3 replies to this topic

[contextion]

We are using different viscositys of oil in the manufacturing of engines and need to blend 1 viscosity of - hydraulic oil - that we no longer use into the vicosities we are using. I have the use of a water bath viscometer and some Zahn cups in measuring the viscosity. Instead of doing lots of trial and error to find a relationship of vicosity / Volume %, I first need to know what equation to use so my time is spent wisely. For instance: I need to mix ISO viscosity grade 100 hydraulic oil with 32 to get 46 and 68. Should I start calculating the volume percentages using just viscosity and volume or should any other factors be used like weight? Temperature is being held constant - thank you.

[JMW]

The relationship between viscosity and composition is logarithmic. Small errors can multiply!

I suggest you look for a fuel oil blend calculator. This lets you input the viscosity temp data for each oil and calculate the ratio to produce a target viscosity or the viscosity of a specific ratio.
Try www.Steamesteam.com for a downloadable calculator though you may find Exxon Mobil Marine Fuels, Shell Marine Fuels and DNVPS all do good free programs and will send you a disc. You only need the viscosity relationship from these programs.

Beware the assumptions in these programs so be careful to use the data only for the reference temperature you use.

Now as to how accurate it is... well the relationship may or may not be good, the problem comes from the significance of errors in the oil characterisation data. For example, if you enter the class data for the oil you may be welll out as there is a manufacturing tolerance in the data. You may need to measure the viscosity of each oil pretty accurately before you begin.

[contextion]

Is this something for me to worry about? This was sent to me in some random email I receive.

From "Lubricants and Lubrication"

If possible, different base oils used in industrial gears should not be mixed since it must be expected that the mix will always assume the properties of the inferior product. However, the fact that mixing two base oils leads to unexpected reactions is even more critical. For example, it might happen that mixing mineral oils with polyglycols results in a significant increase in viscosity - as a result of polymerization - which makes it more difficult to pump the mixture through narrow tubes and might lead to the failure of the gears affected due to starved lubrication.

http://www.noria.com...sp?catalogid=56

[Ming Hooi]

I remember there had been a discussion on this topic before. Please see


Blending Operations - Topic Started Oct 22, 2004