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Re: [TowerTalk] tubing vs. pipe-- and a question

To: "Jim Jarvis" <>,<>, <>
Subject: Re: [TowerTalk] tubing vs. pipe-- and a question
From: "Richard (Rick) Karlquist" <>
Date: Fri, 1 Jun 2007 08:50:37 -0700
List-post: <>
> 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.

This is only approximately correct.  "2 inch" Iron Pipe Size (IPS) pipe does
not have exactly a 2" ID.  All 2 inch pipe has an OD of exactly 2 3/8 inch.
The ID depends on wall thickness (ie schedule 40, 80, etc).
Schedule 40 has an ID of about 2 1/16" and Schedule 80 has
an ID considerably less than 2".  The OD is held to a tight
tolerance for threading purposes.  The ID is not tightly
specified, nor is the cross sectional area.   The only case
where the pipe size is the ID is "4 inch" schedule 40
pipe with a listed ID of 3.999.  BTW, the OD for 4 inch pipe
is 4.5 inches.

Irrigation "pipe" is the only "pipe" I know of that is
specified by OD and wall instead of IPS.  Sometimes you
will see it called irrigation tubing.  The size is specified
like tubing but the application is water carrying.  Well, not
exactly, since the tubing also has to have structural strength
for those big wheel systems you see.  The vendor
does give a yield strength of something like 26 KSI.  You should
be fine with a design that keeps the stress down to 10 or 15 KSI.
It may take a set above that, even if it doesn't break.  So
its a special case being both tubing and pipe in one.

2 inch irrigation tubing will slip easily inside 2 inch sch 40 pipe.  Same
3 inch.  4 inch irrigation tubing may or may not fit into
4 inch sch 40 pipe, depending on the particular run of pipe, since
they vary somewhat.  With schedule 80, irrigation tubing will
never slip inside of pipe.  Although irrigation tubing/pipe
is supposedly not rated for structural purposes, the vendor
does give a yield strength of something like 26 KSI.  You should
be fine with a design that keeps the stress down to 10 or 15 KSI.
It may take a set above that, even if it doesn't break.

Pipe connectors are interchangeable, mechanically, between
schedule 40 and 80.  Thus you can use a schedule 80 connector
in a schedule 40 system.  The reverse is true mechanically, but
of course the pressure rating is then reduced to the schedule
40 number.

Rick N6RK

> 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.
> 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!
> N2EA
> Jim Jarvis, President
> The Morse Group, LLC
> We create high-performance organizations.
> 732 548 5573 office
> 443 618 5560 cell
> _______________________________________________
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