Cable glands - STAHL - #11

Text version of the page

11 If the cable gland is not certified as part of the equipmentbut tested and certified as a separate component, and the used cable is substantially compact and circular the selection chart can be used > if the cable is not round, it is not possible to rely upon anelastomeric seal to perform a sealing function around the cable sheath. An example of a cable that fits this scenario is a twisted pair instrument cable where the insulated conductors beneath the inner cable bedding do notusually offer a round (circular) surface on which to seal.If the inner bedding follows the same shape, then an elastomeric seal may struggle to seal effectively around the cable circumference. The effect is often more notice-able with single pair cables,and it may be necessary to fita compound sealing barrier type cable gland to overcome the situation, depending upon the form of protection and cable entry configuration of the apparatus enclosure. > if the cable is not round in appearance, or visually appearsto allow air to pass through its interstices because the cable construction is not adequately filled, then a com- pound barrier type cable gland could be selected. > in the case of flameproof enclosures Ex d, the function of the elastomeric sealing ring, which is applied to the section of the cable entering the equipment is to provide a gas tight seal around the cable bedding and prevent explosion from penetrating the cable sealing point so that the explosion cannot be transmitted to the external atmosphere. > equally, if the cable is not adequately filled, and allowsthe passage of air or gas along the cable length, then there would be no protection to the inner part of the cable when an elastomeric sealing ring is used. In this case a compound barrier type cable gland is the only safe solu- tion, and is necessary in order to maintain the integrity of the equipment and prevent gas migration between equipment or between hazardous areas and safe areas.