User guide

Application Guide | Gas detection in refrigeration systems
12 DKRCI.PA.S00.A1.02 | 520H12772 © Danfoss | DCS (MWA) | 2018.05
The arrangement of the equipment in the room
can also have an impact on the most effective
place to monitor.
Locations requiring most protection in a
machinery or plant room would be around gas
boilers, compressors, pressurized storage tanks,
gas cylinders, storage rooms, or pipelines.
Most vulnerable are valves, gauges, flanges,
T-joints, filling or draining connections etc.
Sensors should be positioned a little way back
from any high-pressure parts to allow gas clouds
to form. Otherwise any leakage of gas is likely
to pass by in a high-speed jet and will not be
detected by the sensor.
Accessibility and space to allow calibration and
service must be considered.
Location of gas detectors Gas detectors must be powered as specified in
the installation guide and located within the
specified cable length from the central control
unit/monitor.
In general:
• Do not mount to a structure that is subject to
vibration and shock, such as piping and piping
supports.
• Do not locate near excessive heat or in wet or
damp locations.
• Do not mount where it will be exposed to
direct solar heating.
• Do not install in areas where condensation may
form.
The two methods of locating sensors:
• Point detection: Sensors are located as near as
possible to the most likely sources of leakage.
• Perimeter detection: Sensors surround the
hazardous area completely.
The most appropriate method is selected
depending on the size and nature of the site.
• Detectors shall be located high/low according
to the density of the actual refrigerant.
• If mechanical ventilation exists in a machinery
room, air will move towards the fan. In
problematic locations a smoke tube can
indicate air movements in a space and assist in
the location of sensors.
• In a cold store, sensors should, if possible, be
placed on the wall in the return airflow below
head height.
• Consideration should also be given to the
possibility of pockets of gas collecting in the
event of a leak.
Important!
Do not place immediately in front of a
coil due to temperature and humidity
fluctuations. These may occur especially
during defrost or loading of a cold store.
Make sure that pits, stairwells and
trenches are monitored since they
may fill with stagnant pockets of gas.
Monitoring where leaked refrigerant
can stagnate is generally required by
standards.
As general guideline:
• If there is one compressor/chiller in the room;
sample at the perimeter of the unit. For two
chillers; sample between them, with three or
more chillers; sample between and on each
side. Ensure that the area being sampled
is sufficiently monitored. Do not skimp on
sensors.
• Place the sensor in the location(s) most likely to
develop a gas leak, including mechanical joints,
seals, and where there are regular changes
in the system’s temperature and pressure or
excessive vibration, such as compressors and
evaporator control valves.