Safety and Preventive Measures when using Grinding Wheels

Grinding wheels, which are composed of abrasive materials and are a commonly used piece of equipment in many workshops and factories. However, their high-speed rotation can pose potential hazards to human safety. To mitigate and control risk, it is imperative to understand what hazards can be caused and the preventive measures that should be taken.

I. Wheel Fracture and Preventive Measures

A fracture in a grinding wheel not only poses a threat to individuals in close proximity but also jeopardizes the integrity of the workshop or surrounding structures. To prevent such incidents, the following precautions should be observed:

1. Handling and Storage: During transportation and handling, moisture ingress into phenolic resin-bonded wheels can compromise their strength. Ceramic-bonded wheels, on the other hand, are sensitive to temperature variations. Uneven moisture absorption can lead to wheel imbalance. Therefore, when handling and storing wheels, they must be gently placed in dry, sheltered areas to maintain their optimal condition.

2. Crack Inspection: New grinding wheels should undergo a thorough inspection to ensure they are dry and undamaged. A simple method involves lightly tapping the wheel with a wooden mallet. Intact ceramic wheels produce a crisp sound, while organically bonded wheels emit a duller sound. This is distinguishable from the sound of a defective wheel. In case of any doubts, clarification should be sought from the supplier.

3. Testing: Before putting a new wheel into formal operation, a full-speed test should be conducted, with careful observation. Following wet grinding, the wheel should be allowed to run without load for a period to shed excess water. Otherwise, retained water may lead to wheel imbalance and potential fracturing during subsequent use.

4. Installation: Improper installation of a grinding wheel, such as mounting it at the end of a polisher's spindle, can lead to accidents and breakage. The spindle should have an appropriate diameter, neither too large nor too small to prevent the center hole of the wheel from expanding and cracking. The flange should be made of low-carbon steel or similar material, with a size no less than one-third of the wheel diameter.

5. Speed: The operating speed of a grinding wheel must never exceed the maximum allowable working speed specified by the manufacturer. All grinders should indicate the rated spindle speed. The wheel should also specify the highest allowable peripheral speed and the corresponding rotational speed for new wheels. Special protective measures must be taken for variable-speed grinders and for mounting wheels on portable grinders to achieve permissible speeds.

6. Operating Rests: Whenever possible, adequately sized and securely installed rests should be provided. The rests should be adjustable and positioned as close to the wheel as possible, minimizing gaps. In spaces between, workpieces may be pushed into the wheel, leading to fractures. In severe cases, an operator's hand may be drawn into the gap, causing injury.

7. Guarding: Protective devices with sufficient strength to shield against fragments from a fractured wheel should be in place. Some countries have detailed regulations on the design and materials of these protective devices. In general, cast iron or cast aluminum should be avoided. The grinding operation openings in the protective device should be made as small as possible, and an adjustable baffle should be installed. In special cases where protective devices cannot be used due to the nature of the work, special safety flanges or safety chucks can be employed for protection.

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II. Eye Injuries and Preventive Measures

In various dry grinding operations, dust, abrasive grains, and fragments are the primary causes of eye injuries. Using safety goggles or glasses can effectively safeguard the eyes. For some intermittent-use wheels and grinding tools, fixed baffles are highly beneficial.

III. Entanglement Accidents and Preventive Measures

In dual-end polishing machines, if the spindle and tapered end are not effectively guarded, there is a potential risk of entanglement with work clothing or hair, leading to accidents.

To prevent such incidents, it is essential to:

1. Ensure that all spindles and rotating elements are adequately enclosed and guarded.

2. Implement strict dress code policies, prohibiting loose clothing, jewelry, and unsecured hair near rotating machinery.

3. Provide thorough training to operators on safe clothing practices and the dangers of loose garments around machinery.

IV. Fire Hazards and Preventive Measures

When grinding magnesium alloy work-pieces, there is a heightened risk of ignition. Strict preventive measures must be taken to prevent ignition and subsequent fire accidents. These measures include:

1. Ensuring work-pieces are appropriately cooled and promptly cleaned of magnesium alloy dust.

2. Conducting high-standard cleaning and maintenance of workshop and equipment exhaust systems to prevent the accumulation of flammable particles.

3. Employing fire-resistant materials for equipment, where applicable.

4. Providing fire extinguishing equipment and emergency response training to personnel.

V. Health Hazards and Preventive Measures

While modern grinding wheels themselves do not cause silicosis, the grinding process can release hazardous silica dust, particularly when working with materials like sand-castings. Some resin-bonded wheels, containing filler materials, can also generate toxic dust, with special attention to compounds containing lead. To counter these health hazards, it is crucial to:

1. Implement high-efficiency local exhaust ventilation systems to effectively remove dust generated during grinding.

2. Provide operators with respiratory protection equipment.

3. Supply protective clothing and ensure proper hygiene facilities, including showers, are available.

4. Conduct comprehensive medical surveillance, especially for workers involved in grinding metal components.

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