Fishers Pallets - Transportation & Storage of Pallets

Fact Sheet: Transportation & Storage

User Responsibility

It is important to note that no wooden pallet can be guaranteed mould free when mould spores, a natural phenomenon, are forever present in the air. Wooden pallets supplied with dried timber to a required moisture content, will ensure the pallets are delivered free of visible signs of mould and potential related problems for the user.

The pallet user must acknowledge they also have a responsibility to prevent mould.

By following the requirements stated to keep the pallets dry, remains the best practice strategy to prevent mould growth:

Transportation

Transportation Vehicle trailers (curtain or box) must be checked before loading palletised goods to ensure they are clean, free of pooled water, wooden flooring is not damp and there are no leaks. Conditions inside closed trailers are affected by climate changes. Condensation, darkness and lack of ventilation, are all factors to be considered particularly involving extended time spent in the trailer and long haul journeys.

Steel shipping containers present different challenges when exposed to extreme internal and external climate changes during shipment across different hemispheres. Condensation on walls and ceilings inside the container will drip water (container rain) onto both the product and pallets. High levels of humidity and temperature inside the container bathed in darkness and no ventilation are favourable conditions for mould growth.

Maintaining the dry condition of the pallets before and during loading of the container is important. The use of desiccants will help to absorb moisture inside the container. Choosing a container lined with plywood will also help to minimise the risk from moisture.

Unloading & Storage

Pallets must be unloaded from the vehicle trailer upon delivery and stored protected from rain in a well-lit and well-ventilated area with good drainage to eliminate standing water, away from other sources of moisture for example, vented from machinery or processing activities.

  • Pallets should not be left in closed trailers longer than 24 hours before unloading.
  • Pallets transported in curtain sided trailers that cannot be immediately unloaded, opening the curtains will improve ventilation in dry weather conditions.
  • Storage under canopy (Dutch barn), pallets must be stored sufficiently inbound of the roof perimeter to afford protection from precipitation, spray and water splash from passing vehicles. Avoid this type of storage environment which is open to prevailing wind from open fields or farmland blowing moisture laden air onto stored pallets.
  • Wherever it is practical to do so, avoid block stacking pallets in close (touch) formation, this restricts airflow between the stacks and inhibits the natural drying of moisture from the wood.
  • Avoid pallet storage in dark or dimly lit areas and warm temperatures without ventilation.
  • Pallets that have become surface wet or frozen in winter should be allowed to dry (thaw and dry) in a well-ventilated environment before being brought into heated environments.
  • Stacks of pallets should be arranged in storage with a minimum perimeter gap of 100 mm for ventilation around each stack. Storage space permitting, air flow across stacks of pallets is improved when pallets are stacked in neat rows in the X axis, orientating the rows in the Y axis (offsetting alignment) improves airflow across the stacks.
  • Stacks must be kept away from direct contact with building walls and steel cladding. This will prevent any damp, moisture condensation or mould spore transfer to the pallets. Dry controlled pallets should not be stored adjacent to or in the same area as uncontrolled pallets stocks to prevent any risk of cross contamination.
  • Operate FIFO, ‘first in first out stock rotation’. Pallets continually blocked in escape notice of any change in condition often until it is realized there is a mould problem.

Mould

Microscopic mould spores are everywhere but they need four key ingredients in order to activate and grow.  In the case of pallets this means:

  1. A food source (timber);
  2. Moisture;
  3. Oxygen;
  4. The right temperature. Eliminate one ingredient of the four and the mould cannot survive.

A green wood pallet (on average between 35% and 60% moisture) is a source of food and moisture for mould spores to grow. Mould spores will only be resisted when the moisture content drops below 20%.

Will heat treatment prevent mould?

No. Heat treatment is typically done to kill insects and larvae that may be in the wood. Yes, the heat treatment will also kill mould that is present but it does not dry out the wood and prevent mould from regrowing if the pallet is not dried or stored correctly.

What about air or kiln dried timber?

A pallet dried to below 20% moisture content should not develop mould growth, as long as the pallet is stored correctly and kept at this low moisture content. Air or kiln drying can be a costly process because of the time involved.

So, how can you prevent mould on your pallets?

It’s simple. Keep them as dry as possible.

  • Store pallets where they can dry and not be rewetted.
  • Avoid storing green pallets in closed containers or spaces for long periods of time.
  • Store pallets in a covered and ventilated environment, (so air can circulate around the pallet).

My pallets are mouldy, what now?

Don’t throw them out just yet. You can take steps to refresh your pallet.

First, you need to kill the mould by drying the pallet to below 20% moisture content. This can be done by air or kiln drying.

Second, fix the look of the pallet. Inactive mould could still be visible on the pallets. Pressure washing the pallets and /or using a diluted 2:1 bleach solution will remove mould stains. (Note: Only use bleach solution if it acceptable for use with the intended cargo).  NP1® Saptstain Control (available from Fisher’s Latrobe Valley Pty Ltd) can be sprayed onto pallets at a ratio of 100:1 to eliminate mould.