Why PVCO?

Technical information and frequently asked questions regarding the use of PVC-O Plastic Piping.

The below information is extracted from our joint partner – MOLECOR

(Sizabantu Piping Systems Official Distributor of Molecor South Africa)

 

What is PVC-O  |  PVC-O characteristics and advantages  |  PVC-O pipes and sustainability  |  Impact resistance in PVC-O pipes  |  PVC-O pipes design criteria  |  Why is PVC-O so unique?  |  What is TOM?

 


PVC-O Technical Information

PVC-O is the result of reorganizing the amorphous structure of PVC-U into a layered structured, providing unbeatable mechanical properties in plastic pipes, such as: high impact resistance (almost unbreakable), high stiffness and fatigue resistance, an excellent behaviour with external loads, crack propagation prevention and maximum flexibility.

This reorganization or alignment is done through an elongation of the plastic in special conditions that allow molecules to rotate following the direction of the deformation. Although these molecular changes are not visible at macroscopic scale, it is fully appreciable with an electronic microscope. As it is a physical process, there is no change chemically, so, there is not significant change in PVC formulation.

What is PVC-O?

A bit of history

PVC-O pipes were developed almost 40 years ago in the UK. The mechanical characteristics of these pipes were quickly recognized due to their great impact and fatigue resistance, elasticity, no crack propagation and tensile strength among others.

During the first three decades of life of this product, there were some limitations such us standardization, manufacturing process, range of products and industrial efficiency.

Standardization

Molecor came to the industry in 2006, and during these years has managed to create a new process to manufacture PVC-O pipes overcoming previous challenges, regarding efficiency and manufacturing processes and has participated very actively in the creation of new standards throughout the world, and in the continuous update of the current ones.

Here it is worth to highlight the last update of the International Standard, ISO 16422 which took place in year 2014 and in which the product range has been extended from the previous maximum DN 630 mm, in the 2006 edition, to a maximum diameter of DN 1000 mm, reflecting the market trend of growing into big diameters.

PVC-O standards

NF*. Mark for DN90 to 315, DN400 and DN500 in PN16, Dn110 to 315, DN400 and DN500 in PN25.

Summary of most representative PVC-O standards in the world and their main parameters

All this without forgetting the market demands that focused on growing in size and pressures, nowadays reaching PVC-O pipes DN 800 mm or 30” and up to PN 25 bar (365 psi) or 305 psi according to standards using imperial units.

Reaching this level of development and state of the art has been possible thanks to the continuous investment in R&D.

Which are the advantages of PVC-O?

Mechanically, the properties obtained after molecular orientation are remarkable, as the resistance to external loads which means that breakages are minimized during installation or during on-site trials caused by dropping or by impacts from stones.

The astonishing mechanical properties of the material allow having lighter pipes with notable increased hydraulic capacity. This, together with the low roughness of its their surface,  increases the efficiency of the water conductions.

PVC-O pipes provide a greater performance in meters / hour installation compared to other solutions. This is mainly due to their lightness and flexibility; these two facts allow a speed of installation that cannot be reached with pipes of other materials.

Find out more information in our website www.molecor.com

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

The application of molecular orientation to PVC improves all the mechanical properties of this material without exception. With this orientation PVC-O becomes a highly resistant material for manufacturing PVC-O pipes which cannot be easily destroyed by regular impacts.

Not only resistance is improved in PVC-O. In the following graph we can see the main mechanical properties affecting to pipes requirements and how they are improved compared with standard PVC.

PVC-O mechanical properties

High short and long term hydrostatic resistance

It is clear how in the short term, PVC-O is a much more resistant material. Analysing the long term behaviour, we can again appreciate a notorious improvement in PVC-O. The slope of the regresion curve is flatter. This means that the material, subjected to a certain stress will be more resistant, so life expectancy is higher.

Corrosion resistance

PVC-O Class 500 is immune to the corrosion caused by natural substances in the soil or agricultural chemicals. Therefore, it is no degradable and does not require any special protection which is translated into cost savings. The quality of the conveyed fluid remains always unaltered.

Regarding the advantages of PVC-O pipes, several can be appreciated compared to pipes of other materials. Among these we can find:

Increased hydraulic capacity

Due to the important reduction in wall thickness, a PVC-O pipe Class 500 can transport for the same nominal diameter much more water than the other traditional materials. In the following image it is possible to appreciate that this difference in water flow capacity is so important that in many cases it will be possible even to reduce the specified diameter for the immediately smaller. This fact contributes of course to reduce the investment in pipelines.

PVC-O pipes hydraulic capacity

Flexibility

Besides this, the ease connection of the pipe and its adaptability to the ground line due to the flexibility of the pipe also influences in the higher installation performance of these pipes and, what is more, depending on the line trajectory and pipe, elbows can be removed.

Flexibility

Excellent response to water hammer

The maintenance cost of this kind of nets is much smaller than in nets of traditional materials. In addition to the extreme resistance to damages during installation that can cause problems in the medium term, it is needed to consider the beneficial behavior of PVC-O Class 500 against the most frequent and worrying effect in a pipe line: water hammer. Due to its elasticity, in the same conditions for a sudden valve closure, a PVC-O Class 500 line, as shown in graphics below, reduces the picks of over pressure acting like a spring, absorbing energy, so the rest of the net is someway “protected”.

Water hammer

Energy efficiency

The innovative manufacturing process of PVC-O pipes requires less energy than the needed for manufacturing pipes of other materials thus becoming highly energy-efficient.

Pressure losses are minimized due to the fact that these pipes have an extremely smooth inner wall so, the energy required for transporting water is also lower. The optimization of the energy consumption results in significant energy savings especially, in the pumping stage.

Energy consumption

Lower material needs

Besides this, maintaining the same performance, PVC-O pipes need less consumption of raw material and this is affecting positively to all the players in the water industry. Less material means less oil consumption, together with a higher flow capacity in the same pipe, and more efficiency for pipe installers.

Material needs

Lower installation costs

One of the main important advantages PVC-O pipe present is the performance in meters / hour installation compared to other solutions. This is due mainly to these facts:

  • Lightness and flexibility. The speed of installation of these pipes is much higher than with pipes of other materials.
  • They are almost indestructible. Their manipulation can be performed with higher discharge and placement performance rates.
  • Ease of connecting pipes. This fact provides very high performance rates.

PVC-O pipes are lighter and can be handled easier than pipes made of other materials: they weigh less than the half of PVC and PE pipes, and between six and twelve times less per linear meter than ductile iron pipes of an equivalent nominal outside diameter. This can be better appreciated in the following graph:

Installation

The lightness of these pipes allows their handling and installation without mechanical aids such as cranes, feathers, etc., being able to be manually connected pipes up to DN 250mm. In this way, both labor and the use of heavy machinery are reduced, reducing thereby, the installation costs.

Find out more information in our website www.molecor.com

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.

As a contribution to improve this problem, TOM PVC-O pipes for the transport of water under pressure, become the most sustainable option that exists in the market due to their lower energy consumption and lower CO2 production associated  since they avoid unnecessary energy consumption throughout its long useful life.

The factors that determine energy efficiency throughout the lifecycle of a pipeline are mainly the type of raw material used, the production process, the finished product and its useful life.

PVC-O lifecycle

During the lifecycle of the PVC-O pipes manufacture, we can distinguish several phases:

1.- Production phase

PVC-O pipes are manufactured by conventional extrusion and subsequent molecular orientation. The extruded base pipe, under certain conditions of pressure and temperature, is subjected to a inside stretching of the pipe, the rearrangement of the polymer molecules, forming a lamellar structure on the pipe wall which significantly improves the mechanical properties of the pipe, while keeping intact its chemical properties.

PVC-O class 500 and PVC-U

At the same time, an optimization of the pipe wall occurs, with less raw material a pipe with higher mechanical properties is achieved as well as an optimization of raw materials. This lower consumption of raw materials, results in energy savings during their extraction and during production.

Extraction and production of materials

It should also be noted that the Molecor manufacturing process, worldwide patented, has great energy efficiency with which an optimization of the energy resources is also produced during the TOM® pipes production stage.

2.- Use phase

The useful life of a pipe to transport water must ensure a 50-year period as established by the regression line that determines its maximum operating tension. This useful life, begins at the time of construction of the network with the installation of the pipes. At this stage, the most important energy consumption is due to pumping.

Regarding the efficiency and energy savings that take place during this stage, we can distinguish several aspects:

• Transport optimization

Thanks to its lightness, we can transport more material, so we have fuel efficiency and minimizing CO2 emissions associated.

• Installation cost efficiency

- Its lightness also minimizes the impact of hand work and the need for special equipment for its placement.

- The efficient design of the socket allows the pipes are assembled with great ease.

Uniting these two factors, high performance installation is achieved, reducing considerably the time of execution of works, obtaining economic and social benefits by saving time and energy.

• Efficiency during operation

TOM® PVC-O pipes have a higher hydraulic capacity, between 15 and 40% depending on the diameter and the material with which it is being compared, so that for the same energy consumption, the transported water is always higher.

Molecor PVC-O

This increased hydraulic capacity is due to the greater useful section that these pipes present due to the optimization of wall thickness. Moreover, their smaller roughness causes the inner pipe surface is extremely smooth, thus the pressure losses are minimized and fluid can flow faster. All these benefits make that to transport the same amount of water less energy is needed, thus reducing energy consumption in pumping stage during use.

Energy consumed by pumping in 50 years

3.- Recycling or final disposal phase.

PVC is a 100% recyclable material that can be reused after its long useful life, mainly by mechanical recycling.

The PVC-O manufacturing process, due to its high technical requirement, does not allow the use of recycled materials, but allows a comprehensive management process because they can be used, after its long life cycle, in the manufacture of other plastic applications such as cable sheathing, gutters and downspouts for evacuation among others, where the technical requirements for raw materials are lower.

Thus, consumption of raw materials and also the volume of waste generated is reduced.

Promoting a culture of reuse and recycling is reflected in the report of the European Commission in April 2004, and in the voluntary commitment of the actors in the sector of waste management at European level in the Vinyl2010 and VinylPlus programs.

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. In this article we are going to focus interest on the damages caused by impacts, commonly happened in the product transport manipulation and in the installation works, which may imply a pipe collapse.

It is being known from more and more hydraulic management specialists and sector people that PVC-O pipes are the new generation of PVC, a product which maintains the advantages and eliminates the weakness of the traditional PVC-U, considered the most efficient solution for water transportation nowadays. Mechanically speaking, one of the feebleness of pipe materials is the impact resistance. Imagine a weight falling as a rock falling and impacting to a pipe which is laying in a trench, or a bad cargo manipulation when unloading; depending of the falling height and the material, it may cause a break, a scratch to the pipe protection that will permit oxidation, or a structural small dislocation that will grow and consequently bring high possibilities of failure in the future.

Pipe failures

Breakages in PVC-O due falling weights are almost impossible to see, because due the nature of the material its impact resistance is one of its best mechanical properties. As per its ductile behavior, elasticity and demonstrated impact absorption, reflected first in its higher standard test requirements and later in its proven successful installations in the field, having a PVC-O pipe is a guarantee of durability in this situations. Even in low temperature situations, when other materials use to show higher brittleness, PVC-O pipes accomplish impact requirements.

Molecor impact resistance

Even there is not a visible break or deep crack and it is just in the surface, when pipe suffers an impact, future loads applied to the pipe will cause a propagation of the crack unavoidably ending in a pipe collapse. PVC-O pipes, due their laminar structure, do not permit the propagation of the cracks because the dislocation cannot jump between lays easily as in other materials. This is one of the most common causes of impact failures, remarkable solved by PVC-O pipe material.

Scratches in surface are always not desired, but unfortunately they are inevitably in works and transport. PVC-O is a non-degradable product, with a layered structure consistent enough for not needing of corrosion-resistant coating.  PVC-O astonishing chemical resistance, quality maintained equal to PVC-U as per its equal chemical composition, is able to bear all kinds of erosive soils, and not affected by corrosion if scratch is produced.

In resume, PVC-O pipes are able to withstand impacts and their derived complications that may arise, without compromise their life expectancy, and definitely being a safe bet for all water resources managers.

Molecor PVC-O pipes

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.

MRS, Safety coefficient, design stressMinimum Required Strength (MRS): Required  σLPL value at 20 ºC and for a period of 50 years.

Hydrostatic Design Basis (HDB): Equivalent to MRS according to the ASTM standard, only calculated for a period of 100,000 hours.

Global Service Coefficient design (C): Overall coefficient with a greater value than one that takes into account not only all service conditions, but also the components that make up a piping system, other than those represented in σLPL.

Design Stress (σs): Based on the value of the long-term hydrostatic strength (σLPL) for the resistance to internal pressure of the material according to ISO 9080 standard. Hydrostatic stress (σ) is expressed in MPa, inducted in the pipe wall when it is subjected to internal hydraulic pressure. It is related with the real PVC-O pipe diameter and wall thickness through the equation:

Pipe design

Hydrostatic Pressure (p): Internal pressure applied to a piping system.

Nominal External Diameter (dn): Numerical designation of size which is common to all components in a thermoplastic piping system other than flanges and components designated by screw-thread size.

Nominal wall thickness (en): Pipe wall thickness expressed in millimeters, which is identical to the minimum wall thickness at any given point ey,min.

The previous formulas are valid for any plastic pipe design. Due to the improvement on the physical PVC-O pipe, its MRS or HDB is considerably superior to other materials, which increases the Hydrostatic Stress value. Moreover, the superior resistance enables a reduction on the safety coefficient, contributing to increase once again the value.

The result, a PVC-O pipe with a reduction of wall thickness between 40-60% or even more compared to other materials.

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.

TOM is a PVC oriented pressure pipe suitable for water distribution, rising sewer and irrigation supply. It provides the latest advancements in PVC pipe technology. The continuous, automated manufacturing process guarantees maximum product flexibility and total quality control of each pipe throughout the entire production process.


Sizabantu plastic piping systems and solutions Molcor South Africa PVC-O is the result of reorganizing the amorphous structure of PVC-U into a layered structured, providing unbeatable mechanical properties in plastic pipes, such as: high impact resistance (almost unbreakable), high stiffness and fatigue resistance, an excellent behaviour with external loads, crack propagation prevention and maximum flexibility.This reorganization or alignment is done through an elongation of the plastic in special conditions that allow molecules to rotate following the direction of the deformation. Although these molecular changes are not visible at macroscopic scale, it is fully appreciable with an electronic microscope. As it is a physical process, there is no change chemically, so, there is not significant change in PVC formulation.PVC-O pipes were developed almost 40 years ago in the UK. The mechanical characteristics of these pipes were quickly recognized due to their great impact and fatigue resistance, elasticity, no crack propagation and tensile strength among others.During the first three decades of life of this product, there were some limitations such us standardization, manufacturing process, range of products and industrial efficiency.Molecor came to the industry in 2006, and during these years has managed to create a new process to manufacture PVC-O pipes overcoming previous challenges, regarding efficiency and manufacturing processes and has participated very actively in the creation of new standards throughout the world, and in the continuous update of the current ones.PVC-O pipes provide a greater performance in meters / hour installation compared to other solutions. This is mainly due to their lightness and flexibility; these two facts allow a speed of installation that cannot be reached with pipes of other materials.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. Why PVC-OIn this article we are going to focus interest on the damages caused by impacts, commonly happened in the product transport manipulation and in the installation works, which may imply a pipe collapse.It is being known from more and more hydraulic management specialists and sector people that PVC-O pipes are the new generation of PVC, a product which maintains the advantages and eliminates the weakness of the traditional PVC-U, considered the most efficient solution for water transportation nowadays. Mechanically speaking, one of the feebleness of pipe materials is the impact resistance. Imagine a weight falling as a rock falling and impacting to a pipe which is laying in a trench, or a bad cargo manipulation when unloading; depending of the falling height and the material, it may cause a break, a scratch to the pipe protection that will permit oxidation, or a structural small dislocation that will grow and consequently bring high possibilities of failure in the future.Why PVC-OThe 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!