FEATURE
INCORPORATING COLD CHAIN
Ammonia systems are generally preferred for large, industrial processing installations. Taken at
Mass Meat.
direct heat transfer systems. This is great
for operations like growing mushrooms
or preserving flowers. Other than that, it’s
usually just indirect heat transfer systems
(that is, fan coil systems with refrigerant)
where humidity isn’t critical.
Everything depends on how much
cooling you need and how fast the
product needs to be cooled. “Process and
product are the key determining factors on
a project,” says Walter.
Whether or not ammonia is an option,
will be determined by how many kilowatts
of cooling you need. “A rule of thumb
is that synthetic refrigerant installations
work for systems up to 500kW in size, while
ammonia is better for the bigger systems,”
says Walter.
“The synthetic-refrigerant-based
installations can be installed for a lower
cost per kWr of refrigeration but have a
higher electrical consumption and this
makes them ideal for smaller applications,”
explains Van der Merwe.
For air conditioning, the refrigerant has
to be safe in case of a leakage into the
inhabited area, advises Amschwand.
In most cases, it should be a secondary
coolant; that is, glycol solution. Direct
ammonia systems are banned over a
certain occupancy rate and systems using
synthetic refrigerants also have limitations,
he says.
Most wineries use packaged water
chillers circulating a glycol solution,
explains Amschwand. Only the biggest use
ammonia plants are where the economies
of scale make this preferable. The benefits
of lower operating costs and longer plant
life become economic then. “Regarding
ice cream, all plants use ammonia.”
“Generally, food production is done on
a large scale and ammonia refrigeration
is used for the reasons given above,” says
Amschwand.
Ammonia is a costly option and
accordingly, is suitable for larger industrial
applications, agrees Van der Merwe.
“Ammonia is one of the most efficient
refrigerants available and the industrial
nature of the installation implies that it has
an effective operating life in excess of 30
years with lower electrical running costs. In
addition, ammonia is a natural refrigerant
with a zero global warming potential and
zero ozone depleting effect.”
RISK
So, what can go wrong if you do not have
proper refrigeration?
COLD LINK AFRICA • May 2019
A huge risk is not getting your certification
to be able to sell the product, explains
Walter. Even if you are not concerned
with certification, the shelf life of the food
is still a big factor for perishables. Without
proper refrigeration, product won’t last
as long.
“The greatest risk is product losses,”
explains Van der Merwe. “If the required
temperatures are not maintained, then
shelf life and quality are compromised, and
this will cost the end user to either dump
product or sell at reduced prices.” Standby
capacity is also an important consideration
to ensure that the temperatures can be
maintained even if one of the compressor
systems trips.
“Food safety is the primary concern;
just look at what the listeriosis outbreak
did to the pork industry in 2017!” says
Kriel. “Obviously, the safety of staff [often,
processing facilities have a large staff
complement] is also critical, and this is often
linked to air quality.”
COMMON MISTAKES
Several things can go wrong in terms of
design and installation of refrigeration
systems for the processing and packaging
link in the chain. What are some common
mistakes professionals make and how can
these be avoided?
Not following the regulations is the
main issue, explains Amschwand.
www.coldlinkafrica.co.za
41