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  6. ASTM D 341 Viscosity – Temperature Relations for Hydrocarbons

ASTM D 341 Viscosity – Temperature Relations for Hydrocarbons

Contents

General Form:

Eq. 1

\log{\log{Z}}=A-B\log{T}

log⁡log⁡Z=A−Blog⁡T\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)

Z=ν+0.7+exp⁡(−1.47−1.84ν−0.51ν2)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)

ν=[Z−0.7]−exp⁡(−0.7487−3.295[Z−0.7]+0.6119[Z−0.7]2−0.3193[Z−0.7]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}

log⁡log⁡(v+0.7)=A−Blog⁡T\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

v=10(10A−Blog⁡T)−0.7v=10^{(10^{A-B\log{T}})}-0.7

Case Guide

Part 1: Create Case

  1. Select the ASTM D 341 Viscosity – Temperature Relations for Hydrocarbons application from the PLTB Misc. Module
  2. To create a new case, click the “Add Case” button
  3. Enter Case Name, Location, Date and any necessary notes.
  4. Fill out all required Parameters.
  5. Make sure the values you are inputting are in the correct units.
  6. 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

  1. If you need to modify an input parameter, click the CALCULATE button after the change.
  2. To SAVE, fill out all required case details then click the SAVE button.
  3. To rename an existing file, click the SAVE As button. Provide all case info then click SAVE.
  4. To generate a REPORT, click the REPORT button.
  5. The user may export the Case/Report by clicking the Export to Excel icon.
  6. 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
Updated on January 4, 2024
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