Allow me to preface my article with a recent accident: A maintenance technician was nearly killed when the tilt cylinder hose assembly that was made by an untrained technician unexpectedly failed, causing the mast to tilt forward and stop a few feet from a steel structure. The victim was apparently spared from severe injury, and possibly death, for two reasons. First, he was wearing a safety harness. Second, the out-of-control mast did not strike the steel structure.At the time of the accident the forklift was apparently being used in strict accordance with OSHA regulations.
Regulatory groups and manufacturers have developed what they refer to as “safe” methods for lifting personnel with a forklift (OSHA 1926.602) — or if you will, licensing forklift owners and operators to use their forklifts as crossover vehicles. In addition to transporting cargo, they can be used as “mobile elevating work platforms for personnel.”
OSHA’s committees did, however, mandate a few stipulations:
1. The work platform must be equipped with standard guardrails or equivalent means, and must be firmly secured to the lifting carriage or forks.
2. The hydraulic system must be designed such that the lift mechanism will not drop faster than 135 ft (41 m) per minute in the event of a failure in any part of the system.
3. The operator must be in the driving seat while workers are on the platform.
4. The operator must be in the driving seat while raising or lowering the platform.
5. The forklift must not travel from point to point with the work platform elevated at a height greater than 4 ft (1.22 m) while the platform is occupied. When necessary, an occupied platform can be moved as long as the forklift is “inched” at a very low speed.
6. The area between the person on the platform and the mast must be guarded to prevent contact with chains or other pinch points.
The preceding stipulations are well-founded. However, could the regulatory groups and manufacturers have overlooked other critical elements that could cause or contribute to the uncontrolled descent of a forklift’s lift or tilt mechanisms?
OSHA’s 135 ft/min descent rate rule is preposterous because it is impossible to control the descent rate of the lift mechanism “in the event of a failure in any part of the system.” Here are a few examples of failures that could cause uncontrolled descent of a forklift’s lift mechanism:
• lift chain failure,
• cylinder retaining pin failure,
• cylinder internal seal failure,
• cylinder rod failure,
• mast guide wear-plate wear, or
• hose failure.
Most of these failures are caused by inadequate maintenance training, poor or non-existent service and repair, or forklift abuse.
Like apples to oranges
From a design point of view, comparing forklifts to aerial platforms is like comparing apples to oranges! The fundamental purpose of a forklift is to transport cargo with the added convenience of self-loading and unloading with the aid of hydraulics. The fundamental purpose of an aerial work platform is to elevate and transport personnel within the guidelines of safe operation.
Forklifts and aerial platforms both share similar hydraulic components from an operational point of view. However, an aerial platform designer has an additional design responsibility — to make sure the platform cannot fail under any circumstances.
An aerial platform has many hydraulic safety valves that are not usually incorporated into a forklift’s hydraulic system design. This makes a forklift inherently unsafe for use in elevating or transporting people. Forklift manufacturers aren’t shy about warning of the consequences of using their products for this purpose.
Forklifts do not have redundant safety components or systems to specifically protect the rider in the event of the unexpected failure of a critical hydraulic or mechanical component. On the other hand, aerial platform designers focus heavily on platform reliability and machine stability, which makes safety the nucleus of aerial platform design. Accordingly, aerial platforms have redundant safety components and systems for the specific purpose of protecting the rider should unexpected failure of a critical hydraulic component occur.
Using a forklift as an aerial platform puts the rider’s life in the hands of the forklift driver. A conventional aerial platform, on the other hand, places the rider in control of all vehicle functions, including propulsion and steering. (For a case history about this, find the colored sidebox on page three.)