Detecting an oil leak is not the same as detecting a water leak. Unlike water, oil does not conduct electricity so can’t be detected by passing a small current through it and looking for a return signal, as you can with water. There are three main types of systems on the market to detect an oil leak, these being, Optical as manufactured by CMR Electrical Ltd, detection cable and small bund in the floor with a float mounted inside. So, what are the advantages and disadvantages with each type of system.
How do optical sensor work?
The mode of operation is the principle of total internal reflection. An LED and photo-transistor are housed in a plastic (Polysulfone) dome. When no liquid is present, light from the LED is internally reflected from the dome to the photo-transistor. When a liquid covers the dome, the effective refractive index at the dome-oil boundary changes allowing some light from the LED to escape. Thus the amount of light received by the photo-transistor is reduced indicating the presents of oil. CMR Electrical manufacture three type of optical leak sensors, the OSP for internal use ,the OSPW for both internal and external applications and the PPS sensor for tanks and pipes.
Detection cable system
How does the detection cable work?
Within the structure of the cable are two sensor wires, separated by a thin rubber membrane that dissolves when in contact with oil. When the internal membrane dissolves, both sensor wires are able to touch allowing an electrical signal to flow from one sensor wire to the other thereby setting up an alarm.
Hole in the floor and standard float
How does the float work?
Exactly the same has your water tank at home, when the level of oil in hole within the floor reaches a certain level, the floats internal micro switch closes.