Expert balancing tips and tricks

Tip 1: "by ear and by touch" diagnostics (preliminary)

Modern instruments are indispensable for precise diagnostics, but sometimes you can make an initial assessment with the old "tried-and-tested" methods. This doesn't replace measurement, but it does help you quickly locate the problem.

Checking bearings with a screwdriver

Take a long screwdriver or a metal rod. With the machine running, carefully place the tip against the bearing housing and the handle against your ear. Metal conducts sound extremely well, and you'll be able to hear the internal condition of the bearing.

• A healthy bearing: an even, monotonous, quiet hum.
• A faulty bearing: you'll hear unusual noises — rustling, grinding, periodic clicking or "trrr"-type sounds. This points to damage to the raceways or rolling elements.

Checking for play and looseness

With the machine stopped, try physically shaking and rocking the components. This helps reveal mechanical looseness, which shows up in the spectrum as a "forest" of harmonics.

• Shake the rotor shaft: grasp the shaft or impeller and move it forcefully in the radial and axial directions. There must be no knocking or noticeable play. Knocking indicates critical bearing wear.
• Check the fastenings: try shaking the motor casing, the bearing supports and the frame. Nothing should "move" or shift. If there is movement, look for loose foundation bolts or cracks in the frame.

Tip 2: how to choose the trial weight mass quickly

Choosing the right trial weight mass is the key to successful balancing. Too light a weight won't produce a noticeable change in vibration and the calculation will be inaccurate. Too heavy a weight can cause dangerous vibration.

A formula for a quick estimate:

For rotors running at 1000–3000 rpm you can use a simple rule of thumb:

Trial weight mass (grams) ≈ (rotor mass (kg) × 10) / (speed (thousand rpm))²

Example: a fan rotor with a mass of 50 kg runs at 1500 rpm (1.5 thousand rpm).

Weight mass ≈ (50 × 10) / (1.5 × 1.5) = 500 / 2.25 ≈ 222 grams.

You can confidently start with a trial weight of 200–250 grams.

Tip 3: always mark up the rotor!

This is the simplest but most important piece of advice. It saves a lot of time and prevents 90% of angle-related mistakes.

1. Direction-of-rotation arrow: before you start work, mark a clear arrow showing the direction of rotation on a visible part of the rotor (or shaft).
2. Angular markings: stick on a phase mark (for the tachometer) and treat it as 0°. Using a protractor — or even a sheet of paper folded in half — mark 90°, 180° and 270° with a marker pen IN THE DIRECTION of rotation.

What this gives you:

• You'll never get confused about which way to count the angle when fitting the correction weight.
• You can find the required angle easily and quickly, with no repeat measurements.

Tip 4: photograph everything

Turn the balancing job into a photo report. It instils discipline, helps with the analysis and serves as excellent documentation for the future.

What to photograph:

• An overall view of the equipment before you start work.
• The mounting locations of the vibration sensors and the tachometer.
• The rotor with the markings applied and the phase mark.
• The trial weight fitted in plane 1, with the angle clearly visible.
• The final correction weight with the fixing clearly visible (weld seam, bolts).
• Screenshots of the Balanset software showing the "BEFORE" and "AFTER" readings.

You can attach these photos to the balancing report, use them to train colleagues, or to analyse what happened if something didn't go to plan.