Conduit pressure test

[chris kennedy]

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

 

[kwired]

Look in 3XX.999 of the applicable raceway article - it covers this in pretty great detail

 

[mgookin]

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

Assuming there will be 3rd party engineer oversight, I suggest talking to them in advance to see if there's anything in particular they will be looking for.

 

[don_resqcapt19]

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 type of conduit? Threaded conduit uses straight thread couplings and will not hold pressure.

Why would someone choose conduit for this application? Why not pipe that is designed to hold pressure?

 

[Smart $]

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

Haven't done it or know anything about it, but I have worked in nuclear power plants a bit over the past few years. I'm thinking what the heck kind of radioactive material would anyone ever want to handle using 4" conduit, and I cannot fathom an answer... any answer. Can you enlighten us?

What kind of conduit?

If these lines are getting pressurized, why not use a type of pipe with standard pressure ratings. AFAIK, conduit is not tested to withstand any pressure, though I know it will withstand some.

 

[jumper]

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

 

[mgookin]

...

If these lines are getting pressurized, why not use a type of pipe with standard pressure ratings. AFAIK, conduit is not tested to withstand any pressure, though I know it will withstand some.

Conduit is pressure tested all the time. You don't see it in your specs because you're not using it in a pressure application.

 

[fmtjfw]

What type of conduit? Threaded conduit uses straight thread couplings and will not hold pressure.

Why would someone choose conduit for this application? Why not pipe that is designed to hold pressure?

Threaded conduit has tapered threads. See 342.28 and 344.28.

Are standard conduit couplings usable in hazardous locations?

501.15 (A)(1) last paragraph ".... Only explosionproof unions, couplings, reducers, elbows, capped elbow ...." I assume explosionproof modifies all the rest of the list, including couplings, but I can not find anyone that sells explosionproof couplings?

As I understand it some government installations pressurize conduits (or raceways) to insure that they are not cut into and the conductors/fibers inside are not tapped. They detect pressure drops for this purpose. Do they use special couplings or do standard coupling suffice for this application?

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?

 

[Smart $]

Conduit is pressure tested all the time. You don't see it in your specs because you're not using it in a pressure application.

I'm not talking about post-manufacturing, prior-to-use pressure testing as required per job specifications. I'm talking about as part of the tests for listing the conduit as conduit.

 

[iwire]

Threaded conduit has tapered threads. See 342.28 and 344.28.

Yes, the conduit does, the conduit couplings have straight threads and do not seal water out.

 

[dfmischler]

As I understand it some government installations pressurize conduits (or raceways) to insure that they are not cut into and the conductors/fibers inside are not tapped. They detect pressure drops for this purpose. Do they use special couplings or do standard coupling suffice for this application?

Back in the 1980s, I wrote software for some equipment that was to be installed in a DOE facility somewhere near Oak Ridge, TN. I was told that the communication cables would be in conduit that was soldered together, pressurized with nitrogen, and that an alarm would go off if the pressure dropped. I had to get a security clearance in case I had to visit the site, but I never had to go.

 

[kwired]

Yes, the conduit does, the conduit couplings have straight threads and do not seal water out.

And are not intended to be completely sealed for explosion proof applications. The idea is to relieve pressure from the explosion through those threads but enough threads need to be engaged that expelled gases are sufficiently cooled after making their way through those threads that they will not ignite the outside environment. For this reason pipe dope or other sealants are not allowed on threads for explosion proof raceway applications.

 

[don_resqcapt19]

Threaded conduit has tapered threads. See 342.28 and 344.28.

Are standard conduit couplings usable in hazardous locations?

501.15 (A)(1) last paragraph ".... Only explosionproof unions, couplings, reducers, elbows, capped elbow ...." I assume explosionproof modifies all the rest of the list, including couplings, but I can not find anyone that sells explosionproof couplings?

The code says that you can use standard couplings in that application. In my opinion standard couplings do not provide a pressure seal and it is unlikely that they are tight enough to provide the required cooling of the hot gasses if there is an explosion in a conduit between an explosion proof enclosure and the seal fitting.

I know the quality of the couplings that I see has gone down a lot since I started in 73...maybe when they evaluated the couplings for that application they used higher quality couplings than I see now, but even back when I started, if you tried to use conduit with a conduit coupling for water, it would leak at the couplings no matter how tight you tried to make the connection.

I have never installed a standard coupling between an explosion proof enclosure and the seal off fitting as, in my opinion, they are not suitable for that application. I do, of course, use standard couplings for the conduit runs in the classified area, but not between an explosion proof enclosure and it sealing fitting.

As I understand it some government installations pressurize conduits (or raceways) to insure that they are not cut into and the conductors/fibers inside are not tapped. They detect pressure drops for this purpose. Do they use special couplings or do standard coupling suffice for this application?

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?

If they apply pressure and measure pressure drop to indicate conduit damage, they must be using special couplings...maybe plumbing couplings like you suggest...our straight thread coupling do not hold pressure.

 

[iwire]

I know the quality of the couplings that I see has gone down a lot since I started in 73...

Last week I dissembled some 1970s-80s equipment and just a simple thing like a 1.25" x 6" GRC nipple with its locknuts was so much better made.

The threads in the nipple where fully cut and looked perfect, the locknuts happened to be die cast but where thick, strong and the threads engaged the nipple fully with no struggle.

I saved it for truck stock, so much nicer to work with quality materials.

 

[Smart $]

Threaded conduit has tapered threads. See 342.28 and 344.28.

Are standard conduit couplings usable in hazardous locations?

501.15 (A)(1) last paragraph ".... Only explosionproof unions, couplings, reducers, elbows, capped elbow ...." I assume explosionproof modifies all the rest of the list, including couplings, but I can not find anyone that sells explosionproof couplings?

Here's an entire thread on the matter:
http://forums.mikeholt.com/showthread.php?t=168902

As I understand it some government installations pressurize conduits (or raceways) to insure that they are not cut into and the conductors/fibers inside are not tapped. They detect pressure drops for this purpose. Do they use special couplings or do standard coupling suffice for this application?

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?

Can't answer the first question, but the last would be a Code violation because the water pipe couplings would not be properly listed.

 

[gadfly56]

The code says that you can use standard couplings in that application. In my opinion standard couplings do not provide a pressure seal and it is unlikely that they are tight enough to provide the required cooling of the hot gasses if there is an explosion in a conduit between an explosion proof enclosure and the seal fitting.

I know the quality of the couplings that I see has gone down a lot since I started in 73...maybe when they evaluated the couplings for that application they used higher quality couplings than I see now, but even back when I started, if you tried to use conduit with a conduit coupling for water, it would leak at the couplings no matter how tight you tried to make the connection.

I have never installed a standard coupling between an explosion proof enclosure and the seal off fitting as, in my opinion, they are not suitable for that application. I do, of course, use standard couplings for the conduit runs in the classified area, but not between an explosion proof enclosure and it sealing fitting.



If they apply pressure and measure pressure drop to indicate conduit damage, they must be using special couplings...maybe plumbing couplings like you suggest...our straight thread coupling do not hold pressure.

Don, I think you may misunderstand. The cooling takes place as the gas travels along the spiral path of the threads and the heat it transferred to the metal of the coupling and pipe. For this purpose they are not supposed to be gas tight, just tight enough to slow the gas down so it has enough time to cool as it escapes.

 

[Barbqranch]

Like a spark arrestor on the carburetor of an off road vehicle, it doesn't take much to stop the flame front.

 

[69gp]

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

If its radioactive I am sure there is a 200 page document telling you every step that must be taken, what to use, how to install, how long to run the test, what equipment used to test. then make sure you have at least a 25 million dollar insurance policy to CYA in case something goes wrong a few years from now.

 

[Smart $]

If its radioactive I am sure there is a 200 page document telling you every step that must be taken, what to use, how to install, how long to run the test, what equipment used to test. then make sure you have at least a 25 million dollar insurance policy to CYA in case something goes wrong a few years from now.

Sounds about right for handling anything involving radioactive material... :happyyes:

 

[don_resqcapt19]

Don, I think you may misunderstand. The cooling takes place as the gas travels along the spiral path of the threads and the heat it transferred to the metal of the coupling and pipe. For this purpose they are not supposed to be gas tight, just tight enough to slow the gas down so it has enough time to cool as it escapes.

I fully understand that concept, but it is my opinion that the threads are too loose to cause enough pressure drop (the pressure drop does most of the cooling) to cool the gasses to below the auto ignition point of the flammable vapors that may exist outside the conduit system.