I Pulling cable through underground ductwork.

AI Thread Summary
The discussion centers on the challenges of pulling heavy-duty underground cable through ductwork, with concerns about the speed of the operation. The foreman insists on pulling quickly, which has led to botched jobs and increased hazards, raising questions about the physical factors involved in cable pulling. Key considerations include the effects of momentum, static versus sliding friction, and the importance of a steady pull to avoid dynamic issues. The use of lubricants and the method of cable handling are also highlighted as critical factors. Overall, the conversation emphasizes the need for caution and experience in cable splicing operations.
Fatboyx
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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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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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Thread closed temporarily for Moderation...
 
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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I think it's easist first to watch a short vidio clip I find these videos very relaxing to watch .. I got to thinking is this being done in the most efficient way? The sand has to be suspended in the water to move it to the outlet ... The faster the water , the more turbulance and the sand stays suspended, so it seems to me the rule of thumb is the hose be aimed towards the outlet at all times .. Many times the workers hit the sand directly which will greatly reduce the water...

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