Crusher Rotor Balancing

A crusher is a machine designed for mechanically breaking down pieces of hard material into smaller pieces. The primary working component of a crusher is the rotor, which is fitted with crushing elements (hammers, teeth, etc.). As the rotor rotates at high speed, it crushes the material fed into the crushing chamber.

Balancing the crusher using the Balanset-1A vibration analyzer. Eliminating crusher vibration.

Types of Crushers

There are several types of crushers, each differing in principle and construction:

Jaw Crushers: Material is crushed between two jaws, one of which is stationary while the other moves back and forth.
Cone Crushers: Material is crushed in the space between a stationary and a rotating conical bowl.
Impact Crushers: Material is crushed by the impact of hammers or blow bars attached to a rotating rotor.
Hammer Crushers: Material is crushed by the impact of hammers attached to a rotating rotor.

Problems Caused by Crusher Imbalance

Imbalance in the crusher rotor can lead to several serious problems:

Increased Component Wear: Constant vibration due to imbalance puts additional stress on all crusher components, leading to accelerated wear of bearings, shafts, drive mechanisms, crushing elements, and other parts. This increases the frequency of repairs and replacements, raising overall operating costs.
Bearings and Bearing Housings: Bearings subjected to constant vibration wear out faster, causing play and further increasing vibration. Failure of bearing housings is an even more severe issue, requiring crusher disassembly, transportation to a repair workshop, rotor disassembly, restoration work, and subsequent reassembly and installation. This results in significant downtime and additional costs.
Loosening of Bolted Connections: Vibration can cause bolted connections to loosen, leading to accidents and equipment failures.

What is Imbalance and Its Types?

Imbalance is a condition where the rotor’s mass is unevenly distributed relative to its axis of rotation. This results in centrifugal forces that cause vibration.

Types of Imbalance:

Static Imbalance: Occurs when the rotor’s center of gravity is offset from the axis of rotation, creating a single-sided force that causes vibration.
An example of a rotor with the static imbalance is presented in Fig.2
Dynamic Imbalance: Occurs due to uneven mass distribution along the length or diameter of the rotor, creating both forces and moments that cause additional vibrations.
Dynamic imbalance of rotor – couple of the centrifugal forces

Why Can’t You Balance Dynamic Imbalance Without Specialized Equipment?

Static imbalance can theoretically be corrected by adding weights to the lighter side of the rotor. However, this method is ineffective for dynamic imbalance, where the exact location and mass of corrective weights in multiple planes need to be determined. This requires a portable balancer or balancing machine to measure vibration amplitude and phase and calculate the necessary corrective weights and their placement.

Balancing Device for Crushers

The portable balancer and vibration analyzer “Balanset-1A” is ideal for balancing crushers on-site.

Main Characteristics and Advantages of Balanset-1A:

Ease of Use: Balanset-1A is easy to learn and use, even for those without specialized knowledge in vibration analysis.
Portability: The compact and lightweight device is easy to transport and use on-site.
High Accuracy: Balanset-1A provides high measurement accuracy, ensuring quality balancing.
Multifunctionality: The device can be used not only for balancing but also for vibration analysis and equipment diagnostics.

Crusher Balancing Process

Preparing the Crusher for Balancing

Cleaning: Remove dirt, dust, and other debris from the rotor and surrounding surfaces that could affect measurement accuracy.
Checking Fasteners: Ensure all bolts and nuts are securely tightened and the rotor is firmly mounted on the shaft.
Checking Bearings: Inspect bearing condition, ensuring there is no play or unusual noise. Replace bearings if necessary before balancing.
Installing Sensors: Mount vibration sensors on the crusher housing near the rotor bearings, oriented perpendicular to the shaft’s axis of rotation.
Installing the Tachometer: Attach a reflective marker to the shaft or pulley and set up the tachometer so its laser beam hits the marker.

Step-by-Step Balancing Process with Balanset-1A

Preparation: Attach vibration sensors to the crusher housing near the rotor bearings. The sensors should be oriented perpendicular to the rotor’s axis of rotation. Attach a reflective marker to the rotor or pulley. Mount the tachometer on a magnetic stand so that its laser beam hits the reflective marker. Connect the sensors to the “Balanset-1A” device, which is connected to a laptop. Launch the specialized balancing software.
Initial Measurement: Select the single or two-plane balancing mode in the software, depending on the rotor’s design and the nature of the imbalance. Weigh the calibration weight and enter its weight and installation radius into the program. Start the crusher and measure the initial vibration level at idle.
Installing the Test Weight: Install the calibration weight on the rotor in the first correction plane. Restart the crusher and measure the vibration. Ensure that the vibration or phase changes are at least 20%. If balancing in two planes, repeat the test weight installation procedure in the second correction plane.
Data Analysis: Using the obtained data, determine the corrective weights and their installation locations for balancing the rotor.
Fig. 7.37. Results of calculation of corrective weights – free position.
Polar diagram
Installing the Corrective Weights: Install the corrective weights on the rotor at the locations specified by the program. Suitable methods for attaching weights include welding, screws, clamps, or other appropriate methods.
Verification: Measure the vibration levels after installing the weights at idle. Ensure that the vibration is reduced to an acceptable level. If necessary, add or remove part of the corrective weight and recheck the balance.

Field Balancing of Crushers

Field balancing of crushers using the portable balancer “Balanset-1A” significantly reduces equipment downtime and avoids transportation costs to a service center.

Advantages of Portable Devices:

Convenience and speed of on-site balancing
Time and cost savings
High balancing accuracy

Devices