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Installation and Configuration Manual 61
Calculated Parameters Modbus Communications
Safety Certification
Factory Default Settings
Appendix B
Calculated Parameters
B.1 Overview
The 7829 Viscomaster
®
/ Viscomaster Dynamic
™
viscosity meter is capable of calculating a number
of parameters based on the measured line dynamic viscosity, density and temperature. From these
results, line kinematic viscosity can be calculated. The Viscomaster (not Viscomaster Dynamic) can
also calculate parameters such as base (referred) kinematic viscosity, CII and CCAI.
B.2 Base density referral
Base density is the density of the fluid at a specified base (or referral) temperature which is different
to the line (i.e., the actual) temperature of the fluid. Base density can be calculated by the API
Referral method.
B.2.1 API density referral
This calculation uses an iterative process to determine the density at the base temperature by applying
temperature and pressure corrections using the API-ASTM-IP petroleum measurement tables.
The information required for the API density is:
• Reference pressure and reference temperature.
• Line pressure: This is not measured by meter, and must be entered as part of the configuration.
• Product type: Refined product, crude product, or user defined.
Density / temperature relationship
Correction factors in the revised API-ASTM-IP petroleum measurement tables are based on the
following correlation equations:
ρt / ρ
15
= exp [-α
15
Δt (1 + 0.8 α
15
Δt)]
where:
• ρt = Density at line temperature t °C
• ρ
15
= Density at base temperature 15 °C.
• Δt = (t - 15) °C
• α
15
= Tangent thermal expansion coefficient per °C at base temperature of 15 °C.
The tangent coefficient differs for each of the major groups of hydrocarbons. It is obtained from the
following relationship:
2
15
1510
15
KK
ρ
ρ+
=α