Offshore structures use a lot of HSS (tubular) structural members. Normally API
5L (Grade B or superior grades) are followed for tubes of 16" diameter and less.
For higher diameters, they are specified to be rolled and welded from plates of
a given specification.We usually specify and get seamless tubes in this smaller
diameter range, internationally. Generally the feedback is that seamless pipes
are cheaper for these smaller diameters. It would be difficult to roll and weld
smaller dia pipes. Spiral welded and Electric Resistance Welded pipes of smaller
dia are available, but we don't use them.
Hope this helps.
Sprague, Harold O. wrote:
> Seamless is still in the ASTM A500 specification, but the reality is that
> cold formed and welded is about all there is on the market.
> Seamless tubes can be drawn over a mandrel, or seamless furnace-buttwelded.
> The seamless tubes are almost never used as structural elements due to their
> expense, although the code does allow them.
> Seamless is more expensive, but the difference is a variable depending on
> size, and quantity ordered. I have seen seamless tube used in power plant
> piping, but never in structural shapes.
> Harold O. Sprague
> > -----Original Message-----
> > From: Nicholas Blackburn [SMTP:nblackburn(--nospam--at)fdgoak.com]
> > Sent: Monday, February 19, 2001 1:39 PM
> > To: 'seaint(--nospam--at)seaint.org'
> > Subject: ASTM A500 Gr B
> > I have a question for all you steel guys who are working on President's
> > Day.
> > Our company specifies A500 Gr B "seamless" for the hollow structural
> > sections we typically use for elevator towers, canopies etc. A contractor
> > has asked us what "seamless" means, i.e. is it extruded.
> > We spoke with a local fabricator and they indicated that all they stock is
> > welded HSS sections and that seamless would be a mill order item of at
> > least
> > 40,000lbs.
> > The question: Is A500 Gr B available as a seamless product? If so, what
> > is
> > the cost impact and will it perform differently than the single welded
> > seam
> > version commonly available?
> > Thanks
> > Nicholas Blackburn, PE