The first difference is that pipe is rated by its ability
to carry a fluid. (gas, water, etc.) As a result, it is
first specified by cross sectional area... inner diameter.
So, 2" pipe has a 2" i.d., in order that you can use flow
tables to calculate both volume and pressure in systems.
Secondary specifications concern temperature and pressure
withstand characteristics. We seldom see those...but there
is black iron pipe and PVC pipe, and copper tube, and they're
all quite different. And, you don't get to specify the
wall thickness, for commonly distributed product. There is
a common thickness, and standard connectors for each type of
Pipe tends to be rolled and welded, rather than extruded.
Tube, on the other hand, is specified by its external
characteristics and strength, and it's sold by the pound
by commercial distributors. So, 2" tube is 2" o.d., and
has a specific wall thickness. It is typically extruded.
You can go to a distributor, like Bethlehem Aluminum, in
Bethlehem PA, and buy a 24' piece of 2" tube with 3/8" wall,
or 1/4" wall, for example, and they'll do a quick calculation
of how many lbs of Al that represents, and quote you a price.
You can also specify the alloy which is used, (e.g. T6061) such
that you can calculate the strength of the tube in service as a
mast, using existing engineering tables.
So, tube is specified by its size and strength, and pipe is
specified by cross sectional area, and suitability for particular
fluid-use environments. i.e. gas pipe vs. water pipe.
There may be something I've missed, here, but I think I captured
most of it. Does anyone know why there is a 24'length limit on the
normally available product? I've always wondered, and never
remember to ask the vendor!
Jim Jarvis, President
The Morse Group, LLC
We create high-performance organizations.
732 548 5573 office
443 618 5560 cell
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