Bearing noises vary. They can indicate a serious flaw, or simply the normal functioning of a bearing. Do you know how to tell the difference?
Bearing noise generated from inside your electric motor is a natural occurrence in rolling bearings. Each of your bearings, clinks or clacks, squeals, or whines indicates simply that a specific part of the bearing is moving around.
Typically, these odd bearing noises are barely audible if they’re audible at all. However, if the bearing sound is loud enough for you to hear clearly, that’s generally a sign of a bearing problem.
Below are the most common noises that a bearing makes.
Race noise - This is the most basic sound in rolling bearings; this occurs when the raceway and rolling elements contact each other. It is smooth and continuous. The faster the running speed, the louder the sound, and if the radial clearance is reduced, the sound also becomes louder. The higher the viscosity of lubrication, the lower the sound, and if the higher the housing rigidity, the smaller the magnitude of the sound. Eliminating this noise is not possible, but it can be minimized by improving the quality of the bearings.
Click noise - This occurs more often in large bearings under radial loads. It is generated at low speeds and happens when the rolling elements and the cage/inner ring collide. Applying a preload is an effective countermeasure to click noise.
A squeal - This noise can be loud, and it sounds like metal sliding on metal. Contrary to expectations, this does not indicate a problem. Squeal noise tends to occur with relatively large bearings used under a radial load. The friction between the outer ring and rolling elements is considered to be the cause of squeal noise. Reducing the radial clearance and employing a very shallow groove in the outer ring raceway can be effective countermeasures.
Cage noises - These come in two types, the first noise suggestive of the cage colliding with the rolling elements (“kacha-kacha”). The second is a low-frequency noise (“gaga-gaga”) caused by the friction between the cage guide face and the bearing component that guides the cage. The first can be reduced by reducing the mounting error. The second noise, frequently problematic due to its decibel level, can be reduced and often eliminated by selecting a special cage designed to reduce this noise and applying the correct lubricant.
Rolling element passage vibration - This occurs in rolling bearings operating under a radial load. “Goro Goro” is the best descriptor of this noise. The reduction of radial clearance or application of a preload can be effective countermeasures.
Flaw noise - Caused by a flaw such as rust or when a dent exists on finished raceway surface or rolling bearing. It causes a pulsating, machine-gun-like sound. The noise occurs at intervals, generally proportional to the speed of the bearing. It can be reduced with the application of high viscosity grease, but usually, this noise means that the bearing must be replaced.
Contamination noise - This happens when a foreign particle makes its way into a bearing. A “chi chi chi” noise, the sound is caused by the foreign particle being caught between the rolling elements and the raceway surfaces. Damage can occur and is more severe in smaller bearings. The best countermeasure is prevention – always handle a bearing safely and reduce outside contamination.
Conclusively, not all bearing noises are problematic. Some indicate typical bearing performance. Other sounds can show a real problem. Keep an ear out, and if you hear a noise that causes concern, contact a bearing specialist.
Ramdevs Motors is leading manufacturer and supplier of LT motors in India. Ramdevs Motors manufacturing plants are located at Coimbatore, India.
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