A REPORT ON RESEARCH INVESTIGATING THE PRACTICAL USEFULNESS OF CURRENT FALL PREVENTION AND PROTECTION METHODS WHEN WORKING AT HEIGHTS

Cameron, Iain Department of Building & Surveying, Glasgow Caledonian University, U.K.

Duff, RoyDepartment of Building and Civil Engineering, University of Manchester Institute of Science and Technology (UMIST), U.K.

Introduction

The UK Construction Industry suffered 84 fatal accidents during the year 2000. Almost half of these fatalities were due to ‘falls from heights’ and around half of these were due to ‘falls from roof edge’ and ‘falls through roof’. The statistics also suggest that new build (e.g. profiled aluminium roofs) are just as dangerous as refurbishment (e.g. asbestos cement roofs). These figures demonstrate that falling accounts for the majority of fatal accidents in the UK Construction Industry.

There are numerous pieces of statute which aim to plan roofwork and introduce technical measures to prevent falls in the UK. Section 2 of the Health and Safety at Work Act 1974 requires contractors to provide a safe place of work and this includes roofwork. Regulation 3 of The Management of Health and Safety at Work Regulations 1999 require the risks associated with working at heights to be assessed and controls introduced to reduce this risk to as low a level as is reasonably practicable. Regulation 4 of these regulations places an emphasis on measures which protect the whole workforce and thus yield the greatest benefit. This means that collective protection (e.g. safety net) is favoured over individual protection (e.g. safety harness) and general preference is given to methods of fall protection which take advantage of technological progress.

Further, Regulation 6 of The Construction (Health, Safety, Welfare) Regulations 96 place an absolute duty to prevent falls when working at a height of over 2 metres. This is achieved by a requirement for guardrails and toeboards and where this is not possible by the introduction of methods which will arrest a fall as a last line of defence. Also, the planing of a safe system of work and risk controls will form an important section of a Principal Contractor’s Health and Safety Plan issued under the Construction (Design and Management) Regulations 94.

In accordance with the principles of risk prevention and protection hierarchy, there are five key areas which this research programme intends to evaluate because they represent the current state of ‘best-practice’ when working at heights in construction:

  1. The benefits and limitations of safety nets during roofwork
  2. The benefits and limitations purlin trolley systems during industrial roofwork
  3. The benefits and limitations of air inflated safety bag systems when working at heights and/or near a leading edge
  4. The benefits and limitations of cable based fall arrest systems as a means of protection when working at heights and/or near a leading edge
  5. The benefits and limitations of the use of currently specified fall arrest systems

when erecting and dismantling scaffold (SG4)

The practical usefulness of these methods of fall protection are currently being investigated through a combination of expert opinion and experiences drawn from live field trials on case study sites.

Research Objectives

This research will investigate the following objectives:

  1. To evaluate the benefits and limitations of safety nets during roofwork
  2. To evaluate the benefits and limitations trolley systems during industrial roofwork
  3. To evaluate the benefits and limitations of air inflated safety bag systems when working at heights and/or near leading edges
  4. To evaluate the benefits and limitations of cable based fall arrest systems as a means protection when working at heights and/or near a leading edge.

5.To evaluate the benefits and limitations of the use of currently specified fall arrest systems when erecting and dismantling scaffold (SG4).

Objectives – Background Information

(1)The benefits and limitations of safety nets during roofwork

These systems are growing in popularity within the UK Construction Industry as a direct result of Regulation 6 of the Construction Regulations 96. The systems are becoming easier to use and install as new suppliers and rigging companies enter the marketplace. Further, the systems have been widely championed in the UK through HSE’. The use of safety nets during industrial roofwork is a published ‘HSE Enforcement Priority for the Year 2001’. It is also possible that safety nets can be used on some refurbishment work for example, to protect falls through fragile rooflights in circumstances where the primary protection (the solid roof light cover) is carelessly removed.

It is the writers’ belief that there are some problems with the use of safety nets which prevent there use on all occasions, and although they are an excellent method of fall protection, they have limitations and these need to be investigated.

For instance,

a. How feasible are nets during refurbishment work with highly serviced roof spaces ?

b. How feasible are nets to install if the site encounters poor ground conditions ?

c. How feasible are nets to erect during mezzanine or swimming pools construction ?

d. How feasible are nets during the construction of tall buildings beyond the reach of

normal access equipment ?

e. What changes do designers need to make to allow easier installation of nets and

their border ropes and how can this be done so as not to impede contraction for

example, gutters ?

Furthermore, are some contractors negating the purpose of safety nets by the systems of work they design. For instance, some contractors are insisting on the use of safety harnesses in addition to the use of nets. They argue that nets gives people a false sense of security and this encourages workers to take risks. These harnesses place a massive shock load on the body and this introduces other problems (‘suspension trauma’ and rescue practicalities and damage to internal organs etc). This introduces another research question in relation to nets:

f. How prevalent is this practice and how can contractors be persuaded to abandon

this practice and let the net serve its purpose ?

(2)The benefits and limitations purlin trolley systems during industrial roofwork

These systems have been around for a long time and are usually used in conjunction with safety harnesses. This is because, traditionally, the purlin trolley has a double handrail on the ‘Leading Edge’ (the opposite side to that being worked on) which provides protection. But, has an open ‘Working Edge’ (the side where the sheets will be progressively installed) and thus requires a harnesses attached to the trolley to prevent falls at the working edge.

However, a number of technological advantages have been made in this area in recent year. For instance, patented systems (e.g. Rossway) now mange to protect the ‘Working Edge’ by means of a trolley which limits the open area by the provision of a horizontal barrier (attached to the trolley) which rests about six inches below the location where the roof sheet will be fixed to. This means that if someone accidentally stands on the unfixed sheet, the sheet will be caught (and therefore the worker) by the horizontal barrier. The system eliminates the need for harnesses etc and has been endorsed by HSE as a safe system of roof work which provides an alternative to the use of nets and/or harnesses (

This system may well be an alternative to nets, for use on occasions where nets are limited, in order to an alternative to nets and possibly limit the risk from net installation. The system is suitable for simple roof designs that do not feature curved surfaces or intricate plan shapes and cost effective systems for industrial warehouses.

This programme of research reported in this paper will investigate the kinds of building designs where this system can be used and the kind of design changes that will require to be made to allow this systems to function effectively. This may include the specification of roof panels of the same modular width and the location of anti sag bars etc.

(3)The benefits and limitations of air inflated safety bag systems when working at heights and/or near a leading edge

There are situations in construction where nets are impractical and the alternative means of fall protection has normally been a harnesses and line. These include the installation of precast slabs where there is always a leading edge at each floor of the building. The concept of air inflated safety bags in growing in recognition within the industry. These systems are being trialed by the Precast Flooring Federation (PFF) at present. Also, it is possible that these systems could augment traditional scaffold ‘crash decks’ by overlaying the air bags on the scaffold deck and thus provide a softer landing during atrium construction etc.

Also, perhaps the greatest opportunity for these systems is in domestic housing, this sector of the industry has always struggled with the concept of safety nets and it is probably fair to say that nets have their limitations when used during low level construction. Further, harnesses are also problematic during this type of work because it is difficult to find attachment points and workers have to attach / detach frequently. Therefore, safety air bags may have much to offer the housing sector.

The opportunities for this systems of work will be investigated by this research. Further, problems of perception will also be viewed which may inhibit the industry’s acceptance of these methods, for example, air bags being viewed as a child’s amusement park toy etc.

(4)The benefits and limitations of cable based fall arrest systems as a means of protection when working at heights and/or near a leading edge.

These systems can be installed as either a last line of defence during new construction work or as a permanent maintenance systems installed during new building. Also, the systems is useful during refurbishment work. The facts are that there are some occasions when it is possible that safety nets could be impractical. This could be the case during unusual new build structures – parabolic and ellipse type roofs. These roof shapes also render purlin trolley systems useless.

Therefore it is possible that steel cable systems which operate with a harness and inertia reel attached to the running line may offer practical and cost advantages over nets. Also, even if cable based systems prove to be of only limited value during new build, it is conceivable that occasions will exist during refurbishment work where cable systems are preferred over nets.

This is particularly the case during the renovation of historic buildings with dome roofs and other unusual features. These buildings may make nets difficult and dangerous to install and may mean that the net is well over 2m below the apex of the roof. Also, it is conceivable that cable systems may need to be specified as part of the maintenance system because they are unobtrusive and thus sympathetic to the architectural needs of historic buildings.

The programme of research reported in this paper will evaluate the types of projects where cable systems should be considered on the grounds of practical usefulness.

(5)The benefits and limitations of the use of currently specified fall arrest systems when erecting and dismantling scaffold (SG4)

The National Federation of Scaffold Contractors (NFSC) published Guidance Note: SG 4 – ‘The Use of Fall Arrest Equipment when Erecting, Altering and Dismantling Scaffold’ during 2000. The guide is endorsed by the Construction Confederation, HSE, several major contractors, NFSC member companies. The guide is in direct response to Regulation 6 of the Construction Regulations 96.

The system appears to be well presented but on close inspection there are a number of limitations that the researchers believe require to be addressed. It is well documented that the guide does not comply with Regulation 6 of CHSWR 96 and is in fact a compromise. The guide only applies when working at a height of over 4m. The reason for this is that if someone wears a 2m lanyard attached at foot level (=worst case position), then they will fall a minimum of 2 metres with a shock load to the body of 12KN (circa 12000Kg). This is unacceptable and has to be reduced to half this load under EU Standards. This requires the introduction of a 1.75m shock absorbing lanyard. This lanyard will ‘tear’ for a distance of 2m when worn as part of a fall prevention strategy. This means that the scaffolder (if clipped on at the worst case foot position) would fall 1.75m plus the 2.0m of the lanyard tear – a total of approximately 4m with the shock load to the body being reduced to 6KN.

It is clear that this does not fully comply with Reg 6 of the Construction Regulations 96 and the possibility of secondary injuries during this 4m fall need to be considered. This point has been forcefully demonstrated by the UK Construction Industry Training Board (CITB) who found that the skull of a mannequin was literally smashed due to striking a scaffold transom during a 4m fall whilst wearing the shock absorbing lanyard. The CITB’s spokesperson believed that the strength of the mannequin's skulls was at least equal to that of a human skull.

A safer systems would be to introduce an inertia reel as part of the installation. These reels are very lightweight and compact and are similar in construction, operation, and looks to a car seat belt. And, if used as part of the fall prevention installation, would drastically reduce the free fall distance of the scaffolder – to around 2m if attached at the worst (foot height) case, and about 0.5m if attached at the best (head height) case. This amended system would comply with the Construction Regulations 96 (Reg 6) and would reduce the risk from secondary injuries. Alternatively, a fixed anchorage point attached to scaffold uprights (standards) would reduce falls to only a short length. For example, ‘The Jordan Clamp’, which ensures that all scaffold lanyard hooks are always attached at above head height.

This programme of research reported in this paper will evaluate the feasibility of this systems and the views of the key stakeholders, and some major contractors, on the worth of this revised methodology.

Related Issues of Concern – Training of Roof workers

The training of roof workers and the equipment they hold has always been an issue of concern. Roofwork is much more dangerous, at least statistically that steel erection. It is fair to say that the modern day steel erector is better trained, older, and more psychologically aware of the danger than a roof worker. The steel worker operates along open steel and is spatially aware. The roof worker on the other hand walks across a platform that appears to be solid and is thus subject to a false sense of security and therefore less aware of the dangers. The roof worker is tends to be younger, had little previous training, and works for a small company with limited access and safety equipment.

The Roofing Industry Alliance Hallmark Scheme in the United Kingdom – a kind of ‘Quality Mark’ or ‘Kite Mark’ – hopes to overcome some of these problems by ensuring the necessary training of experienced construction workers and assessing the quality of companies via a rating scheme. The scheme intends to weed out the ‘cowboys’ and restore credibility to the roofing industry.

The research reported may well investigate the merits of this scheme and the ways in which Principal Contractors can be persuaded to endorse the scheme and therefore reduce the opportunities for non-skilled roof workers to operate in the construction industry. Presently, however, this ‘competency’ objective is less certain because it seems HSE have allocated this research to others.

Research Methodology

The research reported here will be delivered through a combination of a desk top review of the suitability of current technical guidance and standards for fall prevention when working at heights. This will be followed by a series ‘focus group’ meetings of experts and vested interest groups. This group will identify a series of live case study sites of each different method of fall protection which the research team will visit and observe. Also, a research ‘steering group’ maintains the direction of the research. Finally, interviews with experienced site managers, suppliers, and operatives are to be conducted. These interviews will determine the experiences of site managers and operatives in relation to the identified fall prevention methods.

The ‘focus group’ of interested parties may well include The National Federation of Roofing Contractors (NFRC), The National Federation of Scaffold Contractors (NFSC), The Scottish Building Employers Federation (SBEF) and/or The Construction Confederation (CC), The Health and Safety Executive (HSE), The Major Contractors Group (MCG), and other interested stakeholders e.g. designers, suppliers, trade unions, trade contractors.

The focus group will identify case study sites and industrial partners who will provide access for the research team to observe the use of safety nets, purlin trolleys, safety air bags, cable base systems, harnesses during scaffold operations etc. This will allow the research team to evaluate the practical usefulness of the different methods of fall prevention methods for working at heights and the ways in which each of these methods can be improved. This may well involve interviews with construction mangers, construction workers, and construction suppliers in order to investigate the optimum arrangements required for the implementation of these methods of fall prevention.