Handling & Storing
With the proper equipment, filled shipping sacks may be handled safely in whatever volume individual conditions require. It is essential that equipment used for handling or moving filled shipping sacks is free from projections, rough spots, stones, etc. that might snag or damage sacks.
Principal types of equipment generally used are described briefly below. For further information or advice on handling equipment and procedures, shipping sack users are advised to consult with sack suppliers.
Two-wheel hand trucks should have wide extended lips and should be equipped with wheel guards to prevent the damaging of sacks by accidental contact with turning wheels. If narrow- bladed trucks are used, lips should be extended with wooden or metal racks. When loading two-wheel hand trucks, sacks should be placed on trucks by hand and always stacked flat.
Handling can often be simplified by the use of small pallets which can be moved by two-wheel hand trucks. These pallets are easily constructed, will last indefinitely with reasonable care and will safely handle up to six filled shipping sacks.
When loading hand-operated power trucks or forklift trucks, pallets or skid platforms should be used. Sacks should be stacked flat and flush with pallet or platform edges and should be interlocked by alternate stacking. If unavoidable, overhang of sacks should not exceed one inch.
Belts and Conveyors
A wide variety of gravity and power operated belt and roller conveyors are used to carry filled shipping sacks from packer to warehouse, freight car, truck or ship. Such equipment should be free from unprotected wheels, cross bars or rough edges which might damage the sacks.
Conveyor installations should be designed so filled sacks are discharged without severely jolting the ends; when sacks are dropped with force on ends, the closures can be weakened.
When the receiver has equipment for handling unit loads, palletization saves time and labor for both shipper and receiver. However, successful use of pallets in shipping filled sacks requires careful study of conditions at every level of the distribution channel including:
- Analysis of present unloading, handling and storage methods.
- Analysis of critical physical factors such as the heights of platforms, ramps and ceilings; width of aisles; the size and capacity of elevators, conveyors and storage spaces; packing room layouts; strength of floors over which lift trucks must travel; etc.
- Analysis of the size and type of sacks and mode of shipment (rail, truck, barge, steamship) to determine the most suitable size and type of pallet (for example, returnable or disposable).
- Determination of the best stacking arrangement of pallet loads according to pallet size and strength, size and fill of sack and whether sack redesign or the use of load locking devices is desirable.
Loading Pallets Correctly
The most satisfactory method of palletizing filled sacks is interlocked stacking with edges of sacks flush with pallet edges without overhang. If unavoidable, overhang of sacks should never be more than one inch.
Types of Pallets
Permanent pallets are usually made of wood and normally returned to the shipper after unloading.
Disposable pallets are made of paper, paper fiberboard and/or wood or plastic materials. They can sustain loads comparable to permanent pallets during storage or shipping but are inexpensively constructed to allow them to be discarded after one trip.
Filled paper shipping sacks may be shipped on either permanent or disposable pallets; the choice will depend on cost and convenience factors which will vary with the type of product being shipped, mode of shipping and the facilities at the receiving end for ensuring the return of permanent pallets.
The use of automatic palletizers, along with the conveyorized transit of filled sacks, virtually eliminates manual handling from packer to warehouse or shipping dock. In such an operation, the filled sacks travel by conveyor to the automatic palletizer. This machine automatically stacks the filled sacks in a prearranged pattern on the pallet, tier by tier. The stacked pallets are then moved by forklift or conveyor to the storage or shipping location. This arrangement offers these advantages:
- Since automatic palletizers handle up to 30 sacks per minute, important labor savings are achieved.
- Such machines provide more uniform and better balanced pallet loads which enhance stacking ability and allow more efficient storage; damage to loaded sacks is greatly reduced.
- Production is more easily scheduled and controlled.
A number of manufacturers produce automatic palletizers. Their efficiency and versatility are also enhanced by a growing variety of material-handling devices. More shippers are turning to automatic palletizing as the size of their operations and potential labor-savings justify the initial installation expense.
Load Locking Devices
Where the nature of the product being packed in paper shipping sacks prevents secure stacking or the method of shipment requires special protection against filled sacks sliding off unit loads, several load locking devices are commonly used:
The unit load of filled sacks on the pallet is covered with strong wrapping paper and secured with steel or plastic banding.
- Breakaway adhesives:
Filled sacks in the unit load are spot-glued together or held together by strips of adhesive tape to prevent slippage.
- Friction materials:
Anti-slip finishes may be specified for the outer walls of shipping sacks to reduce the tendency of filled sacks to slip from the unit load.
- Shrink or stretch wrap:
Shrink or stretch films in various gauges are available for either palletizing or bundling. High levels of product protection, handling efficiency and economy of unitized loads have led to a greater use of shrink/stretch wrap.
Filled shipping sacks should be stored in cool, well-ventilated rooms. Ideal conditions are a 70-degree temperature and a 50-to-60 percent relative humidity level.
More protective conditions may be required for commodities which tend to cake or harden when exposed to moist air. On request, sacks can be supplied with moisture-resistant walls and sealed closures to protect such products from deterioration during storage.
Filled sacks may be stacked to reasonable heights, depending upon safety considerations and the ability of the commodity packed to withstand the pressure. Stored sacks should be interlocked by alternating the direction of tiers. Wire-tied sacks should be stacked bottom-to-bottom and top-to- top.
Store filled paper shipping sacks on dry floors. Install wooden platforms over dirt floors, floors inclined to become damp or where condensation may cause dampness. If sacks become wet, set them aside and allow them to dry thoroughly before placing in storage. Always protect comers of storage piles with wooden or metal “U or “V” frames to prevent the snagging of sacks by service traffic.
Never pile hard, sharp objects on top of sacks. Men working on warehouse stacks should wear rubber-soled shoes to prevent puncturing sacks.
Don’t store sacks near steam pipes, heaters, kilns, or other sources of dry heat.
Never spray insecticides on sacks filled with foods or feeds, regardless of toxicity of the insecticides used. Residual sprays should be used on floors, walls and ceilings of storage areas and allowed to dry completely before filled sacks are placed on sprayed surfaces.
Food or feed sacks should never be stored or shipped next to toxic materials.
Filled paper shipping sacks not specifically constructed for open storage should be kept dry and under cover.
Filled sacks intended for brief periods of outdoor storage, including occasional rainfall, should be made of several walls of moisture-resistant kraft paper with an outer wall of wet strength kraft paper (paper marked with thin longitudinal stripes).
Where filled sacks are subject to long periods of open storage under all climate conditions, specifically designed waterproof constructions should be used. Such sacks have up to six walls and are sometimes printed with the words “may be used for open storage.”
Filled shipping sacks stored outside should never be placed directly on the ground but on wooden platforms or on a moisture-proof barrier such as polyethylene between the filled sacks and the ground.
Stacking sacks in tiers arranged in alternate directions will add stability in outside storage and prevent filled sacks from shifting.