Endress+Hauser NXA820 - Page 50

Calculations Tankvision
50 Endress+Hauser
MBR - Data to be measured (1)
For the LPG application the following data should be real-time measured on the tank(s):
•Product level
• Product Temperature (spot or average)
• Vapor Temperature (spot or average)
• Vapor space pressure - also called "Vapor pressure"
Input data
• The liquid density at 15 °C (60 °F) has to be input by the operator. This density can either
be obtained from a pressurized hydrometer and corrected via an appropriate table or
should be established on basis of chemical analysis.
• The method as implemented in Tankvision also allows the operator to enter Observed or
Actual density as a manual value. Tankvision wil then calculate the corresponding
Reference Density.
MBR - VCF Calculation (2)
The following formula shows the calculation method.
L00-NXA82xxx-16-00-00-xx-060
MBR - Observed density (3)
The observed density is calculated using the reference density and the VCF:
• Observed density = Density at 15 °C (60 °F) x VCF
The above equation can not be used to calculate the density under reference conditions
(i.e. 15 °C (60 °F)).
MBR - Calculate GSV (4)
The gross standard volume is calculated using the Total observed volume and the VCF
• G.S.V = T.O.V x VCF
MBR - Calculate Liquid Mass (5)
The liquid mass is calculated out of the gross standard volume and the reference density:
• Liquid Mass = G.S.V. x Density at 15 °C (60 °F)
MBR - Calculate Vapor Volume (6)
The vapor volume is obtained using the total tank volume and the liquid total observed
volume:
• Vapor volume = Total Tank Volume - TOV
X
Y1
Y2
TR
TT
VO
VO
VD
VD
V2
VCF
V1
TR
TT
=
=
=
=
=
=
=
=
=
=
=
=
=
=
(DENL15 - 500) / 25
0.296-0.2395*X+0.2449167*X*X-0.105*X*X*X+0.01658334*X*X*X*X
368.8+4.924927*X+13.66258*X*X-6.375*X*X*X+1.08
7503*X*X*X*X
298.2/Y2
(1-TR)^(1/3)
1-1.52816*TT/1.43907*TT*TT-0.81446*TT*TT*TT/0.190454*TT*TT*TT*TT
1-1.52816*TT/1.43907*TT*TT-0.81446*TT*TT*TT/0.190454*TT*TT*
TT*TT
(-0.296123+0.386914*TR-0.0427258*TR*TR-0.0480645*TR*TR*TR)/(TR-1.00001)
(-0.296123+0.386914*TR-0.0427258*TR*TR-0.0480645*TR*TR*TR)/(TR-1.00001)
V0*(1-Y1*VD)
V1/V2
VO*
(1-Y1*YD)
(TL+273.2)/Y2
(1-TR)^(1/3)