What is a Hot Spot?
The hot spot is the heat source produced due to the rubbing of metal surfaces such as Piston rod and glands, crosshead guides, Bearings getting overheated due to oil starvation, or excessive blow-by in the crankcase. The hot spot will be termed only if the spot’s temperature is more than the ignition point of the fuel. The hotspot temperature in the crankcase is in the range of 200 to 400 Degrees C.
Hotspots are generally resulted due to poor maintenance and maintaining improper clearances between the moving parts.
When the oil comes in, the contact of hot spots will get converted into vapors. These vapours travelling towards the colder surface will form a white mist. Over a period, the density of this mist will keep on increasing due to repeated contact with the hot spot. The extent of an explosion will depend upon the amount of mist produced.
Causes of Hot Spots
- High temperature is created due to the reciprocating moment of pistons.
- The high temperature of the bearings.
- Heavy blow by in the crankcase from the combustion chamber.
- Fire in the scavenge trunk.
Methods to detect the presence of hot spots
- Abnormal Engine operation with obnoxious noise.
- The alarm on Oil mist detector.
- High Lubricating oil temperature.
- Dense smoke from crankcase breather.
- High exhaust temperature with sudden surging.
