I'll just respond to the pipe grade portion for now: ASTM A53 Type E Grade B
may have a TENSILE strength of 50-60k, but not a YIELD strength -- that would
be 35K typically. Big difference.
The issue with A53 pipe is that only the larger sizes go through nondestructive
testing of the weld and ductility testing of the weld joint. Different
manufacturers have different criteria. Most do not perform NDT of the weld on
pipe below NPS 2 (2-3/8" OD) and the flattening ductility test is usually only
done on NPS 2-1/2 or larger. This is why 2" O.D. pipe is not suitable for a
mast -- no weld testing is done. If you buy from a reputable steel supplier,
they can show you their suppliers' standards (usually). Whether you believe
the specs from some foreign vendors is a different issue.
Yes, it may be suitable for the legs of a lattice tower, but that is a less
demanding application than a mast, due to the diagonal bracing and shorter span
intervals. US Towers uses A53 E B Fy=36ksi for their MARB 6' base column with
a F.S of 0.63, but not for their tower sections, which are A570 50ksi yield.
If you know what you are really buying and have the correct material and
process specifications and allow adequate safety margins for future added
loads , you could use pipe. Or for 30% more you can use the correct material,
usually, if there is a steel supplier in your area.
Date: Sat, 20 Mar 2010 09:04:10 -0700
From: Kevin Normoyle <firstname.lastname@example.org>
Subject: [TowerTalk] comparing top section of crankup to unsupported
25g (and effects of long mast)
To: Tower Talk List <email@example.com>
Now on whether ASTM A53 Type E Grade A (30k yield) is no good for
structural (which is what my pipe is stamped)
Type E is Electric Resistance Welded. ASTM A53 Type E Grade B is used
for structural stuff. Typical it has a higher 50k yield strength. The
composition of the steel is slightly different.
But the only manufacturing difference I can find is that Grade B heat
treats the weld afterwards, while Grade A doesn't. Grade A is pressure
tested. Grade B isn't.
I've noticed that some crankup manufacturers use ASTM A53 Grade B for
building their towers, along with finding it on a tower plan for the
tubes. (there are some variant Type F and Type S for A53. I can't tell
for sure but am assuming it's Type E also).
People are claiming there are substantial differences in manufacturing
(I know there are higher grades of structural steel...but ASTM A53 Grade
B Type E "is" used for some structural stuff as far as I can tell.
When people say the manufacturing process is no good: are they talking
about "not testing" or something specific like heat treatment of the weld?
When people say "water pipe" are they saying ASTM A53 Type E Grade A
(galvanized) or ???
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