Calculation of Cable Tray Size
December 7, 2014 30 Comments
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%
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