Hand Arm Vibration (HAV) From Nailing And Stapling Tools
The difficulty with vibration measurements for nailing tools is they are a pulse of vibration, and that vibration relates to not just the tool and the length of time used, but other factors, such as how the tool is used by the operator (i.e. bump-fire or single shot), the material being fired into, the length of fastener being fired, the work bench / support, the air pressure being used, how firmly the operator grips the tool, cold or warm hands etc.
As a general rule nailing tools would not be used to such an extent that they would breach an operators daily limit from vibration (ELV - Exposure Limit Value), but this MUST be assessed by each employer.
Two operators using the same tool at the same time with the same timber / bench / air supply / nail can produce a slightly different vibration figure. The only way to get this accurately is to assess tool use in the customer's own environment, but using the manufacturer's information will suffice as a guide..
The EAV (Exposure Action Value) level should be treated as a Risk Assessment Reporting level. If the operator is below the daily exposure action value then no action need be taken, except recording that fact. If the EAV is crossed, a risk assessment should be carried out.The Health & Safety Executive HAV vibration calculator file is extremely useful as it will provide the correct value of Partial and Full Daily Exposure Points (A8). For the HSE, the Health and Safety Laboratory produced a report in 2007 which illustrates real life testing of fastener driving tools, with some examples of how to measure the daily tool vibration.
The EAV exposure action value level is an 'Action” Level, which means if tool use is likely to exceed this limit then the employer has to take action to monitor the risks, while the upper exposure limit value ELV is a maximum 'Stop” Level where the use of ANY tool causing vibration must be stopped, but employers' risk assessment / remedial actions should stop the operator before they get close to this level.
Nailfast can provide the manufacturers' vibration figure for each tool but the employer, or an outside assessment company, will have to provide the correct input figures for 'trigger time”, i.e. the actual time the operator uses each vibrating tool.
In the case of the nail guns, employers need to check each work station and job to determine each individual employees trigger time.
Timber Frame Panel Manufacture Example
For example, when completing a frame including cladding it can be broken down into three nailing / stapling tools in use as follows: -
1) framing nailer used for Xno of shots per panel for X amount of minutes 'trigger time', multiplied x maximum number of panels produced per shift.
This may give a result of 100 shots per panel, taking 20 minutes, of which actual firing time from first shot to last, stopping the timer when the last consecutive nail is fired, and re-starting the timer from the next sequence of shots until the frame is complete, may be 5 minutes trigger time, multiplied by the number of frames per shift, for example 20 frames; so the total trigger time for the framing nailer is 5 minutes x 20 frames = 100 minutes = 1 hour 40mins.
Inputting this figure into the HSE HAV calculator, using an average figure for the strip framing nailers of 4.00m/s2, and using 1 hrs 40 mins trigger time per shift the result is 53 partial exposure points.
2) Cladding nailer used, for example, 10 minutes trigger time per panel x 20 panels per shift = 200 mins = 3hr 20mins.
Inputting this figure using an average vibration of 4.40m/s2, for 3hr 20mins per shift, the result is 129 partial exposure points.
3) the wall membrane fine wire staplers are below the notifiable vibration level, but the HSL tests gave a result of 1.4m/s2 for the tool they had tested. If I use 2m/s2 to overestimate the figure, with 5 minutes trigger time per panel x 20 panels per shift = 100 minutes = 1 hour 40mins.
Inputting this figure using 2m/s2, for 1hr 40mins trigger time per shift, the result is 11 partial exposure points.
The total daily exposure points for nailing and stapling tools alone would be 193 exposure points and a daily exposure m/s2 of 3.5m/s2 across the three tools, which would be in the middle yellow middle zone of the HSE ready reckoner, meaning it is above the exposure action value, so you have to monitor and evaluate risk, but is below the likely to be at or above daily limit amber zone.
In addition to the nailing tools, if the operators use drills or sanders or other vibrating equipment, they have to be included in the employers' risk calculations.
Once you have calculated the real base line for the bench operative dependant on trigger time and model of tool being used, you will be able to see the actual result via the calculator and identify employees at risk from higher than average exposure points, at which time, it would be advisable to rotate workers between low risk operations and higher risk, so the mean exposure is lowered.
Notes and Further ReadingThe following link also explains nailing tool risks which may be considered: http://www.safetyandhealthmagazine.com/articles/print/9196-complacency-is-real
There are companies who can do on-site testing with the operator to determine real world vibration values and help to determine trigger time.
Nailfast can assist in locating a company to assess your own vibration risks.
The above information is for guidance only and is a summary of risks associated with nailing and stapling tools, and should be used only as an aid to assist companies to determine their own risk, as all vibration risk is individual to the company and employee.
The worked example above is not intended as a real-life set of figures, but simply as an illustration of how to determine your own risks.
Whilst every effort has been made to ensure accuracy, errors may exist. We do not accept liability for loss, damage, or injury to any persons who rely on this information.
HSE Ready Reckoner
click here for a link to the HSE exposure points system guide. The HSE ready reckoner is below: -