EN 448:2003 区域供暖管道.直埋式热水供应网用预先绝热连接的管道系统.聚氨酯热绝缘和聚乙烯外覆层钢管用成套配件
District heating pipes - Preinsulated bonded pipe systems for directly buried hot water networks - Fitting assemblies of steel service pipes, polyurethane thermal insulation and outer casing of polyethylene