Recently, Shanghai Municipal Bureau of Quality and Technical Supervision notified the quality spot-checked results of water supply and drain pipe at the second quarter in 2009, Shanghai: 3 batches of unqualified products were exposed.

There are mainly 3 kinds of water supply and drain plastic pipes for the construction industry: PPR pipes, PE pipes, and PVC-U (6395, 65.00, 1.03%) pipes. PVC pipes have been widely used for water supply and drain for the construction field; recently PPR pipes, mainly used for the cold and warm water supply system of the construction field have developed rapidly; and PE pipes as a kind of newly construction material are promoted greatly.50 batches of products were spot-checked, and the qualification rate reached 94%.

And tests showed that there were 3 batches of unqualified products, among of which were 2 batches of PE pipes for water supply. The main unqualified items were hydrostatic strength and oxidative induction time (OIT). OIT, the index shows the autocatalytic oxidation of the tested samples under the condition of high temperature and oxygen, evaluates the heat resistance and degradation of the material during the moulding process, storage, extrusion and application. The oxidation resistance of the material depends on the length of its OIT, which impacts on the quality of the pipes directly. The shorter OIT, the poorer oxidation resistance of the material.

There was 1 batch of unqualified products in OIT. The actual OIT is only 7 minutes (200℃), while the standard is at least 20 minutes, which means the quality is seriously bad. The hydrostatic strength which does not meet the standard indicates that the poor pressure endurance capability of the pipes, easily burst.

In addition, a batch of PPR pipes was unqualified, mainly in charpy impact test. If those products affected external impacts, they may rupture in the process of transport, loading and unloading, installation and application (especially in winter).