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
