Horizontal Fall Arrest Systems
Description
Horizontal fall protection systems are intended to provide continuous, safe access to plant, equipment and work areas on a variety of structures. They feature either a tensioned cable or a rigid rail. Both types of system can negotiate corners and rigid rail systems can also be curved, to closely follow a structures contour. Systems can be installed to a wide range of structures, including masonry, steelwork and timber. Typically, structural calculations will be required when designing horizontal fall protection systems.
Applicable UK Standards & Guidance
Personal fall protection equipment – Type C Anchor devices
Personal fall protection equipment — Anchor devices — Recommendations for anchor devices for use by more than one person simultaneously
Personal fall protection equipment. Anchor systems
Best Practice for the use of Horizontal Safety Lines in Roofwork
Testing of Roof Anchors on Roof Systems
BS EN 795 and the 89/686/EEC Directive
Code of practice for selection, use and maintenance of personal fall protection systems and equipment for use in the workplace
Levels of Safety
Work Restraint
Where it is reasonably practicable to do so systems should be designed in such a way as to provide Work Restraint. The position of the anchorage line together with the specified combination of user equipment will prevent the user from reaching a position from where they can fall.
Fall Arrest
Where it is not reasonably practicable to install a system such that it provides Work Restraint, a Fall Arrest system can be installed. A Fall Arrest system will allow the user to reach a position from where they can fall, but minimise the distance and consequences.
Work Positioning
Horizontal fall arrest systems that utilise a rail or solid posts of a horizontal cable system can be used as anchors in a work positioning system. Where a work positioning is employed the user must maintain two independent connections to the anchor system; one for the work positioning system and a second for a back-up fall arrest system.
Design Considerations
Access & Maintenance Strategy
A personal fall protection system should only be considered where designing out the risk or installing means of collective fall prevention, such as edge protection, are not reasonably practicable. A formal Access & Maintenance Strategy Plan should be developed which considers the access & maintenance requirements of a building or structure over its life.
Access & Egress
Consideration should be given to how a user will access the system. Will a means of access other than a permanent staircase be required e.g. Fixed vertical ladder, powered access equipment, secured portable ladder
The Layout
Where its is reasonably practicable to do so, the layout of the system should allow the user to reach all areas of the structure that require access and maintenance, without risk of a fall occurring i.e. Work Restraint.
Edge distances of no less than 2.30mtrs should be maintained where Work Restraint is specified, which allows for a maximum permitted 2.0mtr lanyard + 0.3mtr for the user. Consideration must be given to cable deflection, which will increase as the spacing between support posts increases.
Horizontal lifeline systems that feature a tensioned cable must not be installed on stuctures with pitches greater than 15°.
Number of Users
How many simultaneous users will need to be connected to the system? Systems have limitations on the number of users that can be attached to the system, or be working in a single span.
Design Loads
Regardless of whether the system of work is Work Restraint or Fall Arrest, systems MUST be designed for fall arrest loads, consider the number of users simultaneously attached the the system and include a safety factor of at least two. The safety factor should be based on the maximum strength of the supporting structure.
User Considerations
Competence
It is a requirement of the Work at Height Regulations 2005 that persons involved in work at height, including those planning, managing & supervising work at height are competent to do so.
Personal fall protection systems require a higher level of competence from the user than collective fall protection systems, such as edge protection. Fall Arrest systems require a higher level of competence from the user than Work Restraint systems.
Users of Horizontal Fall Protection Systems must have the necessary level of knowledge, skill, experience & training in order to use the system safely.
User Equipment
The type of user equipment to be used with the system must be stated within the OEM Manual and its use, including dedicated travelling devices which are able to pass over intermediate and corner support posts, is critically important to the safe operation of the system.
For example, a system where the intended safe system of work is Work Restraint becomes Fall Arrest if the user selects, or is issued, a longer lanyard than specified. If there is insufficient clearance below the system in which to arrest a fall, incorrect selection of user equipment can have catastrophic consequences.
Rescue Planning
The Work at Height Regulations 2005 requires that the planning of work at height includes planning for rescue. When planning work with personal fall protection systems, it is critically important that a rescue plan is in place, along with the resources needed to effect a rescue i.e. trained and competent personnel, a rescue plan, suitable rescue equipment.
Energy Dissipation
In the event of a fall, the system is dynamically loaded. In tensioned cable systems the end & corner anchor posts, in particular, will see high levels of energy, and this energy must be ‘removed’ from the system in order that the structure to which the system is fixed is not compromised.
Tensioned cable fall arrest systems will employ one or two inline energy absorbers, connected to the extremity anchors, to dissipate energy.
Rigid rail or track systems will rely on the energy absorbers built into the user equipment to limit the amount of energy that is transferred to the anchor system
Inline Energy Absorber
In horizontal lifeline systems that utilise a tensioned cable, inline energy absorbers are employed to reduce the amount of energy transferred to extremity anchors in the event of a fall to protect the structure to which the system is fixed.
Lanyard Energy Absorber
Performance requirements specified for personal fall arrest equipment require that in the event of a fall the impact force on the user does not exceed 6kN.
This is typically achieved by incorporating a tear webbing pack or shock pack in an energy absorbing lanyard or braking system in a self retracting lifeline.
Inspection
Provision & Use of Work Equipment Regulations (PUWER)
Regulation 6 requires that inspections of work equipment are made and that records of the inspections are maintained.
Personal Protective Equipment at Work Regulations (PPEAW)
Regulation 7 obliges the PPE provider to ensure it is maintained in an efficient state
BS EN 365
Requirements, 4.4b, recommends that the periodic examination frequency shall be at least every 12 months.