Diesel Engine Marine diesel engine is usually operated on heavy fuel oil as well as marine diesel oil. Marine diesel engines operation principles are based on the “Rudolf Diesel’s” principles. It can be divided to two groups base on the cycle of operation: 2-stroke engine and 4 stroke engine. When the piston moves up and down inside a cylinder, pushes the connecting rod or piston Rod which is connected at a crankpin of the crankshaft. The crankshaft is supported by main bearing and coupled with other components. For 2 stroke engine, it develops one power stroke out of every 2 stokes of the piston. Two strokes of the piston complete on one revolution of the crankshaft, i.e. 360 degrees which is considered as one (1) cycle. In a cycle, the 2-strokes marine engine actions follow: (1) Induction – when piston moves downwards, fresh air is drawn into the cylinder and at the same time removing all exhaust gases. (2) Compression/injection – on the upward stroke, compression begins and completed when the position is at the top dead centre (TDC), creating a power stroke and forces transmitted to the crankshaft. For 4 stroke engine, it develops one power stroke out of every 4 strokes; it is the trunk type engine. In a Cycle, the 4-stroke marine diesel engine produces power by following basic operations: 1. Induction – entry of fresh air into the combustion chamber. 2. compression - air in combustion chamber is being compressed. 3. Fuel injection – Fuel is finely atomized and mixed in compressed hot air. 4. Expansion – fuel ignites in the high temperature compressed air mixture which is expanded rapidly. This expansion of the combustion chamber mixture will in turn move the piston downwards. 5. Exhaust – burnt/waste gases from combustion chamber are directed out through valves and replaced by fresh air. Then the new cycle starts. There are two main reference positions of the cycle and they are: (1) Top Dead Centre (T.D.C.) This position is when the crankpin is at the vertically top most position with the piston also at top most position in the cylinder. MAIN ENGINE SAFETY DEVICE 1. Constitution 1) Safety panel : Incorporated in C/R Control console 1 PC. 2) E/S indicator box: Mounted to E/S 2 pc. 2. Function of Safety Panel Constituted compactly with relays, semiconductors, etc. equipped on the printed circuit board, safety panel has the following functions: 1) Automatic emergency shut down In the case where any one of the following factors becomes abnormal (when the contact of sensor closes), the main engine is stopped by self-holding the relay for emergency shut-down after a certain set time (of 4 sec.) and energizing the emergency shut down solenoid valve (SOL-ESVL) and governor shut down solenoid valve (SOL-GSD). a) Main L.O. low pressure b) Camshaft L.O. low pressure c) Thrust pad high temperature It sends the “AUTO. EMERG. SHUT DOWN” contact signal to C/R control console and the individual cause lamp (LED) lights on this safety panel (until the reset). Reset is made by setting the C/R maneuvering handle (or E/S F.O. regulating handle) in the STOP position and pushing the reset push button of C/R control console. 2) Manual emergency shut down Since a manual emergency shut down pull button switch is provided in C/R and E/S, is main engine is stopped by energizing the emergency shut down solenoid valve (SOL-ESVL) and governor shut-down solenoid valve (SOL-GSD) through the pull button operation. It sends the “MANUAL EMERG. SHUT DOWN” contact signal to C/R control console and the “MANUAL EMERG. SHUT DOWN” lamp (LED) lights on this safety panel (until the reset). Reset is made by returning a pull button operated to the former setting and setting a maneuvering handle having the right of maneuvering in the STOP position. 3) Overspeed shut down An independent overspeed protecting system is equipped in this safety panel. Detecting the overspeed of main engine with this overspeed protecting unit at a high sensitivity, it stops the main engine by energizing the emergency shut down solenoid vale (SOL-ESVL) and governor shut down solenoid vale (SOL-GSV) with this signal. It sends the “AUTO EMERG. SHUT DOWN” contact signal to C/R control console and the “OVERSPEED SHUT DOWN” lamp (LED) lights on this safety panel. Reset is made by setting the C/R maneuvering handle (or E/S F.O. regulating handle) in the STOP position and pushing the C/R reset push button. 4) F.O. limit cancel Operating of the “F.O. LIMIT CANCEL” pull button switch equipped on the C/R control console energizing the F.O. limit cancel solenoid vale (SOL-LLC) built in the governor, with in turn moves the scavenging pressure limit line of governor upward. 5) Slow turning (manual operation) Pushing the “SOLW TURNING” push button on C/R control console in case of starting after about 30 minutes of stopping, a little starting air injects the engine and turn it slowly. 6) Passive failure The safety panel monitors the breaking/disconnection and abnormality of automatic emergency shut down line, line of detection, emergency shut down solenoid vale, governor shut down solenoid valve and pick-up for overspeed detection. It sends the “PASSIVE FAILURE” contact signal to the C/R control console and the individual cause lamp (LED) lights on this safety panel. 7) Indication of cam roller position When the telegraph receiver is in the STOP position or when maneuvering of all the cam roller position is in coincident with maneuvering of telegraph receiver, it sends the “CAM AHEND” or “CAM ASTERN” contact signal to the C/R control console as well as lights up an indicator lamp of E/S indicator box. In time of reversing, the external output signal corresponding to the existing maneuvering of telegraph receiver and the indicator lamp flicker. And when all the cam roller position are changed over, the flickering signal becomes a continuous signal, and the indicator lamp also lights up continuously. 8) Wrong way circuit In the case where maneuvering of telegraph receiver is not coincident with M/E revolution direction after entering the F.O. running by C/R control, it supply the “WRONG WAY” contact signal to the C/R control console. 3. Function of E/S Indictor Box Provided with the following devices, the E/S indicator box is to be mounted in front of the E/S control stand: 1) F.O. cam roller AHEAD indicator lamp 2) F.O. cam roller ASTERN indicator lamp 3) Manual emergency shut down pull button switch 4) Lamp test push button 4. Setting valve for R.P.M. comparator unit. For wrong way: 15 rpm For overspeed : 109 rpm (102rpm*1.07=109rpm