對于一(yi)些(xie)蒸(zheng)汽和熱(re)水管道(dao)可以采用(yong)(yong)(yong)直(zhi)埋的布置方式(shi)，相(xiang)應的管道(dao)材(cai)(cai)料可選用(yong)(yong)(yong)鋼(gang)套鋼(gang)管及(ji)管件、高密度聚(ju)乙烯外護管保(bao)溫管及(ji)管件等材(cai)(cai)料。如圖4-80所示，這種材(cai)(cai)料既(ji)解決了管子熱(re)膨脹(zhang)問題，也(ye)解決了隔熱(re)層(ceng)的防水等問題。詳(xiang)細講述見《工(gong)業(ye)管道(dao)配管設計(ji)與工(gong)程應用(yong)(yong)(yong)》《管道(dao)器材(cai)(cai)選用(yong)(yong)(yong)與工(gong)程應用(yong)(yong)(yong)》。

  有關標準(zhun)規范包括：GB／T 29047《高密(mi)度(du)聚乙烯外護(hu)管(guan)(guan)(guan)硬質聚氨酯(zhi)泡沫塑料(liao)預(yu)制直埋(mai)(mai)保溫(wen)管(guan)(guan)(guan)及管(guan)(guan)(guan)件》［適用于(yu)輸送介質溫(wen)度(du)（長期運(yun)行溫(wen)度(du)）不(bu)高于(yu)120℃，偶然峰值(zhi)溫(wen)度(du)不(bu)高于(yu)140℃的預(yu)制直埋(mai)(mai)保溫(wen)管(guan)(guan)(guan)、保溫(wen)管(guan)(guan)(guan)件及保溫(wen)接頭］

  EN 253《用于區(qu)域(yu)供熱熱水管(guan)(guan)(guan)網一由工作(zuo)鋼管(guan)(guan)(guan)、聚氨酯(zhi)保(bao)溫(wen)層和高密(mi)度聚乙烯外護管(guan)(guan)(guan)組(zu)成的(de)預制直埋保(bao)溫(wen)管(guan)(guan)(guan)》；

  EN 448《用于區域供熱熱水管(guan)網一由工作鋼管(guan)、聚(ju)氨酯保溫層和(he)高(gao)密度聚(ju)乙(yi)烯外護(hu)管(guan)組成(cheng)的預制直埋(mai)保溫管(guan)件》；

  EN 489《用(yong)于區(qu)域(yu)供熱(re)熱(re)水管網一由(you)工(gong)作鋼管、聚氨酯保溫(wen)層和高密度聚乙烯外(wai)護管組成的(de)預(yu)制直埋保溫(wen)管道接頭》。

  有的壓力(li)管(guan)(guan)道設(she)(she)計(ji)人員用普通的隔熱(re)(re)保溫管(guan)(guan)道直(zhi)埋，會導致(zhi)隔熱(re)(re)層失效。有的壓力(li)管(guan)(guan)道設(she)(she)計(ji)人員做地(di)溝，在(zai)地(di)溝內(nei)按(an)地(di)上管(guan)(guan)道布(bu)置設(she)(she)計(ji)蒸汽(qi)或熱(re)(re)水管(guan)(guan)道，不如(ru)直(zhi)埋布(bu)置設(she)(she)計(ji)成本更(geng)低一(yi)些。