• If the purge gas is lighter than air (such as nitrogen), locate the inlet higher than
the outlet, so that the purge gas will displace air from top to bottom.
5. Make sure that there is a tight seal between the inlet connection and sensor case, so
that air cannot be drawn by suction into the case or purge line during the purging
process.
6. Run purge gas through the sensor.
The purge time is the amount of time required for full exchange of atmosphere to
inert gas. The larger the line size, the greater amount of time is required to purge
the case. If purge lines are being used, increase the purge time to fill the additional
volume of the purge line.
Note
Keep the purge gas pressure below 7.25 psi (0.5 bar).
Table 5-1: Purge time
Sensor model Purge rate Time, in minutes
H025 20 ft3/h (566.3 l/h) 4 1/2
H050 20 ft3/h (566.3 l/h) 4 1/2
H100 20 ft3/h (566.3 l/h) 6
H200 20 ft3/h (566.3 l/h) 15
H300 20 ft3/h (566.3 l/h) 25
7. At the appropriate time, shut off the gas supply, then immediately seal the purge
outlet and inlet connections with the purge plugs.
Avoid pressurizing the sensor case. If pressure inside the case elevates above
atmospheric pressure during operation, the flowmeter density calibration will be
inaccurate.
8. Make sure that the purge fitting seals are tight so that air cannot be drawn by
suction into the sensor case.
Supplementary information Installation Manual
January 2019 20002346
22 Micro Motion H-Series
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