5 Supplementary information
5.1 Purge the sensor case
Prerequisites
Make sure the following are available before beginning the purge procedure:
• Teflon
™
tape
• Argon or nitrogen gas sufficient to purge the sensor case
About this task
Whenever a purge plug is removed from the sensor case, you must repurge the case.
Procedure
1. Shut down the process, or set control devices for manual operation. Before
performing the case purging procedure, shut down the process or set the control
devices for manual operation. Performing the purge procedure while the flowmeter
is operating could affect measurement accuracy, resulting in inaccurate flow
signals.
2. Remove both purge plugs from the sensor case. If purge lines are being used, open
the valve in the purge lines.
DANGER
• Stay clear of the rupture disk pressure relief area. High-pressure fluid
escaping from the sensor can cause severe injury or death. The sensor must
be oriented so that personnel and equipment will not be exposed to any
discharge along the pressure relief path.
• Take all necessary precautions when removing purge plugs. Removing a
purge plug compromises the secondary containment of the sensor and
could expose the user to process fluid.
• Improper pressurization of the sensor case could result in personal injury.
CAUTION
Be sure to use thread protectors when removing the purge fitting so as not to
damage the disk membrane surrounding the rupture disk.
3. Prepare the purge plugs for reinstallation by wrapping them with 2–3 turns of
Teflon tape.
4. Connect the supply of nitrogen or argon gas to the inlet purge connection or open
inlet purge line. Leave the outlet connection open.
• Exercise caution to avoid introducing dirt, moisture, rust, or other contaminants
into the sensor case.
• If the purge gas is heavier than air (such as argon), locate the inlet lower than the
outlet, so that the purge gas will displace air from bottom to top.
Installation Manual Supplementary information
20002346 January 2019
Installation Manual 21
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