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Underground Cable Pulling Calculations  DATE:  PRESENTED BY:  PRESENTED TO: Joseph W McAuliffe PE NWPPA E&O Conference April 13, 2016 Senior Product Engineer Spokane, WA

Cable Pulling Calculations  Information needed  Calculation High Points  Impact of Design Decisions  Cable Handling  Duct Systems Impact on Cable Pulling  Field set up and Pulling Procedures  After the Pull

Cable Pulling Calculations  Information Needed  Conduit Type and Size  Cable Type  Cable Weight and Dimensions  Type of Jacket  Number of Bends  Location in the Pull  Radius of each Bend  Any Elevation Changes

Cable Pulling Calculations  What will impact ultimate pulling tension  Coefficient of Friction  Pulling Lube  Amount (or lack of Use)  Back Tension  Placement of bends  Duct installation itself

Cable Pulling Calculations  Factors that need to be checked  Jamming  Cable clearance  Minimum Bending Radius  Side Wall Bearing Pressure  Weight (Weight Correction Factor)  Pulling Tension

Cable Pulling Calculations  Jamming  J= D/d  J Jam Ratio  D = Inside diameter of Duct  d = Cable diameter Jamming can occur when ratio between 2.8 and 3.0

Cable Pulling Calculations  Cable Clearance  Single Conductor  C = D – d’  3 Conductor (Based on Triangular Configuration)  d’ = 1.05d

Cable Pulling Calculations • Bending Radius • Depends on cable construction • Non-shielded depends on insulation thickness • For shielded cables depends on type of shield • Values stated are for permanent training. • Effects side wall bearing pressure • Recommend 20X OD for conduit bends

Cable Pulling Calculations  Cable Weight (Weight Correction Factor)  Single conductor  Three Conductor  Cradled  Triangular  Can be determined from Jam Ratio

Cable Pulling Calculations  Sidewall Bearing Pressure  Radial force that is exerted on a cable being pulled around a conduit bend 1 Single Cable: SP = T/ R 3 Single Cables (cradled) SP = (3w – 2) (T / 3R) 3 Single Cables (triangular) SP = w (T / 2R) T = Tension coming out of the bend, T out (lbs) R = Bend Radius (ft) w = Weight Correction Factor

Cable Pulling Calculations  Allowable Pulling Tension  Conductor Type (CU or AA)  Conductor Size  Pulling attachment  Pulling Eyes  Basket Grip

Cable Pulling Calculations  With Pulling Eye  3 Conductor Pull  Only figure stress from 2 conductors  Basket Grips  1000# (or conductor tension limit if lower)

Cable Pulling Calculations  Actual calculations  All results are cumulative  Start with the back tension on the reel  Elevation angles are degrees  Bend sections are radians  Side wall bearing pressure is often the limit  Always calculate from both ends

Cable Pulling Calculations  Would it be easier to pull cable from A to B or B to A? 30 20 20 A B 50 300 Courtesy American Polywater

URD Cable Pulling  Cables supplied to utilities are the best that they have ever been  Proper handling, Installation, termination, protection and operation are all critical to long term reliability  Field personnel can greatly impact the reliability of the system

URD Cable Pulling  Cable handling  What’s wrong with these pictures?

URD Cable Pulling  Proper Reel handling is important

URD Cable Pulling  Proper Reel Handling Do This Not This

URD Cable Pulling  Duct Installation  Understand the layout  Old System  Occupied before? • What was cable removal like?  Empty before?  Is the Duct Clear?  Is the Duct intact?  Do you know the Layout?

URD Cable Pulling  Duct Installation  Understand the Layout  They all look the same when they are buried

URD Cable Pulling  Duct Preparation  Ensure the duct is clean  Run a brush through the entire length  Removes dirt and clutter  Clean ducts allow for easier pulls

URD Cable Pulling  Duct Preparation:  Run a mandrel through the duct to know the condition  This will help remove obstructions  Ensure that the duct is round  Whether New or Old

URD Cable Pulling  Field Setup  Know what to expect  Have pulling calculations been run?  Where are the bends?  Can make a big difference in the pull • As far as practical bends should be at the beginning of the pull • Down hill is better that up hill

URD Cable Pulling  Field Setup  Reels should be positioned for correct pay off  Cable should be bent in one direction only  Do not “S” the cable into the duct

URD Cable Pulling Field Set up This

URD Cable Pulling  Field Set up Not This

URD Cable Pulling  Field Set up  Sheaves  Use of sheaves should be limited to guiding cables  Minimum bending radius must be maintained

URD Cable Pulling • Field Set up • Always have end caps on cable ends • During installation and before termination

URD Cable Pulling  Installation  Pulling cables  Do not exceed maximum allowable pulling tension  Do not exceed maximum SWBP  Use proper amount of Pulling Lube  Pull with a capstan whenever possible  Max pulling speed should be 40 ft/min  Do not stop a pull unless absolutely necessary  Make sure cable ends are sealed when cut  Sacrifice the first 10ft of cable when pull complete

URD Cable Pulling  Installation  Racking in Manholes  Do not over bend the cables  Support the cables as they follow the walls  Ensure cables are tied down  Must be able to move

URD Cable Pulling  Installation  Racking in enclosures  Make sure there is enough slack for operation and possible repair

URD Cable Pulling  Installation  Termination  Splices, elbows or terminations  Use proper tools  Follow directions  Do not over stress

URD Cable Pulling  QUESTIONS?