[BC] Air-Dielectric Sections

[Mike McCarthy]

I'm thinking hydraulic sub-soil conditions where freeze/thaw or other 
geological pressures creates a force on a rock/bolder and will bust the PVC 
clear through and compressing the line.  Doing that to a 5" #11 or #13 
fiber duct would be brutally difficult since the walls are over 1/2" thick.

On the 3" line we installed for our project, duct was about $2/ft. compared 
to $0.50/ft. for grey electrical PVC in quantity.  But we made up for that 
cost in labor savings.  It took one day for two men to lay out 3000 ft. of 
duct....on 6 spools.  Try that with conduit.

I read it as an open statement not offering preference to one type of line 
over the other.

MM

At 12:02 PM 3/5/2007 -0500, Phil Alexander wrote
>Mike,
>
>Maybe I'm dense, but I thought he meant air dielectric Heliax.
>
>Who would consider running 3-1/8" rigid in u/g conduit? It
>makes no sense and would cost a fortune, even if the line
>was free. (i.e., surplus in the company)
>
>IMHO bare, unprotected PVC is always unwise. Some rodents
>seem to like it, and in areas of spring thaw, rocks can
>abrade it to destruction. Fiber duct would be less expensive
>than laying properly protected PVC. This is a case of the
>low cost solution being the most expensive solution.
>
>
>---------------------------------------------
>Phil Alexander, CSRE, AMD
>Broadcast Engineering Services and Technology
>(a Div. of Advanced Parts Corporation)
>Ph. (317) 335-2065   FAX (317) 335-9037
>
>
>
>On 5 Mar 2007 at 10:39, Mike McCarthy wrote:
>
> > I would not lay rigid line flat unless there is means to support the line
> > every 4 ft. or so from horizontal defection.  That will get really costly
> > real fast in an underground installation.
> >
> > If it were my installation, I would run running Heliax (et al) inside 5"
> > fiber duct instead of rigid line for the above reason.  Also, Heliax
> > doesn't suffer from the same thermal expansion issues as rigid line due to
> > it's inherent ribbed design.  So keep that in mind.
> >
> > As for the access vaults, make sure you have ample room to access and
> > manipulate the line from all directions of passage. A 4 ft. round vault
> > will not be large enough.  Something closer to 8 ft. long will be needed
> > due to the line size.  I would suggest a 4' x 8' drop in place concrete
> > vault with the line running lengthwise and offset to one side.  Then
> > something along the lines of 8' x 8' if there is a bend.
> >
> > Finally, I mentioned fiber duct.  For something that big and costly, I
> > would STRONGLY suggest using #11 or #13  5" fiber duct instead of PVC
> > conduit. While the duct will be more costly from a materials/delivery 
> stand
> > point, the labor to install will be 20% that of conduit. That and the 
> fiber
> > duct with interior ribs creates far less pulling friction than smooth
> > walled conduit.   Been there....on a 700+ ft. pull of 1-1/4" cable, the
> > tension when fully pulled was less than 300 lbs.  I can push the line back
> > and forth in the duct when it's not connected at either end.  Amazing.
> >
> > And I don't need to mention fiber duct won't break like PVC will
> > inevitably.  And thus jamming the line, possibly crushing it.
> >
> > MM
>
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