Pvc conduit in a corrosive environment.

[Ewalsh]

Can you install pvc schedule 80 conduit indoors in a corrosive industial environment.

 

[Gregg Harris]

Can you install pvc schedule 80 conduit indoors in a corrosive industial environment.

352.10 Uses Permitted. The use of PVC conduit shall be permitted in accordance with 352.10(A) through (H).

Informational Note: Extreme cold may cause some non-metallic conduits to become brittle and, therefore, more susceptible to damage from physical contact.
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(A) Concealed. PVC conduit shall be permitted in walls, floors, and ceilings.
(B) Corrosive Influences. PVC conduit shall be permitted in locations subject to severe corrosive influences as covered in 300.6 and where subject to chemicals for which the materials are specifically approved.

 

[kwired]

Corrosive environments is what PVC is for. It does not corrode.

PVC is not good in a location where materials that are a solvent to the PVC would be regularly present.

Heat and cold are problems also but for different reasons.

 

[renosteinke]

That this question is asked is, again, proof that our code focus is simply wrong. What passes for 'logic' these days is simply scandalous. We're educated a generation of idiots.

NEC says only that you must use an approved method, and use listed materials. Only in Article 100 are there the most general of comments about the wires being mechanically protected, and protected from corrosion.

The error is in concluding that all wiring methods are always acceptable, unless the code specifically says different in the section about that particular method. Or, even worse, concluding a method is ALWAYS acceptable where the code says it can be used.

So, I see clearly inappropriate methods used because 'they're legal,' and appropriate methods denied because of some silly bias or assumption.

I'll state the obvious:
1) If the wires are getting damaged - damage to the previous installation is evidence of such - they are NOT mechanically protected. Period. I care not that they are in pipe, or that the NEC says you can use pipe. The damage alone is proof of that;

2) The conduit needs to be there to work. If it rusts away, flakes off, or simply evaporates, you're not protecting the wires. Period. Your method is inadequate, even if 'legal;'

3) If a wiring method succeeds in protecting the wires, it is 'legal,' even if it's not something that you 'usually' do. Even if it means using non-listed materials; Article 100 provides for AHJ approval for this specific reason; and,

4) To repeat: it's all about protecting the wires.

 

[Pierre C Belarge]

Renosteinke

If I understand your post correctly, I disagree with your train of thought.

Art 100 is definitions - definitions are not perscriptive.
Section 90.4 gives the Authority Having Jurisdiction (AHJ) some leeway in his/her decision to allow or disallow an installation - but that AHJ may need to be ready to defend that position in court, and better have a really good reason for his/her decision.

Also, I learned long ago that logic has very little place in the NEC.

*Are you stating that if EMT is permitted in a particular location/installation in the NEC, and we see damage to the installation, that it should not be permitted? (EMT is just an example I chose)

 

[hurk27]

One thing to keep in mind with using PVC in environments that might pose a problem to insulation on wiring, If the vapors are or can dissolve the PVC coating on wiring then PVC will also have this problem, some solvents used to degrease can also dissolve PVC piping, and also since no conduit system is totally sealed care must be taken as to the type of wiring used even if it is inside of a conduit system, just like where the NEC sees an underground conduit as a wet location.

We had a place that used solvents to clean parts and even though we use RMC with seal offs the solvents were still getting into the conduit and dissolving the insulation on the wiring, we had to use a wiring method that was not subject to the solvents being used even paint thinner can be a problem, it was a long time ago so I don't remember what the wire type was but I believe it was a silicone based insulation with a cloth outer covering that was resistant to solvents.

Acids and alkaline are water base and most insulations that protect against water will protect against these types of corrosive elements as will PVC, we used to use Rob Roy coated conduit systems around our anodizing tanks but we still had problems as just one little place where the vapors could get into the conduit the metal under the coating would just dissolve away leaving the outer coating in place, we changed to PVC and or 316 SS and never had another problem.

 

[hurk27]

Renosteinke

If I understand your post correctly, I disagree with your train of thought.

Art 100 is definitions - definitions are not prescriptive.
Section 90.4 gives the Authority Having Jurisdiction (AHJ) some leeway in his/her decision to allow or disallow an installation - but that AHJ may need to be ready to defend that position in court, and better have a really good reason for his/her decision.

Also, I learned long ago that logic has very little place in the NEC.

*Are you stating that if EMT is permitted in a particular location/installation in the NEC, and we see damage to the installation, that it should not be permitted? (EMT is just an example I chose)

Good to see you again Pierre.

I think Reno was pointing out that the NEC is written in a way that allows allot of variables in installations, but many installers who do installs don't have the common sense to know what is appropriate for a type of installation, just like I pointed out above where while the conductors were protected with RMC no thought was taken as to the type of insulation on the conductors that if they were in an environment that can damage the insulation but they thought just because they were in RMC they were protected.

Also installing EMT can have its problems with wet locations, while water it self doesn't really damage EMT on the short term if moisture is allowed to stay in contact with the metal it will cause the EMT to rust, one of the reasons I make sure I mount EMT with a space away from the wall in damp or wet locations to keep dirt and debris from building up between the conduit and wall as the dirt can hold moisture against the conduit and cause it to corrode just like it will do on our cars.

It is this kind of common sense that many newer electricians are not being taught any more.

Just because the code allows something we still need to add some common sense to recognize other hazards that may apply to the materials we might be using when we do our installations.

 

[renosteinke]

It looks like Pierre and Hurk both understand what I was saying, though there's a tendency to try to argue out of it.

Let's use that EMT example. Let's say someone runs EMT along the wall of a warehouse. As far as the NEC section on EMT is concerned, you can run EMT in a warehouse, so it's a 'legal' install.

Now, let's add a twist. You're sent to fix some EMT in a warehouse, EMT that has been trashed by forklift traffic. I submit that EMT is no longer a 'legal' methon for that specific run.

Why? Because the conduit is required to protect the wires. We have proof that, in this case, EMT was not adequate. Since Article 110 requires raceways to provide mechanical protection, and EMT failed to do so, simply replacing the EMT with new EMT is not a compliant solution. IMO, you need another solution.

If you relocate the wire run, or provide additional protection to the run, you've met 110's requirement.

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The same applies to the OP's situation. Using steel pipe over an acid bath does NOT meet code, no matter what the section on RMC might say, since the steel is not going to meet 110's requirement to resist corrosion in that location.

Maybe the customer has learned that only titanium will stand up to that particular environment. Go ahead- use titanium pipe. So what if there's no "UL" mark ... 110 allows the AHJ to approve alternatives. What matters is that the wires be protected - not that there's a particular sticker, or that there's a blanket permission given somewhere.

The issue often came up in Chicago, where "PVC is not allowed." Balderdash. Even Chicago inspectors had no issues approving PVC in corrosive industrial locations. Indeed, they also approved the use of stainless steel plumbing pipe as conduit, as stainless conduit was (for all practical purposes) not available. (UL listed stainless, but no stocking distributors were found, and the conduit companies wanted orders of 10,000+ ft.)

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I object most strongly to the 'logic' that leads a man to say "It's perfectly proper because the book says so, even though I know it will fail." Carrying that a step farther, it's sheer insanity to say "it didn't work the last time, so let's do it again."

 

[kwired]

Let's use that EMT example. Let's say someone runs EMT along the wall of a warehouse. As far as the NEC section on EMT is concerned, you can run EMT in a warehouse, so it's a 'legal' install.

Now, let's add a twist. You're sent to fix some EMT in a warehouse, EMT that has been trashed by forklift traffic. I submit that EMT is no longer a 'legal' methon for that specific run.

Why? Because the conduit is required to protect the wires. We have proof that, in this case, EMT was not adequate. Since Article 110 requires raceways to provide mechanical protection, and EMT failed to do so, simply replacing the EMT with new EMT is not a compliant solution. IMO, you need another solution.

If you relocate the wire run, or provide additional protection to the run, you've met 110's requirement.

I agree to an extent. Not every case of a damaged raceway means it is normally subjected to physical abuse. In the traffic area of a warehouse - it likely is subject to abuse. In some area not normally subject to traffic - accidents still can happen.

Replacing with RMC - RMC is not vehicle/machinery abuse proof either, but does hold up longer than EMT.

 

[dhalleron]

I did some work in a factory that chrome plated the hardware for shelf racks in stores. There were automated lines where material was dipped in various vats of chemicals.

Everything metal in that place including the building steel was rotting away. There were runs of wire where the emt had disappeared long ago. The thhn/thwn wiring was fine and so was the copper wire. We went in and installed pvc.

I'm just glad I didn't have to work in that place full time like the employees did. What will that stuff do you your health over time?

 

[kwired]

I did some work in a factory that chrome plated the hardware for shelf racks in stores. There were automated lines where material was dipped in various vats of chemicals.

Everything metal in that place including the building steel was rotting away. There were runs of wire where the emt had disappeared long ago. The thhn/thwn wiring was fine and so was the copper wire. We went in and installed pvc.

I'm just glad I didn't have to work in that place full time like the employees did. What will that stuff do you your health over time?

I don't know much about chrome plating, have seen a little of hot dip galvanizing. Your chemicals were likely prep chemicals for the plating process. If the plating would be hot like for the galvanizing PVC would not hold up to the temp in the dip area, but there likely is no chemical in that area either.

 

[hurk27]

Reno I can agree with that as long as you know you can't alway protect against stupid (not something obviously subject to be damaged).

In one case one of our workers a few years ago did a job of installing hook ups for diesel truck block heaters for a delivery company, I have always used straight blade receptacles and plugs so if a truck pulls away without disconnection the most he damages is the short 10' extension cord, well he didn't, guess he thought RMC and twist-loc receptacles was the way to go like it would stop a 27' 26,000 # truck, well he spent the next week changing it all out to PVC and straight blade receptacles, as a driver did what is expected and ripped the whole service and all off the building, at least with PVC it just breaks off.

I also use PVC for risers where the riser doesn't support the drop (like at a gable end), since you are not going to prevent a tree or large limb from tearing down a service, let it go with it, most times it breaks the male adapter off at the top of the meter and keeps the SEC's from shorting out, most times the homeowner still has power, I come out glue a new male adapter on it and strap it back up and have their power on in less then 30 min's, I have never had to repair or replace a meter base like this, when I have a RMC service downed by a tree, it damages the meter the house and several time pulls the neutral apart before the hot which blows out electronics in the house, I haven't done one in a while but with the issue of the male adapter in the meter hub which now I think I would K/O the blank hub and use a WP male adapter with the sealing ring?