[TowerTalk] comparing top section of crankup to unsupported

[Steve, W3AHL]

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.  

Steve, W3AHL

Date: Sat, 20 Mar 2010 09:04:10 -0700
From: Kevin Normoyle <knormoyle at surfnetusa.com>
Subject: [TowerTalk] comparing top section of crankup to unsupported
25g (and effects of long mast)
To: Tower Talk List <towertalk at contesting.com>

..snip..

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 ???

-kevin
AD6Z