Pulling cable through underground ductwork.

In summary, the conversation discusses the job of a Cable Splicer and the use of a winch truck to pull heavy duty underground cables through ducts. The main topic is the speed at which the cable should be pulled and the physical factors that come into play. The conversation also touches on the importance of avoiding complex dynamic behavior and using lubricants to improve the pulling process. The thread was temporarily closed for moderation due to the discussion of dangerous activities and will remain closed due to liability concerns.
  • #1
Fatboyx
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TL;DR Summary
Pulling cable through underground ductwork
Hello all,

I am an Engineering dropout turned Cable Splicer. In my job we do a lot of Heavy Duty underground cable pulling. Usually plastic jacketed cable through some type of ductwork (typically plastic as well). We use a winch truck and a heavy rope to pull this cable through the ducts, typically not more than 500 feet.

As of late our Foremans insistence on pulling the cable at a considerate speed has resulted in some botched jobs and what I consider to be an increased hazard. He claims that slowing down or stopping should only occur in an absolute emergency and likes to reference starting from a deadstop is like trying to start a train.

My question for you all:
- What would be the physical factors at play here?
- How substantial of a difference is it? pulling fast, slow, or from a dead stop.
- General conclusions and opinions?

I'm thinking momentum seems to be fairly negligible comparing a fast vs slow pull. Obviously coefficient of friction and how much cable is already in the ducts would be a factor as well.

Thanks for your help
-Chris
 
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  • #2
Welcome to PF.

Fatboyx said:
I'm thinking momentum seems to be fairly negligible comparing a fast vs slow pull.
Sideways momentum will be important.

If you can pull slow and steady, you will avoid complex dynamic behaviour of the cable as it enters the duct. Pull at well below the S-wave sound velocity in the cable.

Do you pull directly from a spool, or do you lay out the cable, so it can enter without un-spooling, or suffer a major change of direction?

Once you stop, you will be faced with the static friction coefficient. That will be worse than the sliding friction coefficient.

Do you use lubricant? Soapy water?

Do you have greater success by pulling with a rope having a diameter slightly greater than the cable?
 
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  • #3
Thread closed temporarily for Moderation...
 
  • #4
After a Mentor discussion, the thread will remain closed. @Fatboyx -- We cannot allow discussion of dangerous activities at PF. Here is some of the Mentor discussion about this thread start of yours:

This problem is not easily analyzed from basic principles, and we cannot comment because of liability.

Point out that experience (the "botched jobs") is pretty much is conclusive.

The OP should be very careful about challenging the boss...

Thread will remain closed.
 
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1. How do I determine the correct size of cable to use for underground ductwork?

The size of cable needed for underground ductwork depends on several factors such as the length of the duct, the type of cable, and the load it will be carrying. It is important to consult with an electrical engineer or follow industry standards to determine the appropriate cable size for your specific project.

2. What is the best method for pulling cable through underground ductwork?

The most common method for pulling cable through underground ductwork is by using a cable pulling machine or winch. This allows for controlled and efficient pulling of the cable through the duct. It is important to use proper lubrication and follow safety precautions when using this method.

3. How can I prevent damage to the cable while pulling it through underground ductwork?

To prevent damage to the cable, it is important to use proper lubrication, avoid sharp bends or corners, and use proper pulling techniques. It is also recommended to use a cable pulling grip or pulling socks to protect the cable during the pulling process.

4. Are there any special considerations for pulling cable through underground ductwork in harsh environments?

Yes, in harsh environments such as extreme temperatures or corrosive environments, it is important to use cables that are specifically designed for these conditions. It is also important to use proper lubrication and follow industry standards for cable pulling in these environments.

5. Can I use the same method for pulling cable through all types of underground ductwork?

No, the method for pulling cable through underground ductwork may vary depending on the type of ductwork. For example, the method for pulling cable through PVC ductwork may be different than that for metal ductwork. It is important to consult with an expert or follow industry standards for the specific type of ductwork being used.

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