Vibration Monitoring - OHSA Occupational Health Services Australia

Whole Body and Arm-Hand Vibration Monitoring

Whole body vibration (and high amplitude jolts and jars – shock) is known to be a contributing factor to muscle fatigue, stiffness, lower back pain and serious physical injury.

OHSA conducts 100’s of whole body vibration (WBV) assessments on mining and transport plant each year with a vibration dosimeter (with simultaneous floor and seat tri-axial accelerometers) to measure exposure levels to determine compliance with the recommended levels in Australian Standard AS2670.

What are the Associated Whole Body Vibration Health Effects?

The health effects that are associated with long term exposure to Whole Body Vibration encompasses:

• Back injury, especially spinal injury
• Musculoskeletal disorders
• Joint and muscle stiffness
• Damage to female reproductive system
• Changes in the balance and vision of workers
• Changes in the Respiratory, Endocrine, cardiovascular & digestive systems

While not a direct health effect from Whole Body Vibration, the difficulty in a task can be increased through poor visions, hand-eye coordination and concentration which may make a task more hazardous. For instance the conditions of roads or observing hazards may be masked due to the vibration, thereby being one significant cause in a workplace accident.

There is also an association in increased risk of manual handling injuries, particularly back injuries, due to exposure of Whole Body Vibration. This is due to the vibration fatiguing muscles and weakening them over time which increased the risk of putting the back out of place. Reducing vibration will place less stress and strain on back muscles so they can work more effectively in preventing injury.

Health surveillance may assist to prevent the Whole Body Vibration and associated manual handling injuries by increasing working health and awareness of risk factors.

Measuring Whole Body Vibration

The Australian Standard for measuring and testing Whole Body Vibration is AS 2670.1-2001 Evaluation of human exposure to whole-body vibration – General requirements.

Whole body vibration is measured through the use of an accelerometer that is placed within a seat pad. The seat pad which, the operator sits on vibrates in rhythm of the worker operating the equipment. The three plane vectors are measured in the x, y & z coordinates and averaged to determine the Whole Body Vibration levels.

The Whole Body Vibration testing is reported in terms of m/s², being a measurement of acceleration and is the Roo Mean Square (RMS) value. The measurements are also filtered to assess only specific frequencies that the body is responsive to. In general the frequencies for Whole Body Vibration are much lower than that which has a significant health impact compared to the weighted frequencies for Hand Arm Vibration (HAV).

As well as the seat being measured for Whole Body Vibration, an additional accelerometer may be used to measure the chassis of the equipment. This testing is used to determine the vibration that is absorbed by the seat. Most seats these days will have cushioning and also adjustable tension to ensure that maximum vibration reductions can be achieved.

Each task that the worker undertakes on the equipment is tested for the RMS vibration and is then also assessed in terms of the duration of the task. The tasks that are conducted over the length of the day are then added to evaluate the overall daily Whole Body Vibration exposure.

Another parameter is also used in Whole Body Vibration assessments which is the Vibration Dose Value (VDV) which is the cumulative measurement of vibration and increases as a function of the dose and magnitude of the vibration value. The units of the Dose Vibration Value are is reported in m/s^1.75. The Vibration Dose Value provides a measurement of the presence of jolts and jars experienced. As an example, think of the whole body vibration from a small truck where the average vibration levels is the vibration of the vehicle and riding over the road, then the truck hits a large pothole. It is this large jolt or jar that is a significant risk of injury from the cumulative exposure of these large vibration doses.

What are the Whole Body Vibration Exposure Standards?

The state based WHS Regulation in Australia fail to provide exposure limits for Whole Body Vibration in a similar manner to exposure standards for noise or chemical exposures; however the two most commonly referred standards in regards to Whole Body vibration in Australia are:

• Australian Standard AS 2631.1 Mechanical vibration and shock- Evaluation of human exposure to whole-body vibration and the Australian Standard AS 2670 .1 Evaluation of human exposure to whole body vibration. AS 2670.1 which is basically adopted from ISO 2631-1; and
•  European Union Health and Safety Directive 2002/44/EC – Vibration.

Both guidance documents quantify the Whole Body Vibration measurements through the average Root Mean Square acceleration values and the Vibration Dose Value (VDV). The recommended Whole Body Vibration action and limit levels are tabulated as follows:

Recommended action an limit vibration values based on the a 8 hour work day

Further application of r.m.s. weighted acceleration and VDV values are provided by the Australian Institute of Occupational Hygienists to provide a semi quantitative risk assessment of Whole Body Vibration in terms of likelihood and consequences, to determine an overall Health Risk Rating.

Controlling Whole Body Vibration

The main forms of controlling whole body vibration requires a holistic approach. This includes reducing the whole body vibration from rotating parts and the machinery, ensuring that they are well maintained. Assessing the surface that the equipment is moving on and reducing vibration through the road surface and train tracks.

Another way to reduce Whole Body Vibration is assessing the vibration dampening effect that is offered by the seat. The spring tension of most new seats can be optimised to suppress the transmission of vibration through to the person, as well as through padding an cushioning.

Require assistance with Testing, Assessment and Controlling Whole Body Vibration?

OHSA can assist to reduce Whole Body Vibration health effects to assist in managing your workplace risk. We conduct Whole Body and Hand Arm vibration testing and assessments throughout Australia.