What is the operational principle of the oil mist detector in a two stroke Main Engine?
An oil mist detector in a two stroke M/E is a safety device designed to prevent catastrophic failures. Its basic principle is to detect and alert the presence of oil mist in the crankcase of an engine, which can indicate serious engine problems such as overheating or a bearing failure that could potentially lead to a crankcase explosion if not addressed promptly.
Here’s how it works in simple terms:
Air Sampling: The oil mist detector continually draws in air samples from the crankcase.
Mist Detection: These samples pass through a detection chamber within the device. If there’s oil mist present in the sample, it means that the oil inside the engine is getting heated excessively and vaporizing, which can be a sign of a significant engine problem.
Light Scattering: Inside the detection chamber, there’s a high-intensity light source (like a bulb or an LED) and a photoelectric cell. When the air sample containing oil mist enters the chamber, the oil particles scatter the light.
Signal Generation: The scattered light hits the photoelectric cell, generating an electrical signal proportional to the amount of oil mist present in the sample. The greater the amount of oil mist, the more light is scattered, and thus the stronger the signal.
Alarm Triggering: If the signal surpasses a certain predetermined threshold, it’s taken as an indication of a dangerous level of oil mist, and the detector triggers an alarm. This alarm alerts the ship’s crew, who can then take appropriate action to investigate and resolve the engine issue, preventing potential damage or even a catastrophic explosion