PROJECT
INCORPORATING COLD CHAIN
The ethylene gas concentration is
measured in the room via the PLC and
ethylene sensors. From this value ethylene
is supplied to the rooms through solenoid
coils at each room being supplied gas
from a bank of gas bottles located at the
plant room.
An interesting fact is that when the
bananas begin to ripen, they release
ethylene gas themselves and this system
will monitor the rising levels and ventilate
fresh air into the rooms to hold a constant
gas level and hence also ventilate out
other deleterious byproduct gasses such
as CO 2 .
The fresh air system mentioned above
consists of ducting in and out of the room
with non-return dampers to seal air tight
until they are required, when the fans will
come on and vent fresh air into the room
while exhausting the ethylene and CO 2 -rich
air from the room.
ALL ABOUT CONTROL
The ripening room control system uses
Eliwell Free Advance programmable logic
controllers (PLCs), explains Ben Milne of
Keystar. Its standard ripening application
is configurable to modulate heating and
cooling, ventilation based on ethylene/
CO 2 levels, humidity control and ethylene
modulation. Using up to four PT1000
Class A/NTC spiked sensors, the average
14
JoJo tank holding cooling system water.
www.coldlinkafrica.co.za
Canvas air curtains dropping from stainless steel coils.
COLD LINK AFRICA • June 2019