INSTALLATION, OPERATION AND MAINTENANCE MANUAL – COSA
9610™
17 | Page
After these sequences, the pressure within the enclosure is above the minimum level. The
equipment within the enclosure can be energized.
1.6.2.5. Purge Timing
When using the X-Purge in a gas or gas and dust location, the time for purging an enclosure
can be based either on a known purge rate and time (fixed purge time), or based on the
flow rate being measured from the vent (dynamic purge time). Both methods base the time
on the flow measurement at the vent, and complete the process in steps. The EPCU will take
the readings from the vent and use the appropriate reading (listed below) as the useable
flow rate. For example, if the flow rate measurement from the EPV-6000 vent is 7 SCFM, the
EPCU will use 5 SCFM as the flow rate for evaluation. The flow rate measurement steps and
corresponding enclosure pressures are as follows:
•
5 SCFM @ 1.3” w.c. , (141 l/min @ 33 mm w.c.)
•
12 SCFM @ 2.5” w.c., (340 l/min @ 64 mm w.c.)
•
20 SCFM @ 3.1” w.c., (565 l/min @ 77 mm w.c.)
•
30 SCFM @ 3.4” w.c., (850 l/min @ 86 mm w.c.)
The COSA 9610™ uses the first setting of 5 SCFM @ 1.3” w.c. to establish the purge within
the enclosures. This volume exchange and purge timing is factory set to 8mins, but can be
re-configured to a different value if required by the Area Authority having jurisdiction at the
installation site.
1.6.2.6. Fixed Purge Time
If the purge time must be held to a specific time, then this time is based on the known
enclosure volume, number of volume exchanges, and flow rate through the vent. If the flow
rate is below the required minimum, then the purging cycle will reset and will not start until
the flow rate is above the selected rate. This set up does not allow purge flow to go below
the value required and will not recalculate the time for purging if it goes above the required
purge rate.
1.6.2.7. Dynamic Purge Time
Dynamic purge time allows the purge time to be updated to the purge flow through the
vent. This method is not dependent on a constant flow from the protective gas source. It
bases the purge time on the measured flow and not a set flow. This is very useful when the
protective gas supply pressure varies throughout the purging cycle or when it may vary from
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