Work Tool Vibration – Dangers of Continuous Exposure

 

DON’T LOSE THE FEELING!

 

Constant Vibration causes Long Term Physical Damage by Stealth.

Short Term symptoms being: Tingling Fingers; White (to deep Red) Finger Tips; Pins and Needles in Forearms; Painful aching in Hands and Arms; Irritation and Inflammation in Wrist, Elbow and Shoulder Joints.

Longer Term damage to Nerve endings; Skin Tissue, Muscle and Tendons; Ability to accurately manipulate fingers; Strength to grasp / control objects with hands; Loss of Strength in Arm, Elbow, Shoulder; Chronic pain and Discomfort.

Yes this is unfortunately all true. There is more than 50 years of evidence proving that continuous exposure to harmful levels of Vibratory Shock can cause long term detrimental health effects to your quality of life. In this article I will try to simplify what can be a somewhat complicated topic.

Any of us that have experienced the tingling of fingers after using a motorised or powered tool, will know what the early warning signs are. Because this ‘short term’ discomfort goes away over time, we tend to not worry about it until the next time it happens when working with Vibrating machinery again.

The trouble is that each time we are exposed to these short term high speed pieces of equipment, our bodies are experiencing changes in our blood vessels and consequently our skin and muscle tissue. At first this does not appear to be of a major concern, but over time the accumulated effect (time weighted) of this constant exposure begins to become more apparent.

By the time that we start to notice the physiological discomfort remains long after the exposure to high levels of Vibration has occurred, it is too late to repair the damage done to our bodies system.

The message for users of vibrating work tools, is to take precautionary steps to reduce the amount of exposure by decreasing the Vibration transmission through our bodies.

Vibration is measured in m/s2 (meters per second squared), the International Standards Organisation scientists have been hard at work arriving at a guideline for how much Vibration we can be exposed to in any given day, before causing ill effect to individuals and corrective steps need to be taken; reference AS ISO 5349.1-2013.

One of the most useful pieces of data from these studies is a table providing the amount of exposure per 8 hour day verses the speed / acceleration (vibration magnitude transmitted by the tool) measured in m/s2.

 

From this table (1); Your daily exposure to vibration is measured by a formula known as an A(8) value. This is the average (A) exposure over an eight-hour (8) day and takes into account the magnitude of the vibration and how long you are exposed to it. The rate of vibration of a tool or piece of machinery is measured in metres (m) per second (s) per second – its movement (acceleration) per second.

 

The relevant Australian Standard, is adopted from the accepted International Standard ISO 5349.1-2013. This predominately European Standard specifies daily exposure levels at which employers will be required to take action to control risks. These are known as Exposure Action Values (EAVs). The regulations also set out Exposure Limit Values (ELVs). Where these are reached, the employer must prevent further daily exposure.

For hand-arm vibration (HAV), the daily ELV is 5 m/s2 A(8) and the daily EAV is 2.5 m/s2 A(8).

Accurate task at hand Vibration readings can be taken by a mobile sensor being attached to the grip handle of the tool / machinery being operated. The exposure levels can then be calculated as a factor of the Intensity of Vibration (m/s2) and the actual Time Exposed (operation trigger time).

Once again, from the Vibration Exposure table (1), one can see that at 2.5m/s2 exposure an 8 hour Maximum day is the cut off before some form of preventative action must be taken. At 5m/s2 any exposure over 1 hour approaches potentially dangerous levels of Vibration Transmission to the Hand and Arm of the body.

In realising that not everyone (or every company) is in the position to Hire or Purchase the monitoring equipment necessary to take accurate m/s2 readings, there is another alternative, this format is available to calculate the potential exposure and therefore better understand the average m/s2 reading from the reported generic output of each tool type.

From these reported average readings we can continue to use the exposure table (1) by correlating the given m/s2 value against our Vibration exposure time. N.B: It is wise to build into your calculations a 20% uncertainty factor when adopting a stereotypical ‘generic’ measurement of tool types.

Table 2 provides examples of vibration magnitudes measured by the Health and Safety Executive (HSE) UK.

It is interesting to note that almost all of the tool types listed and measured by the UK Health and Safety Executive are producing readings of over 5m/s2. This of course means that action needs to be taken to reduce the levels of exposure. Control measures such as changes to engineering controls or work practices; procurement of newer low vibration transmission tools for the task; Potential Cessation of this type of work; or Provision of suitable Vibration Frequency reduction P.P.E.

 

 

Recent scientific studies have reported that Vibration Oscillation intensity alters at each specific frequency range. Therefore any tool, dependant on exact force being applied and the corresponding selected material type being worked, can produce different Vibration Transmissions at potentially the same working tool RPM.

Raw material advancement and Manufacturing developments in relating to Vibration Reducing Hand Protection (P.P.E gloves); Are now linking up with laboratories to refine testing and product compound calibration for increased Vibration Frequency reduction. We now have specially developed Frequency Tuned Vibration / Shock absorbing material compounds that work best at calculated frequency ranges.

In fact we now understand that any one specific type of shock absorbing material will not perform well over the complete Vibration Frequency range (80 to 1,000Hz). Meaning that there is no so called “Anti-Vibration” glove that will provide protection across all Tool application outputs. Therefore it is very important for us to know what Frequency in Hertz (Hz) or Revolutions per Minute (RPM) that the Vibratory equipment is operating at, in order to match the correct glove to the task.

Most manufacturers of Power and Impact Tools will have each specific tool data containing the operating Hz and or RPM. From this we can then analyse the exact type of protective material best suited to that tools Vibration Frequency operating range. As an easy reckoner, 300Hz is considered the changeover Frequency between Low and High octave band, and most impact tools and powered garden equipment operate below 300Hz in maximum operation range. N.B: 300Hz = 18,000RPM.

This article is intended as educational opinion, derived from years of associated study and manufacturing partners research on the topic of Vibration Transmission Reduction. Apart from the ISO and EU standards quoted as reference, major acknowledgement and Thanks must go to Safe Work Australia for their 2015 paper on ‘Workplace Exposure to Hand Arm Vibration’, of which the major tables used here are associated. Their full paper on this important topic is able to be viewed at: https://www.safeworkaustralia.gov.au/system/files/documents/1703/guidetomeasuringassessinghandarmvibration.pdf