Purpose

Fall arrest systems have been installed in some steel stockholders for use when gaining access to stored stock. This SIM identifies the range of factors to be considered in a suitable risk assessment for their use in steel stockholders to indicate whether their use in this application is likely to be appropriate.

Introduction

1  Several examples have come to light of the provision of fall arrest systems for use by workers who have to gain access to the top of stored steel stock in steel stockholders to attach /detach lifting equipment.  Often these workers climb up and walk along products including tube, bar, beams or sheet/plate steel stored above head height. The provision of fall arrest systems appears to be an attempt to comply with the Work at Height Regulations.

2  Concerns have been raised by some inspectors that this appears to undermine the existing guidance in HSG246 ‘Safety in the storage and handling of steel and other metal stock’ which recommends that storage arrangements should avoid the need for climbing onto and walking over stock.

3  Investigations have been made with one manufacturer/supplier whose fall arrest equipment has been installed to provide fall protection in these circumstances. They confirm that their equipment are safety systems, not access systems, and that a suitable and adequate surface should be available or provided for the worker to walk on, before their restraint systems are used to prevent a fall, or fall arrest systems used to arrest a fall (if it is not possible to design a restraint system).

Principles of safe work at height

4  Work at height in steel stockholders should follow the legal requirements and generic principles for access to height applicable to all industries, i.e. by following a hierarchy of:

1. Work should not be carried out at height where it is reasonably practicable to carry out the work safely otherwise than at height;
2. If work at height is essential ensure that workers are prevented from falling;
3. Where it is not possible to eliminate the risk of falling use a suitable fall protection system to minimise the consequences of a fall.

5  HSG 246 (which was drawn up by HSE in consultation with the National Association of Steel Stockholders and Wolverhampton CC (as partners with HSE in the Steel Stockholders Lead Authority Partnership) identifies that:

1. Common causes of injury in steel stockholding include falls from height e.g. when accessing stock and storage systems, and being struck by moving stock eg when it moves or falls during lifting operations;
2. Storage systems should be designed to provide safe, clearly defined means of access both through and within storage areas, including safe access on all sides of a stack to allow for the safe slinging of loads;
3. Safe systems of work should include limiting the height of stored stock, particularly where access needs to be made for attaching/detaching lifting slings;
4. Safe means of access should be provided for working at height eg safety steps or safety platforms.

6  Fall protection PPE should be considered only as the last resort if fall prevention and collective fall mitigation measures are not reasonably practicable. Any system should be verified as being safe for its intended application by a competent person, usually the supplier.  Particular care should be taken when different components of a fall arrest system are combined eg fall arrest block and a horizontal flexible anchor line.  The supplier should be able to demonstrate by appropriate testing that the system is safe and that potential problems (see paragraph 12) will not be present.

Use of fall arrest systems in steel stockholders

7  One system known to be installed in a steel stockholders operates by suspending a retractable type fall arrest block from a permanently installed, overhead horizontal wire, with the retractable wire from the fall arrest block attached to a harness worn by the worker.  The fall arrest block is connected to the horizontal wire by a gate latch mechanism which allows free movement along the length of the wire, including across rings supporting it. The horizontal wire is fitted with an energy absorbing device designed to limit the forces on the wearer of the harness (and the building) when the arrest block locks the retractable wire in position within a short, specified, distance in the event of a fall. The specifications from the maker/supplier require a minimum freefall distance to guarantee effective operation of the locking mechanism and to allow the energy absorber on the overhead wire to operate. The minimum freefall distance is dependent on the distance between the supporting points of the overhead horizontal wire, but as a minimum is approximately 2m.  [Exemption: S43 - Commercial Interests]

8  It is understood that in at least one steel stockholder the horizontal overhead wire has been installed on the underside of an overhead traveling crane to allow full flexibility on the use of the system throughout the storage area. In this system the harness wearer has to attach and detach from the fall arrest block each time and move to a safe position, before the crane moves to transfer a load.

9  Alternatively if the fall arrest block is attached to a horizontal wire installed near the roof above the crane the fall arrest system is limited in its application by the position of the wire. The installation of numerous such wires and fall arrest systems to cover all positions of work in a storage area is likely to be prohibitively expensive.  The advantage of this system is that the harness wearer could remain attached to the fall arrest system before the crane was moved – provided he was in a safe position. However, if the crane is inadvertently moved towards him, or a second crane is moved incorrectly, the harness wearer is at risk of being swept away.

10  The installation and use of fall arrest systems may be attractive to some steel stockholders who are reluctant to revise their storage layout to allow access to stored stock for slinging without having to climb and walk on product/racking, as this would mean a loss of storage capacity. The cost of a single fall arrest system including installation of an overhead horizontal wire, supply of a retractable fall arrester and harness, and basic training in its use may be less than £2000.

11  However, there are a number of additional factors that need to be taken into account in any risk assessment for the safe access to height in steel stockholders:

1. The operation of the fall arrest block and line should essentially be vertical, [Exemption:  S43 - Commercial Interests]
2. There is a minimum freefall distance for successful operation of the fall arrest system, which may be impossible to maintain across steel storage areas due to differing heights of adjacent stacks;  
3. Persons falling (and successfully stopped from falling) may be injured if they come into contact with sharp edges of stored stock or parts of racking;
4. Stored stock may not provide secure footing and persons walking on stacked materials are at risk of serious injuries from stock moving;
5. To hook the harness on to the retractable line in the fall arrest block a pilot line is attached to the end of the retractable line to enable it to be pulled down to the harness. This pilot line can be secured at ground level (e.g. on the building wall or stanchion) if the overhead horizontal line is fixed in one place, but would trail free if the line was attached to the underside of an overhead traveling crane – with a risk of becoming trapped or possibly dislodging stock;
6. The choice of lifeline i.e. webbing or wire should take into account the environment in which it is to be used; webbing is vulnerable to sharp steel edges;
7. If the system operates in a fall the whole arrest system should be examined/checked and parts replaced/renewed as –
8. - required before the system is re-used. This will include replacement of the energy absorber in the overhead horizontal line; 
9. Consideration must be given to operator training and pre-use checks;
10. Suitable arrangements need to be put in place to rescue anyone suspended in the event of a fall;
11. Fall arrest systems are designed with a maximum weight for the person in the harness (usually 100kg).

12  HSE has sponsored research into the use of retractable fall arresters, which should be published by the end of summer 2007, and which may affect the factors to be included in the risk assessment, above.  One of the issues being investigated is the effect of combining the device with other anchor devices including horizontal lifelines, which may increase the risk of a worker hitting an obstruction or the ground, caused by:

1. Ratchet pawl bounce - when a worker falls, the horizontal line can spring up and down during arrest.  The spring up can cause the locking mechanism in the inertia reel to disengage causing another fall and subsequent arrest, unlock, arrest etc. This will increase the fall distance;
2. Ineffective locking - the energy absorbance within the retractable device and the energy absorption device in the horizontal wire may counteract each other to an extent that the retractable device won't lock-on in sufficient time;
3. Swing falls - if the retractable device does not remain overhead i.e. lags behind as the worker moves along the steel stock, any fall will cause the worker to swing back.  The velocity of this movement may be insufficient to activate the retractable devices lock-on capability and lead to a delayed arrest.

Conclusions on the use of fall arrestors in steel stockholders

13  While the use of fall arrestors may have a part to play in ensuring safe access to heights in some circumstances, and possibly as an interim precaution while more suitable storage arrangements are provided, it is likely the limitations outlined in paragraph 11 would outweigh the advantages in most circumstances for access to the top of stored stock.

Further advice

14  NASS and Wolverhampton CC have been consulted in the preparation of this guidance.  

Further advice on the selection, use etc of fall arrest systems is available in the Technical Guidance Notes produced by The Work at Height Safety Association.

The NASS H&S Committee includes members with many years of practical experience in the steel stock holding industry.  They have advised that they would be happy to provide advice to any steel stockholder (whether a member of NASS or not) on safe working, including safe access to height, safe (un)loading of steel stock and other issues. Contact should be made with NASS or First Floor, The Citadel, 190 Corporation Street, Birmingham B4 6QD Tel: 0121 200 2288.

The contacts on this issue are:

• Peter Woolgar, HSE Manufacturing Sector  Tel: 0121 607 6254; or
• Alison Stephens, Wolverhampton CC  Tel: 01902 554383.