MGS-250 Manual
18 6490-9000
Revision
4
2.2.2. Machinery Rooms
There is no absolute rule in determining the number of gas detectors and
their locations. However, a number of simple guidelines will help to make
a decision. Gas detectors monitor a point as opposed to an area. If the
gas leak does not reach the detector then no alarm will be triggered.
Therefore, it is extremely important to carefully select the gas detector
location. Also consider ease of access for maintenance.
The size and nature of the site will help to decide which method is the
most appropriate to use. Locations requiring the most protection in a
machinery or plant room would be around compressors, pressurized
storage vessels, refrigerant cylinders or storage rooms or pipelines. The
most common leak sources are valves, gauges, flanges, joints (brazed or
mechanical), filling or draining connections, etc.
x
In machinery rooms where there is
little or no airflow
, placement
options are:
o
Point
Detection, where gas detectors are located as near as
possible to the most likely sources of leakage, such as the
compressor, expansion valves, mechanical joints or cable duct
trenches.
o
Perimeter
Detection, where gas detectors completely surround
the area or equipment.
x
Halocarbon and hydrocarbon refrigerants are
heavier-than-air
gases
and as such the gas detectors should be located near ground
level (6 to 18 inches from the floor).
NOTE:
Gas detectors should be positioned just far enough
back from any high-pressure parts to allow gas clouds to form
and be detected. Otherwise, a gas leak might pass by in a high-
speed jet and not be detected by the gas detector.
x
Make sure that pits, stairwells and trenches are monitored
since they may fill with stagnant pockets of gas.
x
For racks or chillers pre-fitted with refrigerant gas detectors,
these should be mounted so as to monitor the compressors.
x
Do not mount the gas detector directly to pipes or structures
that are subject to strong vibration.
2.2.3. Refrigerated Spaces
In refrigerated spaces, gas detectors should be located away from doors,
in the return airflow to the evaporators on a sidewall (below head-high is
preferred), or on the ceiling, not directly in front of an evaporator, nor in
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