Falls from height continue to be an all-too significant statistic when it comes to fatalities, according to the latest Safe Work Australia Notified Fatalities Report (2008-09).
In 2009, 20 people were fatally-injured when falling from height, including from buildings, scaffolding, ladders and roofs. This is a rise from 16 people (25%) over 2008 - made all the more disappointing since falls from height are largely preventable.
Where a risk analysis has identified the potential need for a person to work at height, the first step is to look at the Hierarchy of Control to see if the risk can be eliminated or isolated. If not, focus then turns to developing the work method proposed, leading in turn to the selection of the best personal protective equipment (PPE) for the task.
However, it's not enough to assume that the correct selection and use of equipment is adequate to keep you safe. Roofsafe Industrial Safety (RIS) managing director, Michael Bermejo, who is a member of the Fall Protection Manufacturers Association (FPMA), says that one of the key factors that need to be considered in this process is the fall clearance available to the operator.
"This must encompass accessing and returning from the work site as well as whilst executing the actual task. The theoretical fall clearance required must always be less than fall distance available," he said.
Vertical and swing falls
The selected work method needs to allow for sufficient clearance below the operator so that he will not strike the ground or any intermediate objects in the event of a fall. There is little point in providing fall arrest equipment if there is chance that the operator can hit other objects before the equipment has deployed.
There are two different conditions that need to be considered: the straight vertical fall, from any position in the system; and the risk from a swing fall where the connection between the operator's harness and the anchor point may be deflected, or where the operator may swing against another structure.
For any operation, regardless of the differing conditions, there are a number of factors that need to be considered when calculating the required fall clearance.
1. Deflection of the anchor point
Where this is a fixed anchor point, the deflection may be small. However, if the operator is connected to a horizontal lifeline system, the deflection in the lifeline could be significant. Any lifeline system must be installed by an accredited installer, so reference should be made to that installer for details of the expected deflection in the system.
2. Length of connection between anchor and full body harness
This calculation needs to take into consideration a number of factors. Where the anchor point is above the harness fall arrest connection, the difference in the overall lanyard length and the vertical distance from the anchor point and the connection to the harness will give a measure of the free fall distance. However, where the anchor point is below the fall arrest connection, the overall lanyard length must be added to the distance between the connection and the anchor.
3. Self Retracting Lifeline
Self retracting lifelines usually operate on a fixed arresting distance, based on limiting the force to below 6kN. Where these are used, Australian Standards recommends a fixed allowance of 700mm. If a type 1 arrestor is in use, whether on a rope or cable system, an arresting distance of 1000mm should be allowed. Consideration still needs to be given to swing falls if the anchor point is not directly above the operator.
4. Anchor Point Location
Where the anchor point is not vertically above the operator, an additional allowance equivalent to the lateral offset needs to be added to the fall distance.
5. Shock absorbing Lanyard
In the shock absorbing lanyard, the tear webbing can be activated with the length of the extension depending on the distance of the initial free fall. The table below shows the average extension based on the initial free fall distance.
Free Fall Distance Extension
600mm 300mm
1000mm 500mm
1500mm 600mm
2000mm 900mm
In the event of a fall, there is a deceleration process, i.e. the process that limits the forces exerted on the body to below 6kN. This process is quite different between a shock absorbing (tear webbing) lanyard and a self retracting lifeline.
6. Operator height
The final allowances for required fall clearance relate to the actual height of the operator, from his feet to the attachment point between the full body harness and the shock absorbing lanyard connection.
7. Safety Distance
The recommended additional safety distance in any calculation is 1000mm.
For more specific details, reference should be made to AS1891.4 (2009) Section 7 Fall Clearance and Section 8 Effect of Equipment Configuration on Free Fall Distance.
The Fall Protection Manufacturers Association of Australia comprises all leading Australian companies in the design and manufacture of fall protection equipment. This professional association has strongly supported the tightening of Australian Standards surrounding the selection, use and maintenance of height safety equipment.