel can be produced as a single casting or fabricated from cast steel sections and steel plates welded together. With this design, there is no separate bedplate, frame and entablature as with a 2 stroke slow speed engine. The photograph above shows the frame of an engine with the liners and crankshaft in place. An alternative method of construction consists of a separate bedplate, which is bolted to an entablature which holds the underslung crankshaft. When the Crankshaft is underslung, the load on the bearing caps is transferred back to the frame by the use of tie bolts. Note the use of the side tie bolts - which locate the bearing cap, and prevent sideways movement. THE CONNECTING ROD : The connecting rod in a medium speed 4 stroke engine is subject to an inertia whip loading due to the mass of the con rod swinging about the piston pin. (Because of the lower speed of a 2 stroke engine...
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Marine Refrigeration and Air Conditioning

Marine Refrigeration System Vapour Compression System: The vapour compression cycle takes place in a closed system, comprising a compressor, a condenser, a liquid receiver, an evaporator, and a flow control or expansion valve, interconnected by discharge, liquid and suction lines. Principle of refrigeration: 1) Absorption of heat by the evaporation of a liquid refrigerant in the evaporator at a low pressure; 2) Raising the pressure ( to raise the condensing temperature ) of low pressure vapour coming from the evaporator by the compressor; 3) Removal of heat from the high pressure  vapour in the condenser so as to liquefy or condense the vapour; 4) By the use of the throttling device, reducing the pressure of the high pressure liquid ( from the condenser ) to the level of pressure needed in the evaporator. Expansion valve ( flow control ): The liquid refrigerant is stored at high pressure in the receiver. The liquid flows from the receiver through...
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