Bulk material handling – belt conveyors The rated capacity of a belt conveyor depends primarily on two factors. If one is the effective cross-sectional area of the material on the belt, the other governing factor is the __________ of the belt.

Introduction / Context:
Belt conveyors are widely used in mining, cement, food, and packaging industries. Their rated capacity is a basic design parameter that determines how much bulk solid can be transported per unit time. Understanding which variables truly control capacity helps in sizing drives, belts, and transfer points.

Given Data / Assumptions:

• Belt is troughed; loading cross-section is well defined by troughing idlers and surcharge angle.
• Material is free-flowing and the belt is operated within allowable troughing and speed limits.
• No spillage; steady continuous operation.

Concept / Approach:
Conveyor capacity (mass flow rate) is the product of the bulk density ρ_b, the effective cross-sectional area A of the load on the belt, and the belt linear velocity v. Thus, capacity depends directly on A and v. While thickness and length are important for strength and layout, they do not directly set the instantaneous capacity.

Step-by-Step Solution:

Verification / Alternative check:
Design handbooks provide capacity tables in terms of belt width (which sets area) and belt speed. For the same width and loading, doubling belt speed approximately doubles capacity, confirming the relationship.

Why Other Options Are Wrong:

• Thickness: relates to tensile strength, impact resistance, and life; it does not directly change the loaded cross-section or velocity.
• Length: affects total power and tension distribution but not the instantaneous mass flow rate at a given section.
• None of these: incorrect because speed is the co-determining factor with cross-sectional area.

Common Pitfalls:
Assuming belt width alone fixes capacity; if the speed is too low, capacity falls short. Conversely, excessively increasing speed can cause dusting, belt wear, and spillage, reducing effective capacity.

Final Answer:
speed