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Hazardous Area Operation
Other Hazardous Area Considerations
Air Conditioner
Remote / Dual
RMS and Instrument
in Hazardous Area
RMS in Hazardous
Area and Instrument
in Safe Area
A-20
Prima PRO & Sentinel PRO Mass Spectrometers User Guide
The air conditioner is made suitable for hazardous area operation by
locating ignition capable parts of the system within the purged
enclosure. The only parts exposed to hazardous atmospheres are the
condenser coil and the air circulation associated with this.
Air circulation over the condenser coil is achieved by use of air
amplifiers as fans, suitable for all area classifications were
considered inappropriate, principally due to size. Air amplifiers are
non-electrical and have no moving parts.
Three air amplifiers are used in parallel to ensure good air
distribution over the condenser coil. The compressed air requirement
is 100 to 300 Nl/min, dependent on ambient temperature conditions,
and controlled by the onboard regulator.
The remote RMS (or second RMS in a dual valve configuration) is
RMS
housed in its own enclosure. This additional enclosure also requires
pressurising and purging to enable it to be used in a hazardous area.
There are two variants.
The remote RMS enclosure is linked to the main enclosure via a 32
mm conduit that carries all the required connecting cables and pipe
work, and an additional 16 mm conduit, which is deliberately empty.
Two conduits are required to ensure there is an unobstructed path for
purge air to flow from the remote to main enclosure (obstruction of
this path could result in an overpressure condition in the remote
enclosure).
Serial purging of the enclosures is used where compressed air is
connected to the remote RMS enclosure via a regulator and is ducted
to the main enclosure through the interconnecting conduit.
Compressed air will also be required at the instrument enclosure, to
operate the air conditioner air amplifiers, so there are two
compressed air connection points to instruments with this
configuration. Compressed purge air will then exit the main
enclosure through the purge controller as normal. As the air flows
into the remote RMS enclosure first this will be at a higher pressure
than the main enclosure. Providing the pressure and flow rate
detected by the purge controller in the main enclosure are within
required limits, then the purge status of the remote RMS enclosure
must also be OK.
In the case that RMS is in a hazardous area and the instrument in a
safe area, the remote RMS is a self-contained purged unit with purge
controller and compressed air regulator mounted on the side. Rather
than use an Exd enclosure for power isolation, the appropriate
components are located in the main instrument enclosure,
communicating with the purge controller via a cable in the 32 mm
Thermo Fisher Scientific
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