MARINE ENGINEERING KNOWLEDGE

Wärtsilä Low-Speed Dual-Fuel Engines (+playlist)

Hot lay-up, Cold lay-up

Hot lay-up
Hot lay-up condition, the machinery is kept in operation for the sake of fast re-commissioning, but measures
may be taken to reduce various operational costs.

Cold lay-up
In cold lay-up condition the machinery is taken out of service and the vessel is kept “electrically dead” with the
exception of emergency power.

Single Phasing of a Motor?

Single Phasing is where one of the 3-phase's supplying the Motor becomes disconnected. The Motor will continue to run if this happens and can result in Motor Burnout. The effect of Single Phasing is to increase the Current in the two remaining Lines and cause the Motor to become very noisy due to uneven Torque produced

How is 15ppm reached in an Oily Water Separator?

15ppm is achieved in an Oily Water Separator by normally passing through a Two Stage Separator where in the first stage Oil/Water is passed into the coarse separating compartment. Here some oil will rise to the top of the Compartment due to its lower density, Heating Coils may aid this.

The remaining Oil/Water will flow down into the Fine separating Compartment and moves slowly between Catch Plates. More Oil will separate out onto the underside of these Plates and travel outwards until free to rise to the oil collecting space.

The almost Oil Free Water (usually being at 100ppm at this stage) will then pass to the second stage of the separator, which is a Filter Unit comprising of two Filter Units.

The first Filter Stage removes Physical Impurities present and promotes some Fine Separation.

The second Stage Filter uses Coalescer Inserts to achieve the fina, Oil/Water Mixture leaving this Stage at less than 15ppm.

Why is Simultaneous Injection of Fuel Oil and Starting Air into a Main Engine Cylinder Undesirable and How is it Prevented?

Simultaneous Injection of Fuel and Starting Air into a Cylinder is Undesirable as it could lead to an Explosion in the Start Air System.

It is prevented by means of Interlock, which prevents Fuel being Injected when the Air Start Auto Valve is Open.

The Interlock Operates a Stop Solenoid, which keeps the Fuel Rack at Zero Position.

What are the Safety Devices fitted to an Air Compressor?

Low Lub Oil Pressure Shut Down

High Air Temperature Shut Down

1st Stage Relief Valve

2nd Stage Relief Valve

A Fusible Plug is fitted after the 2nd Stage Cooler, Set at 120°C

If Water Cooled, a Jacket Water Safety Valve is fitted.