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March 30, 2011

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Work at height – Return descender

Ian Wake examines the practical and legal issues that should be considered so that a work-at-height rescue and evacuation procedure can be carried out both safely and in compliance with the law.

An essential element in meeting the Work at Height Regulations 2005 is planning for rescue and evacuation if an emergency should arise.1 There is a similar requirement outlined in BS8437:2005, the code of practice for the use and maintenance of fall-protection systems, which states: “It is essential that there is a specific rescue plan in place at each work site. . .”2

In many cases, the plans will involve the provision of personal fall-protection systems (PFPSs) and the use of rescue descender devices (RDDs) but, if these are to be effective, they must be chosen and used with care.

As always, the starting point for the planning is to carry out a risk assessment for the work in hand. The primary objective in every case is to try to eliminate the need for work to be carried out at height. If work at height can’t be avoided, the next step is to look at preventing falls by implementing control measures. These are divided into collective measures, such as guardrails and scaffolding, which protect a group of people, and individual measures, which take the form of PFPSs, and which protect only the person who is wearing the equipment. It is important to note that individual control measures should only be chosen as a last resort – eliminating the need to work at height, or implementing collective measures are always preferred.

Two-phase response

There are many situations where a PFPS is the only practical solution, and these are the situations where the most detailed rescue planning is needed. Before discussing planning in more detail, however, two definitions will be useful. In the context of this article, “rescue” is defined as helping someone out of a dangerous, harmful or unpleasant situation, while “evacuation” is defined as moving a person from a position of danger to a position of safety.
With these definitions in mind, it is apparent that working-at-height emergencies are typically addressed in two phases. The first is the rescue phase, where a fallen worker is released from their “arrested fall position” and transferred to an evacuation system. In many situations, this involves the use of an RDD and might also include moving the worker into a stretcher, or body splint. Next comes the evacuation phase, where the rescued worker is moved to a safe area.

The key points that must be addressed in rescue planning are the safety of the persons carrying out the rescue, the anchor points to be used for the rescue equipment, the suitability of the PFPS equipment, the type of rescue system that will be used, and the method that will be adopted for attaching the casualty to the rescue system. In addition, consideration must also be given to the route that will be used to move the casualty to a safe area, and what first-aid requirements the casualty might need with respect to injury, or suspension trauma. Many of these points can, of course, only be meaningfully considered in the context of a specific situation, but it is possible to provide general guidance on the important issue of pre-syncope and on the selection and use of PFPS equipment.

First-aid response

Pre-syncope is a condition sometimes experienced by persons suspended in fall-arrest harnesses and is usually an indicator that loss of consciousness (syncope) is imminent if no steps are taken to alleviate the condition. Symptoms include light-headedness, nausea, flushing sensations, tingling or numbness of the arms or legs, anxiety, and visual disturbances.

Issued in September 2008, HSE guidance for first-aiders responding to harness-suspension incidents3 states that most people, when suspended in a head-up position, experience pre-syncope within an hour, but also notes that 20 per cent of people experience this condition within just ten minutes. It advises that the best way of dealing with pre-syncope is to release the casualty immediately from the suspension system. In such cases, it advises that elevating the casualty’s legs, provided that it is safe to do so, may help delay the onset of pre-syncope, or at least reduce its symptoms and the risk of the casualty losing consciousness.

Personal fall-protection systems

PFPS equipment essentially comprises three physical components – anchor devices, bodywear and connecting devices – which can be conveniently remembered as the ABC of fall-arrest systems. The fourth component – training – is as important as the other three, and, unless all four components are in place, the PFPS will not work safely and reliably.

In Europe, PFPSs are divided into three categories. The first is travel/work restraints, which are covered by EN358,4 and are designed to prevent a worker from moving into an area from which a fall is possible. The second category is work-positioning systems, also covered by EN358, which connect workers to an anchor point to allow hands-free working. A typical application is to provide protection for a person working on overhead telephone cables. The third category of PFPS, which is the main focus of this article, is the fall arrestor. This category is covered by EN3615 and EN3636 and relates to equipment that is designed to stop a fall safely before the worker can impact with structures at a lower level, or the ground.

Returning to the components that make up a PFPS, anchors can either be permanent or temporary. Fall-arrest anchors must be type-tested at 12kN for three minutes, and every individual anchor must be re-tested annually. Temporary anchors, such as a choked webbing sling wrapped around a scaffold tube, are very convenient in many cases, but the anchor point must always be chosen with care. Structural supports often provide suitable anchor points, but the supports must be free from cracks and obvious flaws, and they must also be free of rust.

For fall-arrest purposes, the bodywear must take the form of a full-body harness; the use of work-restraint belts is not permissible. Harnesses must be designed in such a way that they: hold the body securely as the fall is stopped; distribute the forces from the fall as evenly as possible; and, after a fall, suspend the worker in the head-up position. Body harnesses for fall-arrest systems usually have rear attachment points but types are also available with front attachments, and these can have benefits for use in confined spaces.

Connecting devices link the harness to the anchor point and can take the form of wire, rope or webbing lanyards, or retractable devices. However, whatever type is chosen, such a device must include some form of energy (shock) absorber in fall-arrest applications. One way to provide this is to use a fibre strip inside a protective nylon sheath. When subjected to the shock load of a fall, the strip tears and absorbs energy, thereby reducing the forces on the body of the person using the fall arrestor.

Rescue scenarios

It is important to note that many different methods of rescue exist to suit different situations, and there are many variables involved. For these reasons, no two rescues are ever the same and, therefore, the procedures described below should only be considered as illustrative rather than directly applicable in any particular set of circumstances.
The scenarios described involve the use of a RDD, which is essentially a specially-designed braked rope system used to lower persons safely. Versions with or without a handwheel to control the descent are available but in these scenarios the use of types with a handwheel is assumed. The performance and testing of RDDs are covered by EN341:1992 (BS EN341:1993),7 or the new prEN 341:2008 standard.

The first scenario (illustrated, right) involves a worker who falls while climbing on an open structure. In this case, the rescuer climbs to a position above the worker and makes an anchor point on the structure. If possible, a rope grab is then attached to the RDD live rope karabiner, and to either the victim’s fall-arrest lanyard, or to their fall-arrest rope. After the trail rope has been placed into the pigtail and locking cleat, the victim is lifted until the lanyard or fall-arrest rope is loose. Next, the victim’s lanyard or fall-arrest rope is removed from the structure, ensuring that it cannot be snagged on steelwork or other obstacles during the latter stages of the rescue. The victim can then be lowered to the safe zone.

It may be necessary to introduce rope deflections (also known as deviations) to divert the RDD rope away from obstacles or hazards found on the natural descent path. The selection of anchor points for such deflections must, however, be considered carefully. In general, deflection anchor points do not need to have the same load capacity as the main anchor point, but they still need a high degree of strength, as wide deflections can generate high loadings.
In the second scenario (illustrated overleaf), the rescuer is able to reach the fallen worker’s harness without being exposed to undue risk. In such a case, the rescuer identifies the anchor point and attaches the sling and RDD to it. The rescuer then extends the live rope from the RDD and connects it to the (EN361) attachment point on the worker’s harness. The next step is to place the trail rope through the pigtail and into the locking cleat. The rescuer is now in a position to raise the fallen worker by winding the handwheel on the RDD until the connection to the worker’s fall-arrest system is loose enough for it to be removed. When the connection has been removed, the worker can be lowered to a safe zone and the rescue is complete.

Summary

This article has aimed to provide a useful introduction to the control of hazards associated with working at height and related rescue and evacuation procedures.

In closing, however, it is essential to stress again the importance of training. Proper training is a legal requirement for all those who are required to work at height, and this includes appropriate training on any PFPS equipment that their work involves. Furthermore, only trained rescuers are permitted to use RDDs. Modern equipment has an essential role to play in helping to ensure the safety of those who work at height but, in every situation, it is training that provides the foundation stone for safety.

References

1 Work at Height Regulations 2005, reg. 4.2 – www.legislation.gov.uk/uksi/2005/735/contents/made
2 BSI (2005): BS8437:2005 Code of practice for selection, use and maintenance of personal fall-protection systems and equipment for use in the workplace
3 www.hse.gov.uk/firstaid/harness.htm
4 BSI (2000): BS EN358:2000 Personal protective equipment for work positioning and prevention of falls from a height. Belts for work positioning and restraint and work-positioning lanyards
5 BSI (2002): BS EN361:2002 Personal protective equipment against falls from a height. Full body harnesses
6 BSI (2008): BS EN363:2008 Personal fall-protection equipment. Personal fall-protection systems
7 BSI (1993): BS EN341:1993 Personal protective equipment against falls from a height. Descender devices

Ian Wake is Miller by Sperian sales manager for the UK with Sperian Protection.

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