1. Calculation of Cable Tray Size

CALCULATION OF CABLE TRAY SIZE

Calculate Size of Cable Tray for Following Cable Schedule. Cable Tray should be perforated and 20% spare Capacity. Distance between each Cable is 10mm. Cable are laying in Single Layer in Cable Tray. (1) 2 No’s of 3.5Cx300 Sq.mm XLPE Cable having 59.7mm Outer Diameter and 5.9 Kg/Meter weight (2) 2 No’s of 3.5Cx400 Sq.mm XLPE Cable having 68.6mm Outer Diameter and 6.1 Kg/Meter weight (3) 3 No’s of 3.5Cx25 Sq.mm XLPE Cable having 25mm Outer Diameter and 0.5 Kg/Meter weight

CALCULATION:

TOTAL OUTER DIAMETER OF ALL CABLE PASSING IN TO CABLE TRAY:

Diameter of 300Sq.mm Cable =No of Cable X Outer Diameter of Each Cable * Diameter of 300Sq.mm Cable =2X59.7 = 119.4 mm * Diameter of 400Sq.mm Cable =No of Cable X Outer Diameter of Each Cable * Diameter of 400Sq.mm Cable =2X68.6= 137.2 mm * Diameter of 25Sq.mm Cable =No of Cable X Outer Diameter of Each Cable * Diameter of 25Sq.mm Cable =3X28= 84 mm * Total Diameter of All Cables laying in Tray = (119.4+137.2+54)mm * Total Diameter of All Cables laying in Tray = 340.6mm

TOTAL WEIGHT OF CABLES PASSING IN TO CABLE TRAY:

Weight of 300Sq.mm Cable =No of Cable X Weight of Each Cable * Weight of 300Sq.mm Cable =2X5.9= 11.8 Kg/Meter * Weight of 400Sq.mm Cable = No of Cable X Weight of Each Cable * Weight of 400Sq.mm Cable =2X6.1= 12.2 Kg/Meter * Weight of 25Sq.mm Cable = No of Cable X Weight of Each Cable * Weight of 25Sq.mm Cable =3X0.5= 1.5 Kg/Meter * Total Weight of All Cables laying in Tray = (11.8+12.2+1.5) Kg/Meter * Total Weight of All Cables laying in Tray =25.5 Kg/Meter

TOTAL WIDTH OF ALL CABLES:

Total Width of all Cables = (Total No of Cable X Distance between Each Cable) + Total Cable Outer Diameter * Total Width of all Cables = (7 X 10) + 340.6 * Total Width of all Cables = 410.6 mm * Taking 20% Spare Capacity of Cable Tray * Final Width of all Cables = 1.2%X4106.6 * Calculated Width of All Cables = 493 mm

TOTAL AREA OF CABLE:

Total Area of Cable = Final width of Cables X Maximum Height Cable * Total Area of Cable = 493 X 69.6 =28167 Sq.mm * Taking 20% Spare Capacity of Cable Tray * Final Area of all Cables = 1.2%X28167 * Calculated Area of all Cable =33801 Sq.mm

CASE-(I):

Considering Single Run of Cable Tray having Size of 300X100mm, 120Kg/Meter Weight Capacity * Area of Cable Tray =Width of Cable Tray X Height of Cable Tray * Area of Cable Tray =300X100 = 30000 Sq.mm * Checking Width of Cable Tray * Calculated Width of Cable Tray as per Calculation=No of Layer of Cable X No of Cable Tray Run X Width of Cables * Width of Cable Tray as per Calculation=1X1X493 =493 mm * Checking Depth of Cable Tray * Actual depth of Cable Tray = No of Layer of Cable X Maximum Diameter of Cable * Actual depth of Cable Tray=1X68.6 =68.6mm * Checking Weight of Cable Tray * Actual Weight of Cables=25.5 Kg/Meter

Results:

Calculated Cable Tray width (493mm)> Actual Cable Tray width ( 300mm) = Faulty Selection * Calculated depth of Cable Tray (68.6mm)< Actual Depth of Cable Tray (100mm) = O.K * Calculated Weight of all Cables (25.5Kg/Mt) < Actual Weight of Cable Tray (125.5 Kg/Mt) =O.K * Required to select higher size Cable Tray due to small Cable Tray width.

CASE-(II):

Considering Single Run of Cable Tray having Size of 600X100mm, 120Kg/Meter Weight Capacity * Area of Cable Tray =Width of Cable Tray X Height of Cable Tray * Area of Cable Tray =600X100 = 60000 Sq.mm * Checking Width of Cable Tray * Width of Cable Tray as per Calculation=No of Layer of Cable X No of Cable Tray Run X Width of Cables * Width of Cable Tray as per Calculation=1X1X493 =493 mm * Checking Depth of Cable Tray * Actual depth of Cable Tray = No of Layer of Cable X Maximum Diameter of Cable * Actual depth of Cable Tray=1X68.6 =68.6mm * Checking Weight of Cable Tray * Actual Weight of Cables=25.5 Kg/Meter

Results:

Calculated Cable Tray width (493mm)< Actual Cable Tray width ( 600mm) = O.K * Calculated depth of Cable Tray (68.6mm)< Actual Depth of Cable Tray (100mm) = O.K * Calculated Weight of all Cables (25.5Kg/Mt) < Actual Weight of Cable Tray (125.5 Kg/Mt) =O.K * Remaining Cable Tray width Area =100%-(Calculated Cable tray width/ Actual Cable Tray Width) * Remaining Cable Tray width Area =100%-(493/600)% =17.9% * Remaining Cable Tray Area =100%-(Calculated Cable tray Area/ Actual Cable Tray Area) * Remaining Cable Tray Area =100%-(33801/60000) =43.7% * Selection of 600X100 Cable Tray is O.K

CONCLUSION

Size of Cable Tray= 600X100mm * Type of Cable Tray=Perforated * No of Cable Tray Run= 1No * No of layer of Cables in Cable Tray=1 Layer * Remaining Cable Tray width Area =17.9% * Remaining Cable Tray Area =43.7%