Which is more expensive, furnace tube T9 or P9 for reformation heaters?
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As the title suggests, I’d like to ask the experts. The technical agreement specified T9, but the manufacturer insisted on changing it to P9; I wonder if there’s something suspicious behind this
Is it an ASME pipe? If so, then T9 refers to tube, while P9 refers to pipe (nominal pipe), and they follow different material specifications. Tube is in accordance with SA-213, while Pipe is in accordance with SA-335. The UNS numbers of the two are the same, as are their chemical compositions, allowable temperatures, and allowable stresses; these can be found in ASME Volume II. What differs is the ordering specifications: the size of tube pipes is generally smaller, not exceeding 5“ ； The specification range for pipes is quite wide. For tubes, unless a specified average wall thickness is given, the default ordering specification is outer diameter + minimum wall thickness; these are tubes with positive tolerances ； Nominal pipes can be ordered based on outer diameter + nominal wall thickness, outer diameter + minimum wall thickness, inner diameter + nominal wall thickness, or inner diameter + minimum wall thickness. Based on my experience, tube pipes are generally used for the heating surface tubes, while pipe pipes are used for the pipes and headers. As for other specific differences, I haven’t compared them in detail again; it is recommended to check those two material standards. If not, I don’t know.
As you mentioned, T9 represents the minimum wall thickness option for purchase; it is cheaper than P9 in terms of its nominal wall thickness, while its other properties remain the same.
Without a detailed inspection, it seems that the wall thickness tolerance for P-tubes is +/- 12.5%, while that for T-tubes is +29%; with that information you can tell which one is more expensive