Electrical Contracting News (ECN) June 2016 - Page 30

CABLE TIES VS CLEATS more steel in a cleat than a tie. Therefore, in order to make a direct comparison you need to consider the cross sectional area of the material being used – a calculation based on width, thickness and the number of times it is wrapped round the cables. Cable ties are typically less than 20mm wide and less than 0.4mm thick and so have a cross sectional area of less than 8mm2. If the strap is wrapped round twice we have material with a maximum cross sectional area of 16mm2 securing the cables. In comparison, a top of the range stainless steel cleat will have a cross sectional area of 100mm2. Harking back to simple physics, the ultimate tensile strength of a material is proportional to its cross sectional area. Therefore, using the information above, and all relevant supporting short circuit test data, if the calculated fault level for a system required the installation of a top of the range cleat every 300mm, it would be unlikely if the cost of the equivalent appropriate number of cable ties was less than the cost of the cleats. And that’s before you even take into account the time it would take to install them all. “ • The cable tie can be fed through perforations on the ladder rung if they are present. Of these three methods, both option one and option three introduce significant variables that will have an impact on likely performance during a fault. In both cases a foreign body is being introduced to the loop that contains the cable. As such everything from ladder material to rung profile; types of hole and sharpness of edges; and even surface finish and cable diameter can have an impact on the whole arrangement. As such, it’s impossible to say that t H\[وHܝ X\Z]\ۂHZ[\Y[XHYH\[ٙ\XBHX[ܛ [\H[[][ۈ\šY[X[H\[] ]\ و\K[[][ۈ[ۈ\›[ܙHZ[H[]\X[YH\ܛX[B]X]\ܝ X\Z]\[œ\ܛX[H܈HXHYK][\œ[\[HوH\œ\]Z\Y [H[[][ۈ[YH[[ܙX\HYۚYX[KXZ[]][\˜\]]]H[H\وY\˜X]][\Z[[X[ HSPTHӐTԈSHSQSSPPSPHSSUSӔSHQUKܝ X\Z]\[‚H[[X\[ۂH[[[Y\\ܝ X\Z]\[[[\X[\H]Y\[ۈق]\H]H]\YHH\\[ٙ\XHHX[YH[[][ۏ\\\XHX]\Hۘ\Y H[\\\X[HY\ˈ\\X]\K[\][ۙ][ۜHXHX]ۜZ[[Hܘ\[\]Y]Y[HX\ˈH[[[X\H\š[Y[HۈHX]8&\\ܛX[H[š][\ܛH]H][[X]YۂHܝ X\Z]\\YX]KH]X][ۈ\\HX\\][YY[]Y\Z[\œY[XHY\8$XZ[HX]\HوBY\[H[^[Y]ˈ\X[H\B\HYH^\[XHXHYH\\Y]XXHY\(HXHYH[Hܘ\Y\[HXH[H[˂(HXHYH[H[[Y\[B[[[X] X^\H[˂]YYH[Y[X\Y[ۜY\[H\X]HY\]وZ[\Y[XHX][XHY\š\]H[X\Hۘ\܈[B[Y[[XX[XH[[][ۜœ[HY]K[ܙ\܈[[XX[[[][ۂHY[YYYKX\YY˜H\Z[Y[HX[\][][Hܘ\^H[\]K[Y[H[\]Y\[Bܝ X\Z] Y\XHY\[XHX]š]HZ\XH[HXYX][ۂX\K[Y\\H\HZ[[X[[[[وݙ\\\H]\X\XB][[[\܈XYY\[BۙHݙ\H\]]\Z[[X[ [HXYX][ۈX\[ۈ[&]BXYH\YۈZ\XY[Z[\Z[YY]X\[H][\Z[[H[\وBYY \Y[\Y][ۋX\YYH\Z[Y[HX[\][][Hܘ\^H[\]KXHY\\H\X[H\[ YH[\[ X˂KLXHY\X]8$[\˚[ L Ǩ M MM