Introduction to Molecularly Oriented Polyvinyl Chloride

PVCO pipe, short for molecularly oriented polyvinyl chloride pipe, has been utilized in North America for over forty years, boasting an impressive installation span of more than 20,000 miles. This type of pipe shares many similarities with conventional polyvinyl chloride (PVC) pipe, including the ingredients and cell classifications. The journey of PVCO begins with an equivalent PVC compound, which undergoes extrusion to form PVC pipe. However, PVCO is then subjected to a physical modification process that imparts molecular orientation, enhancing its mechanical strength and toughness. Initially, both PVC and PVCO qualify for cell class 12454 per ASTM D1784 and possess a hydrostatic design basis (HDB) of 4,000 psi. However, through the manufacturing process, PVCO's molecular structure undergoes realignment from random to circumferential orientation, resulting in an increased HDB of 7,100 psi. Due to PVCO's distinct HDB values, it is not classified using the dimension ratio (DR) system employed for conventional PVC; instead, PVCO is referenced solely by pressure class (PC) or pressure rating (PR). In North America, PVCO products are available in Cast Iron Outside Diameter (CIOD) and Iron Pipe Size (IPS) configurations, with various pressure classes and ratings. The first North American installation of PVCO pipe occurred in Kansas in 1979, following its development in Europe in the early 1970s. By the 2000s, multiple manufacturers were offering PVCO pipe in North America. The introduction of ASTM F1483 in 1993 marked the first product standard for PVCO pipe, primarily used in rural water and irrigation applications. Subsequently, AWWA C909 was published in 1998, establishing the first PVCO municipal water pipe standard. This standard was updated over time to accommodate larger sizes and align with revised design procedures. In 2009, the Canadian Standards Association (CSA) published PVCO standard B137.3.1, further solidifying the acceptance and usage of PVCO pipe in North America.

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