Aluminum vs steel gantry crane lifting systems

Steel has been the primary material for lifting applications since the 1870s, replacing iron structures. On the other hand, aluminum is a relatively recent addition to the lifting industry, becoming significantly prominent only in recent years.

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Each material, aluminum and steel, offers unique advantages and drawbacks when used in industrial lifting. This article delves into gantry cranes, examining the differences between these materials and providing guidance for users and specifiers.

Aluminum vs steel - strength-to-weight ratio

In gantry cranes with similar load ratings and sizes, steel can be 2.5 to 3 times heavier than aluminum. This substantial difference in strength-to-weight ratio means aluminum gantries are easier to handle manually due to their lower overall weight.

In today’s commercial environment, where worker health and safety are paramount, the ease of assembly, operation, and disassembly of tools is crucial. The portability of aluminum gantries translates into significant economic benefits.

Corrosion resistance

Steel surfaces require protective coatings to prevent rust. Over time, these coatings can peel, chip, crack, or erode, exposing the steel to rust, decreasing the equipment's lifespan, and potentially causing safety issues if not inspected regularly. Aluminum, especially when anodized, does not encounter these problems.

A study by E.W. Skerrey from the Research Laboratories of British Aluminum demonstrated minimal change in anodized aluminum surfaces over 30+ years of salt spray testing, indicating negligible degradation in mechanical properties. This characteristic is particularly beneficial in coastal or marine environments, where salt spray or high humidity would accelerate rusting in steel.

According to BS EN ISO 12944-2 (British Standard), very high corrosion areas can cause 80-200 microns of low-carbon steel thickness loss per year. With aluminum, there's no need for frequent repainting or surface treatment, leading to lower maintenance costs over the equipment's lifecycle.

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Deflection

Deflection, or the curvature of a beam under load, tends to be more pronounced in aluminum gantries. While the ratio of length to deflection varies by material and design, a steel beam usually stays level under load, whereas an aluminum beam may bend but returns to level once the load is removed.

Interestingly, deflection can act as a safety mechanism. When an aluminum gantry exceeds its load limit, it bends gradually until it reaches its yield point, known as soft or benign failure. This slow bending gives the operator time to reduce the load before structural failure occurs and serves as a visual indicator of an overload.

Conversely, steel structures under excessive load remain stiff and suddenly snap, leading to catastrophic failure where the load is dropped abruptly. However, steel systems have the advantage of a flat, stable beam under load, aiding in the smooth movement of trolleys.

For aluminum systems, the deflection creates slight inclines, making trolley movement difficult, especially with heavier loads or longer beams. This issue can be mitigated with multiple trolleys or geared systems that use mechanical advantage to manage the slope, but it remains a significant consideration.

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