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Technical information

The main purpose of the hydraulic dimensioning of a pipeline is to determine the diameter of the pipe. The basic design conditionings are the required flow rate and the pressure required at the endpoints of the network. In addition to this, other factors such as the design speed or the head losses (continuous and localized) are also involved, as well as the characteristics of the materials of the network (roughness and cost, mainly).

The water quality circulating inside the TOM® pipes is kept completely unaltered, thanks to the fact that it is a chemically homogeneous and corrosion resistant material, that is to say, without interior coatings or protections, so that there is no degradation of the pipe nor migrations of products from the pipe to the water.

For these reasons, and for its exceptional technical characteristics, PVC-O is a suitable material for the transportation of water for human consumption.

TOM® PVC-O pipelines of a pressure network are part of an integral system that interact with the rest of the elements and equipment that form it.

It is necessary to distinguish between the hydraulic pressures exerted on the pipeline or the network and the pressures each component is capable of withstanding individually.

Hydraulic pressures exerted on the pipe network

Any design project for a water transport or distribution network is based on the determination of a need for hydraulic supply (Qh) at one or several consumption points.

In the case of transport between two points, there will be a need for a certain flow at the outlet point that matches the flow along the entire network (Qt). However, in the case of a distribution network with several consumption points, there will be different flow rates along the network depending on the mesh, flow rates and consumption points (Q1, Q2,…Qn).


First of all, it is important to note that the pipes must be transported in accordance with current traffic regulations. To optimize transport we recommend the following guidelines:

The article below outlines the differences between making a push-fit connection on PVC-O pipes and Butt Fusion Welds required for PE pipes.

PVC-O Pipe Joint Procedure

Although other applications are not ruled out, TOM® pipe is especially suitable for underground installations.

In this article, we would like to provide the information and necessary points to study for dimensioning the trenches correctly:


For calculation purposes and for this article, we are going to consider the most common installation case: Installation in trench or in fill.  The required data are:

Stresses and strains

Prior to the analysis of the types of stresses and deformations that are subjected to a buried pipe, the main factors should be identified.  

One of the main values on which is based Molecor is its commitment to the environment; due to this most of its efforts in R&D are used to develop increasingly efficient systems to manufacture sustainable PVC-O pipes.

Pressure pipes can have different types of damages and defects, due different causes occurred in all product value chain; from industrial pipe production until the installation and end of their working life. Since microstructural defects as tiny holes due air and bad gelation in the manufacturing process, passing by the incorrect packaging and wrong secure cargo in transportation, installation and manipulation bad practices, to their usage with non-projected hydrostatic pressures due non satisfactory net design or usage.

Bearing in mind the problem of global warming affecting the planet due to the greenhouse effect, many governments are planning environmental policies seeking greener and environmentally friendly solutions to apply in all areas and so maintain a proper sustainable development of the available resources.

PVC-O gathers a series of characteristics that make this material optimal for pipe manufacturing and, as we will see, pipes made of this material present extreme advantages and savings for pipe manufacturers, as well as large benefits for potential pipe customers and end users.

Among the characteristics of PVC-O we find:

Unbeatable impact resistance

Molecularly Oriented PVC is the result of reorganizing the amorphous structure of PVC-U into a layered structured, by a mechanical process, to provide unbeatable mechanical properties in a plastic pipe, such as: high impact resistance (almost unbreakable), high stiffness and fatigue resistance, excellent behaviour with external loads, elimination of crack propagation and

The durability of PVC-O pipes is not negatively affected by weather changes or by extreme low temperatures. What is more, PVC-O pipes have performed well in extreme climates being, regarding installation and use, fully operational. What is more, PVC-O pipes characteristics become more advantageous as temperature decreases and it has been demonstrated, by a research from the National Research Council of Canada, that buried PVC pipes used for the conveyance of water perfectly accommodate the stress created by water freezing.

Molecor is a machinery manufacturer that integrates the concept of remote assistance and surveillance for technical support and quality control of the customer's production process.

As an international leading company in the molecular orientation of PVC, Molecor provides comprehensive support to its customer’s business through the latest available technology, as a result of the continuous R & D process with individual and monitored projects.

PVC-O pipe specifications for a certain working pressure are regulated mainly by ISO 16422:2006 and ASTM F 1483-05, although there are several national PVC-O pipe standards.

The parameters considered are:

Long-term hydrostatic strength (σLPL) for 50 years at 20ºC: Quantity with the unit of stress, MPa, which can be considered to be a property of the material under consideration. It represents the 97.5% lower confidence limit for the long-term hydrostatic strength and equals the predicted average strength at a temperature of 20ºC and for a time of 50 years with internal water pressure.

The oriented PVC material is significantly stronger and tougher than PVC-U and therefore provides better performance overall. It is approximately twice the strength and ten times more impact resistant than PVC-U!

PVC-O is a product that was first manufactured at the end of the 1970's. Since then, many technical improvements have arisen to improve productivity and make it profitable. Molecor Technology has developed the latest technology to be highly profitable for pipe manufacturers together with the rest of the water industry participants.