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The Height of Safety

Published: 01st Jul 2013

ARTICLE CONTINUES BELOW

From the seemingly innocuous changing of a light bulb atop a step ladder, to installing bolts 60 metres in the air, Ruslan Ponomarenko addresses the hazards of working at height.

‘Nothing is going to happen to me’, ‘I have carried out this job a thousand times’ and ‘It’s just two metres - it’s not dangerous at all’ are just a few examples of complacency, voiced across all levels of employment when executing work at height.

The Health and Safety Executive (HSE) report that in 2008/09, more than 4,000 employees suffered a major injury as a result of a fall from height and that in the same period more than 10,000 employees suffered a major injury as a result of a slip or trip at work.

The question is, how can we prevent these incidents from occurring? According to the Swiss Cheese Model of Harm, incidents occur when holes in the cheese, or weaknesses in the respective systems, are aligned.

Much like the holes in a slice of Swiss cheese, there are sometimes holes or imperfections in a worker’s ability to stay safe. When this occurs only in a minority of workers, potentially hazardous actions can be diffused by their colleagues’ correctly following safety procedures. It is when several workers are missing vital work at height safety knowledge that these holes in knowledge become aligned and hazards come into fruition.

Fall prevention and fall protection are the basics of safe working at height. These should be implemented with no holes to ensure work at height can be carried out safely.

Fall prevention

The following sections will address the main requirements of the most frequently used equipment to perform work at height, including fixed platforms, standard railings, fixed ladders, fixed stairs, fixed anchorage points, and skylights.

Fixed platforms

A platform is required when the working or standing area cannot be safely accessed from the floor, when routinely accessing an area and when unloading or loading hazardous chemicals.

As outlined in American National Standards Institute (ANSI) A1264.1-1995, Occupational Safety and Health Administration (OSHA) 1920.27 and European Standards (EN) 365, personnel platforms must be designed for a live, uniform load of 488kg/m2 minimum, with a minimum platform size of 60cm by 60cm. An additional egress is required if the furthest location on the platform is more than 22.8m from the main platform egress. Supports and fasteners must be able to simultaneously support the cargo load, the weight of the platform and the weight of all attached appurtenances.

Standard railing

Standard railings are required for all open sided floors and platforms 1.2m or more above the adjacent floor or ground level, as well as for platforms and walkways located above or adjacent to hazardous areas - regardless of height from the floor.

Standard railings must have:

• A smooth top railing located at approximately 1.07m and able to withstand a 90kg force in every direction

• An intermediate railing located 0.48m below the top rail, which is able to withstand a 22.5kg force in every direction

• Toe boards of 104mm minimum height with a maximum spacing of 6mm between the toe board and the platform

• Vertical posts placed a maximum of 1.8m apart. If the railing surrounds a platform that is occupied with people, local building codes may require closer spacing of intermediate rails

Temporary railings follow the same requirements as permanent railings. The ends of the railings should be turned into the wall or arranged so as not to constitute a projection hazard. Wood may only be used for temporary installations and if it is used must be at least 5cm x 10cm stock, with posts placed at 1.8m maximum spacing (ANSI A1264.1-1995, OSHA 1920.27 and EN 365).

Skylights

Skylights should be guarded by a standard skylight screen capable of withstanding a 91kg load applied perpendicularly on any one area. The construction should either be grill work with openings of not more than 10.1cm long, or slat work with openings not more than 5cm wide with unrestricted length.

Alternatively, use either fixed standard railing on all exposed sides with a nominal height of 1.1m from the upper surface of the top rail to the floor, or a plastic skylight that can provide the necessary structural integrity to support the 91kg load, which would not require further safeguarding since it would also meet the intended function of a screen.

As expressed in 29 CFR 1910.23(e) (8), the primary function of the screen is to support at least a 91kg load. This provision further relates that the screen shall provide a minimum deflection so as not to break the glass, but that portion of the requirement may be inapplicable when no glass is present. The concern for breaking the glass results from the possible fragment exposure to persons beneath the skylight.

Fixed ladders

Fixed ladders must not be installed to view, service, or maintain an area from the ladder - the ladder must lead to a platform.

Fixed ladders must have:

• Maximum spacing between the rungs of 305mm

• Rungs or cleats of 19.5mm minimum diameter, increased to 25mm minimum diameter in corrosive atmospheres

• Uniform spacing between rungs, except for the top and/or bottom rungs

• Minimum clearances - 457mm between vertical side rails of the ladder; 762mm on climbing side of a 90° vertical ladder without cage; 380mm on each side as measured from centre line of ladder on the climbing side; 178mm on the backside of a fixed ladder, between the centre line of the rung and any permanent object behind it. Where there are unavoidable obstructions this minimum clearance can be waived, so long as there are at least 38mm between the top of an obstruction and the centre of the affected rung above it, and at least 114mm between the bottom of an obstruction and the centre of the rung below. Refer to OSHA 1910.27, section C item 4, for a picture of this data description

• A protective finish for use in corrosive environments is required, as per ANSI standards

• Vertical side rails extending at least 1,067mm above the landing or platform line, which flair out above the landing or platform line to a minimum of 610mm and a maximum of 914mm. A standard railing must extend 1.8m on either side of the fixed ladder if the ladder terminates on a roof

A landing platform is generally required - except for chimney ladders - every 9m or every 6m if no cage is provided around the ladder. The minimum platform size is a 610mm wide by 762mm long instalment. Ladders longer than 9m with cages must be offset in multiple sections, with platforms at each section. Every platform should be guarded by a standard railing and the passage should be guarded with a swinging gate so that a person cannot walk directly into the opening. The minimum overlap required for offset sections is between 0.9m to 1.8m.

Angled fixed ladders should be between 0° and 15° from vertical. Angled fixed ladders from 15° to 30° from vertical are considered substandard, but are acceptable if conditions require it. Fixed ladders must not exceed 30° from vertical.

In the case of railcar unloading, maintain railroad clearance distances in both vertical and horizontal planes. Consult the site traffic and railroad coordinators prior to installation of stairways and platforms adjacent to rail tracks.

Anchorage

Anchorage points must be:

• Designed with the capacity to support a minimum 22.2kN per user or must maintain a safety factor of at least two times the maximum arresting force (MAF) expected

• Designed by a legally qualified engineer

• Installed and used according to a legally qualified engineer’s instructions

• Identified and marked in the field or in procedures

• Tagged with specific use instructions if designed to support less than 22.2kN or for use with a specific type of equipment

• Designed for only one person to use at a time, unless specifically designed and marked otherwise

• Located at shoulder level or above to minimise the free fall distance and to allow for an adequate clearance distance, as per the design

• Located directly over the work area to minimise any swinging in case of a fall

• Overhead for all retraction devices - the anchorage points must change as work position changes to maintain the shoulder height anchorage point

When personnel work under pipes or between layers of the pipes, the overhead piping and supports may provide a point for safe anchorage. Placement of the anchorage must follow the previously listed requirements.

Fall protection

Fall protection is anything which could eliminate or reduce the consequences of a fall that has already happened. As detailed below, this includes body harnesses, energy absorbing and self retracting lanyards, vertical and horizontal lifelines, safety nets, and connectors such as snaphooks and carabiners.

Full body harness

On a full body harness, the tongue and buckle leg straps should be used when available and must have metal grommets. Strap keepers should be present, especially in leg straps, and must be correctly used to prevent accidental disengagement. When a tool belt is used, the belt must be separate from the full body harness. If the belt is attached to the full body harness the arresting force will be concentrated around the waist during a fall, causing damage to the wearer’s internal organs.

The harness must have a minimum of one D-ring for fall arrest at the back of the harness, and a front D-ring to be used only for rescue purposes or with a ladder climbing device.

The harness must be the correct size for each person and ideally each person should have his/her own harness if doing regular, routine work. The weight range for commercially available harnesses is 59kg to 140kg. If the worker is outside of this range, a special size order must be placed with a manufacturer. The harness must remain adjusted to the body throughout the work. When the user is freely suspended after a fall, the connection of the fall arrester must be capable of maintaining the person in an upright position.

In optimal conditions, such as being stored away from direct sunlight, being cleaned by hand and being hung to dry, the harnesses have a typical life of three to four years. Harnesses should not be marked with pen, as the ink in most markers breaks down the harness fibres, as seen in ANSI Z359.1-1999 and EN 361.

Lanyards

Lanyards can be made of webbing, synthetic rope or metal cable, not natural fibres. Each lanyard must have an energy or shock absorber. During use the lanyard’s energy absorber is connected to the back D-ring of a full body harness.

Lanyard material selection is dictated by the hazards present in the workplace and the environment for the work. In areas where chemical resistance is required, evaluate and specify a material resistant to this type of hazard, such as a polyester impregnated with urethane.

In situations where the lanyard may be exposed to sparks or chemical burn risks, use a stainless steel lanyard with an energy absorber. Metal cable has several advantages compared with synthetic materials as it provides a longer working life, especially for construction activities. The disadvantage, however, is that it has a fixed length.

Double lanyards such as Y-type, dual or twin are recommended when the work requires changing elevations and work locations. Using a double lanyard, a user attaches the second lanyard to an anchorage point and then removes the first lanyard, maintaining their fall protection the entire time. These lanyards are mandatory for work involving changing anchorage point locations.

For work position changes, the second connector must be placed before disconnecting the first connector. If the equipment is correctly used, only one of the lanyards will be used once the worker has reached his/her work position and is stationary. The free lanyard may be hooked to a free D-ring on the harness or placed inside a trouser pocket.

Whenever possible the length of the lanyard should be minimised. Both the maximum length and the free fall distance must be 1.8m. Consider the clearance distance to avoid hitting the ground or floor, the function and type of the lanyard and the location of the anchorage point. The alternatives for short heights are to use an adjustable length lanyard, to use only the energy absorber or to use a self retracting lanyard.

Never wrap a lanyard around a structural element and then connect the snaphook or carabiner back on the lanyard as this reduces the strength of the lanyard by a minimum of 50%, and greatly increases the chances that the lanyard will be cut or will roll out of the connector. A temporary anchorage point such as a beam strap should be used in these situations. Do not use two lanyards as an alternative to using a dual lanyard. ANSI and OSHA prohibit connecting two connectors to the same D-ring.

Connectors

Connectors must be constructed of a stainless steel alloy with a finish that is corrosion resistant. The connectors must have a system or lock that prevents them from being opened by one action. All connectors must only open by using two consecutive, deliberate actions.

In accordance with the manufacturer’s instructions, the diameter of the connector must be compatible with the diameter of the item that it is connected to. It is not generally necessary to lubricate the connectors, but when lubrication is required, graphite is the preferred choice. Using oils and greases should be avoided because the hydrocarbon will attack the nylon’s connections.

The following connections can result in accidental disengagement caused by excessive force on the side gate. Workers must therefore avoid using:

• Two snaphooks connected to one D-ring

• Two snaphooks connected to each other

• A snaphook connected to itself - hooked to its own lanyard

• A snaphook on a ribbon loop or a ribbon lanyard

• A snaphook connected to a horizontal lifeline - a carabiner must be used to connect a lanyard to the horizontal lifeline

Lifelines

Both vertical and horizontal lifelines must be designed, installed and used as part of a complete fall arrest system. This must include supervision by a qualified person, designed criteria including at least a safety factor of two and the capacity to support double the MAF.

Vertical lifelines must have tension resistance strength of at least 2.273kg and a minimum diameter of 79mm for metal cable or 159mm for other materials. Vertical lifelines must include a fall arrester directly connected to a lanyard with a strength capacity of at least 16kN.

As the worker is climbing up, he/she must push the fall arrester so that it stays above their D-ring.

Horizontal lifelines must be capable of supporting a weight of at least 22kN per person connected to the lifeline, applied in all directions. They must be made of metal cable or synthetic fibre rope - natural fibres should never be used. The lifelines must be continuous from anchorage point to anchorage point and cannot have knots or bends.

It is mandatory to include an energy absorber in the horizontal lifeline system independent from the worker’s shock absorber in the lanyard. The energy absorber is connected on one end of the system and can reduce the force requirements by 50%.

Safety nets

Designed for fall protection, safety nets are located close to the building to minimise the possibility of a falling worker missing the net. The suspension points for the net must be reviewed by a legally qualified engineer. Typically, each point must support 4.48N. In order to avoid having a net that is heavier than required the smallest size net must be selected that covers the open area and allows the work to be performed.

The use of a small holed debris liner is recommended to catch falling objects, to avoid a person’s arms and legs from going through the net in the case of a fall and to distribute the MAF across the body.

Conclusion

There are many fall connected incidents in the workplace. Knowing and following the basic fall prevention and protection requirements will close the holes in the Swiss Cheese Model of Harm. Although work at height training may not seem fun, do not forget that it will help you to prevent fatalities.

Published: 01st Jul 2013 in Health and Safety International

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