KEEPING THE WAREHOUSE MOVING

Logistics Asia, 1/11/2007

If you have ever wondered about all the diff erent trucks used for transportation, storage and picking functions in the warehouse, AHMAD JAMALUDIN provides this useful guide.

Warehouses come in an extremely diverse variety of shapes and sizes to meet the individual needs of every conceivable type of industry – both industrial and commercial. The mobile handling equipment used in these warehouses covers the complete product spectrum: simple pump trucks, powered pallet trucks, pallet stackers, reach trucks, order pickers, very narrow aisle trucks, electric tractors and counterbalance trucks.

The choice of truck type will depend on the supply chain requirements and objectives of the business as well as the design of the warehouse including any limitations imposed by using existing facilities if the warehouse is not a new build.

Other factors are the operating surfaces, the types of loads to be handled and the throughput and turnover ratios required, as well as the type of racking and method of storage.

Knowledge of the movements of the goods to be stored according to their nature and quantity is essential. To this end, the following operations should be considered separately:

• Transporting – conveying unit loads between the storage area and the goods-in/goods-out sections

• Stacking – placing and retrieving of unit loads in the warehouse

• Order picking – breaking up of unit loads and the batching of items for specific orders Factors to consider related to storage include whether it is block storage (on the floor, mobile racks, drive-in racks, gravity racks) or fixed-aisle racking storage. Also key is the unit load stacking height, of which there are four basic categories:

• Low level – up to 5 meters
• Mid level – up to 7 meters
• High level – up to 12 meters
• Very high level – over 12 meters

Thus, to select the most suitable truck it is necessary to define the operating criteria more clearly:

• Operating area (receiving, storage, dispatch) • Activity (transporting, stacking, order picking)

• Maximum lifting height Only after considering the operating criteria and the range of trucks available is it possible to select the equipment which will provide the best solution for each handling requirement.

PALLET TRUCKS
Used for general loading and unloading tasks, internal pallet transfers, marshalling and occasional order picking at ground level, pallet trucks (also known as hand pallet trucks or hand pallet jacks) represent a base level of warehouse handling equipment. Available in non-powered and powered versions, for the latter category there is the “walkie” where the operator walks along with the truck, and the “rider” where the operator stands on a platform andmoves with the truck.

PALLET STACKERS
These are generally used for lowheight storage and retrieval of small quantities. Extremely space efficient, a stacker truck has load support legs which locate either under the base pallet of a stack or the bottom beams of the racking and is able to operate in narrowaisles.

Loads must be aligned in vertical stacks to avoid causing problems of access. Maximum lift height of a pallet stacker is usually 4 to 5 meters, and aisle widths for pallets stacked lengthwise (1,200 meters deep) is 2.2 to 2.5 meters.

In terms of operating activity, pallet stackers can be used to transport from the goods-in to the goods-out section as well as for storage. For short distances, pedestrian operated tiller trucks can be used. For longer distances, rider stand-on or rider seated stacker version should be selected.

Conventional pallet stacker trucks cannot be used where the pallets have base boards. However, the straddle-type stacker truck can be utilized for this purpose.

RIDER COUNTERBALANCE TRUCKS
These trucks (commonly known as “forklifts”) represent an excellent alternative for low and medium level storage and for general purpose loading and unloading duties. A counterweight located at the rear offsets the weight of theload to keep the truck stable.

Normally available as engine powered or electric powered varieties, engine trucks can be considered for some internal applications subject to environmental considerations and fitment of approved particulate filters, while electric trucks benefit from zero emissions and can be used inside and outside.

ORDER PICKERS
As their name implies, order pickers are used for item-level transfer with the operator riding up to the load and transferring item by item onto the vehicle pallet or forks. Goods are picked according to a typed list or data provided by mobile data terminals. Order pickers are available in a variety of forms based on the vertical heightof the load.

Low level order pickers with steering wheels or tiller steering are driven along the picking aisles for item transfer at ground level with occasional step-up, second level picking and transferring of picked loads to marshalling areas. Elevating operator platforms are available for first and second level picking.

Medium level order pickers – typically for items up to 3.5 meters high. (usually the third level). Can be fitted with either a supplementary lift for picking onto pallets and roll cages, or a walk-through facility topick bulky or awkward items.

High level order pickers, which operate typically up to 10.5 meters high, are invariably used in very narrow aisle (VNA) system applications.

REACH TRUCKS
Exhibiting high stability from being able to retract most of the load within the wheel base, reach trucks are suitable for operation in mid to high level storage up to 12 meters lift height. These trucks are able to turn in standard and narrow storage aisles.

The reach and retraction feature of the mast gives improved maneuverability and means that aisle widths can be reduced to make greater use of available space. Reach trucks can operate in aisles down to 2.6 to 3 meters wide, dependingon the load depth.

TURRET TRUCKS
Providing high lift storage and retrieval of palletized unit loads, turret (or VNA) trucks can operate in very narrow operating aisles, often down to 1.5 meters depending on the application parameters. In the “man-down” version, the operator stays at floor level, while in the “manup” truck, the operator compartment rises to the load level.

The key feature of turret trucks is their ability to transfer the load to either side of the aisle without the truck having to turn to face the stack. Because the load is moved sideways into the racking, turret trucks are able to operate in aisles only slightly wider than the truck and the loads being handled. To achieve this, the truck is normally guided in aisles by either mechanical rail or wire guidance system.

These are “system trucks” meaning that the load, pallet, racking, aisles, floor surface, floor loadings, headroom, operational clearances and truck parameters must all be fully interfaced using carefully defined dimensions and tolerances.

Man-up trucks can also be dual-purpose combination trucks, to provide both unit load storage and item order picking functions.

Riderversion pallet truck

Pallet stackers

Order picker

Rider counterbalance trucks

Reach trucks

turret trucks

Ahmad Jamaludin is Area Manager, Linde Material Handling Asia Pacific. (www.lindemh.com.sg)

Current Rating:

 Excellent
 Very Good
 Good
 Quite Good
 Poor

 Rate This Article