A. Drum type winches - A common practice is using the same drum puller for overhead and underground, or a bed winch, to pull in the URD conductor. A drum type puller or winch has no way to monitor actual line tension. Also, the maximum pulling capacity is obtained when the drum is empty. As the drum fills up with cable, the speed increases and the pulling tension decreases. At the end of the pull when the drum is full, the winch is at its minimum capacity; and that is when the pull is at its maximum tension.
B. Bullwheel type pullers - A puller with bullwheels maintains the same speed and tension when the drum is empty as when the drum is full. The actual drum on this type puller is merely a storage drum with no effect on the speed or tension.
C. Underground pullers - A puller designed specifically for underground normally has a dynamometer and footage counter to allow the operator to monitor and maintain desired pulling tensions and speeds for safe and efficient cable installation.
3. Reel Trailers
A. Reel trailers are built in various designs and configurations and normally carry from one to four reels. Care should be taken in the selection of a safe and functional reel trailer with capacities equal to the size and weights of the conductor reels.
B. A Manual Reel Trailer is most commonly used for underground construction. This trailer allows the puller to remove the conductor at it's own speed with a manual overspin brake to prevent overspinning.
C. A Hydraulic Reel Trailer allows the operator to adjust the speed and tension of the conductor hydraulically as it flows from the reel stands. However, care should be taken to ensure enough slack is available to prevent the reel trailer from pulling against the puller, which causes unnecessary tension on the conductor.
D. Regardless of the design, manual or hydraulic, the trailer should be equipped with a ball bearing on the reel shaft to prevent the additional pulling tension and friction required just to turn the reel.
4. Rigging, Blocks, and Accessories A. Properly installed rigging ensures safe and efficient cable installation with a minimum amount of damage to the conductor. If the rigging slips during a pull, causing the pull to stop, the conductor settles to the bottom of the conduit. When the pull resumes, the pulling tension required to move the conductor is much greater than the tension required before the pull stopped.
B. The diameter of the blocks used should be selected to ensure proper bending radius and installation without damage to the conductor. The cable manufacture will provide its recommendations for specific cables and applications.
C. Conduit Rollers are available to assist the conductor from the conduit to the puller or reel trailer. This roller is designed to fit the inside of the conduit and provide protection for the conductor as it slides past the end of the conduit.
D. Lip Rollers are used to assist the conductor over the lip of the vault or manhole without unnecessary damage.
E. Jamb Skids and Quadrant Blocks are normally used on larger conductor installations. The jamb skid is designed to rest on the floor of the vault and is secured to the manhole.
F. Feed Tubes assist the conductors from the reel trailers into the vault and conduit. The round tube helps form the conductors into a triangle shape to allow proper entry into the conduit. Without this tool, normally someone has to assist the conductors into the conduit.
5. Lubricant A. It is very important to maintain a proper amount of lube on the conductor as it is pulled into the conduit. Inadequate lubricant can cause damage and unnecessary tension to the conductor during installation. How much lube is "proper" or "adequate"? Pulling conditions vary with conduit, conductor, length of pull, and layout designs. Attached is a general chart that can be used to determine the quantity of lubricant. However, the quantity needs to be adjusted according to the pulling conditions.
All of the above areas of consideration are very important steps to ensure safe, reliable, and long lasting cable installation.
1. A tested and proven Conduit System.
2. Select a Cable Puller to meet your specific needs.
3. The Reel Trailer should be designed to safely transport the conductor.
4. Make sure your rigging is safe and secure.
5. Use adequate amounts of lubricant.