Siemens FUG1010 IP65 NEMA 4X, Руководство по эксплуатации, Страница: 98 / 271

Functions
7.1 Gas Parameters Menu
FUG1010 IP65 NEMA 4X
Operating Instructions, 01/2013, A5E02951519-AC
97
The internal AGA8 lookup table provides the flow meter with the actual gas density (Kg/m
3
)
and compressibility factor (Z Actual) for the indicated pressure and temperature (as obtained
via the analog input or fixed P/T entry). These values are then used to compute either mass
flow rate or standard volume corrected flow rate as indicated in the Flow/Total Units menu.
The table must first be generated externally using a software package which computes the
appropriate density and compressibility factors for the specified gas composition.
Note
Siemens recommends using Si-Ware to generate this lookup table.
After the lookup table is generated and appropriately formatted, it can then be downloaded to
the flow meter via the serial data port. At any time during operation a new table may be
downloaded to the flow meter, should a change in gas composition require the calculation of
new Z-factors and Density values.
The AGA8 lookup table is essentially a 10 x 10 array or grid containing both Z-factor and
Density, with a 10 point temperature and 10 point pressure index. Based on the current
temperature and pressure measurement, Z-factor and Density are interpolated to provide
accurate volume correction. The table should be configured to cover the full range of
operating temperature and pressure; however, if the measured pressure or temperature falls
outside the table limits the flow meter lookup algorithm will extrapolate the Z-factor and
Density values accordingly.
Note
Table values are installed into the flow meter using a facility providing direct access to many
system variables without error handling, therefore, care should be exercised during the
formatting of this table prior to downloading to the flow meter.
When generating an AGA8 lookup table follow these guidelines (refer to Example #1 table
below).
●
The table values for pressure must be arranged in ascending order and consist of exactly
10 points. The units of entry must be PSIA.
● The table values for temperature must be arranged in ascending order and consist of
exactly 10 points. The units of entry must be degrees Kelvin.
● The table values for Density and Z-factor must be entered for each combination of
entered temperature and pressure (100 points for each). The units of entry for density
must be Kg/m3.
AGA8 Table Generation and Installation Instructions
1. Start by first creating the gas composition file within the Si-Ware software application.
2. Next customize the output units by selecting PSI absolute and degrees Kelvin.
3. Now determine the application range for pressure and temperature with sufficient margin
to insure that the measured temperature and pressure always falls within the table limits.
4. Compute the temperature increment for 10 points: Tincr = (Tmax – Tmin) / 9, then round
off Tincr to the next higher integer. Now recomputed Tmax = Tmin + 9*Tincr.