Text version of the page

dust-explosion protection

The basics of dust-explosion protection - 9224 8 installation and maintenance

28 > > Cables with thermoplastic or elastomeric wireinsulation, screened or armoured cable and an outer sheath of PVC(poly-vinylchloride), PCP (polychloroprene rubber), or a similar material. Cables with a seamless aluminium sheath withor without armouring. 8. Installation and Maintenance > Mineral-insulated cables with metal sheath. Cabel installation Note: > When cables are externally provided with protection, or when there is no danger of me- chanical damage, cables with thermoplastic or elastomeric insulation and a sheath of PVC, PCP, or a similar material are permitted. These cables and wires may have tobe operated below their rated valuues to limit the surface temperature from exceeding the required values. > Cables must be placed so that they cannotbecome electrostatically charged by moving dust (friction effect). The protective measures described in Section 4alone are not sufficient to prevent an explosion. Installation carried out according to requirements, punctual, correct and consistent maintenance are all crucial for maintaining safe operations (EN 50281-1-2).During installation, the manufacturer’s operation conditions in the operating instructions must be followed carefully. In general, the common types of cables are permitted, if they are installed into screwed, solid, drawn or steamed welded conduits. Cables whose construction ensure that they are dustproof and suitable for mechanical stress may also be used. Examples are: > Cables runs shall be arranged insofar possiblethat no large dust deposits can be collected. Sufficient access for cleaning must be possible. 8.1 Installation of Cables Selection of Cables > > > If possible, cables shall not pass through areaswith potentially explosive dust atmosphere if they are not connected to this area. If cables pass through walls or other structures,this must be done so as to prevent the passage or collection of combustible dust. If metal conduit is used, care should be taken to ensure that there is no possibility of cabel damage at the connecting points, that the connectingpoints are dustproof, that the im- permeability of the connected equipment is not reduced, that the connecting points are included in the potential equalisation. > > If dust layers form on cables, preventing free aircirculation, a reduction of the current carrying capacity of the cable shall be considered. This applies especially to dusts with a low ignition temperature. For transportable electrical equipment, a suitable cable type must be used. For these purposes, often a suitable connection box must be placed between the moving and fixed cable routing.
R.STAHL Explosion protection