Installation and Commissioning of Vibrating Feeders

1. Introduction

Vibrating feeders play a critical role in iron ore mining and processing plants. They are the mechanical link between bulk storage systems such as hoppers, bins, or stockpiles and downstream equipment like crushers, screens, and conveyors. While they may appear mechanically simple, vibrating feeders are highly sensitive to installation quality and commissioning discipline.

A large percentage of vibrating feeder failures in mining plants can be traced back not to poor design, but to incorrect installation practices or improper motor rotation during commissioning. Among these issues, the wrong direction of rotation of vibrating motors is one of the most frequent and most damaging errors.

This article focuses on the practical aspects of installing and commissioning dual-motor linear vibrating feeders for iron ore service, with special emphasis on understanding motor rotation, eliminating lateral forces, and verifying correct electrical connections before start-up.

2. Why Vibrating Feeders Are Critical in Iron Ore Handling

Iron ore presents a demanding duty for vibrating feeders due to:

• High bulk density (typically 2.0–2.6 t/m³)

• Abrasive particle characteristics

• Wide particle size distribution

• Potential moisture variation

A vibrating feeder must:

• Deliver a consistent feed rate

• Protect crushers from shock loading

• Prevent segregation and material surging

• Operate continuously under harsh conditions

Incorrect installation compromises all these objectives.

3. Working Principle of Dual-Motor Vibrating Feeders

Most heavy-duty iron ore feeders use two identical vibrating motors, mounted symmetrically on the feeder body. Each motor contains eccentric weights that generate centrifugal forces during rotation.

The centrifugal force generated by one motor is:

"Centrifugal Force":
F = m × r × ω²

Where:
m = eccentric mass (kg)
r = eccentric radius (m)
ω = angular velocity (rad/s)

Each motor produces a rotating force vector. The behaviour of the feeder depends entirely on how these vectors interact.

4. Why Opposite Motor Rotation Is Mandatory

When the two motors rotate in opposite directions at the same speed:

• Horizontal (lateral) force components cancel each other

• Vertical and longitudinal force components combine

• The feeder experiences pure linear vibration

This linear motion causes the iron ore to move forward uniformly, with minimal stress on the structure.

If the motors rotate in the same direction, the following occurs:

• Lateral forces are introduced

• The feeder twists instead of vibrating linearly

• Springs are unevenly loaded

• Structural fatigue accelerates

• Material flow becomes erratic

This is not a theoretical issue; it is one of the most common commissioning failures on mine sites.

5. Mechanical Installation Requirements

5.1 Foundation and Support Structure

• Foundation mass ≥ 3 times operating feeder mass

• Level tolerance ±2 mm per meter

• Isolated from surrounding steel structures

• No rigid connections restricting vibration

5.2 Springs and Isolation System

• All springs must have identical stiffness

• Installed height variation ≤ 3 mm

• Springs must operate within the elastic range

• No coil binding at maximum amplitude

6. Electrical Installation Fundamentals

Each vibrating motor is typically a three-phase induction motor.

Key requirements:

• Independent overload protection per motor

• Synchronised start command

• Identical cable lengths were practical

• Secure earth bonding

7. Checking Motor Rotation Before Start-Up

7.1 Why Rotation Must Be Verified First

Starting a vibrating feeder without confirming motor rotation can:

• Instantly overload the structure

• Cause the feeder to walk sideways

• Damage chute connections

• Crack springs or welds

7.2 Phase Rotation Meter Method

A phase rotation meter determines the phase sequence of the supply (R-S-T).

Procedure:

1. Connect the meter to the incoming supply

2. Observe the indicated rotation direction

3. Compare with the required motor rotation

This method avoids mechanical stress and guesswork.

8. Bump Testing (Only When Safe)

If mechanical access permits and the feeder is empty:

• Energise motors for 1–2 seconds

• Observe the shaft rotation direction

• De-energize immediately

This must never be done with material present.

9. Correcting Rotation Direction

In a three-phase system:

• Swapping any two phases reverses motor rotation

Example:

• Original: R-S-T

• Changed to: R-T-S

Only one motor should have its phases swapped to achieve opposite rotation.

10. Commissioning Procedure

10.1 No-Load Commissioning

• Start motors

• Confirm linear motion

• Measure motor current

• Inspect vibration symmetry

10.2 Load Commissioning

• Introduce iron ore gradually

• Monitor feed rate

• Check motor current stability

• Inspect structural response

11. Common Failures and Root Causes

12. Conclusion

Correct installation and commissioning of vibrating feeders is not optional; it is essential for reliability, safety, and production efficiency. Ensuring opposite motor rotation is one of the simplest yet most critical steps in the entire process.