FEATURE
INCORPORATING COLD CHAIN
Continued from page 45
Pallet conveyors that have a minimum
capacity of around five pallets can allow
the machines in both areas to maintain
a more constant work rate by using the
pallets on the conveyor to balance
changing work rates. This magazine
effect can significantly improve material
handling productivity.
5. Dual cycling
Dual cycling is where reach trucks inside
the freezer and forklifts on the loading
dock can place a pallet on the outfeed
conveyor and then immediately pick
a pallet up from the infeed conveyor
or vice versa. This in theory allows
machines in both directions to be
productively moving a pallet on their
forks at a higher rate than would be
possible without conveyors. To achieve
dual cycling, there must be a minimum
of two conveyors and their loading/
offloading positions must be in close
proximity.
In practice, the ability to dual cycle can
be affected by other factors, including
the requirements of the warehouse
management system. While there are few
South African stores with pallet conveyors
designed for dual cycling, dual cycling
can significantly increase productivity.
DISADVANTAGES
Some of the disadvantages of pallet
conveyors in freezer stores are as follows:
1. Restricting pallet flows inside a freezer
The positioning of conveyors inside
a freezer room is important. In some
instances, especially in high volume
throughput situations, pallet conveyors
can restrict throughput as in where they
block a potential access gangway. There
are however few South African stores
TOP: Dual cycling conveyor configuration inside a freezer store.
RIGHT: Triple chains have taken over from rollers for pallet conveyors in freezer stores,
as the change can accept different sizes and designs of pallets as well as some of
those that are somewhat damaged.
where this sort of volume throughput
is achieved and at least some of
these concerns can be designed out
depending on the store design. In Europe,
floor-level slat conveyors have been
developed where man on machines
can drive over them, which provides a
solution, but at a cost.
2. Pallet conveyors are not cheap and
require regular maintenance
At about R40 000 per running metre
(including tunnel steelwork), they
are sometimes traded off in favour
of additional forklifts, which can be
leased rather than purchased. Where
the conveyors are relatively short and
do not require expensive 90-degree
bends sometimes known as dog legs,
they can be more cost-effective than
one or sometimes two additional
machines with the added personnel
and maintenance costs.
3. Semi-broken pallets, forklift impacts,
and excessive moisture can create
conveyor downtime
Freezer rooms should be designed to
allow for a night door to be accessible
when a conveyor breaks down or requires
maintenance. Too often, once there is a
conveyor problem, the emergency door
gets used full time and the conveyor is
discarded. Staff need to be trained how to
use conveyors, but maintenance backup
is also important.
COLD LINK AFRICA • May 2019
Cold store conveyor design has also
changed over the years, with driven rollers
giving way to triple chain designs, which
are more resilient to broken pallets.
4. Loss of pallet positions
Pallet conveyors occupy more floor
space than single static racks. The
space above the conveyors can be
lost for pallet storage. While this is true,
in-store conveyors can be designed with
tunnel steelwork, which allows pallet
racking above the conveyor. Normally,
only the bottom two pallet levels will be
sacrificed to the pallet conveyor. The
additional freezer footprint can often be
resolved by making each access aisle
slightly narrower. CLA
www.coldlinkafrica.co.za
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