AL vs RGS conduit in a corrosive areas for analog signalling cable, is there an issue with AL cond? 1

[bdn2004]

We have a standard at this plant that requires RGS conduit for analog signalling conduit. However it's been pointed out that this area has proven to be highly corrosive due to the raw material used at the site and its reaction with steel, rain, etc over time.

The question is...which is worse....corrosion - which we know will be a future problem, or some kind of electrical noise issue with the AL conduit? Like what is the issue with AL conduit and analog signalling?

 

[7anoter4]

You are right ,I am afraid.See the following opinions:

http://www.steeltubeinstitute.org/pdf/conduit/ASCO_CS.pdf

"According to the study, steel conduit can reduce EMF at 60 Hz power frequency levels by as much as 95%. It showed that aluminum conduit reduced EMF by just 10%, and that nonmetallic conduit was ineffective in reducing field levels."

http://www.wheatland.com/electrical-conduit

"Electrical Conduit
We supply a full range of steel conduit (RMC, IMC and EMT) that offers superior physical protection for electrical conductors, is recognized as an equipment grounding conductor by the NEC® and acts AS AN EFFECTIVE shield against electrical magnetic interference (EMI). All three products are available in 10-foot lengths. Many trade sizes of RMC and EMT are also available in 5-ft and 20-ft. lengths, which helps speed installation, and reduce costs.
Wheatland also supplies Rigid Aluminum Conduit (RAC), which provides: extra protection in most corrosive and industrial atmospheres, ease of installation, reduced maintenance costs and a bright, attractive appearance"

 

[7anoter4]

I used-in a sea water vicinity only- rigid steel conduit pvc covered and the client was very content. See[for instance]:

http://www.tnb.com/pub/node/942

 

[dpc]

It's possible that the Steel Tube Institute might have a slight bias. Steel conduit will be superior for EMI shielding, but if you are running good quality shielded instrument cable, it may not matter that much, unless the electrical environment is extremely noisy. Corrosion issues will depend on the nature of the corrosion. Galvanized steel is good in some situations and not so good in other environments. PVC-coated steel conduit is very expensive and the corrosion protection is highly dependent on the workmanship of the electricians doing the installation.

 

[MikeHalloran]

Two coats of epoxy paint after assembly will keep steel conduit looking decent for quite a long time.

I'd worry about aluminum's natural oxide film making it useless for equipment grounding, and it's already next to useless for shielding, so I'm not seeing an upside to it.



Mike Halloran
Pembroke Pines, FL, USA

 

[SceneryDriver]

Can you use a non-corroding conduit (aluminum or PVC) and use analog cable with better shielding?


SceneryDriver

 

[HTNeighbors]

I agree with dpc! Bite the bullet and install PVC Coated Rigid Steel. Installed correctly, it will last for years. Wired correctly, you should not have an issue with the circuits.