Operating a forklift with the mast raised is one of the most hazardous conditions in material handling. The higher the load, the greater the risk of tip-over, load loss, and pedestrian injury. Understanding and following mast-raised safety rules is critical for operator protection and workplace safety.
The Core Problem: Stability Changes with Height
When the mast is raised, the forklift's combined center of gravity shifts upward and forward. This movement pushes the center of gravity toward—and potentially beyond—the edges of the stability triangle formed by the front wheels and rear axle pivot point.
Higher lift height means less stability. A forklift that is perfectly stable with a load at ground level can tip forward or sideways when that same load is raised to full height, especially during turns or sudden stops.
Travel Rules: Never Move with a Raised Mast
Primary rule: Never travel with the mast raised. Doosan's manual explicitly states: "Do not travel with a raised load. Do not travel with the mast raised. The lift truck can roll over and cause injury or death".
The only exception allowed by OSHA is "very slow inching" for final positioning—not full travel across the warehouse floor.
Travel position: The forks should be carried 4 to 6 inches (10-15 cm) above the floor, with the mast tilted fully back. This position keeps the load's center of gravity low and rearward, maximizing stability.
Mast Tilt Rules: Never Tilt Forward with a Raised Mast
Tilting the mast forward when the forks are elevated is extremely dangerous. The Komatsu manual warns: "Do not tilt the mast forward when the forks are loaded and raised. There is danger that the load may fall and that the lift truck may tip".
Safe tilt practice:
Only tilt the mast forward when picking up or depositing a load at low height
Tilt only when the load is positioned directly over the rack or stack
Never tilt a raised load forward during travel
Always tilt back before moving
Clearance Rules: Watch Overhead
A raised mast increases the forklift's total height significantly. The operator must check for overhead obstructions before raising the mast.
Hazards to watch: Sprinkler systems, light fixtures, pipes, electrical wiring, doorways, mezzanine structures, overhead conveyors, and rack beams.
The forklift's stability is also affected by the lift height. When stacking at height, the operator should:
Bring the mast to vertical at 6-8 inches (15-20 cm) above ground
Then raise the load to final height
Never attempt to tilt the mast beyond vertical with the load raised high
No One Under the Forks (The "Danger Zone")
Multiple manuals emphasize the same warning: Never allow anyone to stand, walk, or work under raised forks.
What the manuals say:
Komatsu: "The area under the forks is a danger area. If the forks come down, the person under the forks may be crushed, seriously injured or killed"
Algonquin College safety program: "Not allow anyone to pass under the elevated portion of the truck, such as the forks or the load"
This rule applies even if the load appears stuck or caught. A raised load can fall suddenly at any moment due to hydraulic failure, seal failure, or mechanical malfunction.
Pedestrian Exclusion Zones
When operating with a raised mast or elevated load, create a clear safety zone around the forklift. The OSHA Oregon manual requires that no one passes under the elevated portion of the truck. Pedestrians must be kept well clear of the fall zone.
Personnel Elevation Rules (If Using a Work Platform)
When a forklift is used to elevate workers on an approved platform (never on forks alone), additional rules apply:
Safety platform requirements:
The platform must be secured to the forks or mast to prevent movement
Must include guardrails and toeboards meeting safety standards
Platform floor must have slip-resistant surface with holes no larger than 1 inch
Safe operations for personnel lifting:
The operator must remain at the controls at all times
The mast must be kept vertical (not tilted)
The parking brake must be engaged
Never move the truck from point to point with workers on the platform
Lowering and Parking
Lowering procedure: Before lowering the load, return the mast to the vertical position. Never lower with the mast tilted forward.
When parking or leaving the forklift:
Fully lower the forks to the ground
Mast tilted vertical
Neutralize controls
Set parking brake
The OSHA Oregon standard specifies that when an operator leaves the truck (within 25 feet and in view), the forks must be down, controls in neutral, and brakes set.
Daily Inspection of Mast and Lift Components
Before any shift where the mast will be raised, inspect the mast components:
Check mast chains for wear, elongation, and lubrication
Verify hydraulic hoses are not leaking or damaged
Ensure all rollers move smoothly
Confirm sheaves are free-turning
Test lift cylinder for smooth operation
A chain or hydraulic failure at height is catastrophic. Preventive maintenance is the only protection.
Pre-Travel Checklist
Before moving any distance with the mast raised (even for minor positioning):
Ensure mast is vertical
Brake is applied
Path is clear of pedestrians
Overhead clearance is confirmed
Only move at very low speed for final positioning
Summary Table: Mast Raised Safety Rules
Activity Safe Practice Prohibited Action
Travel Forks 4-6" high, mast tilted back Traveling with mast elevated
Tilting Tilt only when picking/depositing at low height Tilting forward with raised load
Positioning Move only very slowly for final placement Full-speed travel at height
Pedestrians Establish exclusion zone Anyone under raised forks
Overhead clearance Check before raising mast Hitting pipes, lights, sprinklers
Parking Lower forks fully before leaving Leaving with mast raised
The Bottom Line
Forklift safety with the mast raised is governed by three non-negotiable rules: do not travel with the mast raised, do not tilt forward with a raised load, and never allow anyone under raised forks. The stability triangle shrinks as the mast rises. Respect that fact, follow the rules, and stay alive.