UN-305: Wet Gas Orifice(Calc Dens, Calc Std Dens, Calc CV)
Description
Calculates the uncertainty in the corrected gas mass flowrate from an orifice plate encountering a wet gas flow using the wet gas correction described in ISO TR 12748. Mass uncertainty is based on “dry gas” uncertainty (as per Module 301) in addition to wet gas parameters and their uncertainties. Standard density and energy flowrate uncertainties are also estimated from this corrected gas mass flowrate. Pressure, temperature and differential pressure uncertainties are determined using the technical specification for the transmitters selected from the integrated transmitter selection tool.
General
The General tab is used to enter information, which is saved along with the uncertainty calculation and included in reports which are generated.
The tabs used for inputting data and calculating the uncertainty in the individual components of the uncertainty can be seen along the top of the module window.
The report tab is only visible once the calculation has been run and will not be visible if any parameters are changed until the calculation has been run once more.
Options
The options section controls how the calculation is performed and dictates which inputs are required.
DP transmitters
This option is used to select the number of differential pressure transmitters which are used in parallel. If two transmitters are selected an additional Differential Pressure will be displayed so that information can be entered on both high and low transmitters. If three DP transmitters are selected a third Differential Pressure tab will be included for the mid transmitter.
Pressure units
This section gives the option of entering the pressure as either an absolute value or as a gauge value with reference to atmospheric (barometric) pressure. If Absolute is selected inputs are required for Absolute pressure and Atmospheric pressure and if Gauge is selected inputs are required for Gauge pressure and Atmospheric pressure. This ensures that whichever is chosen both the gauge and Absolute pressure value is available to other sections of the module.
Note: Gauge pressure is equal to the Absolute pressure – the Atmospheric pressure.
Inputs
Pressure
This is the line pressure of the stream measured upstream of the orifice plate. As described above, if Absolute is selected inputs are required for Absolute and Atmospheric pressure and if Gauge is selected inputs are required for Gauge and Atmospheric pressure.
Differential Pressure
This is the differential pressure measured across the orifice plate. If multiple transmitters are used the appropriate transmitter will be selected based on the transmitter ranges and the DP transmitter switch point.
DP Transmitter Switch Point
This options allows you to enter the percentage that shows the relation between the input over the span where the DP transmitter will switch to the higher transmitter.
Note: this input is available if more than one DP transmitter is selected from the options.
Temperature
This is the measured temperature of the stream.
Outputs
The outputs section shows the calculated flow rate and uncertainty taken from the Wet Gas Orifice Plate .
Calculation Tabs
The following tabs are used within this uncertainty module:
Calculated Gas Standard Density