Fieldbus detector - Duct Modbus, BacNet, etc.
Gas monitoring and
control in cold stores. Gas monitoring in cold stores should meet two
To warn if the amount of harmful CFCs (environmentally
and ecologically) reaches an unhealthy level.
To minimize the emission of expensive
Freon is a heavy and suffocating gas which in
case of combustion can cause the formation of the highly toxic gas
phosgene. Since the gas does not warn you of its presence through
its smell it is advisable to monitor the gas as a safety precaution.
cold stores containing more than 25 kg of Freon must be equipped
with a gas monotoring system. In cases of system fillings,
other relevant areas must also be monitored.
When considering freon from a monitoring
point of view, it is appropriate to have two alarm levels, where the
first gives an alarm at around 300-500ppm and the second at about
500-1500ppm. The recommendation differs from the hygienic threshold
If you require a higher sensitivity, alert
level 1 can be set at a lower level so that the plant gives an alarm
for very small leakages. In this way, the gas monitoring facility
can save on the very expensive freon.
The recommendation is a sensor density of
about 1 sensor/100m2 or more if a higher leakage warning
capability is required.
In some cases, you can supplement these facilities with an asphyxia
warning system. Since the hygienic limits for hazardous atmosphere
is much lower for freon, this measuring method is normally
The ventilation in the col
d stores is generally
temperature controlled since refrigeration compressors produce a
great deal of heat.
This means that fans in cold stores run at
full speed during summer.
Irrespective of how the ventilation control
system is solved, it is important to "override" the temperature
control so that at level 1 the fans at least run at half speed and
at level 2 at the 1/1 power alternative, analog with a frequency
Choice of instrument
Given the importance of providing the staff with a concentration
reading ability prior to entering the monitored space, it is
recommended that the facility be equipped with
with a central instrument and display (the display can also be
affixed to the sensor).
The instrument can be a single controller or one designed for
The instrument should be located so that the
alarm and any readings can be easily read. It should also be located
in a frequented and meaningful place (outside the cold store).
To manage the monitoring- and control data,
the instrument should have two alarm levels (with associated relays)
and concentration readings.
The instrument must furthermore be able to
identify faults in sensors, cables and instruments.
Analog detector -
AFRE, Analog detector - Duct
Field Bus detector - Wall Modbus, BacNet, etc.
Electrical products in an explosive environment
A small amount of energy - a flame, spark, high surface temperature
or similar is required to ignite an explosive gas mixture.
Products installed in an area with a potential explosion hazard must
of course in themselves not be a potential explosion hazard.
For this reason, the products are manufactured in such a way that
this cannot occur.
The equipment must also be labeled and tested - ATEX classified - by
the approved testing authority.
The Ex-class information is available in "Swedish Standard" The choice of which Ex-classification is required is determined
by factors such as type of gas, permissible maximum surface
temperature and potential explosive hazards in the area where the
products are to be installed.
The potential explosion hazard in the different areas is determined
by the zone classification according to "Swedish Standard".
More about ATEX-products can be found in the following link