The Kappa System Viscosity for Synthetic Oils - Issue 20110714

Vanair Enterprises again wishes to thank Markus Raabe of MESYS in Switzerland (www.mesys.ch) which writes bearing design programs and other machine design programs. He has supplied the missing formulas that allow a user of the Kappa (k) oil film system* to transpose the mineral oil system values to synthetic or other oil film values. 

In order to do this, the following equations were used to generate the end formula >>> 

From ISO 281 – 2007, the following approximate formula was used (the Dawson & Higginson equation for line contact) >>> 

k ≈ Λ^1.3 (1)

Where >>>

k = is the scalar value in the kappa oil film value system.
Λ = is the scalar value in the Lambda oil film value system. 

The following formula establishes the kappa relationship between synthetic and mineral oils >>>

k_syn = k_mineral [α _syn / α _mineral ]^(x)(y) (2)

Where >>>

k_syn = is the synthetic oil scalar value for in the kappa oil film value system.
k_mineral = is the mineral oil scalar value for in the kappa oil film value system.
x = is the exponent for G in the oil film thickness equation and is equal to 0.54.
y = is the exponent of Lambda in k – Λ (1) equation and is equal to 1.3.
α = is the pressure viscosity coefficient for each type of oil.

Therefore, the approximate formula has the final form of >>> 

k_syn = k_mineral [α_syn / α_mineral ]^(0.7) (3) 

(*) For the original natural or mineral oil formulas see Vanair Enterprises’ original TDM on this topic on its website.

A PDF version of this article is available at http://vanairent.com/Kappa-Viscosity-for-Synthetic-Oils-20110706.pdf.