Hazardous Area Operation
Purge Operation
Thermo Fisher Scientific
Prima PRO & Sentinel PRO Mass Spectrometers User Guide
A-15
This section provides further details on the operation and testing of
the different purge types. The manufacturer’s operation and
maintenance manuals for the purge controllers should also be
consulted. If there are any doubts about any part of the following,
consult the factory for further information.
Power and signal switch box
The flameproof enclosure mounted on top of the main enclosure
contains the 24 Vdc power supply for the purge controller and
the main power contactor. The contactor (and hence power to the
instrument) can be switched off manually by the emergency stop
switch on the side of the flameproof box (all purge types) or
automatically (in the case of ATEX, IECEx and X-purge
systems). It also contains the comms isolation PCB that provides
relay isolation of the serial ports and a limited number of discrete
digital signals in the event that the main power is shut off either
manually or by the purge controller.
Purge air inlet
The unit contains a pressure regulator and needle valve to set the
purge flow rate to the required level. Air flow into the enclosure
is split to allow better distribution within the enclosure and flow
is constant throughout the initial purge and CDP phases.
The purge outlet / monitor unit is powered by 24 Vdc and handles all
the purge control logic, timing, etc. and monitors the enclosure
pressure and outlet flow rate. Pressure and flow set points are
adjusted using controls within the unit that also provide the signal to
operate the enclosure power control contactor (located in the power
switch box, see above). The air exhaust incorporates a spark
suppresser to ensure safe operation in the event of a serious internal
enclosure problem.
The purge controller includes an override function (password
required) that enables the system to operate with the door to the
purged enclosure open for maintenance purposes. A digital output
from the purge controller provides an indication of the purge
override status through the control interface software GasWorks and
hence remotely via the available communication channels.
To test the purge functionality, start with the system operating in full
purge mode with the override off. Open an enclosure door – the
instrument should be powered down at this point. Close the
enclosure door to start the purge process. Use a stopwatch to check
the initial purge time. Verify that at the end of the purge cycle the
Purge Operation
and Testing
All System Types
ATEX, IECEx and
X-Purge Systems
