Hazardous Area Operation
Other Hazardous Area Considerations
A-18
Prima PRO & Sentinel PRO Mass Spectrometers User Guide
Thermo Fisher Scientific
gas to enter the analyser vacuum system, either through the vent port
if open to ambient air, or through the inlet system, if hazardous gases
are still present. On restarting the pumps, it is feasible that the turbo
molecular pump could cause ignition of the atmosphere with the
analyser and that this combusting gas could propagate ignition to an
external explosive atmosphere.
Note:
Filling the analyser with nitrogen or other inert dry gas and
maintaining a small positive pressure during any shutdown
period prevents the possible ingress of flammable gases into
the analyser.
Use of this inert gas vent is a requirement of the
ATEX/IECEx certification of the system.
Power for the pump (or pumps) is switched from within the main
enclosure, although the pump is located externally and is
independently protected for hazardous area operation. If the pump
requires replacement, it should be noted that both the voltage and
frequency of the pump need to be specified. Care must be taken to
correctly reinstall the flameproof gland onto the replacement pump.
The pump motor includes a thermal trip connected to the Ex Pump
Thermal Trip on the instrument power distribution unit (PDU). In the
event of an over-temperature condition, power to the pump will be
tripped followed by a vacuum system shut down shortly after. This
trip does not automatically reset; the Thermal Trip Reset button on
the PDU must be pressed when the over-temperature condition has
been removed. Note that the trip circuit contains a latching relay,
such that the trip status is ‘remembered’ through instrument power
cycles.
For testing purposes, the functionality of the trip circuit can be
checked by disconnecting the trip cable from the PDU and verifying
that the pump switches off. The pump should not restart until the
cable is reconnected and the reset button pressed.
Although the pump is certified for use in an external hazardous
atmosphere, the internal flow path is not certified for pumping
hazardous gas. For Zone 1 / Div. 1 applications, an inert gas
Rotary Vacuum
Pump
General
Thermal Trip
Purge
