Conduit pressure test

[Fulthrotl]

The NSA search gremlins are going to see "missile, transfer, and radioactive" in this thread and Chis K. is gonna disappear.

along with anyone who quotes those words.... so i guess they better get a bigger bus.....

wherever they take us, for however long we remain there, it's in your best interest to
request a different cell. i snore.

you've been warned.

 

[Fulthrotl]

Finally could one use "water-pipe" couplings with tapered threads in stead of conduit couplings,
after making sure the coupling would not abrade pulled conductors?

pardon my "inner machinist" for chiming in, but SAE pipe threads
rated for WOG (water, oil, gas) are all tapered. electrical couplings
are not SAE threads, just a straight thread, so they won't hold pressure
very well, as in not very much.

so, as long as you cut a full SAE thread on the pipe (at least a full thread of
pipe sticking out the end of the die) the pipe should be able to handle
whatever the pressure rating of the fittings is... usually 150 or 300 PSI.

if i was going to put in something like this, i'd chase the factory threads
to make sure they were cut cleanly, and a fully formed thread. and use
pipe rated WOG for whatever pressure is specified.

and put the fittings togeather with keytite, in the absence of a specified sealant.

i can't imagine process piping containing radioactive material being installed
without a bunch of engineering specs... :?

 

[Smart $]

pardon my "inner machinist" for chiming in, but SAE pipe threads
rated for WOG (water, oil, gas) are all tapered. electrical couplings
are not SAE threads, just a straight thread, so they won't hold pressure
very well, as in not very much.

so, as long as you cut a full SAE thread on the pipe (at least a full thread of
pipe sticking out the end of the die) the pipe should be able to handle
whatever the pressure rating of the fittings is... usually 150 or 300 PSI.

if i was going to put in something like this, i'd chase the factory threads
to make sure they were cut cleanly, and a fully formed thread. and use
pipe rated WOG for whatever pressure is specified.

and put the fittings togeather with keytite, in the absence of a specified sealant.

i can't imagine process piping containing radioactive material being installed
without a bunch of engineering specs... :?

SAE (Society of Automotive Engineers) is not involved here. I believe the NPT standard is covered by ANSI (American National Standards Institute).

 

[Fulthrotl]

SAE (Society of Automotive Engineers) is not involved here. I believe the NPT standard is covered by ANSI (American National Standards Institute).

yup. blew that one. duh.

"NPT is defined by ANSI/ASME standard B1.20.1."

-wikipedia

 

[ritelec]

Not to get off topic.
Rigid and intermediate conduit threads are tapered but the threads in the couplings are not? Now that you say that, I guess your right.
Where does that leave explosion proof piping??

I believe it's stated about no running threads. Wouldn't that coupling thread be running threads ?? How would it seal out vapors ?

Thanks

 

[iwire]

I believe it's stated about no running threads.

Close.

342.42 Couplings and Connectors.

(B) Running Threads. Running threads shall not be used
on conduit for connection at couplings.

 

[ritelec]

Ok. So no running threads on CONDUIT but it's ok on (in) the coupling ?
?? Sorry still don't get it. How does this make the conduit system vapor proof ?

Or is the conduit system NOT vapor proof? They know that, they expect that and that's why seals go in ???

Why not make couplings with tapered thread ?

Thanks

 

[kwired]

Ok. So no running threads on CONDUIT but it's ok on (in) the coupling ?
?? Sorry still don't get it. How does this make the conduit system vapor proof ?

Or is the conduit system NOT vapor proof? They know that, they expect that and that's why seals go in ???

Why not make couplings with tapered thread ?

Thanks

The tapered threads of the conduit will still jam enough to make a decent bond and reasonable but not perfect seal.

The prohibition of running threads I believe is mostly to eliminate using a standard coupling as a union, such an install will not be very tight as the small end of normal taper is all that will be in the coupling and will fit pretty loose.

In explosion proof applications the conduit is not vapor proof, the enclosures aren't necessarily vapor proof either. Making them vapor proof seems logical, until you consider how long they may last before there is some leakage. So they design the system not to prevent explosions but rather to contain one when it does happen.

 

[gadfly56]

The tapered threads of the conduit will still jam enough to make a decent bond and reasonable but not perfect seal.

The prohibition of running threads I believe is mostly to eliminate using a standard coupling as a union, such an install will not be very tight as the small end of normal taper is all that will be in the coupling and will fit pretty loose.

In explosion proof applications the conduit is not vapor proof, the enclosures aren't necessarily vapor proof either. Making them vapor proof seems logical, until you consider how long they may last before there is some leakage. So they design the system not to prevent explosions but rather to contain one when it does happen.

Not quite. I was under this misapprehension for many years. The purpose is to contain the explosion just enough so that the gases, when they exit the conduit or box or enclosure, are cooled enough so that they can't ignite the potential explosive atmosphere on the exterior. That's why the threads are loose. Some of the heat of the gases is transferred to the metal, which has a lot more mass than the gases, and some of it is due to Joule-Thompson cooling.

 

[kwired]

Not quite. I was under this misapprehension for many years. The purpose is to contain the explosion just enough so that the gases, when they exit the conduit or box or enclosure, are cooled enough so that they can't ignite the potential explosive atmosphere on the exterior. That's why the threads are loose. Some of the heat of the gases is transferred to the metal, which has a lot more mass than the gases, and some of it is due to Joule-Thompson cooling.

That is my understanding as well, I guess technically it doesn't contain the explosion but rather contains the hazards that may otherwise ignite the outside environment, anything released is supposed to be safe, I just didn't quite explain it well enough.

 

[Smart $]

That is my understanding as well, I guess technically it doesn't contain the explosion but rather contains the hazards that may otherwise ignite the outside environment, anything released is supposed to be safe, I just didn't quite explain it well enough.

That's all semantics. If the explosion occurs only within the confines of the enclosure and/or conduit, then it contains the explosion.

When a very slow-leaking bucket is full of water, it contains the water. Eventually it will not. But for the time being it does. That is the purpose of an explosionproof design.

 

[don_resqcapt19]

... That's why the threads are loose. Some of the heat of the gases is transferred to the metal, which has a lot more mass than the gases, and some of it is due to Joule-Thompson cooling.

I still have very strong doubts that the currently available conduit coupling can actually do that. There is little mass there as compared to an explosion proof enclosure and the tightness of the metal to metal in the conduit/coupling connection is much much less than in the connection between the explosion proof enclosure and its cover.

 

[kwired]

I still have very strong doubts that the currently available conduit coupling can actually do that. There is little mass there as compared to an explosion proof enclosure and the tightness of the metal to metal in the conduit/coupling connection is much much less than in the connection between the explosion proof enclosure and its cover.

Has been touched already though that you wouldn't have a coupling between an enclosure with ignition hazards and the conduit seal, in fact I believe (going from memory here) that there is limitations on what fittings can be between the enclosure and the seal fitting, and they are mostly limited to explosion proof unions, explosion proof capped elbows and explosion proof flexible couplings.

I would think a standard coupling wouldn't even be desired in most cases over a union type of coupling for assembly reasons.

 

[Smart $]

... but I can not find anyone that sells explosionproof couplings? ...

An explosionproof coupling isn't what you think it is if you haven't worked in C1D1 environs alot.

 

[kwired]

An explosionproof coupling isn't what you think it is if you haven't worked in C1D1 environs alot.

View attachment 14344

I thought that was a flexible coupling that also happens to be explosion proof.

 

[Smart $]

I thought that was a flexible coupling that also happens to be explosion proof.

That'd be correct thinking.

 

[Fulthrotl]

I still have very strong doubts that the currently available conduit coupling can actually do that. There is little mass there as compared to an explosion proof enclosure and the tightness of the metal to metal in the conduit/coupling connection is much much less than in the connection between the explosion proof enclosure and its cover.

the entire point of a threaded fitting in a classified location,
is for there to be enough threads engaged, that WHEN
the atmosphere inside the conduit/fitting/panel/whatever
explodes, and it will, the expanding burning gases will have enough
metal as a heat sink, to cool the burning gases below the
point of ignition of the surrounding atmosphere, before they
reach that atmosphere.

the rule of thumb is five full turns of engagement of the threads.
a CL I DIV I j box with a threaded cover doesn't have to be tightened
to work. five full turns is enough.

the reason running thread is not permitted, is the highly reduced wall
thickness of the running thread weakens the conduit excessively.

if the wall thickness wasn't an issue, running thread would be fine,
as long as 5 full turns of engagement were present.

with a flanged bolted enclosure, the thickness of the flange is enough
for the same cooling effect, when bolted. this is why any nicks, or bumps
on the flange are not a problem as long as they are stoned away, so the
surface mates completely. the flange isn't a seal, it's a heat sink.

this is why classified locations are gasket free. nothing that degrades over
time or repeated opening is used.

 

[RichB]

I have a project where 2 4" conduits will be missile bored for transfer lines for radioactive material.
Anyone ever done this?
Assuming I use plumbing test ball, what pressure and for how long?
No specs on test.

Thanks

What am I missing here-I am sooooo confused:?:?--Why would you transfer radioactive material through conduit instead a more robust, corrosion resistant material?:?

 

[kwired]

What am I missing here-I am sooooo confused:?:?--Why would you transfer radioactive material through conduit instead a more robust, corrosion resistant material?:?

Just speculation, corrosion resistance isn't much of an issue for their conditions, and maybe they have easier or less cost access for whatever reason to some 4" RMC then they do to regular pipe?

 

[fmtjfw]

The female threads on Explosion Proof boxes and such are taper threaded.