Why is kerosene floating on the water?

Jet A-1 or kerosene is a mixture of higher-chain hydrocarbons (carbon number C9-C16) and contains more than 500 individual substances. The composition of the kerosene depends on the crude oil, the refining process and the blending of the individual refinery flows. It is a narrow fractionation cut from the middle distillate of a petroleum refinery or is obtained from heavy fuel oil through a cracking process. In addition to antistatic agents, corrosion protection agents, anti-foaming agents, flow agents and anti-silting agents, emulsifiers are also added to the kerosene, which allow a low level of water binding. Water in the tank is completely undesirable in an aircraft, but the formation of water cannot be prevented due to the large surface area of ​​the tank and the resulting condensation. In the case of large helicopters, water measurement in the kerosene is even part of the pre-flight check.

Possible technological approaches to determine the water content

1st possibility: Measurement of the water content with near-infrared spectroscopy

2nd possibility: weakening of the light radiation after crossing the kerosene

3rd option: Determination of the turbidity in accordance with the ISO 7027 standard

Search for the best technical solution and weigh up the advantages and disadvantages

1st possibility:

Near-infrared spectroscopy turned out to be the method with the least chance of success in our test. It turned out that the measurement of dissolved water at approx. 1900nm is not practical. The reference of the measurement showed higher values ​​than the actual measurement signal.

2nd possibility:

The attenuation of the light (the simplest method of measuring turbidity) showed good results and can be used to determine the water content. The disadvantage of this method is that the lack of a reference means that there is no way to compensate for the formation of deposits on the optical windows.

3rd possibility:

The determination of the kerosene turbidity caused by water in accordance with the ISO 7027 standard also gave good results with regard to the correlation between turbidity and water content. The great advantage of this measuring method lies in the automatic compensation of color changes and the formation of deposits on the optical windows. The operation of an inline measurement should be as error-free as possible and without a lot of maintenance.


The kerosene turbidity caused by water in accordance with the ISO 7027 standard is the preferred measurement method for the inline determination of water in kerosene.


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