"Nominal" yog hais txog cov yeeb nkab hauv cov ntsiab lus tsis tshwj xeeb thiab txheeb xyuas txoj kab uas hla ntawm lub qhov nrog tus lej uas tsis yog-dimensional (piv txwv li - 2-inch nominal steel yeeb nkab" muaj ntau ntau yam ntawm cov yeeb nkab steel nrog tib qhov kev ntsuas. a 2. {8}}inch inch yeeb nkab, Teem caij 40").
NPS feem ntau tsis raug hu ua National Pipe Size, vim tsis meej pem nrog Asmeskas tus qauv rau cov yeeb nkab xov, "lub teb chaws cov yeeb nkab ncaj", uas tseem hu ua "NPS". Lub npe European thiab thoob ntiaj teb sib npaug rau NPS yog DN (diamètre nominal / nominal inch / Nennweite), uas qhov ntau thiab tsawg yog ntsuas hauv millimeters. Lub sij hawm NB (nominal bore) kuj nquag siv sib hloov nrog DN.
