"Double stacker forklift" is not a single, standardized equipment classification. Rather, the term is used informally to describe several different types of forklifts or attachments that perform double stacking, double handling, or double-deep storage. Depending on the context, it can refer to one of the following material handling solutions:
1. Double Stacker Attachment – Handling Two Pallets at Once
The most common interpretation is a forklift equipped with a double fork attachment (also known as a twin fork or double pallet handler). This allows the forklift to pick up and transport two pallets side by side in a single trip.
Feature Description
Design Two sets of forks mounted on a single carriage, operated hydraulically
Capacity Typically 2,000–5,000 lbs per pallet (total capacity varies by forklift)
Applications High-volume warehouses, distribution centers, retail logistics
Benefits Doubles productivity per trip, reduces travel time, lowers fuel/electricity costs
Key Considerations:
Requires a forklift with sufficient load capacity for combined weight
May reduce maneuverability in tight aisles
Operators require additional training for wider loads
Attachment must be approved by the forklift manufacturer (OSHA 29 CFR 1910.178(a)(4))
2. Double-Deep Reach Truck – Two-Deep Racking Access
Another possible meaning is a double-deep reach truck, designed to access pallets stored two positions deep in high-density racking systems.
Feature Description
Design Reach truck with extended pantograph mechanism and longer forks
Racking Depth Accesses pallets stored two positions deep
Applications High-density warehousing, cold storage, large distribution centers
Benefits Increases storage density by 30–40% compared to single-deep racking
Key Considerations:
Requires wider aisles than standard reach trucks (typically 10–12 feet)
Operator visibility to the second row is more challenging
Specialized training required for deep-reach operations
3. Double-Stacking Forklift – High-Bay Stacking
"Double stacker" may also refer to a forklift's ability to stack loads two pallets high in a single operation, using specialized attachments or extended mast height. This is common in high-bay warehouses and cold storage facilities where maximizing vertical space is critical.
Feature Description
Design Extended mast height (triplex or quad mast) with high-visibility configuration
Stacking Height Typically 15–30+ feet
Applications High-bay warehousing, cold storage, manufacturing
Benefits Maximizes vertical storage capacity
4. Two-Stage Mast (Duplex Mast)
"Double stacker" can also be a colloquialism for a forklift with a double-stage mast (duplex mast), which provides two stages of lift height extension for standard stacking operations.
Feature Description
Design Mast with two telescopic sections (outer and inner)
Lift Height Typically 3,000–4,500 mm (10–15 feet)
Applications Standard warehousing, container loading, light industrial
Benefits Cost-effective, compact collapsed height
Double Stacker vs. Standard Forklift – Key Differences
Feature Double Stacker Configuration Standard Forklift
Loads per Trip 2 pallets (with double forks) 1 pallet
Racking Depth 2 positions deep (with double-deep reach) 1 position deep
Productivity Up to 100% higher per trip Standard
Aisle Width Wider (double-deep reach) Narrower
Training Required Specialized Standard
Cost Higher (attachment or specialized truck) Lower
Applications and Industries
Double stacker configurations are used across a wide range of industries:
E-commerce and Fulfillment Centers: High-volume pallet movement and dense storage
Cold Storage: Maximizing expensive refrigerated space with double-deep racking
Retail Distribution: High-turnover palletized goods
Manufacturing: Moving raw materials and finished goods efficiently
Food and Beverage: High-density storage of dry or refrigerated goods
Buying Considerations
Define Your Application – Determine whether you need double pallet handling, double-deep racking access, or high-bay stacking.
Match Capacity to Load – Ensure the forklift's rated capacity exceeds the combined weight of two pallets plus attachment weight.
Check Aisle Width – Double fork attachments and double-deep reach trucks require wider aisles.
Verify Attachment Compatibility – Double fork attachments must be approved by the forklift manufacturer.
Update Data Plate – Any attachment that changes capacity requires an updated capacity plate (OSHA requirement).
Retrain Operators – OSHA requires retraining for any new attachment or configuration.
Consider Total Cost of Ownership – Factor in higher initial costs against productivity gains and storage density benefits.
Summary
"Double stacker forklift" is an informal term that can refer to several different material handling configurations: double fork attachments (handling two pallets side by side), double-deep reach trucks (accessing two positions deep in racking), double-stacking forklifts (high-bay stacking), or double-stage masts (duplex mast for standard stacking). Each configuration offers significant productivity or storage density benefits but requires careful capacity planning, wider aisles (for double-deep reach), and operator retraining. When considering a double stacker configuration, always verify attachment compatibility, update the capacity plate, and ensure operators are properly trained.