???? code violation

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luckylerado said:
So, hang a sign on the rigid stating "Means of Support"
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jap said:
If that's the case, let's just say the air line is supporting the (2) rigid conduits and be done with it.
JAP>
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:lol::lol:

If the air line is supporting the RMC, it's a violation of mechanical codes. If it's the other way 'round, the aforementioned 300.11(B).

Besides, that's not an air line, it's a "future use prototype EMT type-conduit undergoing an indefinite pressure test". Now what? :D
 
The RMC about has to be more "rigid" then the air line, take the strut out of the picture and the air line is likely much less "rigid" then it is now. So the RMC in this case is securing/supporting the air line, since the stut is not fastened to anything else.

Is it a major problem though? Probably not.

If there were one more pipe involved that served no purpose other then providing physical support, this shouldn't be an issue at all from electrical or mechanical codes.
 
kwired said:
The RMC about has to be more "rigid" then the air line, take the strut out of the picture and the air line is likely much less "rigid" then it is now. So the RMC in this case is securing/supporting the air line, since the stut is not fastened to anything else.

Is it a major problem though? Probably not.

If there were one more pipe involved that served no purpose other then providing physical support, this shouldn't be an issue at all from electrical or mechanical codes.
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Exactly. Suppose you disconnect the two of them, and apply the same pounds of load in the same manner to each. The member that deflects the least, will be supporting the member that deflects the most, when you reconnect them.

In some cases, even code-compliant ones, the conduit is supporting the support method, as opposed to the other way around. Example: a 6 ft RMC between two enclosures, has just one hanger strap in the middle. If you beat it with a sledge hammer, the strap is going to break before the conduit or terminations do. Another example: an 18 ft span of 2" RMC runs across a gap, strapped twice to a parallel piece of standard profile strut. Disconnect the straps, and the strut is going to deflect a lot more than the conduit, under the same load.

I think it is a conservative rule that we don't allow RMC or raceways in general to support anything external. I think it is more critical to apply this rule to plumbing pipe, because pressure loading is a lot more serious to the pipe's structural integrity, than the weight of loose wire. Having this blanket rule is one way to ensure that there is no issue in all cases.

Suppose we had a rule such as, that "conduits supporting external loads must limit the load such that the yield stress safety factor is 4 or more, and the deflection ratio does not exceed L/240". It would be practical, safe in concept, and allow more solutions to situations like a large and small conduit running together. But anyone who is not a structural engineer wouldn't know what to do with this information.
 
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Carultch said:
You still can use an empty conduit as a support structure, but bear in mind that RMC is a weaker alloy of steel than its plumbing, fencing, and structural pipe counterparts.
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That's interesting where do you get that information on the alloys used in the different pipes?
 
tortuga said:
That's interesting where do you get that information on the alloys used in the different pipes?
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I had planned a PV racking system using empty RMC as part of the support structure. Then I stumbled on the following from the Steel Tube Institute, which caused me to revisit it, and plan for fence pipe instead.

While researching it further, I seldom found any alloy identifier or strength rating on any RMC datasheet. The stiffness young's modulus for deflection calculations is the same for nearly all alloys of ferrous steel, but the strengths are different. I did end up finding one RMC datasheet that had a yield strength of around 26 ksi (can't remember where). Compare this with plumbing and structural pipe where the weakest pipe available is 30 ksi. It is plausible that RMC is intentionally weaker steel, so that it can be bent in the field. Possibly steel that is weak in yield strength and strong in ultimate strength, which would be desired for steel that is intended for reshaping at room temperature.

https://steeltubeinstitute.org/steel-conduit/frequently-asked-questions/

Question: Is RMC the same as Schedule 40 pipe?
Answer: No. The term “Schedule 40” originated with an ASTM specification and has come into general usage. It is still addressed in a number of ASTM specifications, whose requirements typically include dimensional and strength parameters.
Rigid conduit is intended for electrical applications, not structural ones. Its requirements are governed by UL and ANSI specifications, not by ASTM. The main issue here is that, whereas dimensions may be similar between the two, rigid conduit is not intended for, is not designed for, and is not tested for any strength or structural requirements
If a job specification calls for “schedule 40 conduit” or “schedule 40 rigid” confirm that the requirement is for rigid steel conduit, since “schedule 40” is still a term that applies to PVC conduit.
 
Carultch said:
I had planned a PV racking system using empty RMC as part of the support structure. Then I stumbled on the following from the Steel Tube Institute, which caused me to revisit it, and plan for fence pipe instead.

While researching it further, I seldom found any alloy identifier or strength rating on any RMC datasheet. The stiffness young's modulus for deflection calculations is the same for nearly all alloys of ferrous steel, but the strengths are different. I did end up finding one RMC datasheet that had a yield strength of around 26 ksi (can't remember where). Compare this with plumbing and structural pipe where the weakest pipe available is 30 ksi. It is plausible that RMC is intentionally weaker steel, so that it can be bent in the field. Possibly steel that is weak in yield strength and strong in ultimate strength, which would be desired for steel that is intended for reshaping at room temperature.

https://steeltubeinstitute.org/steel-conduit/frequently-asked-questions/

Question: Is RMC the same as Schedule 40 pipe?
Answer: No. The term “Schedule 40” originated with an ASTM specification and has come into general usage. It is still addressed in a number of ASTM specifications, whose requirements typically include dimensional and strength parameters.
Rigid conduit is intended for electrical applications, not structural ones. Its requirements are governed by UL and ANSI specifications, not by ASTM. The main issue here is that, whereas dimensions may be similar between the two, rigid conduit is not intended for, is not designed for, and is not tested for any strength or structural requirements
If a job specification calls for “schedule 40 conduit” or “schedule 40 rigid” confirm that the requirement is for rigid steel conduit, since “schedule 40” is still a term that applies to PVC conduit.
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Wow that's interesting Ill check that out.
 
It has always been explained to me, that if you removed the conduit would the airline be unsupported? If so, the conduit is supporting the air line. It looks to me like that would be the case here. If you removed the conduit and straps the air line would be left unsupported. I would say this is a violation. As others have said though, you see it all of the time in industrial environments. Doesn't make it right, but happens a lot.


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In this case it was in a power plant so it didn't really matter since they aren't subject to the National electrical code. I've seen this kind of thing a a bunch of times it's completely safe there's no reason not to do it other than the fact that it doesn't meet code.
 
midamericairon said:
It has always been explained to me, that if you removed the conduit would the airline be unsupported? If so, the conduit is supporting the air line. It looks to me like that would be the case here. If you removed the conduit and straps the air line would be left unsupported. I would say this is a violation. As others have said though, you see it all of the time in industrial environments. Doesn't make it right, but happens a lot.


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If you removed the conduit the air line is probably still supported, just not as well supported :p

If it weren't supported at all it should fall down, right?
 
Not supported as per the requirements of the installation. Why do individuals on this site feel like they have to nit pick everyone's responses?


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midamericairon said:
Not supported as per the requirements of the installation. Why do individuals on this site feel like they have to nit pick everyone's responses?


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Those little details are what fail inspections?

Occasionally when you assume someone understands a small detail, you later find out they didn't, especially when communicating via text to someone you really don't know that well.

Besides that I can't get a word in around the wife and her acquaintances whether it is something significant or not, so have to let it out somewhere else:D
 
kwired said:
If you removed the conduit the air line is probably still supported, just not as well supported :p

If it weren't supported at all it should fall down, right?
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If you were standing on a platform that could withstand your current weight, but just one more pound would cause it to rupture, would you consider yourself supported? Probably not.


Similarly, if something that requires support per construction codes is supported in a manner that cannot withstand its own dead load and most applicable environment loads, with a reasonable safety factor, you would not consider it supported either.
 
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