Controlling noise from grinders

Protecting employees from exposure to noise

Employers have a duty to protect the health and safety of their employees. This duty includes protecting employees from exposure to noise. The Occupational Health and Safety Regulations 2017 (OHS Regulations) set a noise exposure standard measured in units called decibels (dB). The noise exposure standard is an 8-hour average of 85 dB(A) and a peak noise level of 140 dB(C) at the employee's ear position.

Exposure to noise that exceeds the standard is considered dangerous to employees' hearing. Employers must ensure employees' exposure to noise does not exceed the noise exposure standard.

If there is uncertainty about whether noise exposure exceeds or may exceed the standard, employers must determine an employee's exposure to noise in the workplace. When determining noise exposure, employers must not take into account the effect of any hearing protectors employees may be using.

Employers must take into account:

• the level of noise to which employees are exposed
• the duration of the exposure
• plant and other sources of noise at the workplace
• systems of work at the workplace
• any other relevant factors

Information about employers' duties is available on the WorkSafe website, including the Noise compliance code. The Noise compliance code provides practical guidance on how to comply with obligations under Victoria's occupational health and safety legislation to manage risks associated with workplace noise exposure.

Grinders

Grinders are power tools that remove, cut, grind or trim excess metal. They are common in metal fabrication industries and in foundries. Common types include:

• hand-held grinders
• pedestal or bench grinders
• linishers

Linishers and bench-mounted grinders can produce noise levels of about 88 to 95 dB(A).

Hand-held angle grinders can produce noise levels of about 90 to 115 dB(A).

Control measures

Use the hierarchy of control

The hierarchy of control is a step-by-step approach to eliminating or reducing risks. It ranks risk controls from the highest level of protection and reliability through to the lowest.

Employers must control noise in line with the following hierarchy of control measures:

• eliminate the source of noise
• substitute noisy plant with quieter plant or processes, isolate the plant or use engineering controls
• use administrative controls
• provide hearing protection

Employers must apply each level of the hierarchy so far as reasonably practicable before moving down to the next control measure. This means employers cannot go straight to hearing protection to control the noise without applying the higher-level control measures, so far as reasonably practicable.

It is often necessary to use a combination of control measures to effectively control noise.

The following are examples of risk control measures to control noise from grinders:

Elimination

Eliminate the use of grinders by:

• buying pre-cut or pre-fabricated materials
• improving the production process. For example:
  • use laser cutting to eliminate the need for grinding
  • improve mould design in a foundry process. This would eliminate or reduce the amount of excess metal to be ground off, or fettled, after casting.

Substitution

If elimination control measures are not reasonably practicable, employers may substitute grinders with quieter plant or processes, for example:

• use a quieter grinding process, for example, a linisher, which is generally quieter
• use power hacksaws, guillotines or hand shears for cutting sheet metal
• use low-noise grinding discs or wheels. These may reduce noise levels by as much as 8 dB
• use smaller grinders. For example, using a 4-inch or 125 mm grinder instead of a 9–inch or 228 mm grinder can reduce noise levels by 6 to 10 dB
• use grinders with quieter motors. Ask manufacturers for information on noise levels.

Engineering controls

If elimination and substitution control measures are not reasonably practicable, employers may use engineering controls, for example:

• use isolation mounts such as resilient rubber pads on bench-mounted or pedestal grinders. Isolation mounts reduce vibrations caused by grinders and can reduce noise by 2 to 4 dB.
• clamp work pieces as close as possible to where grinding is happening. Use clamps lined with rubber-type material.
• use damped rest pads on bench-mounted or pedestal grinders
• install full or partial acoustic enclosures/rooms. Rooms lined with 50 to 100 mm high-density mineral wool or foam will reduce employee exposure to noise.
• use fixed or portable acoustic lined partitions or screens to reduce employee exposure to noise. While not as effective as full or partial enclosures, they may be enough where grinding takes place for very short periods. Screens should be of sufficient height and close to the employee doing the grinding. Minimise gaps at ground level.

Machines working at the same time can increase noise exposure. For example, the noise exposure of one employee working alone with a grinder might be 100 dB(A).

But where there are two employees working side by side and each generating 100 dB(A), the combined noise exposure will increase to about 103 dB(A).

To reduce employee exposure to a level below the noise exposure standard:

• introduce partitions of screens between grinding bays
• use a combination of additional control measures

Administrative controls

If elimination, substitution, and engineering control measures are not reasonably practicable, employers may use administrative controls to control noise from grinders, for example:

• move the grinding process to another room, building or outdoors if practicable
• move employees who are not using grinders further away from noisy grinding processes
• avoid placing noisy grinding processes in corners with highly reflective concrete or brick walls
• line walls with sound-absorbing materials to minimise noise reflection
• rotate employees to reduce their duration and exposure to grinding noise. Halving the time an employee spends grinding reduces their exposure by 3 dB(A).

Personal protective equipment

If a risk from noise exposure remains after implementing higher-order controls, use hearing protection to ensure employee exposure is below the noise standard.

Maintenance

Regular maintenance of machinery can make a significant difference to noise levels. Maintenance includes:

• keeping cutting tools sharp
• regularly dressing grinding wheels
• replacing worn parts, for example, bearings, brushes etc.
• tightening loosened parts