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Showing posts from March, 2023

Secondary Injection in fuel pump and fuel valve

Reopening of the fuel valve after the main injection id terminated is secondary injection . The sudden closing of the injector needle cause a pressure wave to be setup which reflects from the delivery valve back to the injector needle . If the residual pressure and reflected pressure together exceeds the injector lifting pressure , secondary injection takes place.

Why con rods are I sections ?

Con rods during operation are subjected to buckling loads Buckling strength is directly proportional to moment of inertia. So , I section is having maximum area moment and least weight. Hence introduce the vibration of conrod and also reduce side thrust acting on the cylinder. I section can be easily manufactured

Shroud Ring

Shroud ring is a component in turbocharger which forms a part of the inner exhaust gas casing adjacent to the turbine The area around the turbine is always in contact with highly corrosive exhaust gas. If no shroud ring is fitted , the turbine inner casing will be slowly wasted and complete housing to be renewed for repair . Otherwise only shroud ring can be replaced with new one

How piston rings are manufactured ?

Manufactured using Pot casting method , producing a short cylinder of oval cross- section from which the rings are machined in a cam turning lathe. This produces a balanced and homogenous casting around the entire circumference of the ring. The lathe is equipped with an interchangeable copying cam , which controls the cutting tool By changing the shape or ovality of the cam , the circumferential pressure distribution at the ring can be altered

Why air compressor valves are concentric ?

They have a low inertia of moving parts and good flow characteristics. It is highly efficient at higher rotational speed. Concentric valve is compact and a combination of suction and discharge valve , which make it compact and space saving with the lowest possible clearance volume. Plate type suction and discharge valve , whose larger diameter and small lift after the least resistance to the flow of gases

Fire in drydock

The possibility of fire aboard the ship or elsewhere within the dockyard complex is always unwelcome, but the fact remains it is a possibility at virtually any time of day or night. In the event that the possibility becomes reality, common sense and past training should automatically come into the equation.  As with any other fire incident the alarm should be raised as soon as possible after the discovery of the fire and the following procedure is suggested. Assuming that the crew have remained on board and the fire is on board the vessel, after the alarm has been raised:  Muster an emergency fire party and attempt to contain and extinguish the fire immediately following its discovery. Non-essential personnel should be evacuated to the shore and the fire brigade should be contacted. A gangway watch should be set to ensure that the access to the vessel is not blocked which as such would deny accessibility to fire fighters. The minimum water volume should be used when tackling fires in d

VEC and VEO of sulzer RT Flex engine

  VEC (Variable Exhaust - valve Closing ): Adopting compression pressure to keep the firing ration (Pmax / Pcomp) within permitted range during injection. VEO ( Variable Exhaust - valve Opening ): Keeps the exhaust gas pressure blowback constant by earlier valve opening at higher speed for fuel economy and less deposit at piston underside

Advantages of Electronic Oil Record Book ( e ORB )


Matching of Turbocharger

It involves matching of reciprocating engine to rotary compressor and turbine of Turbocharger. Impellor of compressor is chosen to provide desired airflow at engine power 80 - 90% MCR , thus taking into ( a ) Operating temperature and Engine room pressure ( b ) Pressure drop across air cooler. Once impellor output is fixed , diffuser is chosen which will provide compressor efficiency high , but ample surge margin. When compressor side design is final , turbine power requirements are known. The main variable on the  turbine side is nozzle size and this is matched to provide required compressor work and minimum restriction to exhaust gas flow. Smaller nozzle area: ( a )Work output increase   ( b ) T\C speed increase ( c ) Air delivery pressure increase

Why check bumping clearance in Main Air Compressor but not in Aux Engines

 In air compressors requirement is to discharge the maximum amount of compressed volume of air out of 1st stage cylinder so that maximum cool fresh air should come in. If the bumping clearance is more then air left inside stage will be more and at higher temperature after discharge so less mass of air will get inside in the suction stroke now due to this there will be increased suction temperature of air and consequently less work done and reduced efficiency of air compressor. Where as in Aux Engine we need maximum air to remain in cylinder head at TDC for better and efficient combustion of the fuel . Thats why enough clearance is provided between piston top and underneath of cylinder head . No danger of contacting or banging of piston to cylinderhead.

Anemometer / Wind vane

A wind vane is an instrument that measures wind direction while anemometer measures wind speed.   PRINCIPLES OF WIND VANE AND ANEMOMETER The measuring principle of anemometer is simple: the stronger the wind blows, the faster the half-open plastic cups turn. The speed of the cross rotation determines the wind speed. The cup anemometer records the number of rotations per minute and thus the wind speed very accurately. Information obtain by wind vane and anemometer are converted and can be read directly form ship’s bridge.   HOW THE DATA IS CONVERTED                                                     Information generated by wind vane and anemometer are converted and can be read directly form ship’s bridge. Through advance technology, wind speed and direction can be seen directly through a display unit in the ship’s bridge and no need for manual calculation.

Torsional vibration damper .Diagram


Sulzer Reversing servo motor mechanism . Diagram