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Use of fall arrest systems in steel stockholders

SIM 03/2007/15

OG Status:  Fully open

Author Unit/Section:  Manufacturing Sector

Target Audience:  All visiting staff including Local Authority Inspectors

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. This SIM does not apply to work activities in the loading/unloading of delivery vehicles.

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 working surface should be available or provided for the worker to walk on.

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 the hierarchy as specified in Regulation 6 of the Work at Height Regulations 2005.

5 HSG 246 (which was drawn up by HSE in consultation with the National Association of Steel Service Centres (NASS) (formerly known as the National Association of Steel Stockholders) and Wolverhampton City Council (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, being struck by moving stock during lifting operations or when stacked stock is disturbed or distabilised;
  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 whatever the activity involved.

Note - For existing premises a stock profiling exercise may identify slow moving product which could be rearranged and reduced to enable improved storage organisation so enabling alternate empty aisles to be provided and thereby negating work at height (as per recommendations in HSG246).

6  Fall arrest systems should be considered only as the last resort if fall prevention measures (including work restraint) are not reasonably practicable. Any system should be verified as being suitable for its intended application by a competent person, usually the system supplier.  Particular care should be taken when different components of a fall arrest system are combined eg retractable fall arrester used in conjunction with a horizontal flexible anchor line.  The supplier should be able to demonstrate by appropriate testing that the system functions as intended and that potential problems (see paragraphs 11 & 12) will not be present.

Use of fall arrest systems in steel stockholders

7 One system known to be installed in a steel stockholder operates by suspending a retractable type fall arrester from a permanently installed and tensioned overhead horizontal wire, with the retractable wire from the fall arrest block attached to a harness worn by the worker. The retractable fall arrester is connected to the horizontal wire by a gate latch traveller mechanism which allows free movement along the length of the wire, including across anchoring rings supporting the wire. In the event of a fall the retractable fall line locks after a short distance to arrest the fall. This along with the energy absorber fitted to the horizontal line are designed to limit the forces acting on the falling person and the building. [Alternatively, rigid anchor lines could be used to attach work restraint or fall arrest systems].

8  The specifications from the maker/supplier require a minimum freefall distance below where the user stands to guarantee effective operation of the combined retractable fall arrester and the overhead horizontal line. This includes the length of the wire paid out by the retractable fall arrester before locking, plus the deflection of the horizontal wire and an allowance for harness stretch (up to 30cm). The vertical minimum freefall distance is dependent on the distance between the supporting points of the overhead horizontal wire, but as a minimum is approximately 2m. This freefall distance for the installation should be confirmed by the manufacturer or installer. The positioning of the horizontal line should be directly above the working position if possible. Where a deviation from the vertical is allowed/necessary when using the retractable line, this will increase the required height to be provided. This is due to a swinging pendulum effect. [A standard lanyard fitted with energy absorption is unlikely to be suitable for falls under 2m].

9 It is understood that in at least one steel stockholder the horizontal overhead wire has been installed on the underside of an overhead travelling 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 at a safe position before each time the crane moves to transfer a load. 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 the worker was in a safe position. However, if the crane is moved (inadvertently or deliberately) towards the worker, or a second crane is moved incorrectly, the fall arrest block retractable line is in danger of entanglement with the crane(s) with consequent risks to the person wearing the harness.

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 (for one user) including installation of an overhead horizontal wire, supply of a retractable fall arrester and harness, and basic training in its use may be around £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. Operators should always have a safe place at which to attach and detach from any fall protection devices;
  2. The operation of the retractable fall arrester and line should essentially be vertical (although some systems can operate satisfactorily over a limited angle of inclination from the vertical) and be provided with a mechanism to prevent 'ratchet bounce' if used with a flexible anchor point;
  3. 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;  
  4. 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. Also where the retractable fall arrester is used at an angle inclined to the vertical a swinging pendulum effect increases the risk of injury.
  5. Stored stock may not provide secure footing and persons walking on    stacked materials are at risk of serious injuries from stock moving;
  6. To connect the harness on to the retractable line in the fall arrester 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 detached and stored at ground level (e.g. on the building wall or stanchion) if the overhead horizontal line is fixed in one place. However,  if the horizontal line was attached to the underside of an overhead travelling crane the pilot line would effectively be permanently attached and result in it trailing free (when the user is not connected) with a risk of it becoming trapped or possibly dislodging stock;
  7. 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;
  8. If the system operates in a fall the whole arrest system should be examined/checked and parts replaced/renewed as required before the system is re-used. This will include replacement of the energy absorber in the overhead horizontal line;
  9. Users should be trained how to fit and wear a harness properly, and  how to attach and use the fall prevention measures or fall arrest system provided;
  10. Suitable arrangements need to be put in place to rescue as quickly as possible anyone suspended in the event of a fall, to deal with any injury sustained and to minimise the potential of harm from continuing suspension in a harness;
  11. Fall arrest systems are designed with a maximum weight for the person in the harness (usually 100kg). The manufacturer/supplier of the installed equipment should be consulted if users are likely to be heavier.
  12. Once installed or assembled, inspection is required by a competent person before first use and thereafter following any single event liable to jeopardise the safety of this equipment and at suitable intervals if exposed to conditions causing deterioration. The frequency and type of inspection should be determined by the competent person with reference to the manufacturer's recommendations, British Standards BS 8437:2005, BSEN 365:2004 and HSE leaflet INDG367 also give guidance. When used in arduous conditions the inspection period may need to be reduced as advised by the competent person;
  13. Pre-use/daily visual checks of the equipment by the operator;
  14. Safe means of access to check and inspect anchor points, in-line energy absorber, retractable anchorage on a horizontal line and the retractable device itself;
  15. Considerations of any human factors/behavioural issues of individuals in terms of potential horseplay, risk taking etc.

12 Other issues that should be considered are the potential effects 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 retractable fall arrester 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, or works to the side of the anchor point, any fall will cause the worker to swing back delaying the retractable devices locking on which could lead to an extended fall. The swing effect could also increase the likelihood and degree of injury.

Conclusions on the use of fall arrestors in steel stockholders

13 The use of fall arrestors may have a part to play as an interim measure until more suitable stock storage arrangements are provided. However, it is likely the limitations outlined in paragraph 11 12 would outweigh the advantages in most circumstances for access to the top of stored stock as a permanent system of work. Fall arrestors may be considered for other working at height activities such as maintenance work.

Further advice

14 NASS and Wolverhampton City Council 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 at First Floor, The Citadel, 190 Corporation Street, Birmingham B4 6QD Tel: 0121 200 2288.

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Updated 2014-02-17