???????:???\???\????\?????  

                               ?????????????????? 

     ?????????????????????????????????????????????в?????????????????????????????PN????????-??????.?????????????????????????????￡???????в??????
    ??????????(nominal diameter)??????????(mean outside diameter)?? ?????????????赺???????????????????????????????????????????????????????
?????λ?й???(mm)?????(inch)????????????????е????????
1. ?????(mm)???????? DN (metric unit)
2. ?????(inch)????????NB(inch unit)
3. DN (nominal diameter)
   NB (nominal bore)
   OD (outside diameter)
4. ??????
??????:DN50??sch 20 ?????:??????NB2”??sch 20
5. ??:DN??NB,  OD???????￡?
DN(mm)--------NB(inch)-------OD(mm)
15-------------- 1/2--------------21.3
20--------------3/4 --------------26.7
25-------------- 1 ----------------33.4
32-------------- 1 1/4 -----------42.2
40-------------- 1 1/2 -----------48.3
50-------------- 2 ----------------60.3
65-------------- 2 1/2 -----------73.0
80-------------- 3 ----------------88.9
100------------- 4 ---------------114.3
125--------------5 ---------------139.8
150------------- 6 ---------------168.3
200------------- 8----------------219.1