General Form:
Eq. 1
\log{\log{Z}}=A-B\log{T}
Where:
𝑍 = (𝑣+0.7+𝐶−𝐷−𝐹+𝐺−𝐻)
Terms C through H are exponentials on the natural base e.
Eq. 2
Z = \nu + 0.7 + \exp(-1.47 – 1.84\nu – 0.51\nu^2)
Eq. 3
\nu = \left[Z – 0.7\right] – \exp \left(-0.7487 – 3.295\left[Z – 0.7\right] + 0.6119\left[Z – 0.7\right]^2 – 0.3193\left[Z – 0.7\right]^3\right)
Inserting Eq. 2 into Eq. 1 above, will permit solving for the constants A and B for a fluid in which some of the experimental kinematic viscosity data fall below 2.0 mm2/s (cSt). This form can also be used to calculate the temperature associated with a desired kinematic viscosity.
Conversely, the kinematic viscosity associated with a stated temperature can be found from the equation determined as in Eq. 2 by solving for Z in the substituted Eq 1, and then subsequently deriving the kinematic viscosity from the value of Z using Eq. 3.
Crude Oil Form:
\log{\log{(v+0.7)}}=A-B\log{T}
Where:
𝐴 = log(log(𝑣1+0.7))+𝐵log𝑇1
𝐵 = log(log(𝑣1 + 0.7)log(𝑣2 + 0.7) / (logT2/T1))
𝑣1 − Kinematic Viscosity cSt (mm2/s) at 𝑇1
𝑇1 − Absolute Temperature (K)=(℉+273)
𝑣2 − Kinematic Viscosity cSt (mm2/s) at 𝑇2
𝑇2 − Absolute Temperature (K) = (℉+273)
v=10^{(10^{A-B\log{T}})}-0.7
Case Guide
Part 1: Create Case
- Select the ASTM D 341 Viscosity – Temperature Relations for Hydrocarbons application from the PLTB Misc. Module
- To create a new case, click the “Add Case” button
- Enter Case Name, Location, Date and any necessary notes.
- Fill out all required Parameters.
- Make sure the values you are inputting are in the correct units.
- Click the CALCULATE button to overview results.
Input Parameters
- Select Method
- Product Type
- Temperature (℉ ) (Pair 1)
- Viscosity (cSt) (Pair 1)
- Temperature (℉ ) (Pair 2)
- Viscosity (cSt) (Pair 2)

Part 2: Outputs/Reports
- If you need to modify an input parameter, click the CALCULATE button after the change.
- To SAVE, fill out all required case details then click the SAVE button.
- To rename an existing file, click the SAVE As button. Provide all case info then click SAVE.
- To generate a REPORT, click the REPORT button.
- The user may export the Case/Report by clicking the Export to Excel icon.
- To delete a case, click the DELETE icon near the top of the widget.
Results
- Viscosity (cSt)
- Temperature (℉)


References
- Hydraulics for Pipeliners – C.B. Lester
- API standard 2540 Manual of Petroleum Measurement Standards, Chapter 11.1-Volume Correction Factors, Volume X – Background, Development, and Program Documentation.
- API RP 1117 Movement of In-Service Pipeline