Spirit flow-x, Function Reference

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Flow-X─ Function Reference
4-79
Flow-X General functions - fxAPI_Dens15C_1980
5. The Alpha factor is calculated according from the density at [15

C, equilibrium
pressure] and the K0, K1 and K2 factor. If API2540 rounding is enabled, then the
intermediate results are rounded or truncated as specified API-2540 Table 53.
6. The CTL value is calculated according to API-2540 Table 53 from the Alpha factor
and the differential temperature (= observed temperature – 15°C). If API2540
rounding is enabled, then the intermediate results are rounded or truncated as
specified API-2540 Table 53.
7. Depending on the type of API2540 rounding the calculated CTL value is rounded
to 6 decimal places or not rounded at all.
8. The density at [15

C, equilibrium pressure] is calculated by dividing the observed
density by the new CTL value and the CPL value from the previous iteration.
9. The compressibility factor is calculated according to API MPMS 11.2.1M from the
density at [15

C, equilibrium pressure] and the 'Observed temperature'. If API
11.2.1M rounding is enabled then the density and temperature are rounded and
the calculations are performed in accordance with the rounding and truncating
rules of the standard.
10. The CPL value is calculated from the compressibility factor and the 'Observed
pressure' and 'Equilibrium pressure' input values.
11. The density at [15

C, equilibrium pressure] is calculated by dividing the observed
density by CTL and the new CPL value.
12. If API2540 rounding is enabled then the density at [15

C, equilibrium pressure]
value is rounded to 3 decimal places as specified in the standard.
13. Steps 4 through 12 are repeated taking the density value from step 12 as the
starting value until the absolute difference between two consecutive density
values is either 0.05 (or 0.07 for the transition area) or 0.000001, depending of
API2540 rounding being enabled or not.
14. For refined products the entire iteration loop is repeated if the density at [15

C,
equilibrium pressure] appears to be in a different product region than the
observed input density. This is required because a different product region
means different K0, K1 and K2 factors.
15. When API2540 rounding is enabled, the final density at [15

C, equilibrium
pressure] is rounded to 1 decimal place.
Conversion method 2: from standard to observed conditions.
The function performs straightforward calculations to determine the density at observed conditions:
9. First the inputs are rounded in accordance with the API2540 standard, provided
that API2540 rounding is enabled.
10. When the type of product is set to ‘B – Auto select’ (automatic selection of the
refined product range) the K0, K1 and K2 factors are determined based on the
input density
11. The Alpha factor is calculated according from the input density and the K0, K1
and K2 factor. If API2540 rounding is enabled, then the intermediate results are
rounded or truncated as specified API-2540 Table 54.
12. The CTL value is calculated according to API-2540 Table 54 from the Alpha factor
and the differential temperature (= observed temperature – 15°C If API2540
rounding is enabled, then the intermediate results are rounded or truncated as
specified API-2540 Table 54.
13. Depending on the type of API2540 rounding the calculated CTL value is rounded
to 4 or 5 decimal places or not rounded at all.
14. The compressibility factor is calculated according to API MPMS 11.2.1M from the
input density and temperature'. If API 11.2.1M rounding is enabled then the
input density and temperature are rounded and the calculations are performed
in accordance with the rounding and truncating rules of the standard.