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MLT 2 / BINOS
®
100 F
ATEX Instruction Manual
ETC01035
January 2004
Emerson Process Management Manufacturing GmbH & Co. OHG1 - 4
1-3-3 Description of Pressurization Systems
1-3-43 Description of Pressurization Systems
An internal overpressure inside the pro-
tected housing prevents outer (possibly ex-
plosive) atmosphere to enter.
Instruments intended to be installed in Zone
1 are automatically prepurged before power
is supplied. This ensures that all possibly
explosive atmosphere present inside the
instrument is removed. The prepurge
process is controlled by the pressurization
control unit which also acitivates switching
on the analyzer when the prepurge phase
has elapsed.
While the Zone 2 unit mainly consists of a
pressure monitor with alarm contacts the
Zone 1 unit contains a purge gas inlet valve
(proportional valve), a controller unit with
microprocessor and an outlet valve (high
pressure version only). The controller unit
permanently monitors the parameters (e.g.
prepurge phase, purge gas flow, internal
overpressure, and more) and therefore
ensures safe operation. A separate instruc-
tion manual provides more detailled infor-
mation.
The Zone 1 system is available in two
differing variations due to different
requirements for measuring flammable and
non-flammable gases:
Measuring non-flammable gases:
The system provides an internal over-
pressure of 14 mbar during operation.
Measuring flammable gases:
The standard configuration is designed to
hold an internal overpressure of 90 mbar.
Optionally 14 mbar may be adjusted if it is
ensured that the gas pressure within the
Containment System is allways below
12 mbar.
In addition one differential pressure switch
is installed within any gas path to ensure the
instrument‘s overpressure is always at least
50 Pa (0.5 mbar) above the pressure in the
containment system.