"Regular" sch40 pipe is often specified as 30kpsi yield strength, but
schxx IPS is available to 70kpsi. The example fence folks are
specifying 50kpsi and a non-standard wall thickness of 0.120" which is
in between sch20 and sch40 normal pipe sizes, 0.105" and 0.145"
respectively. If I calculated correctly, the radius of gyration/section
moment of inertia is 0.423/0.495 = 0.85 for fence "high strength" vs
sch40. Given the yield stress ratio is 50k/30k = 1.67 then the relative
bending yield is 1.67 x .85 or 1.42x better for the 0.120" wall "high
strength" fence pipe. It's an interesting result to trade the amount of
steel for better steel to yield higher bending yield stress.
Here is one fence pipe manufacturer's brochure with what they call W40,
W30, W20, and W15 grades, with varying wall thickness, usually not the
same as IPS sch40, 20, or 10. Note the W30 which seems to be the pipe
mentioned earlier in the post is hot dip galvanized on the outside, but
something different inside and also has additional polymer coatings.
The W15 goes down to 0.047 wall.
http://www.wheatland.com/images/fence_framework/Fence_Framework_Brochure.pdf
if you want to see all of the choices in "standard" pipe here is the USS
pipe brochure
http://usstubular.com/resources/library/brochures-and-catalogs/u-s-steel-tubular-products-standard-and-line-pipe
Yield strength is not the only variable in pipe performance. High
strength tube (not pipe) is Drawn Over Mandrel (DOM) to insure
uniformity of wall and strength. It may have been seam welded or
pierced bar to make the rough shape. Then there may be heat treating to
a specific hardness/strength.
Using fence pipe for gin poles which have a significant risk of life
hazard, is a risk I would not take. Rather, a DOM structural tube in an
appropriate wall thickness.
Using EMT with a 0.065" wall for a tribander on tower mast, welded seam
and electro-galvanized only on the outside is just plain nuts. There are
NO specs for the steel properties.
YMMV,
Grant KZ1W
On 3/13/2016 18:27 PM, Steve Maki wrote:
On 3/13/2016 9:01 PM, Richard (Rick) Karlquist wrote:
A good alternative to schedule 40 pipe is the tubing used nowadays for
fence top rails, known as SS40. It's lighter (thinner wall) but
stronger
and actually less expensive than galvanized sch. 40 pipe if purchased
from the right place.
We routinely use it on cell sites for antenna masts in place of sch.
40.
Here are the specs:
http://www.hooverfence.com/catalog/chart.htm
-Steve K8LX
Note that the outer diameter of fence tubing will always
be the same as the outer diameter of some standard water
pipe size. E.G. Both "1 7/8 inch" fence tubing
and "1 1/2 inch" water pipe (any schedule) actually
have an outer diameter of 1.900 inch. Either can be
shimmed with standard 2" OD aluminum irrigation pipe with
0.050 inch wall to fit standard 2.000" mast clamps
or bearings.
I don't know why they make fence tubing and pipes the
same size. One theory is that you if you want to build
a fence on steroids, water pipe can be substituted for
fence tubing very easily. (Attention: Donald Trump :-)
Or maybe they make both of them on the same equipment.
(Obviously, I have spent way too much time loitering
in hardware stores.)
Hehe.
But I'm not sure why substituting schedule 40 for SS40 in fence
applications or any other (except plumbing perhaps) would be an
*upgrade*. A quick search didn't yield specs for sch. 40 that would
lend itself to an applicable comparison, but the fence people claim
that SS40 is *stronger* than sch. 40.
In the fence business there are numerous tee couplers, etc. already
sized for stand sch 40 OD's, which probably drove the size constraints
for SS40.
-Steve K8LX
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