发布时间:2025-02-06 13:47:52
DN适用于所有管材一般是钢管,是指管道的公称直径,注意:这既不是外径也不是内径,是指平均值。dn主要用作塑料管材,是指管道外径,一般采用dn标注的,均需要标注成外径X壁厚的形式,比如dn400X17.5表示外径400mm壁厚17.5mm
电线电缆中quotbvblvbvvbbvrrvrvsrvvqvravvrvvvlvkvvquot是什么意思
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