# 6 Oil Viscosity Cutting vs Flash

[brochon]

To control our # 6 oil viscosity, we can cut with the following cutterstocks,

crude unit diesel flash ~ 180 °F
merox kerosene flash ~ 160 °F
distillate hydrotreater diesel flash ~ 180 °F
visbreaker gas oil flash ~ 190 °F

At times, usually when we're cutting with a lot of kerosene, the #6 oil flash will be < 150 °F.

How can this be, when the individual component flash points are > 150 °F? Are there any guidelines or mixing rules that apply? Or is there some other phenomenon going on here?

Thx Brian

 

[25362]

It is strange, normally the fuel blends' FP you mention are never lower than the lowest FP of any of the components. Assuming you're using the ASTM D93/IP34 tester, contaminations would explain such an abnormal behaviour. I don't know the repeatability or reproducibility levels of these tests, but it would be worthy to have a look at the ASTM books on this subject.

Representative sampling -of the components and the blends- seems to play a role. For example, if the components have a &quot;range&quot; of FP, due to layering of some sort or unsuccesful mixing, or to changes in processing. Low sulphur diesels can go as low as 125^oF, and aviation kerosines &quot;minimum&quot; specs call for 100^oF.


Keep us posted on any discovery, for us to learn from your experience.