We enter pressure values for gas calculations. Are these values absolute or gauge pressure values?
QuantityWare BCS implementations for LPG/NGL, LNG and natural gas support both the data entry of absolute or gauge pressure values. Crude oil and products CPL calculations do require entry of gauge pressure values.
The conversion group configuration for LPG/NGL, LNG , natural gas, crude oil and products can thus be made to support entry of either gauge or absolute pressure values – by adding or removing dedicated MQCI pressure calculation functions to the conversion group function module sequence.
If you execute the Conversion Group Check, a message is issued that informs if pressure values (input data) are considered as absolute or gauge values.
Example 1: Template Conversion Group Q741:
Example 2: Template Conversion Group Q154:
If function /QTYW/MQCI_BCP_ABS_PRESS_CALC or /QTYW/MQCI_BCG_CALC_ABS_PR_LPG is assigned to your NGL/LPG conversion group (e.g. Q731): All observed pressure values are considered as gauge values and are converted to absolute values utilizing the base pressure defined in the conversion group. However, if you enter a pressure value with the UoM defined as base pressure UoM, that value is interpreted as absolute value. Also, depending on the FM type setting of the function, a gauge pressure entry in e.g bar is converted to the absolute pressure value in kpa and is displayed as such in the QCI dialog subscreen.
If you do not require this logic, assign function /QTYW/MQCI_BCP_ABS_PRESS_CALC2 or /QTYW/MQCI_BCG_CALC_ABS_PR_LP2 to your NGL/LPG conversion group (e.g. Q72A), such that all pressure values you enter, also those with the UoM defined as base pressure UoM, are considered as gauge pressure values.
For crude oil and products, you may assign either /QTYW/MQCI_BCP_GAUGE_PR_PROD or /QTYW/MQCI_BCP_GAUGE_PR_PROD2 to your MQCI conversion groups, which convert absolute pressure values to gauge values, with the difference in calculation logic as described above.
For LNG and natural gas, you may assign either /QTYW/MQCI_BCG_CALC_ABS_PRESS or /QTYW/MQCI_BCG_CALC_ABS_PRESS2 to your MQCI conversion groups, which convert gauge pressure values to absolute pressure values, again with the difference in calculation logic described above.
IMPORTANT: The FM Type of all pressure conversion functions needs to be set to 9 or 7 for the exception logic functions, and to 7 for the standard logic functions.
Read Note 000078 for additional details.
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