Endress+Hauser NXA820 - Page 47

Tankvision Calculations
Endress+Hauser 47
The stock-tank oil net mass shall be determined as a difference of a stock-tank oil gross mass
and a dead matter mass. The dead matter mass shall be determined as a total mass of water,
salts and mechanical impurities in stock-tank oil. For this purpose the mass fractions of
water, mechanical impurities and chloride salts shall be determined in stock-tank oil and
their masses calculated.
The stock-tank net mass shall be calculated using the formula:
•m = m
total
- m
dead matter
Where:
•m
total
= the stock-tank gross mass, determined as described below
•m
dead matter
= the dead mass, calculated as described below.
Formula Details
This calculation is based on the correction of volume to 20 °C, in the Tankvision system 15 °C
is the default temperature for reference condition – not 20 °C as per requirement for the
GOST R 8.595-2004 standard.
The formula is fixed for 20 °C reference condition, configure VCF to use also 20 °C as
reference.
•m = m
total
- m
dead matter
Where:
•m
total
= (1 / g) × P × V
20
(1 + 2α(T
CT
- 20)) / H
And
•V
20
= TOV
•m
dead matter
= m
Water
- m
FloatingRoof
+ m
Sediment&Water
•m
Water
= FWV × Wat. Density
•m
Sediment&Water
= SW_Volume × S&W% × Ref. Density
•m
FloatingRoof
= FRA × Obs. Density
• g = 9.81 m/sec² (adjustabel system environmet setting)
• P = Product Pressure (P_PRESS)
• α = Temperature expansion factor (Fixed value shall be used: 12.5*10
-6
1/°C)
•V
20
= Gauged Volume corrected to 20 °C (TOV shall be used)
•T
CT
= tank wall temperature (PROD_TEMP Product Temperature shall be used)
• H = Product level (P_LEVEL)
• FRA = Floating Roof Adjustment
• Obs. Density = Observed Density
• TOV = Tank Observed Volume
• VCF = Volume Correction Factor
• FWV = Free Water Volume
• Wat. Density = Density of Water
• NSV = Net Standard Volume
• Ref. Density = Reference Density
• S&W% = Percentage of Sediment and Water
• SW_Volume = the volume used according to the configuration set by the user to define
how to apply the sediment and water effect, according to this setting it could be equal to:
–TOV
–TOV – FWV
– (TOV – FWV)*CtSh, with CtSh is Tank Shell Correction factor
– (TOV – FWV)*CtSh +FRA
– GOV = Gross Observed Volume
–NSV