Vibration Effect

Vibration effects are more dangerous, it affects human health and machinery. Exposure to vibration may have negative health effects, it may damage joints, muscles, and nerves, etc. Vibration can cause annoyance and noise to the human body and physical damage to machines and structures. Vascular disorders may occur in the form of white fingers. Workers need to be trained on the hazards of working with vibrating tools. The purpose of this article is how to manage the risk of vibration and its health effects. Before we discuss vibration effects let us know what is vibration and what its sources are.

What is vibration?

Vibration is a physical factor that acts on the human body by the transmission of mechanical energy from sources of oscillation. Sources of oscillation may be knocks and friction of machine parts,  unbalanced or inaccurately centered rotating parts, pressure pulses of compressed fluid, etc.

Source of vibration

1. Relation with unbalanced loads or bent shafts.
2. Misalignment of driving and driven shafts.
3. Impact of a moving part against another part moving or stationary.
4. Water hammer in hydraulic systems.
5. High velocity air ducts.
6. Looseness of equipment parts which causes them to rattle like sheaving.
7. Bend on bearing or steel wheels.
8. Belt or gear slippage.
9. Lack of adequate snubbing devices in pneumatically operated equipment.

• Frequency, amplitude and duration are the characteristics (nature) of vibration. Like noise, frequency is measured in cycles per second or Hertz. Frequency that coincides with the body’s own resonance tends to be the most uncomfortable; this being in the range of 2-30 Hz. Amplitude is the acceleration given by meters per second (m/s2)and denotes how far the surface moves each time it vibrates. Duration is the period how long it goes on. The longer is the exposure, the higher the risk.
• Vibration transmits more easily through solid materials than through air.

Effect of vibration on human body:

Pain is the beginning of the health effects due to exposure to vibration. When vibration exposure continues the pain may develop into an injury. White finger disease is the most common health effect due to vibration. Vibration may affect joints, bones, muscles, and it may affect the nervous system. Long-term exposure to vibration may cause severe health issues.

When a chain saw or jackhammer is operated, a vibration that affects hands and arms is called hand-arm vibration exposure; when a worker sits or stands on a vibrating floor or seat, the exposure affects almost the entire body and is called whole-body vibration exposure. The vibration causes the blood vessels to contract and restrict the blood supply to the fingers creating an effect similar to the fingers being cold.

TLV of vibration:

Hand-arm Vibration:

It is also known as HAV (Hand-arm vibration). Hand-arm vibration is caused by regular or long-term exposure to handheld tools and equipment such as grinders, concrete breakers or jackhammers, polishers, strimmers, chainsaws, power drills, etc. Using these tools, the vibration is transmitted from the tool to hand. Vibration can damage muscles, sensory nerves, joints, etc. These effects are known as Hand-arm vibration syndrome (HAVS). This is especially dangerous when proper damping techniques are not applied. Examples of musculoskeletal disorders related to hand-arm vibration include wrist tendinitis and tenosynovitis.

Hand-arm vibration syndrome:

Hand-arm vibration syndrome (HAVS) causes symptoms in fingers, hands, and arms. About millions of workers are exposed to hand-arm vibration in the whole world. Most of the hand-arm vibration effects are found in various industries such as construction industries, mining industries, and forestry, etc.

• Tingling in the fingers.
• Numbness.
• Lose grip strength.
• White fingers.

Whole-body Vibration

Whole-body vibration can cause fatigue, insomnia, headache, and shakiness shortly after or during exposure. The symptoms are similar to those that many people experience after a long car or boat trip. It is established that the performance of workers is decreased who are exposed to whole-body vibration.

1. Increase in oxygen consumption.
2. Difficulty in maintaining steady posture.
3. Narrows the field of vision.
4. Increase in pulmonary ventilation and cardiac output. Affects CNS, damages internal organs.
5. Effects on visual acuity and narrows the field of vision.
6. Marked changes in bone structure –
   • Spondylities.
   • Deformations.
7. Blood changes –
   • Hypoglycaemia.
   • Hypocholesteremia.
   • Low ascorbic acid levels.

Effect of vibration on machines and structures:

• Badly vibrating machines not only consume more power but also damage to the machine and its supporting structures.
• The vibrations also travel through the structure of the building and be radiated as noise at distant points. This is structure borne noise.
• Vibration causes metal fatigue which results in failure of rotating parts and other stressed mechanical equipment. It can cause rupture in a pressurized equipment, the higher the pressure, more changes of rupture.

Vibration control measures:

1. Vibration Isolators can effectively reduce transmission of vibration waves when properly install. This is isolation at source.
2. Reduction of surface response (damping) when isolation at source is not possible, vibration absorbers (dampers) can be effectively used.
3. Reduction of mechanical disturbance that produce vibration. This is possible by reducing impacts, sliding or rolling friction or unbalances.

Other methods of vibration control:

1. Technical and engineering measures.
2. Organizational measures includes good preventive and corrective maintenance.
3. Prophylactic and therapeutic measures, pre employment and periodical medical examination play an important role.
4. Special vibration absorbing handles fitted to hand tools, springs, suspension seats and shock absorbers are useful.
5. Reduction in exposure time.
6. Personal precautions.
7. Automation and remote control system.

Vibration damping:

• Vibration dampers (absorbers) are used under machine foundation and the machine should be installed on an inertia block with a damping sandwich between it and the building foundation.
• Before this provision, efforts should be made to balance the moving parts of the machine which is the better remedy.
• The method chosen should depend on the size and weight of the machine, the frequency of the vibration to be controlled and the degree of isolation required.

FAQ for Vibration effect: