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Two assessment systems — don’t mix them up
| Sistem | Enota | What it assesses | When to use |
|---|---|---|---|
| ISO 10816 / 20816 | mm/s (vibration velocity RMS) | The assembled machine on its supports | Field balancing, machine acceptance |
| ISO 1940 / 21940-11 | g-mm (residual unbalance), G grades | The rotor itself | Balancing machines, the rotor’s data sheet |
The device shows both: vibration in mm/s and residual unbalance in g·mm.
Assessment by vibration (mm/s)
The general scale (typical industrial machines):
| Območje | RMS, mm/s | Pomen |
|---|---|---|
| A | up to 1.4 | excellent — like a new machine |
| B | 1,4 – 2,8 | good — fit for long-term operation |
| C | 2,8 – 4,5 | acceptable for limited time — plan measures |
| D | above 4.5 | unacceptable — damage risk |
Field adjustments:
- Mulchers/mowers: up to 4.8 mm/s is normal; on soft (spring) supports up to 7.1 mm/s; with the agricultural factor of 1.2–1.3, “below 8 mm/s is already good”. Chasing 0.5 mm/s on a mulcher is pointless.
- Ventilatorji (ISO 14694): flexible mounting (rubber supports) has its own limits — a machine with a 3.05 mm/s 1x component on rubber mounts rates as “Good”. Sometimes the manufacturer sets its own limit (a real example: 2.78 mm/s).
- Watch not only the overall vibration but the 1x component: balancing reduces exactly that. If overall is 5 mm/s but 1x is only 1 mm/s, further balancing gains almost nothing — the rest is “shaken” by other causes.
Assessment by residual unbalance (g·mm, G grades)
A G grade is the permissible “specific unbalance” taking RPM into account. The faster it spins — the smaller the tolerance.
| Razred | Tipična uporaba |
|---|---|
| G16 | cardan shafts, agricultural rotors |
| G6.3 | fans, drums, pulleys, general-purpose electric motors — the default choice |
| G2.5 | turbines, machine tools, precision rotors |
| G1.0 / G0.4 | spindles, high-precision rotors |
The program has the Kalkulator toleranc ISO 1940: rotor mass + RPM + grade → the permissible residual unbalance per plane. The “balancing tolerance” field is optional — it is informational.
Examples from real support:
- a ~80 kg rotor at 3000 rpm: G6.3 ≈ 802 g·mm per plane, G16 ≈ 2037 g·mm;
- spindles are balanced to G1.0–G0.4 (support practice has reached G0.1);
- a marine/industrial fan after balancing: 0.5–0.6 mm/s is an excellent result.
What a normal job’s outcome looks like
“Before → after” reference points from real cases:
- a mulcher: 25 → 3 mm/s and 40 → 11 mm/s (a badly bent rotor — 11 mm/s is the ceiling there);
- a Seppi mulcher: >50 mm/s → “runs very quietly”;
- a 4500 kg crusher rotor: 6 and 8 → 0.9 and 1.3 mm/s;
- a university fan: 4 and 7 → 0.5 and 0.6 mm/s;
- a 24-tonne sugar fiberizer: 3.2 → 0.47 mm/s;
- a cardan shaft: 0.5 mm/s final.
A 3–10× drop within 1–2 iterations is normal for a sound machine. No drop after two iterations — don’t weld on more; switch to root-cause hunting (chapter 07).
The report
The program generates a balancing report (templates in the reporttpl folder — you can substitute your letterhead): initial and final vibration, RPM, weight masses and angles, residual unbalance. For the customer this suffices as a work-completion document.
About “certificates”: the device ships with the manufacturer’s calibration certificate. If the customer requires an accredited-laboratory certificate (ISO/IEC 17025), that is done at a local lab for a separate fee; the device itself needs no annual calibration.
