Marine solutions

*Circuit breakers. *Fuses *Over current relay *Dead front panel *Rubber insulation mat *Insulation resistance *Reverse power trip *Ebonite Handel *Earth fault lamp *Under voltage trip *Over voltage trip *Preferential trip

Hot corrosion             It is basically vandium corrosion. Vanadium is present in fuel oil,when vandium and sodium is present in a ratio of 1:3 vanadium pentoxide a hard component is formed whose melting point is 630°. Due to high temperature in combustion chamber these melts into metal surface and leaving the surface exposed to corrosion is called as hot corrosion. Cold corrosion           Cold corrosion occur due to presence of sulphuric acid inside liner surface. This abnormal corrosion can cause wear and tear inside liner. This occurs due to new regulations that engine should be operated at high pressure and low temperature. This temperature below due point will result in deposit of water droplets inside liner surfaces and this water combine with sulphur in fuel to form sulphuric acid.

Main bearing           It is measured between journal pin and top shell when the piston is at any convenient position. Crosshead bearing           It is measured between top shell and crosshead pin, piston should be at 45° aftrr TDC. GUIDESHOE CLEARANCE             Measured between GUIDESHOE and guide bar. Bottom end bearing             Measured between bottom shell and con rod. Piston should be at BDC.     NOTE ALL CLEARANCE SHOULD BE BETWEEN 0.25-0.4MM

In B&W engine,there is a measured set of channels in the lower shell of crosshead bearing, through which lub oil can supply. The geometry is such that loaded area of pin are flushed with cooling oil twice during every engine cycle.           In sulzer a separate pump is provided to supply crosshead lub oil at a pressure of 12 bar.

Thrust blocks : The main thrust block transfers forward or astern propeller thrust to the hull and limits axial movement of the shaft. Some axial clearance is essential to allow formation of an oil film in the wedge shape between the collar and the thrust pads (Figure 8.6). This clearance is also needed to allow for expansion as parts warm up to operating temperature. The actual clearance required, depends on dimensions of pads, speed, thrust load and the type of oil employed. High bearing temperature, power loss and failure can result if axial clearance is too small. A larger than necessary clearance will not cause harm to the thrust bearing pads, but axial movement of the shaft must be limited for the protection of main machinery. The accepted method of checking thrust clearance, involves jacking the shaft axially to the end of its travel in one direction and then back to the limit of travel in the other. Total movement of the thrust shaft (about 1 mm being typical) is registere

NPSH NPSH is the difference between pressure at the suction of the pump and vapour pressure of the liquid. It is very important to avoid cavitation in centrifugal pumps. NPSH=PRESSURE AT SUCTION INLET-                         VAPOUR PRESSURE OF LIQUID Available NPSH - NPSH a  or NPSHA The Net Positive Suction Head available from the application to the suction side of a pump is often named NPSH a . The NPSH a   can be estimated during the design and the construction of the system, or determined experimentally by testing the actual physical system. Required NPSH - NPSH r  or NPSHR The NPSH r , called as the Net Suction Head as required by the pump in order to prevent cavitation for safe and reliable operation of the pump. The required NPSH r  for a particular pump is in general determined experimentally by the  pump manufacturer  and a part of the documentation of the pump.                      The available NPSH a  of the system should always exceeded the required N

Causes of Crankcase Explosion As we all know, for a fire or explosion to take place, there are three basic elements that are required to complete the fire triangle. These three components are – heat/energy, oxygen and fuel. In the presence of all these three elements, in proportional ratio and within the flammable limits, the reaction which causes fire or explosion becomes cyclic. In the crankcase of the main engine, the oil particles are churned into small particles of up to 200 micro meters in diameter. These small particles cannot ignite readily even with some naked flame. If a hot spot comes in contact with these small particles, it reduces the size of these particles, resulting in the formation of mist, which can be readily ignited with a hot spot. In the crankcase of the main engine all the three elements required for fire are available. Lubricating oil as the fuel source is sufficiently present, the air as one of the three things necessary is also present and the heat or