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Thermo Fisher Scientific Prima PRO & Sentinel PRO Mass Spectrometers User Guide 3-11
It is the responsibility of the user to determine the required flow of
compressed air for a given leakage rate and to provide a means of
monitoring the purge.
Instrument quality air must be used – the air supply must be clean
and dry. Connection is 1/4” / 6 mm compression. A needle valve is
provided inside the unit for flow adjustment.
Warning! For further description of the operation of the following
supplies, see Appendix A: Hazardous Area Operation . 
Use of the dry gas vent facility is a requirement for ATEX/IECEX
systems.
Warning!
For hazardous area systems, the dry gas vent is
connected and used in the same way as for safe area systems, but
serves an additional function. Filling and pressurizing the analyser
with a gas such as nitrogen ensures that hazardous gases cannot enter
the vacuum chamber and pumping lines while the system is switched
off. On startup there is then no possibility of gas in the analyser
volume being ignited (such an ignition could propagate outside the
instrument enclosure).

The following is applicable to Zone 1 (ATEX/IECEX) and Div. 1
applications.
Warning! Use of the rotary pump purge facility is a requirement
for ATEX, IECEx and Div. 1 systems.

To avoid the possibility of an explosive gas mixture igniting
during passage through the rotary pump, a nitrogen purge is
applied to the ballast port of the pump to suppress oxygen
levels below the ignition limit.

A flow of 0.6 Nl/min is required.

This supply is shared with the dry gas vent and hence has the
same pressure requirements. Failure of the supply will result
in power to the pump being switched off.

If nitrogen is to be supplied from a cylinder, ensure that
backups and automatic changeover functions are in place.
Hazardous Area
Systems
Dry Gas Vent
Rotary Pump Purge