Function/Parts/overhauling of slide type fuel valve on modern 2 stroke engine in ship

At the time when engine is stopped so from the booster pump 9 bar fuel oil is coming and going out from the recirculation hole

Bụt some time surveyor ask that why to keep the recirculation pressure so high (ike 8-9 bar)so the reason for this is to prevent vapour formation (if we keep on increasing the pressure the temperature at which vapour formation will take place will also increased)

1. During normal running of the engine fuel start coming from the fuel purmp at high

pressure which act on the primary valve and due to this primary valve lifts up against the primary spring and due to its lifting it will close the recirculation hole

2. After the recirculation valve closes there will be the sudden rise in pressure due to

which secondary valve lifts up against the secondary spring and oil finally come to

the injector nozzle hole

3. Primary valve normally lift at 10 bar pressure

4. Secondary valve normally lift at 300 bar pressure against the tension of the

secondary spring

Q- why we are using slide valve type fuel valve now

Ans - Evolution of fuel injection valve design for MAN B&W Dicscl MC two-stroke engines;smoke and NOx emissions were lowered by reducing or eliminating the sac volume.Due to this sac volume continuous dripping of fuel will be there after the effective injection.so due to this black smoke and Nox will be increased and continuous dripping of fuel also the waste of money so that was the reason we are using zero sac volume type of fuel valve

now a days which you can find out in slide valve type of fuel injector as shown below in the diagram

Note - The slide is lubricated by the oil only but at the time of testing the injector on the

testing machine in workshop, we cannot able to provide the enough lubrication to slide valve type of fuel valve so just test once and remove from the testing machine because if you keep on testing then definitely you are going to effect the slide in the injector and again the problem of dripping will start

1. NOW LETS OVERHAUL A FUEL VALVE AND SEE ITS VARIOUS PARTS IN DETAIL