對于一(yi)些蒸汽和熱(re)(re)水管(guan)(guan)(guan)道(dao)可以采用(yong)直埋(mai)的布置(zhi)方式，相(xiang)應(ying)的管(guan)(guan)(guan)道(dao)材(cai)(cai)料可選用(yong)鋼(gang)套鋼(gang)管(guan)(guan)(guan)及(ji)管(guan)(guan)(guan)件、高密度聚乙(yi)烯外護(hu)管(guan)(guan)(guan)保溫管(guan)(guan)(guan)及(ji)管(guan)(guan)(guan)件等材(cai)(cai)料。如圖(tu)4-80所示，這種材(cai)(cai)料既解(jie)決了管(guan)(guan)(guan)子熱(re)(re)膨脹問題(ti)，也(ye)解(jie)決了隔熱(re)(re)層(ceng)的防水等問題(ti)。詳細講述見(jian)《工業(ye)管(guan)(guan)(guan)道(dao)配管(guan)(guan)(guan)設計與(yu)工程(cheng)應(ying)用(yong)》《管(guan)(guan)(guan)道(dao)器材(cai)(cai)選用(yong)與(yu)工程(cheng)應(ying)用(yong)》。
有關標準規范(fan)包括：GB／T 29047《高密度(du)(du)聚乙烯外護管硬質聚氨酯泡沫塑(su)料預(yu)制(zhi)直埋保(bao)(bao)溫(wen)(wen)(wen)管及管件》［適用(yong)于(yu)輸送(song)介(jie)質溫(wen)(wen)(wen)度(du)(du)（長期運行溫(wen)(wen)(wen)度(du)(du)）不(bu)高于(yu)120℃，偶然峰值溫(wen)(wen)(wen)度(du)(du)不(bu)高于(yu)140℃的預(yu)制(zhi)直埋保(bao)(bao)溫(wen)(wen)(wen)管、保(bao)(bao)溫(wen)(wen)(wen)管件及保(bao)(bao)溫(wen)(wen)(wen)接頭］
EN 253《用于(yu)區域供熱熱水管(guan)網一由工作鋼管(guan)、聚氨酯保(bao)(bao)溫層和高密度聚乙(yi)烯外護管(guan)組成(cheng)的預(yu)制(zhi)直埋保(bao)(bao)溫管(guan)》；
EN 448《用于(yu)區域供熱熱水(shui)管(guan)網(wang)一由工作(zuo)鋼管(guan)、聚氨酯保溫(wen)層(ceng)和(he)高密度聚乙烯外護管(guan)組成的預制直(zhi)埋保溫(wen)管(guan)件》；
EN 489《用于(yu)區域供熱熱水管(guan)(guan)網一(yi)由工作(zuo)鋼管(guan)(guan)、聚氨(an)酯(zhi)保溫(wen)層和高密度聚乙烯外護管(guan)(guan)組成(cheng)的預制直(zhi)埋(mai)保溫(wen)管(guan)(guan)道接頭》。
有的壓力(li)管(guan)道設計人員用普通的隔熱(re)保溫管(guan)道直埋，會導致隔熱(re)層(ceng)失效。有的壓力(li)管(guan)道設計人員做地(di)溝，在地(di)溝內按地(di)上管(guan)道布置設計蒸(zheng)汽或(huo)熱(re)水管(guan)道，不如(ru)直埋布置設計成本(ben)更低一(yi)些。
