Dear Aaron,
If you go to http://en.wikipedia.org/wiki/Nominal_Pipe_Size you will
find that the nominal pipe sizes are just a loose (some might say
sloppy) way of guessing what size a pipe might by. Let's take the
example of a nominal two and a half inch pipe. When you scroll down to
the tables, you will find that there are seven different two and a
half inch pipes to choose from. Note that all (seven of these seven)
are not two and a half-inch pipes.
The words, two and a half inch pipe names are simply nominal, they are
not intended to be, and they never were intended to be, actual
measurements. If we use the example that you chose for a half inch
pipe, you will see that 6 out of 7 options are not for a half inch
pipe either.
However, the decisions made by the learned engineers in 1927 have
caused a lot of confusion and a lot of grief to many people for the
last 82 years. This confusion will last until someone decides that
both pipe and tubing are specified something like 10/12 for a copper
tube that has an internal diameter of 10 millimetres, a wall thickness
of 1 millimetre, and an external diameter of 12 millimetres. One of
the lines in the table might then look something like this:
Nominal and actual internal diameter
Thickness
0.5
Thickness
1.0
Thickness
1.5
Thickness
2.0
Thickness
2.5
Thickness
3.0
Thickness
3.5
10 mm
10/11
10/12
10/13
10/14
10/15
10/16
10/17
All dimensions in millimetres
Cheers,
Pat Naughtin
Geelong, Australia
On 2009/04/11, at 3:27 PM, Aaron Harper wrote:
It is too bad we don't have a US plumber or piping engineer on this
list to settle this, so I will do my best.
In the US, for good, bad, or otherwise, the following conventions
hold for traditional pipe and tubing sizes.
For pipe:
The published size is based on the nominal ID. Thus, 1/2 inch pipe
will have a nominal inside diameter of 0.5 inches and an outside
diameter of approximately 0.75 inches This does not matter if it is
iron, galvanized, copper, or plastic. It will be the ID that counts
and the OD may vary.
For Tubing:
The published sizes are based on the OD. Therefore, 1/4 inch tubing
will have an outside diameter of 0.25 inches, while the ID will
depend on the wall thickness of the material, thus causing the ID
measurements to vary.
Conduit is yet another beast:
It depends on the material and type, which relates to wall
thickness. I believe the sizes are based on inside diameter.
My employer is converting to metric units depending on the
requirements of the customer. Since I don't deal with the piping
and structural guys very much, I am not yet familiar with how the
units are applied, or converted. I just know that all of our
control system vendors document and deliver their control cabinets
in mm.
Aaron Harper
On Fri, Apr 10, 2009 at 7:50 AM, Jeremiah MacGregor <[email protected]
> wrote:
That depends on what you mean by inch based. Spanish plumbers as
well as all others in the world (except the US) buy their pipe by
metre lengths.
Pipe diameters are express using inch trade names but don't measure
according to the name. A half inch pipe is no where near a half
inch. It is much, much bigger..
Recently the ISO establish metric names for the pipes based on a
closer metric dimension. A half inch pipe has a metric designation
of DN15. I have done something you hate to do and actually measured
some pipe. I have some half inch (12.7 mm) electrical conduit that
measures 16 mm ID, is 1 mm thick and has an 18 mm OD. I find it
strange that the pipe is actually 3 mm plus larger then the imperial
trade name. Care to explain why?
Care also to explain why you are satisfied with the use of a name
that does not reflect the real dimension?
Why do you confuse trade names with actual measurements?
Jerry
From: Stephen Humphreys <[email protected]>
To: U.S. Metric Association <[email protected]>
Sent: Monday, April 6, 2009 8:03:44 PM
Subject: [USMA:44459] RE: Reasoable Language (was Metrication US)
There's the odd exception - eg TV's.
Also - isn't Spanish plumbing based on inches for some historical
reason?
Date: Mon, 6 Apr 2009 12:28:59 -0700
Subject: [USMA:44449] RE: Reasoable Language (was Metrication US)
From: [email protected]
CC: [email protected]
To: [email protected]
The Spanish word for inch is "pulgada." Like most words for inch, it
is similar to word for "thumb," which in this case is "pulgar." Of
course no Spanish-speaking country uses inches or feet. Naturally
the original pulgada, pre-metrication, was not equal to 25.4 mm or
the barley-based system you mention. But the word "pulgada" now
refers to the 25.4 mm international inch. Similarly the word "pie"
means "foot," in both the measurement and anatomy.
Stephen Mangum
On Sun, Apr 5, 2009 at 7:26 PM, Jeremiah MacGregor <[email protected]
> wrote:
Martin,
I agree that the duim is a body part that some people used it to
measure things with in the past like the foot. I don't agree that
it is the same as the inch. The inch was defined as three barley
corns round and dry. Can you tell me the original official
definition of the duim? I would suspect that it was not related to
barley corns. Thus my point is, the two are not the same. No
disrespect was intended.
I'm sure we can find a list of units that were used in various
countries that have no equivalent to English units.
Jerry
From: Martin Vlietstra <[email protected]>
To: [email protected]; U.S. Metric Association <[email protected]
>
Sent: Sunday, April 5, 2009 3:53:03 PM
Subject: RE: [USMA:44374] RE: Reasoable Language (was Metrication US)
Jerry,
Two things:
1) Please do Han the courtesy of assuming that is command of Dutch
is better than yours – the “.nl” at the end of his e-mail address
suggests to me that Dutch is probably his mother tongue..
2) I can vouch for the fact that the word “duim” means both “thumb”
and “inch” in both Dutch and Afrikaans (I speak both languages). In
English, the word “foot” can either be part of the human anatomy or
it can be a unit of measure. In Dutch and in Afrikaans, both the
words “voet” and “duim” are units of measure and are also parts of
the human anatomy.
From: [email protected] [mailto:[email protected]] On
Behalf Of Jeremiah MacGregor
Sent: 05 April 2009 14:28
To: U.S. Metric Association
Subject: [USMA:44374] RE: Reasoable Language (was Metrication US )
… snip
Doesn't the word "Duimstok" literally mean "thumb stick"? A thumb
and an inch are not really they same thing, even if they are close.
… snip
Jerry
From: Han Maenen < [email protected] >
To: U.S. Metric Association <[email protected]>
Sent: Sunday, April 5, 2009 5:54:11 AM
Subject: [USMA:44369] RE: Reasoable Language (was Metrication US )
I agree with Bll Potts. Leave expressions like 'inch by inch' or
'not an inch' alone. Those opposed to metric would love it if we
wanted to change such things.
In the Netherlands a folding measuring stick is called a 'duimstok',
which is 'inch stick' in English. I have a wooden duimstok or inch
stick with centimetres only on it. I just avoid measuring
instruments with dual units like the plague.
Just west of of Dublin is the suburb Inchicore, how lunatic it would
be to change that to 2.54cmcore, or Sixmilebridge near Limerick to
'9.6 km-Bridge'. Of course, the distance to Sixmilebridge is always
given in km on road signs: 'Sixmilebridge 10 km'. There is a small
place in Ireland called Inch.
And people in metric countries should never give an inch to Imperial
and/or U.S. Customary in their own environment. That would be very
beneficial to metrication.
Han
----- Original Message -----
From: Bill Potts
To: U.S. Metric Association
Sent: Monday, 2009, March 30 22:30
Subject: [USMA:44234] RE: Reasonable Language (was Metrication US )
Pat and John:
For years, some of us on this list have tried to be reassuring to
the metrication-averse and to also counter some of the stranger
statements made by the more virulent opponents of metrication.
<snip>
Pat Naughtin
PO Box 305 Belmont 3216,
Geelong, Australia
Phone: 61 3 5241 2008
Metric system consultant, writer, and speaker, Pat Naughtin, has
helped thousands of people and hundreds of companies upgrade to the
modern metric system smoothly, quickly, and so economically that they
now save thousands each year when buying, processing, or selling for
their businesses. Pat provides services and resources for many
different trades, crafts, and professions for commercial, industrial
and government metrication leaders in Asia, Europe, and in the USA.
Pat's clients include the Australian Government, Google, NASA, NIST,
and the metric associations of Canada, the UK, and the USA. See http://www.metricationmatters.com
for more metrication information, contact Pat at [email protected]
or to get the free 'Metrication matters' newsletter go to: http://www.metricationmatters.com/newsletter
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