Wednesday, May 13, 2020

Oil mist detector

LIGHT SCATTERING METHOD (NEPHELOMETRY)


In this form of crankcase oil mist detector individual sensors are placed at each monitoring point – each crank throw space and chain case (where applicable). A suction fan draws the sample through each detector. Light is transmitted at one end of the head where the sample flows through. Directly opposite the transmitter is a compensating receiver. This adjusts the light intensity by  feeding back a signal to the transmitter. A measurement sensor picks up the scattered light produced by the oil mist particles. The result is transmitted as an analogue signal back to the monitor twice per second. The monitor compares this signal against a set point, and an average of the other readings. When the scattered light picked up by the sensor reaches a pre determined point an alarm condition will be reached.

Advantages claimed for this system are:
    •    Sampling points fitted close to crankcase - no long runs of piping.
    •    Continuous parallel sampling - no high maintenance selector valves.
    •    Fast response time - may save the engine from bearing failure.

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