For general-duty belt conveyors handling bulk solids without cleats or special surfaces, what is the typical maximum slope (inclination) that can be used reliably?

Introduction / Context:
The allowable slope for a belt conveyor depends on friction between the belt and material, particle properties, and the presence of cleats/sidewalls. Exceeding the recommended angle risks rollback and spillage.

Given Data / Assumptions:

• Smooth, standard belt without cleats or high-friction lagging.
• Typical bulk solids (e.g., ores, grains) in continuous service.
• Conventional industrial design practices.

Concept / Approach:
General practice limits smooth belts to about 12–15° for many materials. While special belts with ribs/sidewalls can climb much steeper (even >30°), the typical textbook maximum for standard belts is around 15°. This balances capacity, stability of the bed, and housekeeping considerations.

Step-by-Step Solution:
Identify belt type: smooth, general-duty.Check common design heuristics: 12–15°.Select the conservative standard maximum: 15°.

Verification / Alternative check:
Vendor handbooks list 12–18° ranges depending on material “angle of surcharge”; 15° is a widely taught value.

Why Other Options Are Wrong:
30°/45°/60° require special cleats or corrugated sidewalls; not general-duty smooth belts.

Common Pitfalls:
Assuming angle of repose equals allowable conveyor slope; rolling behavior differs from static repose.

Final Answer:
15°