[BC] Air-Dielectric Sections

[Robert Meuser]

If you are going to bury large air dielectric line,  a concrete duct 
about 4 to 6 feet in diameter is in order and the line should be on hangers.

R

Mike McCarthy wrote:

> 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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