suspended waste line over creek 3

[bdruehl]

Need to suspend a septic waste line over a creek about 90 feet. Want to use pvc (a painted ("pvc can not be exposed to direct sunlight") outer 3-4" line around an interior supply 1 1/2" line) I can find (and also calculate) the maximum support points for the pvc in tables (plumbing code), probably 4 ft. conservative. Want to use a steel cable and come along system. Can not find any good references for any wind calc analsyis. I can not figure any reason to put a heavy metal pipe around the supply line, (painting pvc should take care of the uv exposure despite the building official finding the quote "pvc shall not be exposed to direct sunlight" in the plumbing code.

 

[Frank1344]

Hi,

If you have wind velocity and air density then:

P=1/2 pV^2

in which P=pressure, p=density,V= velocity

Your Force will be:

F=P*S*A

in which F is the Force, S=Shape Factor= 0.65 for Pipe and A is your PROJECTED AREA of Pipe.

 

[MiketheEngineer]

And the constant movement will probably cause a fatigue failure....

If a couple of squirrels can take apart my sump pump PVC drain line.... a little wind should be no problem... NOT!!

 

[chicopee]

I would not want to use PVC piping over the creek. The likelyhood of damage is relatively high from malicious acts and physical damage by air born debris. Steel would be my preference

 

[bdruehl]

i can see how a steel pipe would be better, except for the weight. Fatigue loading and such.

http://www.eng-tips.com/viewthread.cfm?qid=49424

is a good forum, but i dont think it addresses if you are suspending from a steel cable, only rigid support. i need more info, before i google myself into oblivion. surely there is some table out there....

 

[bdruehl]

also this thread, but it doesnt help much and again, im still at the recreating the wheel stage.

 

[bdruehl]

http://www.eng-tips.com/viewthread.cfm?qid=246530

 

[MikeHalloran]

Given that you want to suspend the pipe from a cable, your search should include the word 'catenary'.



Mike Halloran
Pembroke Pines, FL, USA

 

[StephenA]

If you have to use a plastic pipe I would use High Density Polyethylene (HDPE or HPPE) and not PVC.

Stephen Argles
Land & Marine

http://www.landandmarine.com

 

[BigInch]

For the cheapest option, use the strongest pipe, otherwise you'll spend more on the supports than you will on the pipe.

 

[vpl]

You'll also spend a lot more on lawsuits if the pipe breaks and the waste gets into the creek. Besides wind loading, you might want to make sure that your supports are not subject to any seismic or other ground movement.

Somebody on here has a tagline: "First, design for graceful failure ..."



Patricia Lougheed

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[1gibson]

Make sure it can resist loading up to the tensile strength of fishing line.

 

[bdruehl]

yes... ofcourse there are seismic and wind loads! always are here! i have the design easily for vertical loads. not finding good resources for wind and seismic loads on a pipe supported only "catenarily" by one cable, seems such a system provides for very limited lateral support for the pipe. *(will sleave pvc in a steel pipe for leaking issues over the crossing)

here: google this for great resource on this thread

"Suspension Canyon and Gully Crossings for Small Scale Community"