Depends on whether its seamless or not... :)
There are both types for various service (primarily it is very high
pressure applications that justify the higher cost of seamless).
Years ago (as in when first opening up the North Sea oilfields, J Ray
McDermott a large supplier of offshore equipment purchased the entire
Babcock & Wilcox Company simply to get the patented proprietary
technology and fabrication facilities of the Seamless Tubing Division.
B&W and developed the particular process specifically for nuclear fuel
cladding tubing in support of their position as the Navy nuclear fuel
vendor as well as for their commercial nuclear fuel. McDermott wanted
it for the new deep offshore and demanding applications of the North
There are seamed, seamless, and Bundy tubing which is common in
automotive brake lines. Bundy uses a double wrapped construction which
is then oven treated to fuse the braze coating on the base tubing.
Good stuff for high pressures.
Comment on black iron pipe: any one who has had to thread BI for an
air compressor or NG project lately will note that the product from
China is not perfectly round. Our overseas supplier has yet to master
the finesse that American suppliers apply to the BI seams. I suspect
many pros are using special cutters to chamfer outer edges so that
pipe dies can start a smooth, and continue straight. These days I
always dig out the angle grinder and reshape the cut pipe before
attempting to thread it. Saves time in the end.
OK, thanks everyone. I knew tubes and pipes are different and people in
the business like to laugh at people that call a tube a pipe (like we
poke fun at someone with a hot water heater). No major importance to
me, I had just bought some 6" pipe for a project and when I noticed the
seam I thought I'd ask.
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