SECTION 2: SAFETY IN SCAFFOLDING - Continued

2.5 Fall arrest systems

Fall arrest systems are designed to support and hold a person in the event of a fall. They are not designed to support a person while working. This would be a work-positioning system. An evaluation of the different types of equipment combined with a task assessment is needed to make a practical and safe selection for a particular job.

The arresting force applied to the worker should a fall occur must be less than 6 kN (610 kg). Employing a 2 metre lanyard incorporating an energy absorber or a type 2 or 3 fall arrest device should achieve this. For the 2 metre lanyard system the lanyard or anchor line must be attached to the top dorsal position (at chest height) or the frontal chest attachment. Anchorages for a lanyard should be fixed as high as practical but within easy reach. An anchorage at foot level will allow a person to fall the length of the lanyard plus the distance between the anchorage and harness fixing point.

All attachment hardware is to be designed to withstand a load of 15 kN (1530kg).

2.5.1 Hazards associated with fall arrest systems

Problems that may arise while employing fall arrest systems include:

• Attaching to anchors that are insufficient in strength resulting in anchorage failure.
• Employing anchor lines or lanyards parallel to the fall edge resulting in the pendulum effect.
• Attaching to anchors that are too close to the ground resulting in insufficient fall clearance.
• Attaching to anchors that are too close to the fall edge resulting in excessive free fall distance
• Using harnesses in hazardous environments that damage equipment or cause system failure.
• Impeded mobility resulting in scaffolders disconnecting from anchors.
• Incorrect connection of attachment resulting in failure under loading.

The pendulum effect

This is a potential hazard when using individual fall-arrest systems. It results in workers striking the ground or other obstructions during the fall arrest process. The "pendulum effect" requires consideration prior to deciding the location of anchorage points.

Swing down

This can occur if an inertia reel or work-positioning device is extended diagonally so that the line makes an extreme angle with the perimeter edge of the structure. In this situation the forces generated in an arrested fall over the edge will cause the line to rotate back along the perimeter edge until it reaches a position directly in line with the anchorage point of the inertia reel and at right angles with the perimeter edge.

As the line moves back in this way, its unsupported section lengthens, thus dropping the attached worker further than the original (arrested) fall distance. If the length of the unsupported line equals the height above the ground then the worker will hit the ground.

To eliminate the pendulum effect place the anchorage point perpendicular to the position of the line at the perimeter edge. At the most, an anchor point must be within 30 degrees of the work position. A mobile anchorage helps here. The use of second anchorages and belay devices is another way of minimising this effect.

Swing back

In an arrested fall, particularly from a perpendicular edge, a person will swing back into the building structure and collide with any obstructions in the path of the swing. If this situation can arise, the use of an individual fall-arrest system should be re-assessed.

Fall clearance

It is essential that users of fall arrest systems allow sufficient fall clearance in their system design. Free fall distance must be calculated to ensure you do not hit the ground. A number of factors need to be taken in to account. These may include:

• Height of user.
• Start position of fall arrest devices.
• Lateral offset of anchor point.
• Length of lanyard.
• Shock absorber extension.
• Fall arrest device extension or travel.
• Extension of unusually long anchor lines.
• Static line or temporary lifeline deflection.
• Residual clearance.

Figure 5: Example of calculation of fall clearance

In figure 5 the total fall clearance requirement when using a 2m lanyard with shock absorber when attaching to an anchor point is 6.5m.

Figure 6: Impact of horizontal safety line deflection on minimum fall clearance

Attaching to a horizontal safety line means additional distance must be included in clearance calculations to allow for deflection of the horizontal safety line, as indicated in figure 6. Manufacturer's information must be referred to so as to determine the deflection of a particular system.

Free fall distance

Free fall distance is the distance someone will fall before the system begins to arrest the fall. Free fall distance must be calculated to ensure rated capacities of your equipment and your body are not exceeded. In all cases the free fall distance should not exceed 2.0m. Distances more than this will exceed the equipment's design capabilities and could result in failure and excessive shock loading to the victim. Fall arrest equipment, specifically harness and lanyard assemblies meeting the requirements of AS/NZS 1891, will not necessarily be capable of arresting falls in excess of 2.0m without compromising the in-built safety factor. It is critical that anyone using fall arrest systems has calculated their potential free fall distance before they set up and begin work.

Free fall distance for a scaffolder using a 2m fixed length lanyard is calculated from the following:

L - S + H = Free fall distance.

L = the length of the lanyard before any shock absorber extension.

S = the straight line distance between the anchor point and the point on the edge over which the user falls.

H = the maximum expected height of the harness attachment point when the user is standing up (1.5m).

Examples for calculating free fall distance

See also figure 7 below.

Example 1: L - S + H = Free-fall distance; 2.0 - 2.0 + 1.5 = 1.5 m Acceptable

Example 2: L - S + H = Free-fall distance; 2.0 - 1.5 + 1.5 = 2.0 m Acceptable

Example 3: L - S + H = Free-fall distance; 2.0 - 0.0 + 1.5 = 3.5 m Unacceptable

Figure 7: Calculations of free fall distance

2.5.2 Type 1 fall arrest devices (inertia lock rope grab)

This consists of a unit that will slide up and down an anchor line and will lock onto the line in the event of a person falling. In permanent applications non-corrosive rails and stainless steel lines can be attached to structures such as chimneys, towers or vertical ladders. Other types of anchor lines that may degrade over a short-term period should be rigged each time they are needed.

The maximum length of a lanyard used between the harness and a type 1 fall-arrest device, including the energy absorber, is 2 metres. All lanyards should be rigged and used with the least possible slack by keeping the arrest device above head height. Where a vertical ladder rail, or similar system, is being used for a restrained fall the lanyard should be no longer than 300 mm.

2.5.3 Type 2 and type 3 fall arrest devices (inertia reels)

These are spring-loaded reels that fix to an anchorage. An anchor line plays out as a person moves away from the reel and is reeled back as the person approaches. The difference between type 2 and type 3 is that type 3 can be used as a winch to allow a person to be wound back after loading the unit. With this equipment the anchor line is attached directly to the dorsal position on the harness.

Do not use a lanyard in conjunction with a Type 2 or 3 arrest device; the anchor line attaches directly to the harness.

2.5.4 Horizontal lifeline and rail systems

A static line is a horizontal line that is anchored at both ends and rigged so that a fall-arrest device or lanyard can run along its length. AS/NZS 1891.2 sets out acceptable criteria for three types of horizontal lifeline and rail systems. These are: proprietary systems, prescribed configuration systems, and rigid life rail systems. Refer to the standard for further information.

The force on the anchorage points of a static line will be much greater than those on an anchor line because the anchor line is in direct tension along its length while the static line is under tension at right angles between the anchorages. Special shock-absorbing units that attach to the static line are available to reduce this force to an acceptable level (see figure 8). These are not the same units as used in a lanyard. The static line must have a minimum breaking strength of 44 kN (4490 kg) or be an engineered design.

Specialist advice and training is needed in the rigging of static lines.

When using static lines care should be taken to ensure that loose objects between the anchorage and the worker cannot be dislodged by movement of the lines.

Figure 8: Fixed static line with a shock absorber for use with safety harnesses and lanyards

2.5.5 Design guidelines for static lines

When planning the site layout and sequence of construction for installing a static safety line system consideration should be given to the most appropriate fall-arrest system and method of installation. Do not use guardrails as an anchor; they are not designed to take the forces involved in arresting a fall. The correct tensioning of the static line can be achieved by a framed turnbuckle or a removable ratchet and pawl. The static line must be correctly tensioned. Where a slack static line is suddenly pulled by a person slipping, this could jerk others off balance, causing harm. An over-tensioned line will exert too much force on the anchorage points, and reduce the amount available to arrest the fall.

For guidance on static line systems please refer to AS/NZS 1891.2 Supp1:2001 Industrial fall-arrest systems and devices - Horizontal lifeline and rail systems.

2.5.6 Emergency procedures

This is the most important component of any fall arrest system. The effects of suspension trauma can be serious and strike some people very swiftly. It is essential that an emergency retrieval plan is in place that can be quickly implemented by anyone who may need to rescue a workmate from a suspended situation.

Items that may be included in the rescue plan are:

• Emergency services role in the rescue. Do they know about your operations? Do they have appropriate equipment that they can use for rescue? What will be their response time?
• Have you ever been trained in or ever practised your rescue plan and techniques?
• Does everyone know their responsibilities in an emergency situation?
• Do you have all the necessary equipment on hand, including first aid supplies and a means of cutting a fall victim free from their system?
• How will you reach the victim? Possibly with a crane lift platform, cherry picker, scissor lift or ladder. Is this equipment available? Do you have rope access equipment and trained staff to use it safely?
• Do you have a means of communication?

2.5.7 Longevity and inspection of equipment

All fall arrest equipment must be regularly inspected. The various requirements for the inspection of personal and common use equipment are summarised in table 2 (from AS/NZS 1891.4). A competent person (this would generally be the trained user or qualified supervisor) should check harnesses and equipment prior to every use and a log book should be maintained documenting an inspection at least every six months. Inspection of equipment should include synthetic materials, checking for cuts, burns, fraying, abrasions, chemical contamination, mould or mildew, sun rot, and stretching. Hardware should be checked for cracks, bends, deformity, corrosion, and to ensure that all locks close and engage. Check all sewing and any shock absorbers for signs of loading.

Most fall arrest equipment in New Zealand will have a theoretical service life of about 10 years from the date of manufacture. However, due to the harsh work environments on construction sites, the reality is that equipment may only last a few years before it will have to be discarded. The use of bags or cases for the transport and storage of equipment can be an advantage. Equipment should be carefully stored when not in use.

Keep equipment from exposure to:

• Sunlight.
• Heat.
• Moisture.
• Chemicals.
• Sharp edges and abrasives.
• Heavy objects.

The construction, selection, rigging, and use of harnesses, lines and fall arrest devices must comply with AS/NZS 1891.1: Parts 1 - 4 or equivalent international standard. All equipment except type 2 and 3 fall arrest devices may be inspected by people who are suitably trained to give equipment a careful visual inspection. Type 2 and 3 fall arrest devices must have their 12 month inspection performed by a trained professional. (Contact supplier or manufacturer for details.)

Table 2: Summary of inspection requirements for fall arrest equipment

Activity	Application
Inspection by operator before and after each use	PPE including harnesses, lanyard assemblies, connectors, and fall-arrest devices - including common use devices
3-monthly inspection by competent person	Type 2 and 3 fall-arrest devices - external check only
6-monthly inspection by competent person*	Belts, harnesses, lanyard assemblies and associated personal equipment
12-monthly inspection/service by competent person*	Permanently installed anchoragesType 2 and 3 fall-arrest devices - full service including dismantling where indicatedHorizontal lifelines and rails, including integral components and permanently installed mobile attachment devices
In accordance with other standards	Ropes and slings
Inspection on entry or re-entry into service	All items of personal and common use equipment.
Inspection after a fall-arrest (and before further use)	All items that have been stressed as a result of a fall

* Or more frequently if recommended by the manufacturer or supplier

2.5.8 Safety harness inspection list

Table 3: Inspection requirements for safety harnesses

Components	Condition/ faults to be checked
Webbing	Cuts or tearsAbrasion damage, especially where there is contact with hardwareExcessive stretchingDamage due to contact with heat, corrosives or solventsDeterioration due to rotting, mildew or ultraviolet exposure
Snap hooks and karabiners	Distortion of hook or latchCracks or forging foldsWear at swivel and latch pivot pinOpen rollersFree movement of the latch over its full travelBroken, weak or misplaced latch springsFree from dirt and rust
D-Ring	Excessive vertical movement of the straight portion of the D-RingCracks, especially at the intersection of the straight and curved portionsDistortion or other physical damage of the D-RingExcessive loss of cross section due to wear
Buckles and adjusters	Distortion or other physical damageCracks and forging laps where applicableBent tonguesOpen rollers
Sewing	Broken, cut or worn threadDamage or weakening of thread due to heat, corrosives, solvents or mildew
Ropes	CutsAbrasions or frayingStretchingDamage due to heat, corrosives, solvents, etcDeterioration due to ultraviolet light or mildew

2.6 Personal protective equipment (PPE)

Industrial safety helmet (hard hats)

Industrial safety helmets complying with NZS 5806 (or suitable approved head protection) must be worn at all times while on site where there is a risk of objects falling from above. In fact hard hats are becoming mandatory on most sites in New Zealand. An elastic chinstrap is recommended to secure the hat and prevent dislodgement by the wind. Hard hats should be replaced after dropping from a height or if there are any visible signs of wear and tear. Follow the manufacturer's instructions for replacement (please check expiry dates).

Safety footwear (safety boots)

Footwear should be comfortable, provide maximum grip and give protection from pinching, jamming and crushing. A range of lightweight flexible footwear with steel or plastic protective toe caps is available (see AS/NZS 2210.1 or 2210.2). Some sites require steel toe caps to be covered to prevent the risk of creating a spark hazard should steel come in contact with the exposed steel cap. Safety boots are becoming mandatory on most sites in New Zealand.

Fall arrest harness (safety harness)

An assembly of interconnected shoulder and leg straps, with or without a body belt, that must be used where there is likelihood of free or restrained fall. The full fall arrest harness in association with a lanyard, which includes a personal energy (shock) absorber, is attached to the harness. The lanyard should preferably have a manulink, karabiner or snap hook designed to attach over a standard scaffold tube. The maximum lanyard length is 2.0m long. Refer to AS/NZS 1891.1. See also section 2.2 above.

Hand protection (gloves)

Leather or split leather snug fitting gloves are recommended to protect scaffolder's hands. They prevent scaffolding components slipping through the hands and protect against cuts and abrasions. In extreme conditions the wearing of specialist gloves may be required e.g. lined gloves in cold conditions or gloves to protect against acid or caustic spills.

Hearing protection (ear muffs or ear plugs)

Noise has been identified as a significant hazard in the workplace. There are a variety of ear muffs, pads or plugs available. In New Zealand to aid selection a system of classes is used. Classes are numbered 1 to 5 with each class increase representing an additional 5 decibels of protection (see table 4). Some earmuffs can be attached to your safety helmet. Seek advice from your supplier regarding general noise protection.

Table 4: Grades of hearing protection

Class	Attenuation	For use in noise up to:
1	6	Up to 90 dB (A)
2	12	Up to 95 dB (A)
3	18	Up to 100 dB (A)
4	24	Up to 105 dB (A)
5	30	Up to 110 dB (A)

Eye protection (safety glasses)

Safety glasses should have wide vision, UV protection, be scratch resistant and have integral side shields. This gives greatest protection for scaffolders for most conditions (see AS/NZS 1337). See manufacturer's instructions for special purpose glasses.

High visibility vests

Fluorescent vests, polycotton or nylon with 50mm reflective tape allow the wearer to be seen under normal site conditions. High visibility vests should conform to AS/NZS 4602 or EN471, the Transit New Zealand Code of Practice and local authority requirements.

2.6.1 Specialist PPE

When working in some hazardous conditions specialist equipment may be required to ensure safety, for example working in an asbestos environment. Firstly ascertain what hazardous conditions you will be exposed to. Then establish the specialist equipment you will require to work safely in that environment. Seek specialist advice if required. Safety is paramount. Examples of specialist safety equipment include:

• Breathing Apparatus (BA).
• Disposable overalls.
• Respiratory protective equipment.
• Specialist gloves.

An employer does not comply with the Health Safety and Employment Act by paying an allowance or paying extra wages or salaries instead of providing protective clothing and/or equipment to an employee. If in doubt seek advice.

2.7. Safe working practice

2.7.1 General principles

1. Always remember that you have a duty to work in a safe manner and to ensure the safety of other workers and the public.
2. Always work in a logical sequence.
3. Do not throw materials about. Always consider the safety of others.
4. Always lower materials in a proper manner during dismantling.
5. Ensure all materials are cleared from the site or job location on completion.
6. Complete a daily hazard identification and controls report when on the job.

The Building Act, Building Regulations, Building Code, manufacturers' specifications, engineers' design certificates, and chartered engineers' producer statements where such statements are required to be provided to a Building Consent Authority (BCA) for the issue of a Building Consent or a Code Compliance Certificate in relation to the Building Act 2004, as well as these Best Practice Guidelines, should be considered to ensure that all practicable steps are taken to assure the safety of the structures and of end users.

2.7.2 Before and during erection

1. Examine all materials on arrival at the site or during unloading and put aside any defective or damaged items. These items should be removed from the site as soon as possible and should not be used in the construction of the scaffold.
2. Make sure that all materials to be used are properly stacked in a safe place, especially where work over or near a public thoroughfare is being carried out.
3. Take any and all necessary precautions to ensure that the public are not endangered. This may entail the erection of diversion barriers and signs.
4. Special care should be taken when working in the close vicinity of overhead or adjacent power cables. All exposed cables and wires should be treated as live.
5. Ensure that you are in possession of all necessary permits and instructions or information relating to the job prior to commencing erection.
6. If possible contact someone in authority on site to inform them that you are commencing erection.
7. Always examine the building or structure against which you are scaffolding and if you have any doubts about any aspect of the job, for example, lack of tie positions, unsafe walls or cornices, etc then seek advice.
8. Take care not to obstruct essential services such as hydrants, service manholes or fire exits.
9. Whenever leaving the site or job location, make sure that materials are not left in unsafe locations such as doorways, pavements, kerb sides etc. Always store materials in a safe and secure location.
10. At the earliest opportunity warning signs or notices such as "INCOMPLETE SCAFFOLD" or "UNSAFE SCAFFOLD" should be prominently displayed. Once the scaffold is safe and ready for use "SAFE SCAFFOLD" signs should be displayed at access and egress points.

2.7.3 During the use of the scaffold

During the use of scaffolding it is important to check that:

1. The standards are correctly aligned and properly supported at their bases.
2. There is no undue deflection in ledgers and transoms or putlogs.
3. No essential member of the structure has been removed.
4. All ties and braces are in place and are effective in stabilising the structure.
5. All couplers are tightened properly.
6. All scaffold planks are sound and are properly supported.
7. All guardrails and toeboards are secured in place.
8. All ladders are in good condition, properly supported and secured.

2.7.4 Before and during dismantling

1. Before dismantling examine and check the scaffold to ensure that all ties and bracing are effectively in position and that the scaffold is in a stable condition. If partial dismantling is being undertaken ensure that the remaining portion is fully safe and stable.
2. Suitable warning notices must be placed for public protection.
3. Dismantling should be carried out progressively from the top level downwards. Ties, braces, ledgers, transoms, planks and guardrails must be removed lift by lift with standards following as joint positions are reached.
4. Where a building or structure is being demolished the scaffold should be dismantled to ensure that no more than 4.0m remains standing above the last vertical tie points at any time.
5. Care should be taken to avoid mishandling of materials, all of which should be lowered regularly and not "bombed" during the dismantle.
6. Small amounts of material may be temporarily placed on lower lifts for convenience during dismantling but care should be taken not to allow this material to build up to an unacceptable load. Where such temporary placement at low levels is carried out, it may be necessary to place raking tubes from the ground level to the lower lift in order to stabilise the scaffold.
7. During dismantling ensure that all scaffolding materials are removed from the building and that no loose materials are left on roofs or projecting cornices, etc.

2.7.5 Scaffolding near power lines or electrical conductors

Power lines and conductors are a potential hazard to persons erecting, working from or in the vicinity of a scaffold. No scaffold should be erected closer to any conductors of an overhead electric line at a distance, in any direction, less than that shown in table 5 (from NZECP 34.4.4).

No scaffold should be erected closer than 4.0m to power lines or electrical conductors without approval from the local electricity network company.

Table 5: Minimum clearance distance in any direction for construction of scaffolding near

Line voltage (under normal conditions)	Minimum Distance
Not exceeding 66 kV (maximum span 125 metres)	4.0 metres
Exceeding 66 kV (maximum span 25 metres)	5.0 metres
Any voltage (span greater than 125 metres but less than 250 metres)	6.0 metres
Any voltage (span greater than 250 metres but less than 500 metres)	8.0 metres
Any voltage (span exceeding 500 metres)	Not less than 8.0 metres[1]

Recommended procedures

If during your initial site inspection you find power lines or conductors in close proximity to the position of the intended scaffold, you or your client should contact the local electricity network company. This company will give you the expert advice you need.

They may:

• Sleeve the lines.
• De-energise the lines.
• Re-route the lines.
• Shield the lines using moisture resistance non-conductive material.

The electricity network companies are the experts. Ensure that you get written approval from them stating the intended scaffold is safe to erect and that they have taken all practical steps to ensure your safety before any work commences.

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Footnotes

^[1] or as agreed with the owner

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