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Lift Truck Mast
The second most important lift truck component is the type of mast. There are two mast specification parameters. The first is the overall extended (lift) height that allows the vehicle to deposit or withdraw a unit load from the highest floor or rack storage position. The second is the lowered (down) or collapsed height of the mast. This height is the clearance for the lift truck to pass through the facility doorways, enter delivery trucks, and enter dense storage rack lanes.
Seven types of masts are available for a lift truck:
(i) Single-Stage Non-telescopic Mast -
It lifts a unit load to a 7- to 8-ft-high floor or rack storage position. In today warehouse operation, the single-stage mast has very limited application and is uncommon in a company lift truck fleet.
(ii) Two-Stage Non-telescopic Mast -
It has little or no free lift. No free lift means that as the forks start to rise, the mast starts to rise. With this mast, the lift truck deposits or retrieves pallet loads at storage positions that are 12 to 13 ft high.
(iii) Two-Stage Standard Mast with Low Free Lift -
With this mast, the lift truck deposits and withdraws a unit load from a storage position that is 15 to 20 ft high. This mast feature of low free lift conserves energy and allows the lift truck to be used as a multipurpose vehicle in a warehouse with a low or high ceiling.
(iv) Two-Stage Mast with High Free Lift -
This free lift mast permits the pallet load to be raised to almost half the mast height without elevating the mast. This feature permits the lift truck to operate as a dock vehicle that loads or unloads delivery vehicles. Also the lift truck deposits and retrieves unit loads from storage positions 20 ft high, and it can operate in an area that has a low ceiling.
(v) Three-Stage Mast with Full Free Lift -
The mast feature allows the lift truck to deposit or withdraw unit loads from 20- to 25-ft-high storage positions. Also the full free lift permits the lift truck to operate in facility areas with low ceiling clearance.
(vi) Four-Stage Mast with Full Free Lift -
This mast feature permits the lift truck to deposit or withdraw unit loads from the 30- to 40-ft-high positions.
(vii) Rigid Mast with or without Free Lift -
The rigid mast permits the unit load deposits and withdrawals from an elevated rack position 40 to 60 ft high. The rigid mast is associated with the hybrid or storage/retrieval system vehicles.
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