ਘੁੰਮਣ ਵਾਲੀ ਮਸ਼ੀਨਰੀ ਵਿੱਚ ਅਸੰਤੁਲਨ ਨੂੰ ਸਮਝਣਾ
ਅਸੰਤੁਲਨ (used interchangeably with ਅਸੰਤੁਲਨ) is the condition in a ਰੋਟਰ where the centre of mass does not lie on the axis of rotation. That offset — the ਐਕਸੈਂਟ੍ਰਿਸਿਟੀ (ਕੇਂਦਰ-ਭ੍ਰਿਸ਼ਟਤਾ) — means mass is distributed unevenly around the shaft. When the rotor turns, the off-centre mass is flung outward by ਕੇਂਦਰਾਪਸਾਰੀ ਬਲ, producing a rotating load that shakes the bearings and the whole machine. Unbalance is by a wide margin the most common source of ਵਾਈਬ੍ਰੇਸ਼ਨ in rotating equipment, and it is the fault that ਬੈਲੇਂਸਿੰਗ exists to correct.
1. Definition and the Physics Behind It
Quantitatively, unbalance U is the product of the offset mass and its radius from the axis — a heavy spot of mass m sitting at radius r gives U = m·r, expressed in ਗ੍ਰਾਮ-ਮਿਲੀਮੀਟਰ (g·mm) or gram-inches. It can equivalently be written as the total rotor mass multiplied by the eccentricity of its centre of gravity (U = M·e). What matters mechanically is the force this creates. The centrifugal force grows with the square of angular speed:
F = m · r · ω² — double the speed and the disturbing force ਚੌਗੁਣਾ ਹੋ ਜਾਂਦਾ ਹੈ.
This square-law relationship is why a rotor that runs smoothly by hand can shake violently at operating speed, and why fast machines must be balanced far more precisely than slow ones. The force rotates with the shaft, so it drives the structure once per revolution — the origin of unbalance’s unmistakable signature.
2. The Classic Vibration Signature
Unbalance is one of the easier faults to diagnose because its fingerprint is so consistent:
- ਫ੍ਰੀਕੁਐਂਸੀ: vibration appears at exactly 1× ਘੁੰਮਣ ਦੀ ਗਤੀ 'ਤੇ (ਇਹ ਚੱਲਣ ਦੀ ਗਤੀ). Change the speed and the peak tracks it precisely — a defining trait that distinguishes it from many other faults.
- ਦਿਸ਼ਾ: the energy is predominantly ਰੇਡੀਅਲ (horizontal and vertical), with little ਐਕਸੀਅਲ (ਧੁਰੀ) (thrust) content.
- ਐਂਪਲੀਟਿਊਡ: it is proportional to the square of speed — doubling RPM roughly quadruples the response, as the physics above predicts.
- ਪੜਾਅ: 1× ਦੀ ਫੇਜ਼ reading is stable and repeatable, which is precisely what makes the heavy spot locatable and correctable.
That stable amplitude-and-phase pair is the raw material for correction: knowing how big the 1× response is and ਜਿੱਥੇ it points lets an analyst calculate the size and angle of the counterweight needed. A pure 1× peak with low axial vibration points to unbalance; a strong 2× component instead suggests ਮਿਸਅਲਾਈਨਮੈਂਟ ਜਾਂ ਢਿੱਲਾਪਣ.
3. The Three Types of Unbalance
ਸਥਿਰ ਅਸੰਤੁਲਨ
Also called “force unbalance,” this is the simplest case: the mass is offset in a single plane, like one heavy spot on a thin disc. It is termed ਸਥਿਰ because it shows up with the rotor at rest — set on frictionless knife edges, the rotor rolls until the heavy spot settles at the bottom. It is corrected with a single weight placed 180° opposite the heavy spot, the domain of ਸਿੰਗਲ-ਪਲੇਨ ਬੈਲੇਂਸਿੰਗ.
ਕਪਲ ਅਸੰਤੁਲਨ
Here two equal heavy spots sit at opposite ends of the rotor, 180° apart. They cancel as a net force but form a ਕਪਲ — a rocking moment that tries to twist the rotor end-over-end. A rotor with pure couple unbalance is statically balanced (it will not roll on knife edges) yet vibrates severely once spinning. Correction needs two weights in two separate planes to oppose the rocking moment.
ਗਤੀਸ਼ੀਲ ਅਸੰਤੁਲਨ
The condition found in almost all real machinery, dynamic unbalance is a combination of static and couple components. Correcting it requires mass changes in at least two planes along the rotor — the process of ਡਾਇਨਾਮਿਕ (ਟੂ-ਪਲੇਨ) ਬੈਲੇਂਸਿੰਗ. A closely related case, where the static and couple effects share the same angular position, is called ਅਰਧ-ਸਥਿਰ ਅਸੰਤੁਲਨ.
4. Common Causes of Unbalance
Unbalance may be present from manufacture or develop in service. Typical sources include:
- ਨਿਰਮਾਣ ਦੀਆਂ ਖਾਮੀਆਂ: ਢਲਾਈਆਂ ਵਿੱਚ ਛਿਦਰਾਂ, ਅਸਮਾਨ ਪਦਾਰਥ ਘਣਤਾ ਅਤੇ ਮਸ਼ੀਨਿੰਗ ਸਹਿਣਸ਼ੀਲਤਾਵਾਂ।
- ਅਸੈਂਬਲੀ ਗਲਤੀਆਂ: mis-installed components, unevenly tightened bolts or misaligned keys that shift the mass distribution.
- ਘਿਸਾਵਟ ਅਤੇ ਟੁੱਟ-ਭੱਜ: ਅਸਮਾਨ ਘਸਾਈ, ਖੋਰ (ਕਰੋਜ਼ਨ) ਜਾਂ ਘਸਾਈ ਪੱਖੇ ਦੀਆਂ ਬਲੇਡਾਂ ਅਤੇ ਪੰਪ 'ਤੇ ਇੰਪੈਲਰ.
- ਪਦਾਰਥ ਦਾ ਜਮ੍ਹਾਂ ਹੋਣਾ: accumulation of dirt, dust or product on the rotors of fans, blowers and centrifuges.
- ਹਿੱਸੇ ਦੀ ਅਸਫਲਤਾ: a thrown balance weight or a broken blade creates a severe unbalance condition instantly.
5. Why Correcting Unbalance Is Critical
Running a machine with significant unbalance steadily damages it, because the rotating force cycles the structure on every revolution:
- ਬੇਅਰਿੰਗ ਦੀ ਅਚਨਚੇਤੀ ਅਸਫਲਤਾ: bearings carry high dynamic loads and wear out rapidly.
- ਥਕਾਵਟ ਅਤੇ ਦਰਾੜਾਂ: cyclic stress accumulates ਥਕਾਵਟ (ਫੈਟੀਗ) damage in the shaft, foundation and structure.
- ਘੱਟੀ ਹੋਈ ਕੁਸ਼ਲਤਾ: energy is dissipated as vibration and heat instead of useful work.
- ਸੁਰੱਖਿਆ ਜੋਖਮ: severe unbalance can escalate to catastrophic failure.
6. Measuring, Correcting and Tolerancing Unbalance
Unbalance is removed by a systematic balancing procedure — one of the most cost-effective ways to raise machinery reliability. On an assembled machine this is done in place rather than on a ਬੈਲੇਂਸਿੰਗ ਮਸ਼ੀਨ। Balanset-1A ਵਰਗਾ ਇੱਕ ਪੋਰਟੇਬਲ ਦੋ-ਚੈਨਲ ਵਿਸ਼ਲੇਸ਼ਕ ਜਿਵੇਂ ਕਿ Balanset-1A measures the 1× amplitude and phase, computes the rotor’s ਪ੍ਰਭਾਵ ਗੁਣਾਂਕ ਤੋਂ ਇੱਕ ਟ੍ਰਾਇਲ ਵੇਟ (ਪਰਖ ਭਾਰ), and tells the engineer the mass and angle of the correction needed for single- or two-plane ਸਾਈਟ ਬੈਲੇਂਸਿੰਗ (ਫੀਲਡ ਬੈਲੇਂਸਿੰਗ). Because it works in the machine’s own bearings at operating speed, it captures the true running state.
Balancing is never about reaching zero — it is about driving unbalance below a defined limit. That limit comes from the balance quality grade (G-grade) ਦੀ ਪ੍ਰਣਾਲੀ ISO 21940-11 (which superseded the long-familiar ISO 1940-1). The grade and service speed translate into a permissible ਬਕਾਇਆ ਅਸੰਤੁਲਨ in g·mm; a free ਰੈਜ਼ੀਡਿਊਅਲ ਅਨਬੈਲੈਂਸ ਕੈਲਕੁਲੇਟਰ (ISO 21940-11) turns a chosen grade and RPM straight into the allowable figure for each plane.
