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Recommendations for rope usage
Recommendations for inspection and care of low stretch kernmantel ropes in use
(EN 1891:1998)
A.1 General
The recommendations in this text are written with polyamide and polyester in mind, as these are the materials from which low stretch kernmantel ropes are usually made. However, unless polyamide or polyester are referred to specifically, the recommendations apply to low stretch kernmantel ropes made from any permitted material.
Ropes made from any material are liable to wear and to mechanical damage, and can be weakened to some extent by various agencies such as chemicals, heat and light. Regular inspection is therefore essential to ensure that the ropes are still serviceable.
It is also emphasized that, no matter what agency has weakened the rope, the effect will be more serious on the small sizes than on the larger sizes of rope. Consideration should be given, therefore, to the relationship of the surface area of the rope and the rope cross-section.
Examinations of about 300 mm at a time may prove to be convenient, the rope being turned to reveal all sides before continuing. At the same intervals, the strands should be untwisted slightly to allow examination between the strands.
To define a standard of acceptance or rejection is much more difficult than to describe the method of inspection. There can be no well defined boundary between ropes which are safe and those which are not because this depends on the stresses placed on a rope in an emergency. In practice, the decision whether to continue to use a rope or discard it should be based on an assessment of the general condition of the rope. Many of the conditions which will guide the examiner cannot be exactly described but can only be stated in general terms.
If, after examination, there is any doubt about the safety of the rope, it should be withdrawn from service. It is again emphasized that the effects of wear and mechanical damage are relatively greater on thinner ropes which, therefore, require more stringent standards of acceptance.
A.2 Physical causes of damage
A.2.1 General external wear
External wear due to dragging over rough surfaces causes surface chafing or filamentation. This is the most readily noticeable cause of weakness, particularly if a new rope is available for comparison. In the extreme, the strands become so worn that their outer faces are flattened and the outer yarns are severed. In ordinary use, some disarrangement or breakage of the fibres on the outside of the rope is unavoidable and harmless if not extensive. Polyamide and polyester filament ropes have a very good abrasion resistance.
A.2.2 Local abrasion
Local abrasion, as distinct from general wear, may be caused by the passage of the rope over sharp edges while under tension and may cause serious loss of strength.
Slight damage to the outer fibres and an occasional torn yarn may be considered harmless, but serious reduction in the cross-sectional area of one strand or somewhat less serious damage to more than one strand should merit rejection. Protection at points where excessive abrasion may occur is economic.
A.2.3 Cuts, contusions, etc.
Cuts, contusions, etc. or careless use may cause internal as well as external damage. This may be indicated by local rupturing or loosening of the yarns or strands.
A.2.4 Internal wear
Internal wear caused by repeated flexing of the rope, particularly when wet, and by particles of grit which have been picked up, may be indicated by excessive looseness of the strands and yarns or the presence of powdered fibre.
A.2.5 Repeated loading
The resistance of polyamide filament rope to damage due to repeated loading is good, but a permanent elongation may occur so that the extension available in an emergency is reduced.
If the original length of the rope is known exactly, a check measurement made under exactly the same conditions will indicate the total extension of the rope but may not reveal local extension of parts of the rope. Measurement of the distance between regularly spaced indelible markers on the rope may help to reveal severe local permanent elongation which may cause breakdown on subsequent loading.
A.3 External causes of damage
A.3.1 Mildew
Mildew does not attack polyamide or polyester ropes.
A.3.2 Heat
Heat may, in extreme cases, cause fusing. Any signs of this should obviously merit rejection, but a rope may be damaged by heat without any such obvious warning. The best safeguard is proper care in use and storage. A rope should never be dried in front of a fire or stored near a stove or other source of heat.
A.3.3 Strong sunlight
Strong sunlight causes weakening of rope fibres, but is unlikely to penetrate beneath the surface. Unnecessary exposure should be avoided.
Solar degradation should be checked by rubbing the surface of the rope with the thumb nail. If degradation has taken place, the surface material will come off as powder. In addition, the surface of the rope will feel dry, harsh and resinous.
Whilst the consequences of such degradation may be significant in small ropes, e.g. less than 20 mm, it is unlikely to be of significance in larger ropes during their expected period of life.
A.4 Chemical causes of damage
A.4.1 General
The variety of possible chemical contaminants of rope is very wide and the information given in A.4.2 and A.4.3 is only a general guide. In cases of uncertainty on the nature of the contaminant and the remedy to be adopted, an expert should be consulted. Attack may be more severe if some drying out occurs.
A.4.2 Polyamide ropes
Chemical attack of a sufficient degree may be indicated by local weakening or softening of the rope so that surface fibres can be plucked or rubbed off as a powder in extreme cases. The chemical resistance of polyamide filament is, in general, extremely good, but solutions of mineral acids cause rapid weakening. It is advisable, therefore, to avoid immersion in acid solutions, either cold or hot.
Polyamide filament is unaffected by alkalis at normal temperature and by many oils although it swells in contact with certain organic solvents. Exposure to fumes, spray or mist of acids or to organic solvents should be avoided, but, if contamination is suspected, the rope should be washed out well in cold water. If there is any doubt after subsequent careful inspection, the rope should be discarded. Polyamide ropes absorb a limited amount of water when wetted and may lose a small proportion of their strength while wet.
A.4.3 Polyester ropes
Chemical attack of a sufficient degree may be indicated by local weakening or softening of the rope so that surface fibres can be plucked or rubbed off as a powder in extreme cases. The chemical resistance of polyester filament is in general extremely good, but hot solutions of strong alkalis progressively dissolve the fibre, causing gradual loss in mass and a corresponding fall in breaking load. It is advisable, therefore, to avoid exposure to alkaline conditions.
Resistance to acids and particularly to sulfuric acid is good, although the concentration should not be allowed to exceed about 80 %. Thus, even dilute solutions of sulfuric acid should not be allowed to dry on a rope. If any contamination is suspected, the rope should be washed out well in cold water. If there is any doubt after subsequent careful inspection, the rope should be discarded.
Resistance to hydrocarbon oils and common organic solvents is good, although polyester filament may swell in certain chlorinated solvents. Attack by concentrated phenols is severe and contact should be avoided.
Source:
European Standards Organisation CEN (1998). Harmonized standard for the approximation of the laws of the European Union member states EN 1891:1998 – Personal protective equipment for the prevention of falls from a height: Low stretch kernmantel ropes. Brussels.
