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Posted By: Admin A Problem With Low Tide And Conduit Runs - 08/13/08 01:47 AM
Quote
I found this in Tacoma, WA at a harbor were my Aunt and Uncle's sailing vessel is moored

The flexible conduit wasn't long enough to accommodate the lengths at the low tide levels so the conduit connections came apart

Tristan S.

[Linked Image from electrical-photos.com]

[Linked Image from electrical-photos.com]
Posted By: Admin Re: A Problem With Low Tide And Conduit Runs - 08/13/08 01:48 AM
Quote
Here's another one I found at the same harbor in Tacoma, WA but on a different dock access ramp.

I don't know what kind of tubing was used to take the place of flexible conduit here but I certain it's not LFNC or any other code approved conduit.

It almost looks like a vacuum hose but I'm not sure.

Tristan S.

[Linked Image from electrical-photos.com]
One thing I forgot to mention about the top two pictures is the PVC conduits seen there are supported by the dock access ramp I was on at that time.
Posted By: jdevlin Re: A Problem With Low Tide And Conduit Runs - 08/15/08 08:06 PM
Looks like they used the wrong glue on the PVC as well. They connections should not come apart like the bottom picture. They should break.
Originally Posted by jdevlin
Looks like they used the wrong glue on the PVC as well. They connections should not come apart like the bottom picture. They should break.


Not if the connections were glued wet, at high tide. smile

I've seen a few joints come apart like that, including one that I put in myself (and I was using the conduit manufacturer's glue!). The problem does seem to have something to do with marine environments.

I've taken to using a clear PVC primer on the pipe and fittings before applying the cement, just like you would on plumbing work. It definitely seems to result in a stronger joint...

Posted By: NORCAL Re: A Problem With Low Tide And Conduit Runs - 08/16/08 02:13 PM
Originally Posted by NJwirenut
I've seen a few joints come apart like that, including one that I put in myself (and I was using the conduit manufacturer's glue!). The problem does seem to have something to do with marine environments.

I've taken to using a clear PVC primer on the pipe and fittings before applying the cement, just like you would on plumbing work. It definitely seems to result in a stronger joint...



Clear PVC primer? Do you have any info on it? Purple primer is quite ugly.
He might actually be using an even thinner product, sold as a 'cleaning' compound. I have seen clear primer, though ... sometimes at the home centers!

The joint in the picture appears to have used a gray cement, which I have seen sold in the plumbing aisle. The stuff I've seen that was actually listed for electrical use has always been clear. The clear glue is definitely thinner than the plumbing cements.

I will admit to changing my practices according to the conditions of the job site. For example, the listed cement is a poor choice in the summer sun - it dries too fast for you to make up your connections - while it works quite well in cooler temps.

Since we do not usually use a primer, I have also found it necessary to apply the glue to both halves of the connection. I think you really need the solvent to have some time to 'open up' the pipe surfaces before you can expect the cement to 'weld' them together.

Not that electricians pay much attention to PVC joints ... it's not like we're worried about electricity leaking out under pressure laugh
The glue sold by at least 2 PVC conduit manufacturers (Carlon and Cantex) is a heavy-bodied grey cement. That's the stuff I generally use.

The clear primer I have used is manufactured by Oatey, sold in the plumbing aisle of the orange box stores:

[Linked Image from oatey.com]

http://www.oatey.com/Plumber/Shared/ProductGroupDetail/174/Clear+Primer+%E2%80%93+NSF+Listed.html

Carlon PVC glue is manufactured by Oatey.

I'd bet that they're the same products, with different labeling.
Just looked in my truck, and the clear stuff I got from the supply house was made by Cantex. I've never seen the gray offered.

That said ... while I can be quite insistent upon UL listing in many cases, PVC glue isn't one of them. As electure suggests, the folks at Oatey probably know how to glue PVC together.
I've never understood why we weren't held to the same standards with PVC as plumbers where primer is required. The only difference we have is that we are trying to keep water from getting INTO the pipe.

I've always used primer, and yes it has been the purple stuff but I'm careful with it where it is exposed so that it looks OK. On underground couplings, I really don't care about being neat with it. Still, it makes sense that the joint should be cleaned prior to gluing.

My experience has been that many joints that pull apart are due to too much glue. It tends to "over-melt" the surfaces and the hardened glue ends up being the only thing holding it together.
It also depends on the manufactuer of the pvc. sometimes the fitting and conduit are loose and other times they are tight. It also depends on the installer. I have seen guys dab a little glue on the and push it together no twist and not enough glue for the weld to occur. You can tell if you look at the break just where the glue was.
Ob
Posted By: bigpapa Re: A Problem With Low Tide And Conduit Runs - 09/07/08 06:30 AM
This installation will always be a problem.
Beyond glue problems, the flex conduit will get stiff with age and nothing will hold it together. The very best legal installation I have seen for this type of application has been hard useabe SOW type rubber cable. Not too useful for multiple circuits though and requires connections and JBs if there is room, and its ugly.

The very best not so legal method I have seen is a tough rubber hose like fuel service hose and hose barbs with clamps at each end. This is the best flex conduit on the planet. Too bad its against the codes. I wish they would make an approved rubber conduit because it takes abuse like nothing else.
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