conduit protection
- Thread starter mwdkmpr
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peter d
Senior Member
- Location
- New England
Re: conduit protection
Allow me to make my best attempt to explain running threads. Someone will probably be able to explain it better than me.
"Running threads" are when you thread one end of the pipe twice the length of a normal thread. You then screw the coupling completely on to the long thread, and then run the coupling back onto the next piece of pipe.
Of course, this is prohibited, because it exposes the whole length of ungalvanized threads to the elements, and the results of that are obvious.
This incorrect technique is used when you are working into a run of pipe that is already fixed in place. The solution is to use a proper fitting. They are expenive, but the code doesn't care if you have to use an expensive fitting.
Allow me to make my best attempt to explain running threads. Someone will probably be able to explain it better than me.
"Running threads" are when you thread one end of the pipe twice the length of a normal thread. You then screw the coupling completely on to the long thread, and then run the coupling back onto the next piece of pipe.
Of course, this is prohibited, because it exposes the whole length of ungalvanized threads to the elements, and the results of that are obvious.
This incorrect technique is used when you are working into a run of pipe that is already fixed in place. The solution is to use a proper fitting. They are expenive, but the code doesn't care if you have to use an expensive fitting.
- Location
- Massachusetts
Re: conduit protection
Running threads are the type of threads on a bolt, no tapper to them.
Typically pipe thread like on the conduit we use is a tapered thread.
The dies we use are "NPT" or "National Pipe thread" they produce a tapered thread.
If you do what Peter describes you will produce a section of running thread that runs into the tapered thread.
The threaded conduit couplings we use have running threads, when you screw a running thread coupling onto a running thread pipe it will never get tight. It would be like a hex nut on a threaded rod. It will just keep spinning until it runs out of threads.
On the other hand with our tapered thread pipe you can only spin on a fitting so far before it hits the tapper and gets tight. This is necessary to produce a good ground fault path.
It will not make a water tight seal because of the running or straight thread on the coupling.
Plumbers coupling have tapered threads and combined with tapered thread pipe will make a water tight seal.
[ December 17, 2004, 04:57 PM: Message edited by: iwire ]
Running threads are the type of threads on a bolt, no tapper to them.
Typically pipe thread like on the conduit we use is a tapered thread.
The dies we use are "NPT" or "National Pipe thread" they produce a tapered thread.
If you do what Peter describes you will produce a section of running thread that runs into the tapered thread.
The threaded conduit couplings we use have running threads, when you screw a running thread coupling onto a running thread pipe it will never get tight. It would be like a hex nut on a threaded rod. It will just keep spinning until it runs out of threads.
On the other hand with our tapered thread pipe you can only spin on a fitting so far before it hits the tapper and gets tight. This is necessary to produce a good ground fault path.
It will not make a water tight seal because of the running or straight thread on the coupling.
Plumbers coupling have tapered threads and combined with tapered thread pipe will make a water tight seal.
[ December 17, 2004, 04:57 PM: Message edited by: iwire ]
Re: conduit protection
So running threads are NPT that have been cut to far or threads made with a NPSM die, correct?
What about my question concerning 300.6B which says that buried non-ferrous metal shall be protected by supplementary corrsion protection. What is the supplementary protection?
So running threads are NPT that have been cut to far or threads made with a NPSM die, correct?
What about my question concerning 300.6B which says that buried non-ferrous metal shall be protected by supplementary corrsion protection. What is the supplementary protection?
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