Why are high visibility tapes not sufficient?
In the Orange Book, paragraph 39 advises as follows:
If walking over large areas of roof is unavoidable, provide obviously demarcated dedicated walking areas and enforce their use. Ensure that persons on the roof cannot approach fragile areas, by an effective means: either by covering or by providing an effective barrier. High visibility tapes, used on their own, are not acceptable.
The ACR considers that fragile areas on roofs are extremely dangerous, because they can mislead people into thinking that there is no hazard when, in fact, there is a significant hazard. Arguably, fragile areas are more dangerous than obvious unguarded edges.
The ACR argues that the perimeter of any fragile area ought to be considered as an edge off which persons could fall, ie, that the fragile area should be considered as not existing and, for all intents and purposes, the roof contains a hole the size of the fragile area. In such circumstances therefore the law would require the hole be guarded.
It is the ACR's opinion that barriers should be used around all fragile areas to prevent falls. The principle exception is that covers could be more appropriate for discrete areas, like rooflights. Where covers are used, they should be marked "hole" and should be treated as "no-step" areas.
An effective barrier is the one which conforms with the performance requirements in the European standard EN 13374. High visibility tape would not meet this specification and therefore should not be used as a barrier.
However, in coming to itís conclusion, the ACR is aware that it could be unreasonable to expect fragile areas which were remote from the area of the work, and which presented no risk to the worker by virtue of such remoteness, to be protected by effective barriers. In these special circumstances, ACR considers that the use of high visibility tape may be justified, subject to a number of provisos, namely:
- A careful consideration of a definition of "remote from the area of work", [the ACR takes this to mean that no person would, in any circumstances, need to be within 2.0m of the fragile area, either to carry out the work or to access the area of work];
- That a contractor can demonstrate that the work is planned to ensure proviso 1; and
- That the requirement for no approach is strictly enforced.
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Moving of nets under Class C assemblies ( reprinted from appendix A)
B1. Roofing assemblies classified as class C under ACR[M]001:2000 are non-fragile. To obtain Class C, the assembly has to survive a single impact applied in the worst possible position on that assembly. Thus whilst being a single drop of exactly the same magnitude as the SIR 30 test, it is actually a more onerous test , which has been demonstrated by testing. An assembly just attaining Class C is, therefore, likely to be safer than a material just attaining non-fragility under SIR 30.
Note 1: The SIR 30 test was a single drop into the center of a sheet. Experience shows that the worst location is invariably elsewhere because of the influence of the fixings, sheet profiles, etc.
B2. That Class C is non-fragile means the following:
a) Once a Class C assembly [sheet or liner] is fully fixed, safety nets may be withdrawn from under them and moved on [leapfrogged]. But note:
(i) The netting, which remains in place, must protect at least 2.5m behind the leading edge and 2.5m in front of the leading edge, unless alternative leading edge protection is provided. In practice, because of the way nets are supplied, this will usually mean that the netting remaining in place would be 1[one] full bay behind the leading edge and the full bay containing the leading edge.
(ii) Special consideration needs to be given to the 1st tier [strip] at the gable eaves, as the edge supports are different. Therefore, evidence that the installation achieved Class C in the support condition adopted at this location should be provided.
b) In a built up roof assembly [with a Class C liner assembly], if the top sheet is subsequently removed, no additional precautions need to be taken whilst working alongside the Class C liner assembly, provided it is still fully fixed, undamaged and was unaffected by the removal process of the top sheet (or the reason for it's removal).
B3. Class C is the lowest class of non-fragile assembly and, particularly if engineered to pass the test criteria, may be close to the boundary between fragile and non-fragile. Its classification and use therefore requires the following to be taken into account:
a) Normal industry recommended best practice is that Class 'C' assemblies should never intentionally be walked upon 2 and appropriate temporary access equipment, such as crawling boards, etc., should always be used.
Note 2: Accidental damage to such assemblies might render the classification void.
b) A Class C assembly must be treated like any other safety critical item, e.g., a safety net. Therefore, any adverse occurrence that could affect its fitness for purpose should trigger an inspection. If an assembly has been subjected to an impact load (such as a trip or stumble), it and be treated as a fragile area and identified and protected accordingly, until it has been replaced and the adjoining fitted panels inspected by a competent person and replaced if necessary. Procedures to ensure this happens must be in place.
c) The workforce must be aware of these limitations, as required by Regulations 3 and 8 of the Managing Health and Safety at Work Regulations [MHSWR].
d) Any person falling on a class C assembly may make it fragile for subsequent loads. While persons may be capable of self-recovery from a fall or stumble, where they are unable to, the additional weight of a rescuer may cause the assembly to fail. And, because all non-fragility classifications depend on the fixings of assemblies, any adjoining assemblies may also have become fragile 3 . In such situations the incident panel and all adjoining panels must be treated as fragile. This is a foreseeable risk of selecting Class C assemblies. Therefore, where class C assemblies are being used, rescue plans must be developed in advance of work starting. Again, in accordance with Reg. 5 and 8 of the MHSWR, the workforce needs to be aware of the Rescue Procedures.
Note 3. This includes adjoining Class B assemblies.
B4. All current non-fragility classifications depend upon correct workmanship during installation. In particular the manufacturer's specification for fixings and other components is of absolute importance and must not be altered, without the manufacturer's written agreement. The type, number, location and spacing of fixings must be clear and completely unambiguous in their meaning. An assembly must be fully fixed before the assembly may be treated as non-fragile. In particular partially fixing of sheets (commonly known as 'stitching') to progress the work quickly, followed on by fully fixing later, is dangerous. Any roof found in such a state must be treated as fragile regardless of the classification of the components being used in its construction.
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