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GFS2102™ OPERATION AND MAINTENANCE MANUAL
© 2007 DH Instruments, a Fluke Company Page 44
4.1.2 GAS DEPENDENT MASS RANGES AND CYLINDER SIZE
SELECTION
Table 11 shows the maximum mass for of each GFS2102 supported gas that will be
available for flow testing after a reference gas cylinder fill. Typical supply cylinder fill
pressures are listed in the table but actual fill pressures may vary from different gas suppliers
and locations. If higher gas supply pressures are available to the user, then higher starting
mass loads may be used, up to the limits imposed by the balance maximum mass range of
2.3 kg, and the maximum reference gas cylinder fill pressure and/or GFS-FS supply inlet
pressure of 20 MPa (3000 psi).
For cylinder selection, the 1.1 liter cylinder with its 690 kPa (100 psi) regulated output is
optimal for all flow ranges with most gases except Helium, Hydrogen, or Sulfur Hexafluoride.
The maximum nominal expected mass of an empty 1.1 liter cylinder is 1650 grams.
With the possible exception of Carbon Tetrafluoride, the 1.1 liter cylinder can not be overfilled
at the typical supply cylinder fill pressures in Table 11.
The 1.5 liter cylinder with its 550 kPa (80 psi) regulated output is optimal for maximizing test
mass and run time available with Helium, Hydrogen, or Sulfur Hexafluoride, but due to the
lower regulated output pressure it is not ideal for the other gases in high flow or high pressure
test conditions (i.e. 10 slm @ 525 kPa). This cylinder can also easily be overfilled with other
gases if taken over the typical maximum fill pressures listed in Table 11 for the 1.5 liter
cylinder. The maximum nominal expected mass of an empty 1.5 liter cylinder is 2100 grams.
The number of accumulations that can be run from a typical cylinder fill varies depending on
several factors, including flow regulation and dwell times, minimum gas pressures, the use
and timing of Balance Zero and AutoZero functions, flow stability, and other influences.
These are not accounted for in the GFS Tools Test Editor “Minimum Required Test Mass”,
this minimum being based only on the mass needed per accumulation, the number of
accumulations per flow rate, and the number of flow rates. GFS Tools will warn of blatant
overages where the actual Cylinder mass is less than the minimum required, but no more. It
is recommended to plan on 25% of the total available mass to be used towards these
unaccounted factors. For example; Nitrogen in the 1.1L cylinder could be up to 219 grams of
gas mass, which would yield 164.25 grams of useable mass, or sixteen 10 gram
accumulations.
Do not exceed the maximum reference gas cylinder fill pressure of 20 MPa (3000 psi).
Do not exceed the maximum gas mass of 650 grams for the 1.1 liter cylinder or 200 grams
for the 1.5 liter cylinder. While exceeding these mass limits will not necessarily harm the precision
balance, it will place the balance in an overload condition beyond its 2.3kg range and require gas
mass to be bled off before a GFS accumulation can be successfully run.