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Manual 111-082010_Nall Mass Flowmeters Page 14 of 23
6.0 PRESSURE EFFECTS
6.1 Standard Transducers:
The Hastings Linear Mass Flowmeter can measure mass flow accurately without corrections for a variation
in line pressure from one psia (.068 ATM) to 250 psig (18 ATMS.) Mass flow indications are possible with
downstream pressures as low as .03 psia (.002 ATM), but the upstream must be much higher because of the
increase in pressure drop across the transducer (see Section 8.0).
6.2 Low Pressure Drop Transducers:
The low pressure drop Mass Flowmeter (using U-Series transducers) can measure flow accurately from .03
psia ( .002 ATM) to 15 psig ( 2 ATMS). The transducer is rated for a maximum pressure of 250 psig ( 18
ATMS). Mass flow indications are possible with downstream pressure as low as .1 Torr with upstream
pressures of less than 30 Torr. This flowmeter has been successful for many years in measuring uranium
hexafluoride flow rate under vacuum conditions, and has also been useful in measuring vacuum pumping
speeds and in atmospheric sampling trains.
6.3 High Pressure Transducers (Optional):
Hastings transducers having a P suffix have been pressure tested to 1500 psig using dry nitrogen gas. The
transducer was cycled between 0 and 1500 psig for two periods with a minimum of 5 minutes each, and held
at the pressure for a combined test period of 10 minutes. It was then leak tested on a Helium Leak Detector
where a leak rate of no more than 3 X 10-6 SCCS was required.
The flowmeter has been designed and tested as described above for line pressure up to 1500 psig under
normal usage. High pressure gas is always potentially dangerous and we strongly urge that extreme caution
be taken in locating, installing, and operating this equipment.