Which method is commonly used to balance a rotating machine?

• A. Hydraulic balancing
• B. Field balancing
• C. Thermal balancing
• D. Acoustic balancing

Answer: (B)

Balancing rotating machinery is about correcting uneven mass distribution so the rotor spins smoothly with minimal vibration. The method used most often is field balancing, which means balancing the rotor while the machine is in its installed location and under operating conditions. This approach uses portable vibration sensors and phase measurements to identify where the unbalance is located and how much weight needs to be added or removed. The key advantage is practicality: large or critical machines are expensive or impractical to disassemble for lab balancing, and field balancing allows corrections without taking the equipment offline for long periods. By measuring real-world running speeds and loads, the correction you apply reflects actual operating conditions, producing a more effective and durable balance.

The other terms don’t describe the standard process of correcting mass unbalance in a rotating part. They relate to different engineering concerns (hydraulic systems, heat distribution, or noise) and don’t provide the focused method for balancing a rotor in the field.