Whether designing a pressurized or a gravity pipe system, the selection of the dimensions of the fit-for-purpose pipes involves calculating losses in the terms of pressure, flow volume and flow speed. There are several methodologies for calculating these values. The most commonly used are the Hazen-Williams and Prandtl-Colebrook-White formulae.
Another factor to be taken into account is the load loss produced by accessories (elbows, reducers, tees etc) and valves.
When determining the flow speed, economic factors must be taken into account; (optimization of the investment in terms of water pumping) as well as the admissible values for water hammers. Generally, the minimum values used for avoiding sediment deposition is 0.5 m/s, and the maximum values are between 2.0 to 2.5 m/s, depending on the diameter of the pipe.
Molecular Orientation reduces the pipe wall thickness, giving TOM® PVC-O pipes a greater internal diameter and flow section. The internal surface is extremely smooth, reducing the load loss and making it more difficult for deposits to be accumulated within the inner walls of the pipes.
TOM® PVC-O pipes offer between 15% - 40% more hydraulic capacity than pipes made from other materials with the same external diameters.
Water hammer can introduce sudden surge in pressure on the pipe working pressure and may lead to breakage, particularly when the pipe has already been damaged by impact or corrosion. Air locks in the pipes during filling can be highly damaging when water hammer is present and can cause an excess of pressure far beyond the rated pressure ratings. TOM® PVC-O pipes can withstand this surge in pressure better than the metallic materials. However as a precautionary measure, it is important to observe the following recommendations:
PVC-O material outperforms the conventional plastics when it comes to strength. The stress-strain curve behaviour of PVC-O resembles closely to the metal behaviour.
The complete transformation of PVC-O mechanical properties compared to conventional PVC can only be achieved in the higher PVC-O class, class 500, such as in HYPRO® PVC-O class 500 pipes.
Materials lose their mechanical performance when they are subjected to stress over a long period of time. This phenomenon, known as creep, appears to a far lesser extent in PVC-O class 500 than in conventional plastics, which results as better materials in the long term. Bearing in mid that PVC-O is exceptionally resistant to fatigue and has a very good chemical resistance, HYPRO® PVC-O class 500 has a design life up to 50 years.
Molecor offers the technology for PVC O pipe manufacturing adapted to any specific need, technical requirement and market standard. For that purpose, Molecor builds long term relationships with its clients to back up every phase of the project, before, during and after the industrial technology implementation.
TOM® PVC-O pipes weigh less than half the conventional PVC and HDPE pipes, and are between six to twelve times lighter than ductile iron pipes of the same diameter. They are easy to handle and they can be lifted without mechanical assistance (for pipes up to DN 315 mm).
During the installation process, the assembly between pipes are faster and there is no need for welded unions, thanks to the pipe socket design and the TOM® PVC-O properties.
Additionally, with the TOM® PVC-O robustness, the stretches caused by impacts are minimal during unloading, installation and trenching.
Total cost of ownership is a financial estimate intended to help buyers and owners determine the direct and indirect costs of a product or system. It is a management accounting concept that can be used in full cost accounting or even ecological economics where it includes social costs. TOM® PVC-O pipes give benefits in various expects especially in cost effectiveness ranging from Water Companies to Installers. Low pumping energy and also, larger bore of nominal diameters give the reduction in utilities cost and maximum hydraulic capacity. Due to its light weight and easier to handle, the handling may not require heavy machinery. In addition, this may increase the speed of installation per metre/day thus, lower the installation cost for the installers or contractors.
