本文件规定了在规定试验条件下，测定预制管道绝缘试样稳态水蒸气传输特性的设备和程序。适用于隔热产品。 它适用于均质材料（见下文注释）和具有某些不同材料的整体表皮或粘附表面的产品。 注意如果一种材料的密度在整个过程中大致相同，即，就质量分布而言，它被认为是均匀的。 e、 如果测量的密度值接近其平均密度。

This document specifies the equipment and procedure for determining the water vapour transmission properties in the steady state under specified test conditions for test specimens of preformed pipe insulation. It is applicable to thermal insulating products. It is intended to be used for homogeneous materials (see NOTE below) and for products which can have integral skins or adhered facings of some different material. NOTE？A material is considered to be homogeneous in terms of mass distribution if its density is approximately the same throughout, i.e. if the measured density values are close to its mean density.