Working at Height
Published: 01st Apr 2007
Working at height is work undertaken at a place where injury could occur should somebody fall from it - often involving the use of scaffolds, ladders, hoists, gantries or general roof work.
Falls from height are the most common cause of fatal injury, and the second most common cause of serious occupational injuries in the UK. 46 people died during 2005/2006, compared with 67 deaths during 2003/2004. Many of these accidents could have been avoided if the right equipment had been available and correct working practices put in place.
Not suprisingly, the European Union has introduced legislation and guidance that either relates directly to good practice for work at height, such as European Directive 2001/45/EC work at height regulations (enacted in the UK as The Work at Height Regulations 2005) or incorporates requirements for preventative measures such as personal protective equipment (PPE), in an effort to reduce accidents.
The working at height regulations cover work where there is a risk of a fall that is liable to cause injury, and describe the duties of those involved with, and responsible for, the work. The regulations define a simple hierarchy and require that:
- Firstly, to assess if it is absolutely necessary to work at a height at all. For instance carrying out the work at another location where there is no risk of a fall
- Secondly, where the above is not possible, measures or equipment such as work positioning harnesses or barriers should be used to prevent a fall occurring
- Finally, where the risk of a fall cannot be eliminated, work equipment or measures must be used to minimise the distance and consequences of a fall should one occur
The regulations require that all work is properly planned and organised, it takes account of weather conditions and those involved are trained and competent. They require the work place to be safe, work at height equipment to be formally inspected and the risk from falling objects to be properly controlled.
When selecting equipment for work at a height, collective protection measures should take priority over personal protection measures and those that prevent a fall should be considered first over those that minimise the consequences of a fall.
What is clear is that when working at a height, it is necessary to use equipment to either prevent or arrest any possible fall. This may be a communal system such as guardrails intended to prevent a fall, or netting and air bag systems designed to safely arrest a fall. Alternatively a personal fall protection system based on PPE can be employed. Such a PPE system will typically consist of a harness, or other body holding device, an anchor point and a series of interconnecting components such as lanyards and karabiners. The effectiveness of the overall system will depend on the weakest link in the chain. For instance, if the harness and lanyard have breaking forces of 20 kN but the anchor fails at 12 kN, the breaking strength of the overall system will be 12 kN. It is therefore important that all parts of the fall protection PPE system are tested so that information about breaking strength can be defined giving guidance on whether or not appropriate requirements are being met.
A specialist fall protection industry has developed to supply personal protective equipment (PPE) for both occupational and leisure activities.
European PPE directiveM
The European PPE Directive 89/686/EEC became an active part of European law back in 1995. Since that date, suppliers of protective clothing and equipment “designed to be worn or held by an individual for protection against one or more health and safety hazards” (the Directive’s definition of PPE) have been required to follow the appropriate approval procedure and to CE mark them. As the European Directive for PPE covers a broad spectrum of products, it divides them into one of three categories dependent on the type and potential severity of hazards. Fall protection equipment is categorised as ‘complex’ or category III (the highest category) and must undergo type examination before being placed on the European market and is also subject to on going production checks by a Notified Body.
|EN 353-1||Guided Type Fall Arrester - Rigid Anchor Rail|
|EN 353-2||Guided Type Fall Arrester - Flexible anchor line|
|EN 355||Energy Absorbers|
|EN 358||Work Positioning Equipment (Belts & Lanyards)|
|EN 360||Retractable Lanyards|
|EN 361||Full Body Harness - Fall Arrest|
|EN 362||Connectors / Karabiners|
|EN 364||Test Procedures and apparatus|
|EN 365||User Instructions & Marking|
|EN 795||Anchor Devices (Classes A - E)|
|EN 813||Sit Harness|
|EN 1095||Deck Safety Harness|
With the introduction of the European PPE Directive, the European Standards agency CEN (Comité Européen de Normalisation) convened a technical subcommittee (referenced CEN/TC 160) - in order to develop a series of harmonised European standards to be used in the testing and certification of fall protection PPE. A list of these standards is given in Table 1.
Most of these test procedures include two main types of test to assess the strength and performance of the product. Firstly, there is a “static strength” test, which involves gradually applying a force to a test specimen until a defined value is reached. This force must then be maintained for a certain time, usually three minutes, without release or catastrophic failure.
Secondly, there are “Dynamic strength/performance” tests where a load is rapidly applied to a specimen and then immediately released. These test conditions are produced by using the test specimen to arrest the fall of a test surrogate such as a 100kg dummy, rigid steel mass or sand bag. It is necessary to include both static and dynamic test procedures as most materials and products will react differently in each scenario. Also as fall arrest systems are required to include “force limiting components” (such as energy absorbers) which work by arresting a fall gradually (i.e. limiting deceleration) a static strength procedure allows for some testing of a likely safety factor in the products strength. For instance, in Europe, arrest forces must be limited to less than 6 kN, hence by including a performance requirement for a product to withstand 12 kN for 3 minutes gives a safety factor of 2 (i.e.12 kN divided by 6 kN).
Not all European standards give the same static strength requirement / safety factor - see table 2. These have largely been determined based on the materials used, the application and historical industry practices.
|Product Type||European Standard Requirement||Static Strength||Possible Safety Factor (assuming 6kN arrest force)|
|Fall Arrest Harness||EN361||15kN||2.5|
|Single Point Anchor||EN795||10kN||1.67|
|Retractable Lanyard (SRL)||EN360||12kN (steel) 15kN (textile)||2.0 2.5|
However, it should be noted that these standards are minimum values and where considered relevant after carrying out the standard static test manufacturers may be encouraged to also test at a higher force to give an indication of by how much the standard minimum value is exceeded by.
In addition to the strength tests, most of the European standards listed in table 1 also include a number of design requirements such as the minimum width of the webbing to be used in a harness or the type of connector to be used on an SRL. They also include a test for corrosion resistance of any metallic components.
Fall protection anchor devices
Anchor devices are a key part of the fall protection system. EN795 is the European standard for anchor devices. It should be noted that it includes a static strength requirement of 10 kN for several classes of anchor, whereas European standards for other parts of the system such as harnesses, lanyards and karabiners include static strength requirements of at least 15 kN. This should be taken into account when determining the overall system performance. The current version of EN795 divides anchor devices into five main classes, see table 3
|Class A1||Single point anchors designed to fit on vertical, horizontal and inclined surfaces|
|Class A2||Single point anchors designed to fit on inclined roofs|
|Class B||Temporary (ie tripod or beam clamp)|
|Class C||Horizontal flexible (ie steel cable system)|
|Class D||Horizontal rail such as abseil rail|
|Class E||Dead weight usually mass made of steel, concrete or water|
The performance testing required by EN795 can be summarised as follows:
- General requirements that apply to all classes of anchor. These include resistance to corrosion, plus design requirements such as radiused edges and a suitable attachment point that will connect to the PPE forming the next part in the protective chain
- Tests and performance requirements that are specific to individual classes of anchor for strength and dynamic performance
The general principles of the strength tests for anchor devices classes A1, A2 and B are all very similar. The static strength requirement is to hold a force of 10 kN for 3 minutes without release and the dynamic strength requirement is to arrest a 2.5m fall of a 100kg steel mass when connected to the anchor via a 2m nylon lanyard. All test forces should be applied in the direction that will occur in use. Where relevant, the anchor device is tested after simulating attachment to materials and using procedures that are representative of a final installation.
For Class C anchors, there are requirements for all components (cable, end fixings etc) to be able to withstand twice the force likely to be applied in service during the arrest of a fall. The magnitude of this force can be predicted by the dynamic performance tests described below or by computer model/software calculations. In addition to the static strength requirements EN795 includes tests for dynamic performance and dynamic strength. Both dynamic tests use a 100kg steel mass to apply a force of either 6 kN (dynamic performance) or 12 kN (dynamic strength) to the horizontal anchor line via the mobile anchor device. During the dynamic performance tests, the peak end loads and cable deflections are measured and must be within 20% of the values predicted by the manufacturers calculations which are usually generated from a software model.
For Class D anchors, the static and dynamic strength tests are similar to those required for Class A and B devices - for instance 10 kN for 3 minutes and a 2.5m fall with a 100kg mass. However, in this case the tests should be carried out with the mobile anchor point located on the rail:
- At mid span between anchor points to the structure
- At an anchor point to the structure
- At the end of any overhang (cantilever)
EN795 also includes tests for Class D anchor rails intended for use by more than one person at a time.
Class E anchors are required to pass a dynamic performance test that involves arresting a 2.5m fall of a 100kg steel mass connected to the anchor via an 8mm steel cable. The requirement of the test is based on final movement of the anchor device on the roof surface and the overall displacement of the 100kg test mass. There is no static strength test for Class E devices.
One final point to mention with regard to the European perspective on anchors is the current uncertainty as to whether or not anchor devices should be covered by the PPE Directive. The lack of a clear definitive statement from the Commission has led to differing views being taken in the various European Member states. Most stakeholders would agree that where the anchor device is for personal use, is transportable and temporary, it should be considered as covered by the Directive and certified accordingly. However, where more permanent devices are concerned, especially if they are intended to protect several persons at the same time, there is not such a clear distinction.
CE Marking - buyer beware!
The CE mark enables free movement of goods throughout the EU, and therefore is an important element of trade. In fact most buyers of complex design PPE will not consider purchasing without seeing a copy of the EC type examination certificate. Whilst most companies follow the rules to legitimately CE mark their products, there are a number who do not (either by mistake or otherwise) and apply the mark without undertaking the necessary procedures.
All fall protection PPE must be submitted to a Notified Body so that the technical file can be assessed independently. Products can then be manufactured in bulk provided that they do not deviate from the model that was examined. The Notified Body should be informed when changes are made, and may require further tests to be carried out. At the very least, the technical file should be updated. Unfortunately, some manufacturers products are changed without consultation with the Notified Body. This process can go unnoticed although if there is a query (from a prospective buyer or an enforcement authority for instance) this may quickly become apparent. It should be noted that the original type approval sample is the model for product certification and therefore any unapproved variations are not covered. ‘Complex’ design PPE are subject to on going production conformity assessment, either based on annual retests or quality assurance system checks and therefore any changes are likely to be noticed by the Notified Body at this time. Type approval certificates for complex design PPE products from some notified bodies contain a caveat that it is only valid when accompanied by documentation less than 12 months old, to show compliance with Article 11 of the PPE Directive. This should act as a reminder to any potential buyer to check for evidence of ongoing compliance.
Forged certificates, where new product descriptions have been added or substituted are not uncommon. In order to minimise this activity, some EC certificates incorporate features such as unique water marked pictures or embossed logos. Whilst it is usual for photocopies to be sent around the world to buyers the only legitimate, certificate should bear this embossment. If in doubt you are advised to check with the particular Notified Body to ensure that the certificate is valid.
Systems exist throughout Europe to identify rogue certificates or withdrawals and suspensions, and where there are problems the appropriate department of the member state government should be informed. The EC type examination system should make CE marking as easy as possible for legitimate manufacturers, whilst protecting the certificate and name from less scrupulous interests.
To summarise: employers, employees, architects and anyone in control of construction or maintenance activities that involve working at height are responsible for ensuring safe working in accordance with legislative requirements and good working practices. As part of these regulations duty holders must ensure that all work at height is properly planned and organised. Risk Assessments must be completed prior to starting work for every procedure that is to be carried out, taking into account all operational and safety considerations, in order to reduce inherent risks. Where the potential for a fall cannot be eliminated, work equipment or other measures must be used to minimise the distance and consequence of a fall should one occur.
Published: 01st Apr 2007 in Health and Safety International