The mast is one of the most important components of an electric pallet stacker because it determines how the forks move vertically and how high the machine can place a pallet.
When buyers compare electric pallet stackers, they commonly encounter terms such as duplex mast and triplex mast.
The basic difference is straightforward:
Duplex mast: two-stage mast
Triplex mast: three-stage mast
A triplex mast generally allows a higher maximum lift height within a relatively compact overall machine configuration. A duplex mast can be suitable when the required stacking height is moderate and the application has simpler vertical handling requirements.
However, lift height is not the only consideration. Buyers should also evaluate lowered mast height, free lift, warehouse ceiling height, door clearance, load capacity and the actual storage rack configuration.
What Is an Electric Pallet Stacker Mast?
The mast is the vertical lifting structure that raises and lowers the forks and load.
According to OSHA, a duplex mast uses two stages, while a triplex mast uses three stages. OSHA also notes that triplex masts can extend farther than duplex designs, allowing higher stacking applications.
The mast configuration can therefore influence:
Maximum lift height
Overall height when lowered
Free lift
Visibility
Suitable warehouse applications
Capacity at specific lift heights
Duplex vs. Triplex Mast
The basic comparison is:
| Feature | Duplex Mast | Triplex Mast |
|---|---|---|
| Mast sections | 2 | 3 |
| Maximum lift potential | Moderate | Higher |
| Free lift | Depends on design | Depends on design |
| Suitable for | Standard stacking | High-level stacking |
| Low-ceiling operation | Often suitable | Configuration-dependent |
| High-rack storage | Moderate heights | Higher rack levels |
| Mast complexity | Lower | Higher |
| Selection priority | Moderate lift height | High lift height |
The exact lift range varies by model, manufacturer and machine design, so buyers should compare the actual technical specifications rather than selecting solely from the word "duplex" or "triplex."
What Is a Duplex Mast?
A duplex mast has two vertical stages.
It is commonly used where the required lifting height is moderate.
For example, a warehouse may need to move pallets between floor level and rack positions around:
2,500 mm
3,000 mm
3,500 mm
4,000 mm
A suitable duplex configuration may meet these requirements depending on the specific machine.
One important advantage is that the buyer can select a mast configuration based on the required lift height without automatically choosing a three-stage design.
What Is a Triplex Mast?
A triplex mast uses three vertical stages.
The additional mast section allows the forks to reach a greater height while keeping the machine's lowered configuration within a practical range.
This is useful for warehouses with:
Higher storage racks
Limited floor space
Multi-level pallet storage
Higher vertical utilization
Requirements above typical duplex lift heights
For example, some industrial forklift specifications show triplex configurations reaching approximately 5,000–6,000 mm and beyond, although actual capacity can decrease at higher lifting positions.
Example: 3,000 mm vs. 5,000 mm Lift Height
Consider two warehouses.
Warehouse A
The highest pallet storage position is 3,000 mm.
The buyer needs:
Required fork height = approximately 3,000–3,300 mm
A duplex electric pallet stacker may be sufficient if its technical specifications meet the required height and capacity.
Warehouse B
The highest storage position is 4,800 mm.
The buyer needs:
Required fork height = approximately 5,000 mm
A triplex mast may be more appropriate because the application requires a substantially higher lifting height.
The important point is that the choice should begin with the actual rack height rather than simply choosing "triplex" because it appears more advanced.
What Is Free Lift?
Free lift is the distance the forks can rise before the mast sections begin extending significantly.
This matters when the stacker needs to operate in areas with limited overhead clearance.
For example, imagine a warehouse with a ceiling height of 2,500 mm.
A stacker with insufficient free lift could raise the load and cause the mast to extend into the overhead area before the pallet reaches the required working position.
OSHA identifies free lift as a key characteristic of mast configurations. Its guidance notes that duplex and triplex masts can provide substantial free lift before the mast extends, depending on the design.
For applications such as:
Truck loading
Container loading
Low-ceiling warehouses
Doorways
Areas with overhead pipes
free lift should be checked carefully.
Why Is Lowered Mast Height Important?
Maximum lift height tells you how high the forks can reach.
Lowered mast height tells you whether the machine can physically pass through the working environment.
For example:
Suppose:
Warehouse door height = 2,300 mm
Stacker lowered height = 2,150 mm
The machine can potentially pass through the doorway, subject to the complete machine dimensions and site conditions.
But if:
Warehouse door height = 2,300 mm
Stacker lowered height = 2,450 mm
the machine cannot pass through that opening.
Therefore, when requesting a quotation, always provide:
Door height + ceiling height + required lift height.
Does Triplex Always Mean Higher Capacity?
No.
Mast type and rated capacity are related to the complete machine configuration, but a triplex mast should not automatically be interpreted as having greater lifting capacity.
In fact, capacity can decrease as lift height increases.
Published forklift load-capacity tables show examples where the same machine configuration has different rated capacities at different lifting heights.
For example, an illustrative machine might have:
| Lift Height | Example Rated Capacity |
|---|---|
| 3,000 mm | 1,500 kg |
| 4,000 mm | 1,500 kg |
| 5,000 mm | 1,300 kg |
| 5,500 mm | 1,100 kg |
These figures are illustrative only, not a universal rating for electric pallet stackers.
The actual capacity must come from the manufacturer's load chart for the specific model, mast and load center.
Duplex or Triplex: Which One Fits Your Warehouse?
The selection should be based on the application.
Choose a Duplex Configuration When:
A duplex mast may be considered when:
Required lift height is moderate
Storage racks are not extremely high
The warehouse has conventional pallet stacking
Overall equipment height is a major consideration
The application does not require very high lifting
Consider a Triplex Configuration When:
A triplex mast may be considered when:
Storage racks are higher
The required lift height approaches or exceeds typical duplex configurations
The warehouse needs greater vertical storage utilization
The machine needs substantial free lift
The overall lowered height must remain practical relative to the available lift height
The correct configuration still depends on the manufacturer's specifications.
Example: Selecting a Mast for a 4.5 m Warehouse Rack
Suppose a distribution warehouse has:
Rack height: 4,500 mm
Pallet weight: 1,200 kg
Pallet depth: 1,000 mm
Load center: approximately 500 mm
Door height: 2,400 mm
Indoor operation
The buyer should not simply ask for a "1.2 ton electric stacker."
A more useful inquiry would be:
"We need an electric pallet stacker with a 1,200 kg working load, approximately 500 mm load center and around 4,500 mm lifting height. The maximum doorway height is 2,400 mm. Please recommend the appropriate mast configuration and provide the capacity chart."
This gives the supplier enough information to determine whether a duplex or triplex configuration is appropriate.
What Information Should You Send to a Stacker Supplier?
For an accurate quotation, provide:
Maximum load: kg
Pallet size: length × width
Load center: mm
Required lifting height: mm
Rack height: mm
Door height: mm
Ceiling height: mm
Indoor or outdoor use
Required aisle width
Operating hours per day
This information is much more useful than asking only for a "2 ton electric pallet stacker."
Duplex and Triplex Mast Selection Example
Consider two applications:
Application 1: General Warehouse
Load: 1,000 kg
Lift height: 3,000 mm
Standard pallet
Normal warehouse ceiling
No unusual overhead restrictions
A duplex configuration may meet the application if its rated capacity and dimensions match the requirements.
Application 2: High-Rack Distribution Center
Load: 1,500 kg
Lift height: 5,000 mm
Palletized goods
High storage racks
Limited floor area
A triplex configuration may be considered because the required lift height is substantially higher.
However, the buyer should still check the capacity at the specified 5,000 mm lift height and load center, rather than relying on the nominal 1,500 kg rating.
Final Takeaway
The main difference between duplex and triplex electric pallet stacker masts is the number of mast stages and the lifting range they can provide.
Duplex = two-stage mast for moderate lifting requirements.
Triplex = three-stage mast for higher lifting requirements and greater vertical storage flexibility.
But mast selection should not be based on maximum lift height alone.
Before purchasing an electric pallet stacker, compare:
Maximum lift height
Lowered mast height
Free lift
Load center
Rated capacity at the required height
Door and ceiling clearance
Rack height
Operating environment
A properly matched mast allows the electric pallet stacker to work within the actual warehouse conditions rather than simply meeting a headline lifting specification.