Rotors Balancing Procedure

Introduction: Pre-Balancing Requirements

Balancing is performed only for technically sound mechanisms, properly fixed in their designated places. Prior to balancing, any malfunctioning mechanism must be repaired, installed on serviceable bearings, and securely fixed. Additionally, the rotor should be cleaned of any impurities that could interfere with the balancing process.

Customer Responsibilities

The Customer is responsible for providing safe working conditions for balancing, including switching the mechanism on and off. The customer also provides personnel for necessary plumbing and welding works, access to the balancing rotor, and installation of testing and corrective weights. Access to a 220 V 50 Hz electrical network is required to power the device.

Types of Rotor Balancing

One-Plane Balancing ("Static")

One-plane balancing is typically performed for narrow disc rotors. Examples include narrow grinding wheels, belt pulleys, and disk flywheels.

Two-Plane Balancing ("Dynamic")

Two-plane balancing is performed for long (shaft) two-bearing rotors. Typical examples include electric motors and generators rotors, compressors and pumps rotors, fans rotor wheels, wide grinding wheels, spindles, and milling machines shafts with bars.

Resonance and Rotor Speed

The rotor speed should not fall within the machine resonance range. A difference of more than 10-20% in the measurement results in amplitude and/or phase from start to start indicates resonance. If resonance is detected, the rotor speed must be changed, or the installation conditions on the foundation must be altered.

Sensor Installation

The vibration sensor can be installed at the measuring point using a threaded rod (rigid mounting) or a magnetic suction cup. The phase angle sensor should be mounted on the machine body with a special tool and oriented towards the rotor's cylindrical or end surface. A mark should be applied to the rotor surface to indicate the phase angle.

Balance Criteria

Balancing is performed according to ISO 10816-1-97 (ISO 2372) standards. Limit values for vibration levels are established for four classes of machines and are provided in Table P.1.

)Machine class*	Admissible vibration levels, mm/s RMS
)Machine class*	Good	Admissible	Still admissible	Inadmissible
1	< 0.7	0.7-1.8	1.8-4.5	> 4.5
2	<1.1	1.1-2.8	2.8-7.1	>7.1
3	<1.8	1.8-4.5	4.5-11	>11
4	<2.8	2.8-7.1	7.1-18	>18

*) Note:

- Class 1 corresponds to small machines installed on rigid foundations (analogue - electric motors with a capacity of up to 15 kW);

- class 2 corresponds to medium-sized machines installed without separate foundations (analogue - electric motors with a capacity of 15–75 kW), as well as driving mechanisms on separate foundations with a capacity of up to 300 kW;

- Class 3 corresponds to large machines installed on rigid foundations (analogue - electrical equipment with a capacity of over 300 kW);

- Class 4 corresponds to large machines installed on lightweight foundations (analogue - electrical equipment with a capacity of over 300 kW).

- Equipment repair is not available.

- This type of work is not covered by the warranty.