PVC & HDD Innovations
PVC has been in use across the United States for water pressure applications since the 1950s. It’s earliest use was for bringing drinking water to rural America. It remains the preferred product for this application and is installed hundreds of miles at a time for many projects. Much of rural America’s water systems have now been installed and the superior performance of these PVC systems are well documented.
By the mid 1970s AWWA published the PVC Standard C900 and municipal communities across America began putting PVC pipe into their distribution systems. Those keen for innovation and improvement were the first to adopt PVC into their systems. Their experiences and PVC’s overall cost and performance have led to tremendous growth and an industry with hundreds of manufacturing facilities across North America and broad acceptance of PVC pipe in municipal America. It’s superior performance is equally well documented.
Because of the tremendous acceptance of PVC pipe, the industry has been well situated to innovate as construction techniques have changed over time. The adoption of trenchless technologies such as horizontal directional drilling has led to a variety of PVC pipe joint innovations designed for HDD applications. One of these more recent innovations, the “Bull Dog” joint has been produced and marketed by several manufacturers across North America.
This joint provides a Rieber style gasketed joint with a locking ring within a casing, all contained within the bell of the PVC pipe. This arrangement permits a cartridge-style construction process that provides joint restraint with tremendous pull force capabilities. The casing and restraint ring are located inside the bell and protected with a highly corrosion-resistant coating. This PVC joint innovation is well suited for HDD applications.
The cartridge style construction process permits construction to precede one 20-ft joint at a time without the need to string pipe out. This is a tremendous advantage on jobsites with limited right of way. Because this joint utilizes the locked in Reiber gasket, which is used by the vast majority of PVC pipe manufacturers, municipalities are quite familiar with its superior water-tight performance.
From an external viewpoint, the bell of this internally restrained PVC pipe looks similar to a standard C900 PVC pipe bell. The construction process for this joint is similar to that of standard C900 PVC bell and spigot pipe. It requires a few additional checks along the way but dramatically reduces time for HDD applications compared with other products. Because contractors have become so familiar with the ease and speed of PVC gasketed bell and spigot construction, the minor changes required to properly construct the internal joint restraint version are relatively simple. Basic installation video instructions are available and are useful in learning these proper procedures.
There are at leaset two other joint configurations, which are designed for HDD applications — a spline assembly and a fused joint. In both instances, the joint is restrained, which allows for pulling in behind a drilling head.
These products are offered in CIOD dimensions in sizes from 4 to 36 in. and pressure classes from 80 to 305 psi. They are manufactured in accordance with AWWA C900. They are NSF certified for use with potable water. The cast iron outside diameter ensures compatibility and availability of fittings valves and other appurtenances.
In IPS dimensions it is available in diameters of 2 to 16 in. and pressure ratings from 160 to 200 psi. They are manufactured in accordance with ASTM D2241.
All of these products have been in use for several years now. The number of manufacturers involved and the substantial capacity of PVC manufacturing across North America along with the ease of installation and performance of these products have driven demand growth over the past decade. The need to avoid existing utilities, to pass under highways and rivers and avoid the disruption that open cut construction causes has increased the overall demand for HDD capable products. PVC has prospered in these applications because of its corrosion resistance, it’s tremendous strength to weight ratio, it’s compatibility to standard appurtenances and it’s ready availability.
Because the manufacturing process is identical to standard C900 PVC pipe with the exception of specialized bell tooling, the product is readily available and maintained in inventory. This allows for quick servicing of projects.
Dennis Bauer is vice president of sales and marketing at Diamond Plastics and provided this article on behalf of the PVC Association.
