I don't know. Maybe you are not looking hard enough. For example, several years ago when my family was pursuing the aquarium hobby, all those pipe/tube/tubing (whatever one calls it) products were either OD x wall or OD/ID. Although obviously in mm, the mm was often with the number(s).
As to the source - I did point you to the ultimate one, iso.org. Asking people who "should know" is generally useless in the U.S. I have as yet to meet anyone associated with tires to acknowledge that they would "ever seen kPa on my tires." That's after twenty years of selling them with the kPa designation as mandated by law. To dismiss the "nonsense" is almost like asking for the dismissal of the hour/minute/second system but worse. Nominal inch pipes are ubiquitous and will cease (i.e., be no longer installed) when superior products take their place. Superiors means cheaper and easier to connect. Ordinary pipes depend on their particular method of joining - threading. The new product must fit the nominal inch pipes - it is the thread, not the OD/ID that keep that "nonsense" in existence. Centuries from now we will still be repairing threaded pipes. Fortunately, most of the non-thread products are metric or both. Partially because most of the quick joining was developed in Europe and those product are coming here in imports such as the HVAC eq't. With them come spare parts. You will probably not find the designation on them, however. They only fit the same product. Concerning the threaded connecting, enough was written about the BS and NP mess earlier. Stan Jakuba ----- Original Message ----- From: Jeremiah MacGregor To: U.S. Metric Association Sent: 09 Apr 11, Saturday 11:58 Subject: [USMA:44584] RE: Pipe Size, was Reasonable Language Why have I never seen this designation marked on the pipes or tubes sold in the stores to the consumers or even in industrial catalogs? I think that it should be required and the so-called half inch nonsense be dropped completely. By keeping it all an inside secret we never get exposed to this type of system. Is there a web site that you know of that gives more details and examples of this system in use? Jerry ------------------------------------------------------------------------------ From: Stan Jakuba <[email protected]> To: U.S. Metric Association <[email protected]> Sent: Saturday, April 11, 2009 11:40:53 AM Subject: [USMA:44582] RE: Pipe Size, was Reasonable Language Your wish has been granted If you go to some earlier discussion (January?) you'll find OD x wall info. Such product is usually called a tube. Either way, OD x wall products have been in ISO from its inception. Stan Jakuba ----- Original Message ----- From: Jeremiah MacGregor To: U.S. Metric Association Sent: 09 Apr 11, Saturday 09:16 Subject: [USMA:44577] RE: Pipe Size, was Reasonable Language Maybe it is time to devise a new pipe name system in which the name is based on the OD and ID in millimetres. Example, a pipe with a 15 mm ID and 17 mm OD (1 mm wall thickness) would be called a 17 x 15. Jerry ---------------------------------------------------------------------------- From: John M. Steele <[email protected]> To: U.S. Metric Association <[email protected]> Sent: Saturday, April 11, 2009 8:01:29 AM Subject: [USMA:44573] RE: Pipe Size, was Reasonable Language Aaron For pipe, I have heard the following claim, although I am not sure if it is true. Originally pipe was approximately the nominal ID size. At that time wall thicknesses were MUCH greater because of the primitive manufacturering conditions of the era. As thinner walls (with adequate strength, longevity) became feasible, a decision was made to keep the OD so fittings would fit and increase the ID from the former nominal value. --- On Sat, 4/11/09, Aaron Harper <[email protected]> wrote: From: Aaron Harper <[email protected]> Subject: [USMA:44566] RE: Reasoable Language (was Metrication US) To: "U.S. Metric Association" <[email protected]> Cc: "U.S. Metric Association" <[email protected]> Date: Saturday, April 11, 2009, 1:27 AM 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
